WorldWideScience

Sample records for 1000-3000km earth orbit

  1. Lunar Orbiter: Moon and Earth

    1966-01-01

    The worlds first view of the Earth taken by a spacecraft from the vicinity of the Moon. The photo was transmitted to Earth by the United States Lunar Orbiter I and recieved at the NASA tracking station at Robledo de Chavela near Madrid, Spain. This crescent of the Earth was photographed August 23 at 16:35 GMT when the spacecraft was on its 16th orbit and just about to pass behind the Moon. This is the view the astronauts will have when they come around the backside of the Moon and face the Earth. The Earth is shown on the left of the photo with the U.S. east coast in the upper left, southern Europe toward the dark or night side of the Earth, and Antartica at the bottom of the Earth crescent. The surface of the Moon is shown on the right side of the photograph.

  2. Objects orbiting the Earth in deep resonance

    J. C. Sampaio; Wnuk, E.; de Moraes, R. Vilhena; S. S. Fernandes

    2012-01-01

    The increasing number of objects orbiting the Earth justifies the great attention and interest in the observation, spacecraft protection and collision avoidance. These studies involve different disturbances and resonances in the orbital motions of these objects distributed by the distinct altitudes. In this work, the TLE (Two-Line Elements) of the NORAD are studied observing the resonant period of the objects orbiting the Earth and the main resonance in the LEO region. The time behavior of th...

  3. Earth orbiting technologies for understanding global change

    Harris, Leonard A.; Johnston, Gordon I.; Hudson, Wayne R.; Couch, Lana M.

    1989-01-01

    This paper considers the technology requirements needed to support the Mission to Planet Earth concept, which will consist of several sun synchronous polar platforms; a series of low-earth orbit equatorial missions, such as Space Shuttle payloads, Space-Station-attached payloads, and the Explorer-class Earth Probes; and five geostationary platforms. In particular, the technology requirements in the areas of space-based observation, data/information, and spacecraft operation are examined.

  4. Orbit Propagation and Determination of Low Earth Orbit Satellites

    Ho-Nien Shou

    2014-01-01

    Full Text Available This paper represents orbit propagation and determination of low Earth orbit (LEO satellites. Satellite global positioning system (GPS configured receiver provides position and velocity measures by navigating filter to get the coordinates of the orbit propagation (OP. The main contradictions in real-time orbit which is determined by the problem are orbit positioning accuracy and the amount of calculating two indicators. This paper is dedicated to solving the problem of tradeoffs. To plan to use a nonlinear filtering method for immediate orbit tasks requires more precise satellite orbit state parameters in a short time. Although the traditional extended Kalman filter (EKF method is widely used, its linear approximation of the drawbacks in dealing with nonlinear problems was especially evident, without compromising Kalman filter (unscented Kalman Filter, UKF. As a new nonlinear estimation method, it is measured at the estimated measurements on more and more applications. This paper will be the first study on UKF microsatellites in LEO orbit in real time, trying to explore the real-time precision orbit determination techniques. Through the preliminary simulation results, they show that, based on orbit mission requirements and conditions using UKF, they can satisfy the positioning accuracy and compute two indicators.

  5. Objects orbiting the Earth in deep resonance

    Sampaio, J C; de Moraes, R Vilhena; Fernandes, S S

    2012-01-01

    The increasing number of objects orbiting the Earth justifies the great attention and interest in the observation, spacecraft protection and collision avoidance. These studies involve different disturbances and resonances in the orbital motions of these objects distributed by the distinct altitudes. In this work, the TLE (Two-Line Elements) of the NORAD are studied observing the resonant period of the objects orbiting the Earth and the main resonance in the LEO region. The time behavior of the semi-major axis, eccentricity and inclination of some space debris are studied. Possible irregular motions are observed by the frequency analysis and by the presence of different resonant angles describing the orbital dynamics of these objects.

  6. The Apsidal Precession for Low Earth Sun Synchronized Orbits

    Shkelzen Cakaj

    2015-09-01

    Full Text Available By nodal regression and apsidal precession, the Earth flattering at satellite low Earth orbits (LEO is manifested. Nodal regression refers to the shift of the orbit’s line of nodes over time as Earth revolves around the Sun. Nodal regression is orbit feature utilized for circular orbits to be Sun synchronized. A sun¬-synchronized orbit lies in a plane that maintains a fixed angle with respect to the Earth-Sun direction. In the low Earth Sun synchronized circular orbits are suited the satellites that accomplish their photo imagery missions. Nodal regression depends on orbital altitude and orbital inclination angle. For the respective orbital altitudes the inclination window for the Sun synchronization to be attained is determined. The apsidal precession represents major axis shift, respectively the argument of perigee deviation. The apsidal precession simulation, for inclination window of sun synchronized orbital altitudes, is provided through this paper.

  7. Nickel hydrogen low earth orbit life testing

    Badcock, Charles C.; Haag, R. L.

    1988-02-01

    A program to demonstrate the long-term reliability of nickel hydrogen (NiH2) cells in low earth orbit (LEO) and support use in mid-altitude orbit (MAO) has been initiated. Both 3.5 and 4.5 in. diameter NiH2 cells are included in the test plan. Cells from all U.S. vendors are to be tested. The tests will be performed at -5 and 10 C at 40 and 60 percent depth of discharge (DOD) for LEO orbit and 10 C and 80 percent DOD for MAO orbit simulations. The goals of the testing are 20,000 cycles at 60 percent DOD and 30,000 cycles at 40 percent DOD. Cells are presently undergoing acceptance and characterization testing at Naval Weapons Support Center (NWSC), Crane, Indiana. Funding has been provided by the Air Force Space Technology Center (AFSTC) and two AF System Program Offices (SPO's) to initiate the testing, but additional funding must be acquired to complete the purchase of cells and to assure completion of the testing.

  8. Orbital perturbation analysis of earth-crossing asteroids

    Knudson, Wade E.

    1995-01-01

    Earth Crossing Asteroids (ECAs) are those asteroids whose orbit cross section can intersect the capture cross section of the Earth as a result of secular gravitational perturbations. This thesis provides a framework for understanding the origin, nature, and types of ECAs. The change in velocity requirements to achieve a two Earth radii deflection for long and short term warning scenarios are developed. Next, a method of developing hypothetical Earth colliding asteroid orbits is presented. The...

  9. Earth Orbiting Support Systems for commercial low Earth orbit data relay: Assessing architectures through tradespace exploration

    Palermo, Gianluca; Golkar, Alessandro; Gaudenzi, Paolo

    2015-06-01

    As small satellites and Sun Synchronous Earth Observation systems are assuming an increased role in nowadays space activities, including commercial investments, it is of interest to assess how infrastructures could be developed to support the development of such systems and other spacecraft that could benefit from having a data relay service in Low Earth Orbit (LEO), as opposed to traditional Geostationary relays. This paper presents a tradespace exploration study of the architecture of such LEO commercial satellite data relay systems, here defined as Earth Orbiting Support Systems (EOSS). The paper proposes a methodology to formulate architectural decisions for EOSS constellations, and enumerate the corresponding tradespace of feasible architectures. Evaluation metrics are proposed to measure benefits and costs of architectures; lastly, a multicriteria Pareto criterion is used to downselect optimal architectures for subsequent analysis. The methodology is applied to two case studies for a set of 30 and 100 customer-spacecraft respectively, representing potential markets for LEO services in Exploration, Earth Observation, Science, and CubeSats. Pareto analysis shows how increased performance of the constellation is always achieved by an increased node size, as measured by the gain of the communications antenna mounted on EOSS spacecraft. On the other hand, nonlinear trends in optimal orbital altitude, number of satellites per plane, and number of orbital planes, are found in both cases. An upward trend in individual node memory capacity is found, although never exceeding 256 Gbits of onboard memory for both cases that have been considered, assuming the availability of a polar ground station for EOSS data downlink. System architects can use the proposed methodology to identify optimal EOSS constellations for a given service pricing strategy and customer target, thus identifying alternatives for selection by decision makers.

  10. Stationary occultations from low Earth orbit

    Percival, Jeffrey W.

    1993-01-01

    The process of stationary lunar occultations is considered for observers in LEO. The orbit of the Hubble Space Telescope (HST) is used as a prototype. The noncoplanarity of the HST and lunar orbits disrupts many of the expected stationary events, and orbital drag complicates the prediction problem. In a typical year, the apparent speed of the lunar limb seen by the HST is slower than a typical ground-based event only about 0.7 percent of the time. The orbit prediction can be wrong by as much as 20 deg in 53 days, with most of the error lying in the plane of the orbit.

  11. LLOFX earth orbit to lunar orbit delta V estimation program user and technical documentation

    1988-01-01

    The LLOFX computer program calculates in-plane trajectories from an Earth-orbiting space station to Lunar orbit in such a way that the journey requires only two delta V burns (one to leave Earth circular orbit and one to circularize into Lunar orbit). The program requires the user to supply the Space Station altitude and Lunar orbit altitude (in km above the surface), and the desired time of flight for the transfer (in hours). It then determines and displays the trans-Lunar injection (TLI) delta V required to achieve the transfer, the Lunar orbit insertion (LOI) delta V required to circularize the orbit around the Moon, the actual time of flight, and whether the transfer orbit is elliptical or hyperbolic. Return information is also displayed. Finally, a plot of the transfer orbit is displayed.

  12. Modeling Earth Albedo for Satellites in Earth Orbit

    Bhanderi, Dan; Bak, Thomas

    2005-01-01

    Many satellite are influences by the Earthøs albedo, though very few model schemes exist.in order to predict this phenomenon. Earth albedo is often treated as noise, or ignored completely. When applying solar cells in the attitude hardware, Earth albedo can cause the attitude estimate to deviate with as much as 20 deg. Digital Sun sensors with Earth albedo correction in hardware exist, but are expensive. In addition, albedo estimates are necessary in thermal calculations and power budgets. We...

  13. Autonomous On-Board Optical Navigation Beyond Earth Orbit Project

    National Aeronautics and Space Administration — To date, navigation solutions are created by ground systems teams and then uploaded to vehicles operating beyond Earth orbit. However with the improvement of...

  14. Modeling Earth Albedo for Satellites in Earth Orbit

    Bhanderi, Dan; Bak, Thomas

    2005-01-01

    Many satellite are influences by the Earthøs albedo, though very few model schemes exist.in order to predict this phenomenon. Earth albedo is often treated as noise, or ignored completely. When applying solar cells in the attitude hardware, Earth albedo can cause the attitude estimate to deviate...... with as much as 20 deg. Digital Sun sensors with Earth albedo correction in hardware exist, but are expensive. In addition, albedo estimates are necessary in thermal calculations and power budgets. We present a modeling scheme base4d on Eartht reflectance, measured by NASA's Total Ozone Mapping...... Spectrometer, in which the Earth Probe Satellite has recorded reflectivity data daily since mid 1996. The mean of these data can be used to calculate the Earth albedo given the positions of the satellite and the Sun. Our results show that the albedo varies highly with the solar angle to the satellite's field...

  15. Applications of low-earth-orbit power transmission

    Arndt, G.D.; Kerwin, E.M.

    1986-01-01

    The use of low-earth-orbit transmission systems to transfer power between two co-orbiting satellites is investigated. A microwave system with a 20 m antenna and 30 m rectenna over a 5-10 km operating range could have possible applications for transmitting 100 kW of power. Antenna/rectenna trade-off sizings, taper analyses, orbital considerations, and possible uses are discussed.

  16. The O/OREOS Mission - Astrobiology in Low Earth Orbit. [Astrobiology in Low Earth Orbit

    Ehrenfreund, P.; Ricco, A. J.; Squires, D.; Kitts, C.; Agasid, E.; Bramall, N.; Bryson, K.; Chittenden, J.; Conley, C.; Cook, A.; Mancinelli, R.; Mattioda, A.; Nicholson, W.; Quinn, R.; Santos, O.; Tahu, G.; Voytek, M.; Beasley, C.; Bica, L.; Diaz-Aguado, M.; Friedericks, C.; Henschke, M.; Mai, N.; McIntyre, M.; Yost, B.

    2014-01-01

    The O/OREOS (Organism/Organic Exposure to Orbital Stresses) nanosatellite is the first science demonstration spacecraft and flight mission of the NASA Astrobiology Small- Payloads Program (ASP). O/OREOS was launched successfully on November 19, 2010, to a high-inclination (72 deg), 650-km Earth orbit aboard a US Air Force Minotaur IV rocket from Kodiak, Alaska. O/OREOS consists of 3 conjoined cubesat (each 1000 cu cm) modules: (i) a control bus; (ii) the Space Environment Survivability of Living Organisms (SESLO) experiment; and (iii) the Space Environment Viability of Organics (SEVO) experiment. Among the innovative aspects of the O/OREOS mission are a real-time analysis of the photostability of organics and biomarkers and the collection of data on the survival and metabolic activity for microorganisms at 3 times during the 6-month mission. We report on the spacecraft characteristics, payload capabilities, and present operational phase and flight data from the O/OREOS mission. The science and technology rationale of O/OREOS supports NASA0s scientific exploration program by investigating the local space environment as well as space biology relevant to Moon and Mars missions. It also serves as a precursor for experiments on small satellites, the International Space Station (ISS), future free-flyers and lunar surface exposure facilities.

  17. Energetic particle environment in near-Earth orbit.

    Klecker, B

    1996-01-01

    The hazard of exposure to high doses of ionizing radiation is one of the primary concerns of extended manned space missions and a continuous threat for the numerous spacecraft in operation today. In the near-Earth environment the main sources of radiation are solar energetic particles (SEP), galactic cosmic rays (GCR), and geomagnetically trapped particles, predominantly protons and electrons. The intensity of the SEP and GCR source depends primarily on the phase of the solar cycle. Due to the shielding effect of the Earth's magnetic field, the observed intensity of SEP and GCR particles in a near-Earth orbit will also depend on the orbital parameters altitude and inclination. The magnetospheric source strength depends also on these orbital parameters because they determine the frequency and location of radiation belt passes. In this paper an overview of the various sources of radiation in the near-Earth orbit will be given and first results obtained with the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) will be discussed. SAMPEX was launched on 3 July 1992 into a near polar (inclination 82 degrees) low altitude (510 x 675 km) orbit. The SAMPEX payload contains four separate instruments of high sensitivity covering the energy range 0.5 to several hundred MeV/nucleon for ions and 0.4 to 30 MeV for electrons. This low altitude polar orbit with zenith-oriented instrumentation provides a new opportunity for a systematic study of the near-Earth energetic particle environment. PMID:11540369

  18. From order to chaos in Earth satellite orbits

    Gkolias, Ioannis; Gachet, Fabien; Rosengren, Aaron J

    2016-01-01

    We consider Earth satellite orbits in the range of semi-major axes where the perturbing effects of Earth's oblateness and lunisolar gravity are of comparable order. This range covers the medium-Earth orbits (MEO) of the Global Navigation Satellite Systems and the geosynchronous orbits (GEO) of the communication satellites. We recall a secular and quadrupolar model, based on the Milankovitch vector formulation of perturbation theory, which governs the long-term orbital evolution subject to the predominant gravitational interactions. We study the global dynamics of this two-and-a-half degrees of freedom Hamiltonian system by means of the fast Lyapunov indicator (FLI), used in a statistical sense. Specifically, we characterize the degree of chaoticity of the action space using angles-averaged normalized FLI maps, thereby overcoming the angle dependencies of the conventional stability maps. Emphasis is placed upon the phase-space structures near secular resonances which are of first importance to the space debris...

  19. Low-Earth Orbit Determination from Gravity Gradient Measurements

    Sun, Xiucong; Chen, Pei; Macabiau, Christophe; Han, Chao

    2016-06-01

    An innovative orbit determination method which makes use of gravity gradients for Low-Earth-Orbiting satellites is proposed. The measurement principle of gravity gradiometry is briefly reviewed and the sources of measurement error are analyzed. An adaptive hybrid least squares batch filter based on linearization of the orbital equation and unscented transformation of the measurement equation is developed to estimate the orbital states and the measurement biases. The algorithm is tested with the actual flight data from the European Space Agency's Gravity field and steady-state Ocean Circulation Explorer (GOCE). The orbit determination results are compared with the GPS-derived orbits. The radial and cross-track position errors are on the order of tens of meters, whereas the along-track position error is over one order of magnitude larger. The gravity gradient based orbit determination method is promising for potential use in GPS-denied spacecraft navigation.

  20. Low-Earth Orbit Determination from Gravity Gradient Measurements

    Sun, Xiucong; Macabiau, Christophe; Han, Chao

    2016-01-01

    An innovative orbit determination method which makes use of gravity gradients for Low-Earth-Orbiting satellites is proposed. The measurement principle of gravity gradiometry is briefly reviewed and the sources of measurement error are analyzed. An adaptive hybrid least squares batch filter based on linearization of the orbital equation and unscented transformation of the measurement equation is developed to estimate the orbital states and the measurement biases. The algorithm is tested with the actual flight data from the European Space Agency Gravity field and steady-state Ocean Circulation Explorer. The orbit determination results are compared with the GPS-derived orbits. The radial and cross-track position errors are on the order of tens of meters, whereas the along-track position error is over one order of magnitude larger. The gravity gradient based orbit determination method is promising for potential use in GPS-denied spacecraft navigation.

  1. MAPPING EARTH ANALOGS FROM PHOTOMETRIC VARIABILITY: SPIN-ORBIT TOMOGRAPHY FOR PLANETS IN INCLINED ORBITS

    Fujii, Yuka [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Kawahara, Hajime, E-mail: yuka.fujii@utap.phys.s.u-tokyo.ac.jp [Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan)

    2012-08-20

    Aiming at obtaining detailed information on the surface environment of Earth analogs, Kawahara and Fujii proposed an inversion technique of annual scattered light curves named spin-orbit tomography (SOT), which enables us to sketch a two-dimensional albedo map from annual variation of the disk-integrated scattered light, and demonstrated the method with a planet in a face-on orbit. We extend it to be applicable to general geometric configurations, including low-obliquity planets like the Earth in inclined orbits. We simulate light curves of the Earth in an inclined orbit in three photometric bands (0.4-0.5 {mu}m, 0.6-0.7 {mu}m, and 0.8-0.9 {mu}m) and show that the distribution of clouds, snow, and continents is retrieved with the aid of the SOT. We also demonstrate the SOT by applying it to an upright Earth, a tidally locked Earth, and Earth analogs with ancient continental configurations. The inversion is model independent in the sense that we do not assume specific albedo models when mapping the surface, and hence applicable in principle to any kind of inhomogeneity. This method can potentially serve as a unique tool to investigate the exohabitats/exoclimes of Earth analogs.

  2. A Geostationary Earth Orbit Satellite Model Using Easy Java Simulation

    Wee, Loo Kang; Goh, Giam Hwee

    2013-01-01

    We develop an Easy Java Simulation (EJS) model for students to visualize geostationary orbits near Earth, modelled using a Java 3D implementation of the EJS 3D library. The simplified physics model is described and simulated using a simple constant angular velocity equation. We discuss four computer model design ideas: (1) a simple and realistic…

  3. Can Sunlight Shift the Earth onto a Different Orbit?

    Esposito, S.

    2011-01-01

    This article comes from a question asked by a student of mine: if the Sun radiates energy in the form of electromagnetic waves, could they shift the Earth from its current orbit on a suitable timescale? The answer to such a question is apparently obvious and trivial. Nevertheless, it requires an instructive reasoning and interesting estimates of…

  4. Optical technologies for the observation of low Earth orbit objects

    Hampf, Daniel; Riede, Wolfgang

    2015-01-01

    In order to avoid collisions with space debris, the near Earth orbit must be continuously scanned by either ground- or spaced-based facilities. For the low Earth orbit, radar telescopes are the workhorse for this task, especially due to their continuous availability. However, optical observation methods can deliver complementary information, especially towards high accuracy measurements. Passive-optical observations are inexpensive and can yield very precise information about the apparent position of the object in the sky via comparison with background stars. However, the object's distance from the observer is not readily accessible, which constitutes a major drawback of this approach for the precise calculation of the orbital elements. Two experimental methods have been devised to overcome this problem: Using two observatories a few kilometres apart, strictly simultaneous observations of the same object yield an accurate, instantaneous 3D position determination through measurement of the parallax. If only on...

  5. PRODUCTION OF NEAR-EARTH ASTEROIDS ON RETROGRADE ORBITS

    Greenstreet, S.; Gladman, B. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia (Canada); Ngo, H. [Department of Physics, Engineering Physics, and Astronomy, Queen' s University, Kingston, Ontario (Canada); Granvik, M. [Department of Physics, University of Helsinki, Helsinki (Finland); Larson, S., E-mail: sarahg@phas.ubc.ca [Department of Planetary Sciences, University of Arizona, Tucson, Arizona (United States)

    2012-04-20

    While computing an improved near-Earth object (NEO) steady-state orbital distribution model, we discovered in the numerical integrations the unexpected production of retrograde orbits for asteroids that had originally exited from the accepted main-belt source regions. Our model indicates that {approx}0.1% (a factor of two uncertainty) of the steady-state NEO population (perihelion q < 1.3 AU) is on retrograde orbits. These rare outcomes typically happen when asteroid orbits flip to a retrograde configuration while in the 3:1 mean-motion resonance with Jupiter and then live for {approx}0.001 to 100 Myr. The model predicts, given the estimated near-Earth asteroid (NEA) population, that a few retrograde 0.1-1 km NEAs should exist. Currently, there are two known MPC NEOs with asteroidal designations on retrograde orbits which we therefore claim could be escaped asteroids instead of devolatilized comets. This retrograde NEA population may also answer a long-standing question in the meteoritical literature regarding the origin of high-strength, high-velocity meteoroids on retrograde orbits.

  6. Monitoring objects orbiting earth using satellite-based telescopes

    Olivier, Scot S.; Pertica, Alexander J.; Riot, Vincent J.; De Vries, Willem H.; Bauman, Brian J.; Nikolaev, Sergei; Henderson, John R.; Phillion, Donald W.

    2015-06-30

    An ephemeris refinement system includes satellites with imaging devices in earth orbit to make observations of space-based objects ("target objects") and a ground-based controller that controls the scheduling of the satellites to make the observations of the target objects and refines orbital models of the target objects. The ground-based controller determines when the target objects of interest will be near enough to a satellite for that satellite to collect an image of the target object based on an initial orbital model for the target objects. The ground-based controller directs the schedules to be uploaded to the satellites, and the satellites make observations as scheduled and download the observations to the ground-based controller. The ground-based controller then refines the initial orbital models of the target objects based on the locations of the target objects that are derived from the observations.

  7. Unscented Kalman Filters for Attitude and Orbit Estimation of a Low Earth Orbit CubeSat

    Grigore, Vlad

    2015-01-01

    In this paper two Unscented Kalman Filters (UKF) are implemented to solve the estimation of a satellite's position in orbit and its orientation relative to Earth's Centered Inertial frame. Their aim is to see if an absolute position accuracy of less than 1 km and an orientation estimation to less than 1 0 are possible for a 3U CubeSat with GPS, sun sensors, magnetometers and a star tracker as sensors. The orbit UKF is based on a Runge Kutta 7(8) th-order integration method for orbit propaga...

  8. Analysis on high-altitude earth Orbit Satellite Determination

    He, J.; Hou, Y. W.; Yang, L.

    2016-02-01

    The difference is introduced between approx circular apogee orbit and approx circular perigee one by error transmitting at first. Then the characteristic of secant compensation is analysed when radar tracking object with high elevation. And two kinds of orbit force be pressed to, their perturbation influence and their earth-core angles are explained. And then the series of emulation results are shown including error data emulated with Monte Carlo method, the influence of the velocity increment from the ejecting force of spring while satellite-rocket separating and their perturbation influence and the length of influence of the data arc. Then decision analysis of Wald method and Bayesian statistics rule and the results from the two rule are introduced. So the suitable orbit determination decision is put forward from the decision method. Finally the result is tested reasonable and feasible via the real data. In the end it is useful to reference to make orbit decision in short injection of circular orbit far from the earth for calculating concurrently precise and timely.

  9. Microwave antenna temperature of the earth from geostationary orbit

    Njoku, E. G.; Smith, E. K.

    1985-01-01

    The microwave antenna temperature of the earth has been computed for the case of a communication satellite antenna viewing the earth from geostationary orbit. An earth-coverage beam is assumed and detailed computations are performed to account for varying land-ocean fractions within the field of view. Emission characteristics of the earth's atmosphere and surface are used with an accurate radiative transfer program to compute observed brightness temperatures. Values of 250 to 290 K commonly used for antenna temperature in satellite communication noise calculations are found to be over-conservative estimates, with more realistic values lying in the 60-240 K range depending on frequency and subsatellite longitude. These values also depend on assumptions concerning antenna beam coverage. Variations in atmospheric and surface conditions, and variations in antenna beam shape (as distinct from coverage), affect the computed results by less than about 10 K.

  10. Effects of DeOrbitSail as applied to Lifetime predictions of Low Earth Orbit Satellites

    Afful, Andoh; Opperman, Ben; Steyn, Herman

    2016-07-01

    Orbit lifetime prediction is an important component of satellite mission design and post-launch space operations. Throughout its lifetime in space, a spacecraft is exposed to risk of collision with orbital debris or operational satellites. This risk is especially high within the Low Earth Orbit (LEO) region where the highest density of space debris is accumulated. This paper investigates orbital decay of some LEO micro-satellites and accelerating orbit decay by using a deorbitsail. The Semi-Analytical Liu Theory (SALT) and the Satellite Toolkit was employed to determine the mean elements and expressions for the time rates of change. Test cases of observed decayed satellites (Iridium-85 and Starshine-1) are used to evaluate the predicted theory. Results for the test cases indicated that the theory fitted observational data well within acceptable limits. Orbit decay progress of the SUNSAT micro-satellite was analysed using relevant orbital parameters derived from historic Two Line Element (TLE) sets and comparing with decay and lifetime prediction models. This paper also explored the deorbit date and time for a 1U CubeSat (ZACUBE-01). The use of solar sails as devices to speed up the deorbiting of LEO satellites is considered. In a drag sail mode, the deorbitsail technique significantly increases the effective cross-sectional area of a satellite, subsequently increasing atmospheric drag and accelerating orbit decay. The concept proposed in this study introduced a very useful technique of orbit decay as well as deorbiting of spacecraft.

  11. Two Earth-sized planets orbiting Kepler-20

    Fressin, Francois; Rowe, Jason F; Charbonneau, David; Rogers, Leslie A; Ballard, Sarah; Batalha, Natalie M; Borucki, William J; Bryson, Stephen T; Buchhave, Lars A; Ciardi, David R; Desert, Jean-Michel; Dressing, Courtney D; Fabrycky, Daniel C; Ford, Eric B; Gautier, Thomas N; Henze, Christopher E; Holman, Matthew J; Howard, Andrew W; Howell, Steve B; Jenkins, Jon M; Koch, David G; Latham, David W; Lissauer, Jack J; Marcy, Geoffrey W; Quinn, Samuel N; Ragozzine, Darin; Sasselov, Dimitar D; Seager, Sara; Barclay, Thomas; Mullally, Fergal; Seader, Shawn E; Still, Martin; Twicken, Joseph D; Thompson, Susan E; Uddin, Kamal

    2011-01-01

    Since the discovery of the first extrasolar giant planets around Sun-like stars, evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered has a radius 1.42 times that of the Earth's radius (R Earth), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R Earth) and the other smaller than the Earth (0.87R Earth), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative...

  12. Ranking upper stages in low Earth orbit for active removal

    Anselmo, L.; Pardini, C.

    2016-05-01

    This paper addresses the problem of ranking the upper stages in orbit in order to evaluate their potential detrimental effects on the debris environment over the long-term, and the relative advantage of having them actively de-orbited. To do so, a new ranking scheme is introduced, applicable to any object in low Earth orbit (LEO) and able to prioritize the target objects potentially most critical for the future preservation of the LEO protected region. Applying the proposed approach, it was found, for instance, that the 22 most massive upper stages abandoned in LEO, at the beginning of 2015, are on the whole equivalent to several hundred average intact objects in sun-synchronous orbit, regarding their latent detrimental effects on the debris environment over the next 200 years. Most of them could therefore be the top priority targets of any worldwide coordinated effort for active removal and the prevention of new collisional debris. The ranking scheme was also applied to other main models of rocket bodies currently in orbit, trying to identify the combinations of orbital elements and upper stage types requiring particular attention.

  13. The role of Jupiter in driving Earth's orbital evolution

    Horner, Jonathan; Koch, F Elliot

    2014-01-01

    In coming years, the first truly Earth-like planets will be discovered orbiting other stars, and the search for signs of life on these worlds will begin. However, such observations will be hugely time-consuming and costly, and so it will be important to determine which of those planets represent the best prospects for life elsewhere. One of the key factors in such a decision will be the climate variability of the planet in question - too chaotic a climate might render a planet less promising as a target for our initial search for life elsewhere. On the Earth, the climate of the last few million years has been dominated by a series of glacial and interglacial periods, driven by periodic variations in the Earth's orbital elements and axial tilt. These Milankovitch cycles are driven by the gravitational influence of the other planets, and as such are strongly dependent on the architecture of the Solar system. Here, we present the first results of a study investigating the influence of the orbit of Jupiter on the...

  14. Optimal aeroassisted return from high earth orbit with plane change

    Vinh, Nguyen X.; Hanson, John M.

    This paper gives a complete analysis of the problem of aeroassisted return from a high Earth orbit to a low Earth orbit with plane change. A discussion of pure propulsive maneuver leads to the necessary change for improvement of the fuel consumption by inserting in the middle of the trajectory an atmospheric phase to obtain all or part of the required plane change. The variational problem is reduced to a parametric optimization problem by using the known results in optimal impulsive transfer and solving the atmospheric turning problem for storage and use in the optimization process. The coupling effect between space maneuver and atmospheric maneuver is discussed. Depending on the values of the plane change i, the ratios of the radii, n = r 1/r 2 between the orbits and a = r 2/R between the low orbit and the atmosphere, and the maximum lift-to-drag ratio E∗ of the vehicle, the optimal maneuver can be pure propulsive or aeroassisted. For aeroassisted maneuver, the optimal mode can be parabolic, which requires only drag capability of the vehicle, or elliptic. In the elliptic mode, it can be by one-impulse for deorbit and one or two-impulse in postatmospheric flight, or by two-impulse for deorbit with only one impulse for final circularization. It is shown that whenever an impulse is applied, a plane change is made. The necessary conditions for the optimal split of the plane changes are derived and mechanized in a program routine for obtaining the solution.

  15. Interaction between subdaily Earth rotation parameters and GPS orbits

    Panafidina, Natalia; Seitz, Manuela; Hugentobler, Urs

    2013-04-01

    In processing GPS observations the geodetic parameters like station coordinates and ERPs (Earth rotation parameters) are estimated w.r.t. the celestial reference system realized by the satellite orbits. The interactions/correlations between estimated GPS orbis and other parameters may lead to numerical problems with the solution and introduce systematic errors in the computed values: the well known correlations comprise 1) the correlation between the orbital parameters determining the orientation of the orbital plane in inertial space and the nutation and 2) in the case of estimating ERPs with subdaily resolution the correlation between retrograde diurnal polar motion and nutation (and so the respective orbital elements). In this contribution we study the interaction between the GPS orbits and subdaily model for the ERPs. Existing subdaily ERP model recommended by the IERS comprises ~100 terms in polar motion and ~70 terms in Universal Time at diurnal and semidiurnal tidal periods. We use a long time series of daily normal equation systems (NEQ) obtaine from GPS observations from 1994 till 2007 where the ERPs with 1-hour resolution are transformed into tidal terms and the influence of the tidal terms with different frequencies on the estimated orbital parameters is considered. We found that although there is no algebraic correlation in the NEQ between the individual orbital parameters and the tidal terms, the changes in the amplitudes of tidal terms with periods close to 24 hours can be better accmodated by systematic changes in the orbital parameters than for tidal terms with other periods. Since the variation in Earth rotation with the period of siderial day (23.93h, tide K1) in terrestrial frame has in inertial space the same period as the period of revolution of GPS satellites, the K1 tidal term in polar motion is seen by the satellites as a permanent shift. The tidal terms with close periods (from ~24.13h to ~23.80h) are seen as a slow rotation of the

  16. Plasma Flowfields Around Low Earth Orbit Objects: Aerodynamics to Underpin Orbit Predictions

    Capon, Christopher; Boyce, Russell; Brown, Melrose

    2016-07-01

    Interactions between orbiting bodies and the charged space environment are complex. The large variation in passive body parameters e.g. size, geometry and materials, makes the plasma-body interaction in Low Earth Orbit (LEO) a region rich in fundamental physical phenomena. The aerodynamic interaction of LEO orbiting bodies with the neutral environment constitutes the largest non-conservative force on the body. However in general, study of the LEO plasma-body interaction has not been concerned with external flow physics, but rather with the effects on surface charging. The impact of ionospheric flow physics on the forces on space debris (and active objects) is not well understood. The work presented here investigates the contribution that plasma-body interactions have on the flow structure and hence on the total atmospheric force vector experienced by a polar orbiting LEO body. This work applies a hybrid Particle-in-Cell (PIC) - Direct Simulation Monte Carlo (DSMC) code, pdFoam, to self-consistently model the electrostatic flowfield about a cylinder with a uniform, fixed surface potential. Flow conditions are representative of the mean conditions experienced by the Earth Observing Satellite (EOS) based on the International Reference Ionosphere model (IRI-86). The electron distribution function is represented by a non-linear Boltzmann electron fluid and ion gas-surface interactions are assumed to be that of a neutralising, conducting, thermally accommodating solid wall with diffuse reflections. The variation in flowfield and aerodynamic properties with surface potential at a fixed flow condition is investigated, and insight into the relative contributions of charged and neutral species to the flow physics experienced by a LEO orbiting body is provided. This in turn is intended to help improve the fidelity of physics-based orbit predictions for space debris and other near-Earth space objects.

  17. The Occurrence Rate of Earth Analog Planets Orbiting Sunlike Stars

    Catanzarite, Joseph

    2011-01-01

    Kepler is a space telescope that searches Sun-like stars for planets. Its major goal is to determine {\\eta}_Earth, the fraction of Sunlike stars that have planets like Earth. When a planet 'transits' or moves in front of a star, Kepler can measure the concomitant dimming of the starlight. From analysis of the first four months of those measurements for over 150,000 stars, Kepler's science team has determined sizes, surface temperatures, orbit sizes and periods for over a thousand new planet candidates. Here, we show that 1.4% to 2.7% of stars like the Sun are expected to have Earth analog planets, based on the Kepler data release of Feb 2011. The estimate will improve when it is based on the full 3.5 to 6 year Kepler data set. Accurate knowledge of {\\eta}_Earth is necessary to plan future missions that will image and take spectra of Earthlike planets. Our result that Earths are relatively scarce means that a substantial effort will be needed to identify suitable target stars prior to these future missions.

  18. European activities in exobiology in earth orbit: results and perspectives

    Horneck, G.

    1999-01-01

    A large portion of European activities in Earth orbit have concentrated on studies of the responses of resistant microbes to the harsh environment of space with the aim of providing experimental evidence testing the hypothesis that interplanetary transfer of life is possible. Various types of microorganisms, such as bacterial or fungal spores, as well as viruses and biomolecules, such as DNA, amino acids and liposomes, have been exposed to selected and combined space conditions outside the Earth's magnetic field (Apollo 16) or in low Earth orbit (Spacelab 1, Spacelab D2, ERA on EURECA, LDEF, BIOPAN on FOTON). Space parameters, such as high vacuum, intense solar ultraviolet radiation, different components of the cosmic radiation field and temperature extremes affected the genetic stability of the organisms in space, leading to increased mutation rates, DNA damage and inactivation. Extraterrestrial solar UV radiation was the most lethal factor. If shielded against the influx of solar UV, spores of Bacillus subtilis survived for more than 5 years in space. Future research will be directed towards long-term studies of microbes in artificial meteorites, as well as of microbial communities from special ecological niches, such as endolithic and endoevaporitic ecosystems. For these studies, the European Space Agency will provide the facility EXPOSE to be accommodated on the External Platform of the International Space Station during the Early Utilization Phase.

  19. Are artificial satellites orbits influenced by an expanding Earth?

    G. Scalera

    2006-06-01

    Full Text Available Albeit in the past great theoretical and experimental efforts were made in proposing and searching for G time-decreasing, a major role could be played by an increase of M. A recent analysis (Scalera, 2003a converges toward an upper limit of the Earth’s mass variation in the order of magnitude of M/M=10-9 /yr. It is here discussed the possible role that can be played by parameters linked to the expanding Earth in the effects we observe in the orbital motion of the artificial satellites. The important result in this short note is the discrimination between the reality of the glacial rebound process and/or the relaxation of the 100m excess of equatorial bulge testified by the high rate of j2 , and the improbable role that glacial rebound can have in driving PM and TPW. It is recommended that the new technology of drag-free satellites be used (Gravity-Probe B is the first step to reveal possible residual orbital parameter variations ascribable to formerly unrecognized fictitious drag terms due to Earth radial increase.

  20. Near Earth Asteroids- Prospection, Orbit Modification and Mining

    Grandl, W.; Bazso, A.

    2014-04-01

    The number of known Near Earth Asteroids (NEAs) has increased continuously during the last decades. Now we understand the role of asteroid impacts for the evolution of life on Earth. To ensure that mankind will survive in the long run, we have to face the "asteroid threat" seriously. On one hand we will have to develop methods of detection and deflection for Hazardous Asteroids, on the other hand we can use these methods to modify their orbits and exploit their resources. Rare-earth elements, rare metals like platinum group elements, etc. may be extracted more easily from NEAs than from terrestrial soil, without environmental pollution or political and social problems. In a first step NEAs, which are expected to contain resources like nickel-iron, platinum group metals or rare-earth elements, will be prospected by robotic probes. Then a number of asteroids with a minimum bulk density of 2 g/cm^3 and a diameter of 150 to 500 m will be selected for mining. Given the long duration of an individual mission time of 10-20 years, the authors propose a "pipeline" concept. While the observation of NEAs can be done in parallel, the precursor missions of the the next phase can be launched in short intervals, giving time for technical corrections and upgrades. In this way a continuous data flow is established and there are no idle times. For our purpose Potentially Hazardous Asteroids (PHAs) seem to be a favorable choice for the following reasons: They have frequent closeencounters to Earth, their minimum orbit intersection distance is less than 0.05 AU (Astronomic Units) and they have diameters exceeding 150 meters. The necessary velocity change (delta V) for a spaceship is below 12 km/s to reach the PHA. The authors propose to modify the orbits of the chosen PHAs by orbital maneuvers from solar orbits to stable Earth orbits beyond the Moon. To change the orbits of these celestial bodies it is necessary to develop advanced propulsion systems. They must be able to deliver high

  1. Dynamic and reduced-dynamic precise orbit determination of satellites in low earth orbits

    The precise positioning of satellites in Low Earth Orbits (LEO) has become a key technology for advanced space missions. Dedicated satellite missions, such as CHAMP, GRACE and GOCE, that aim to map the Earths gravity field and its variation over time with unprecedented accuracy, initiated the demand for highly precise orbit solutions of LEO satellites. Furthermore, a wide range of additional science opportunities opens up with the capability to generate accurate LEO orbits. For all considered satellite missions, the primary measurement system for navigation is a spaceborne GPS receiver. The goal of this thesis is to establish and implement methods for Precise Orbit Determination (POD) of LEO satellites using GPS. Striving for highest precision using yet efficient orbit generation strategies, the attained orbit solutions are aimed to be competitive with the most advanced solutions of other institutions. Dynamic and reduced-dynamic orbit models provide the basic concepts of this work. These orbit models are subsequently adjusted to the highly accurate GPS measurements. The GPS measurements are introduced at the zero difference level in the ionosphere free linear combination. Appropriate procedures for GPS data screening and editing are established to detect erroneous data and to employ measurements of good quality only. For the dynamic orbit model a sophisticated force model, especially designed for LEO satellites, has been developed. In order to overcome the limitations that are induced by the deficiencies of the purely dynamical model, two different types of empirical parameters are introduced into the force model. These reduced-dynamic orbit models allow for the generation of much longer orbital arcs while preserving the spacecraft dynamics to the most possible extent. The two methods for reduced-dynamic orbit modeling are instantaneous velocity changes (pulses) or piecewise constant accelerations. For both techniques highly efficient modeling algorithms are

  2. Space tourism: from earth orbit to the moon

    Collins, P.

    Travel to and from the lunar surface has been known to be feasible since it was first achieved 34 years ago. Since that time there has been enormous progress in related engineering fields such as rocket propulsion, materials and avionics, and about 1 billion has been spent on lunar science and engineering research. Consequently there are no fundamental technical problems facing the development of lunar tourism - only business and investment problems. The outstanding problem is to reduce the cost of launch to low Earth orbit. Recently there has been major progress towards overturning the myth that launch costs are high because of physical limits. Several "X Prize" competitor vehicles currently in test-flight are expected to be able to perform sub-orbital flights at approximately 1/1,000 of the cost of Alan Shepard's similar flight in 1961. This activity could have started 30 years ago if space agencies had had economic rather than political objectives. A further encouraging factor is that the demand for space tourism seems potentially limitless. Starting with sub-orbital flights and growing through orbital activities, travel to the Moon will offer further unique attractions. In every human culture there is immense interest in the Moon arising from millennia of myths. In addition, bird-like flying sports, first described by Robert Heinlein, will become another powerful demand factor. Roundtrips of 1 to 2 weeks are very convenient for travel companies; and the radiation environment will permit visitors several days of surface activity without significant health risks. The paper also discusses economic aspects of lunar tourism, including the benefits it will have for those on Earth. Lunar economic development based on tourism will have much in common with economic development on Earth based on tourism: starting from the fact that many people spontaneously wish to visit popular places, companies in the tourism industry invest to sell a growing range of services to ever

  3. Low Earth Orbital Atomic Oxygen Interactions With Materials

    Banks, Bruce A.; Miller, Sharon K.; deGroh, Kim K.

    2004-01-01

    Atomic oxygen is formed in the low Earth orbital environment (LEO) by photo dissociation of diatomic oxygen by short wavelength (improved durability to atomic oxygen attack, as well as atomic oxygen protective coatings, have been employed with varying degrees of success to improve durability of polymers in the LEO environment. Atomic oxygen can also oxidize silicones and silicone contamination to produce non-volatile silica deposits. Such contaminants are present on most LEO missions and can be a threat to performance of optical surfaces. The LEO atomic oxygen environment, its interactions with materials, results of space testing, computational modeling, mitigation techniques, and ground laboratory simulation procedures and issues are presented.

  4. Geostationary orbit Earth science platform concepts for global change monitoring

    Farmer, Jeffery T.; Campbell, Thomas G.; Davis, William T.; Garn, Paul A.; King, Charles B.; Jackson, Cheryl C.

    1991-01-01

    Functionality of a geostationary spacecraft to support Earth science regional process research is identified. Most regional process studies require high spatial and temporal resolution. These high temporal resolutions are on the order of 30 minutes and may be achievable with instruments positioned in a geostationary orbit. A complement of typical existing or near term instruments are identified to take advantage of this altitude. This set of instruments is listed, and the requirements these instruments impose on a spacecraft are discussed. A brief description of the geostationary spacecraft concepts which support these instruments is presented.

  5. European Student Earth Orbiter: ESA’s educational Microsatellite Program

    Bruzzi, Davide; Tortora, Paolo; Giulietti, Fabrizio; Galeone, Piero

    2013-01-01

    In February 2012, ESA released the invitation for a competitive tender for the European Student Earth Orbiter (ESEO) Phases C0/C1/D/E1. Following tender evaluation, ALMASpace S.r.l., a spin-off company from the Microsatellites and Space Microsystems lab of the University of Bologna, was selected as system prime. The primary objective of the ESEO project is to provide students with valuable and challenging hands-on experience across all disciplines and throughout the project lifecycle in order...

  6. Are artificial satellites orbits influenced by an expanding Earth?

    G. Scalera

    2006-01-01

    Albeit in the past great theoretical and experimental efforts were made in proposing and searching for G time-decreasing, a major role could be played by an increase of M. A recent analysis (Scalera, 2003a) converges toward an upper limit of the Earth’s mass variation in the order of magnitude of M/M=10-9 /yr. It is here discussed the possible role that can be played by parameters linked to the expanding Earth in the effects we observe in the orbital motion of the artificial satellites. The i...

  7. Gas-Surface Interactions in Low-Earth Orbit

    Moe, Kenneth; Moe, Mildred M.

    2011-05-01

    When the space age began, some aerodynamicists expected that the surfaces of spacecraft would be cleaned by desorption in the high vacuum of space; while others, familiar with experiments on engineering surfaces, believed that satellite surfaces would be contaminated. During subsequent decades, satellite evidence has accumulated, showing that surfaces in low-Earth orbit are contaminated by adsorbed atomic oxygen and its reaction products. These contaminants cause accommodation coefficients to be high, and the angular distribution of reemitted molecules to be nearly diffuse. These surface conditions must be considered in calculating satellite drag coefficients in free-molecular flow. We describe the experimental and theoretical developments which have led to these conclusions.

  8. Magnetically levitated space elevator to low-earth orbit

    The properties of currently available NbTi superconductor and carbon-fiber structural materials enable the possibility of constructing a magnetically levitated space elevator from the earth's surface up to an altitude of(approx) 200 km. The magnetic part of the elevator consists of a long loop of current-carrying NbTi, composed of one length that is attached to the earth's surface in an east-west direction and a levitated-arch portion. The critical current density of NbTi is sufficiently high that these conductors will stably levitate in the earth's magnetic field. The magnetic self-field from the loop increases the levitational force and for some geometries assists levitational stability. The 200-km maximum height of the levitated arch is limited by the allowable stresses of the structural material. The loop is cryogenically cooled with helium, and the system utilizes intermediate pumping and cooling stations along both the ground and the levitated portion of the loop, similar to other large terrestrial cryogenic systems. Mechanically suspended from the basic loop is an elevator structure, upon which mass can be moved between the earth's surface and the top of the loop by a linear electric motor or other mechanical or electrical means. At the top of the loop, vehicles may be accelerated to orbital velocity or higher by rocket motors, electromagnetic propulsion, or hybrid methods

  9. Earth-crossing asteroids - Orbital classes, collision rates with earth, and origin

    Shoemaker, E. M.; Williams, J. G.; Helin, E. F.; Wolfe, R. F.

    1979-01-01

    Asteroids that can intersect the orbit of the earth are discussed, which include Aten asteroids (semimajor axis (a) less than 1 AU, aphelion greater than 0.983 AU), Apollo asteroids (a greater than 1 AU, perihelion less than 1.017 AU), and Amor asteroids (perihelion distance between 1.017 and 1.3 AU). The principal sources of earth-crossing asteroids appear to be extinct comet nuclei and collision fragments from regions in the main asteroid belt. The total population of earth-crossers is estimated at 13,000, of which approximately 8% are Atens, 50% are Apollos, and 40% are Amors,and the present collision rate of such asteroids with the earth is estimated at about 3.5 objects, to absolute magnitude 18, per million years.

  10. Capturing near-Earth asteroids into bounded Earth orbits using gravity assist

    Bao, Changchun; Yang, Hongwei; Barsbold, Baza; Baoyin, Hexi

    2015-12-01

    In this paper, capturing Near-Earth asteroids (NEAs) into bounded orbits around the Earth is investigated. Several different potential schemes related with gravity assists are proposed. A global optimization method, the particle Swarm Optimization (PSO), is employed to obtain the minimal velocity increments for each scheme. With the optimized results, the minimum required velocity increments as well as the mission time are obtained. Results of numerical simulations also indicate that using MGAs is an efficient approach in the capturing mission. The conclusion complies with the analytical result in this paper that a NEA whose velocity relative to the Earth less than 1.8 km/s can be captured by Earth by just one MGA. For other situations, the combination of MGAs and EGAs is better in sense of the required velocity-increments.

  11. Radiation measured with passive dosimeters in low Earth orbit

    Zhou, D.; Semones, E.; Gaza, R.; Weyland, M.

    begin center Radiation Measured with Passive Dosimeters in Low Earth Orbit end center begin center D Zhou 1 2 E Semones 1 R Gaza 1 2 M Weyland 1 end center begin center 1 Johnson Space Center - NASA 2101 Nasa Road 1 Houston 77058 USA end center begin center 2 Universities Space Research Association 2101 Nasa Parkway Houston 77058 USA end center begin center Abstract end center The linear energy transfer LET of particles in low Earth orbit LEO is extended from sim 0 1 to sim 1000 keV mu m water The best passive dosimeters for the radiation measurement are thermoluminescence dosimeters TLDs or optically stimulated luminescence dosimeters OSLDs for low LET and CR-39 plastic nuclear track detectors PNTDs for high LET Radiation quantities fluence absorbed dose dose equivalent and quality factor were measured with the passive dosimeters composed of TLDs OSLDs and CR-39 PNTDs for STS-114 mission This paper introduces the operation principles for TLDs OSLDs and CR-39 PNTDs describes the method to combine the results measured by TLDs OSLDs and CR-39 PNTDs and presents the results measured by different dosimeters for different LET band and that combined for all LET

  12. On the prospects of Near Earth Asteroid orbit triangulation using the Gaia satellite and Earth-based observations

    Eggl, Siegfried

    2014-01-01

    Accurate measurements of osculating orbital elements are essential in order to understand and model the complex dynamic behavior of Near Earth Asteroids (NEAs). ESA's Gaia mission promises to have great potential in this respect. In this article we investigate the prospects of constraining orbits of newly discovered and known NEAs using nearly simultaneous observations from the Earth and Gaia. We find that observations performed simultaneously from two sites can effectively constrain preliminary orbits derived via statistical ranging. By linking discoveries stored in the Minor Planet Center databases to Gaia astrometric alerts one can identify nearly simultaneous observations of Near Earth Objects and benefit from improved initial orbit solutions at no additional observational cost.

  13. Magnetic Attitude Control System for Low-Earth Orbit Satellites

    A small spacecraft (SC) under consideration is intended for performing a scientific mission on the low-Earth orbit for a long time (a year or more). A control system of the SC provides the construction of regime of three-axis orientation of the SC in the orbital coordinate system and the stabilization of that regime, and must be autonomous, low-weight and low-cost. The magnetic control system that consists of the information subsystem based solely on three-axis magnetometer measuring and the magnetic actuators satisfies in the best way requirements mentioned above. Such system can estimate both orbital motion parameters and attitude ones of the SC. But the absence of the additional instruments and damping devices complicates the estimation since the range of initial conditions uncertainly is wide and the problem of estimating becomes essentially nonlinear. To get over these difficulties a recursive state estimation algorithm with enhanced convergence is proposed. The magnetic control moment is synthesized byte vector function Lyapunov method

  14. Small asteroid fragments in earth-crossing orbits

    Duha, J.; Afonso, G. B.

    2014-10-01

    The meteorite that fell in Chelyabinsk, Russia, naturally made many people think it could be a smaller companion of the Asteroid 2012 DA14, which passed close to Earth on that same day. Some asteroid specialists discarded this hypothesis for two main reasons: The meteorite was too far away from the asteroid, because the collision happened sixteen hours before the asteroid passed close to Earth. Moreover, it was not traveling, similarly to asteroid DA14, from south to north. However the possibility of the meteorite being a companion of the Asteroid 2012 DA14 cannot be completely discarded. The Asteroid 2012 DA14, with a diameter of 45 meters, is very small. It can be considered an asteroids fragment, which is usually accompanied by other smaller fragments, scattered in space, practically in the same orbit and possibly being separated from each other by long distances. Assuming that 2012 DA14 is not an isolated asteroid, but the biggest remaining fragment from a previous impact, we developed a model to study the dynamics of an asteroid fragment, similar to DA14, and its companions, the smaller fragments. This dynamically interesting encounter with planet Earth is addressed and the orbital changes that could explain the Chelyabinsk event are discussed. As a result we find that, there could be a collision of a meteorite before, during, or after the Asteroid 2012 DA14 passing by, the same way that happens with meteorite showers, which can last several days. Therefore, it would be very interesting to look for asteroid fragments also, close to the larger fragments, more easily found.

  15. Space radiation dosimetry in low-Earth orbit and beyond

    Space radiation dosimetry presents one of the greatest challenges in the discipline of radiation protection. This is a result of both the highly complex nature of the radiation fields encountered in low-Earth orbit (LEO) and interplanetary space and of the constraints imposed by spaceflight on instrument design. This paper reviews the sources and composition of the space radiation environment in LEO as well as beyond the Earth's magnetosphere. A review of much of the dosimetric data that have been gathered over the last four decades of human space flight is presented. The different factors affecting the radiation exposures of astronauts and cosmonauts aboard the International Space Station (ISS) are emphasized. Measurements made aboard the Mir Orbital Station have highlighted the importance of both secondary particle production within the structure of spacecraft and the effect of shielding on both crew dose and dose equivalent. Roughly half the dose on ISS is expected to come from trapped protons and half from galactic cosmic rays (GCRs). The dearth of neutron measurements aboard LEO spacecraft and the difficulty inherent in making such measurements have led to large uncertainties in estimates of the neutron contribution to total dose equivalent. Except for a limited number of measurements made aboard the Apollo lunar missions, no crew dosimetry has been conducted beyond the Earth's magnetosphere. At the present time we are forced to rely on model-based estimates of crew dose and dose equivalent when planning for interplanetary missions, such as a mission to Mars. While space crews in LEO are unlikely to exceed the exposure limits recommended by such groups as the NCRP, dose equivalents of the same order as the recommended limits are likely over the course of a human mission to Mars

  16. Hardware in-the-Loop Demonstration of Real-Time Orbit Determination in High Earth Orbits

    Moreau, Michael; Naasz, Bo; Leitner, Jesse; Carpenter, J. Russell; Gaylor, Dave

    2005-01-01

    This paper presents results from a study conducted at Goddard Space Flight Center (GSFC) to assess the real-time orbit determination accuracy of GPS-based navigation in a number of different high Earth orbital regimes. Measurements collected from a GPS receiver (connected to a GPS radio frequency (RF) signal simulator) were processed in a navigation filter in real-time, and resulting errors in the estimated states were assessed. For the most challenging orbit simulated, a 12 hour Molniya orbit with an apogee of approximately 39,000 km, mean total position and velocity errors were approximately 7 meters and 3 mm/s respectively. The study also makes direct comparisons between the results from the above hardware in-the-loop tests and results obtained by processing GPS measurements generated from software simulations. Care was taken to use the same models and assumptions in the generation of both the real-time and software simulated measurements, in order that the real-time data could be used to help validate the assumptions and models used in the software simulations. The study makes use of the unique capabilities of the Formation Flying Test Bed at GSFC, which provides a capability to interface with different GPS receivers and to produce real-time, filtered orbit solutions even when less than four satellites are visible. The result is a powerful tool for assessing onboard navigation performance in a wide range of orbital regimes, and a test-bed for developing software and procedures for use in real spacecraft applications.

  17. Space environment effects on polymers in low earth orbit

    Polymers are widely used in space vehicles and systems as structural materials, thermal blankets, thermal control coatings, conformal coatings, adhesives, lubricants, etc. The low earth orbit (LEO) space environment includes hazards such as atomic oxygen, UV radiation, ionizing radiation (electrons, protons), high vacuum, plasma, micrometeoroids and debris, as well as severe temperature cycles. Exposure of polymers and composites to the space environment may result in different detrimental effects via modification of their chemical, electrical, thermal, optical and mechanical properties as well as surface erosion. The high vacuum induces material outgassing (e.g. low-molecular weight residues, plasticizers and additives) and consequent contamination of nearby surfaces. The present work reviews the LEO space environment constituents and their interactions with polymers. Examples of degradation of materials exposed in ground simulation facilities are presented. The issues discussed include the erosion mechanisms of polymers, formation of contaminants and their interaction with the space environment, and protection of materials from the harsh space environment

  18. Tracking target objects orbiting earth using satellite-based telescopes

    De Vries, Willem H; Olivier, Scot S; Pertica, Alexander J

    2014-10-14

    A system for tracking objects that are in earth orbit via a constellation or network of satellites having imaging devices is provided. An object tracking system includes a ground controller and, for each satellite in the constellation, an onboard controller. The ground controller receives ephemeris information for a target object and directs that ephemeris information be transmitted to the satellites. Each onboard controller receives ephemeris information for a target object, collects images of the target object based on the expected location of the target object at an expected time, identifies actual locations of the target object from the collected images, and identifies a next expected location at a next expected time based on the identified actual locations of the target object. The onboard controller processes the collected image to identify the actual location of the target object and transmits the actual location information to the ground controller.

  19. Plasma flow measurements in a simulated low earth orbit plasma

    The employment of large, higher power solar arrays for space operation has been considered, taking into account a utilization of high operating voltages. In connection with the consideration of such arrays, attention must be given to the fact that the ambient environment of space contains a tenuous low energy plasma which can interact with the high voltage array causing power 'leakage' and arcing. An investigation has been conducted with the aim to simulate the behavior of such an array in low-earth-orbit (LEO). During the experiments, local concentrations of the 'leakage' current were observed when the panel was at a high voltage. These concentrations could overload or damage a small area of cells in a large string. It was hypothesized that this effect was produced by electrostatic focusing of the particles by the sheath fields. To verify this experimentally, an end-effect Langmuir probe was employed. The obtained results are discussed

  20. Degradation of Spacesuit Fabrics in Low Earth Orbit

    Gaier, James R.; Baldwin, Sammantha M.; Folz, Angela D.; Waters, Deborah L.; McCue, Terry R.; Jaworske, Donald A.; Clark, Gregory W.; Rogers, Kerry J.; Batman, Brittany; Bruce, John; Mengesu, Tsega

    2012-01-01

    Six samples of pristine and dust-abraded outer layer spacesuit fabrics were included in the Materials International Space Station Experiment-7, in which they were exposed to the wake-side low Earth orbit environment on the International Space Station (ISS) for 18 months in order to determine whether abrasion by lunar dust increases radiation degradation. The fabric samples were characterized using optical microscopy, optical spectroscopy, field emission scanning electron microscopy, atomic force microscopy, and tensile testing before and after exposure on the ISS. Comparison of pre- and post-flight characterizations showed that the environment darkened and reddened all six fabrics, increasing their integrated solar absorptance by 7 to 38 percent. There was a decrease in the ultimate tensile strength and elongation to failure of lunar dust abraded Apollo spacesuit fibers by a factor of four and an increase in the elastic modulus by a factor of two.

  1. Shielding distribution for anisotropic radiation in low earth orbit

    The highly directional nature of radiation encountered in low earth orbit (LEO) can be a basis for distributing mass for spacecraft radiation shielding. Trapped (Van Allen) radiation at low altitudes is concentrated within a plane perpendicular to the local geometric field lines. Trapped high-energy protons (which penetrate the relatively thin shielding required for electrons) have a pronounced east-west asymmetry at low altitudes, with the flux from the west much higher than that from the east. By distributing radition shielding mass in response to these anisotropies, spacecraft mass can be reduced, the altitude limits of LEO extended, and the exposure of men and sensitive materials decreased. Geophysical behavior of trapped radiation is reviewed with particular emphasis on the factors responsible for radiation anisotropy. Shielding distribution in response to anisotropic radiation is then explored for consistently oriented spherical and cylindrical spacecraft. The 28.5-deg orbital inclination is considered in detail, with a brief extension of the concepts to other inclinations. These radiation shielding concepts may find near-term application in Space Station design. 21 references

  2. An Investigation of Low Earth Orbit Internal Charging

    NeergaardParker, Linda; Minow, Joseph I.; Willis, Emily M.

    2014-01-01

    Low Earth orbit is usually considered a relatively benign environment for internal charging threats due to the low flux of penetrating electrons with energies of a few MeV that are encountered over an orbit. There are configurations, however, where insulators and ungrounded conductors used on the outside of a spacecraft hull may charge when exposed to much lower energy electrons of some 100's keV in a process that is better characterized as internal charging than surface charging. For example, the minimal radiation shielding afforded by thin thermal control materials such as metalized polymer sheets (e.g., aluminized Kapton or Mylar) and multilayer insulation may allow electrons of 100's of keV to charge underlying materials. Yet these same thermal control materials protect the underlying insulators and ungrounded conductors from surface charging currents due to electrons and ions at energies less than a few keV as well as suppress the photoemission, secondary electron, and backscattered electron processes associated with surface charging. We investigate the conditions required for this low Earth orbit "internal charging" to occur and evaluate the environments for which the process may be a threat to spacecraft. First, we describe a simple one-dimensional internal charging model that is used to compute the charge accumulation on materials under thin shielding. Only the electron flux that penetrates exposed surface shielding material is considered and we treat the charge balance in underlying insulation as a parallel plate capacitor accumulating charge from the penetrating electron flux and losing charge due to conduction to a ground plane. Charge dissipation due to conduction can be neglected to consider the effects of charging an ungrounded conductor. In both cases, the potential and electric field is computed as a function of time. An additional charge loss process is introduced due to an electrostatic discharge current when the electric field reaches a

  3. PLANECHG: Earth orbit to lunar orbit delta V estimation program. User and technical documentation

    1988-01-01

    The PLANECNG computer program calculates velocities for Earth-to-Mooon and Moon-to-Earth trajectories. The flight to be analyzed originates in a circular orbit of any inclination and altitude about one of the bodies, and culminates in a circular orbit of any inclination and altitude about the other body. An intermedate delta V and plane change occurs at the Lunar Sphere of Influence (SOI), the region where the vehicle is near its lowest velocity in the trajectory, and therefore where it is able to make the plane change with the lowest delta V. A given flight may penetrate the SOI at a number of points. Each point has associated with it a unique set of delta V's and total velocity. The program displays the velocities, in matrix form, for a representative set of SOI penetration points. An SOI point is identified by projecting Lunar latitude and longitude onto the SOI. The points recorded for a given flight are defined by the user, who provides a starting longitude and latitude, and an increment for each. A matrix is built with 10 longitudes forming the columns and 19 latitudes forming the rows. This matrix is presented in six reports, each containing different velocity or node information in the body of the matrix.

  4. The NASA-UC Eta-Earth Program: III. A Super-Earth orbiting HD 97658 and a Neptune-mass planet orbiting Gl 785

    Howard, Andrew W; Marcy, Geoffrey W; Fischer, Debra A; Wright, Jason T; Henry, Gregory W; Isaacson, Howard; Valenti, Jeff A; Anderson, Jay; Piskunov, Nikolai E

    2010-01-01

    We report the discovery of planets orbiting two bright, nearby early K dwarf stars, HD 97658 and Gl 785. These planets were detected by Keplerian modelling of radial velocities measured with Keck-HIRES for the NASA-UC Eta-Earth Survey. HD 97658 b is a close-in super-Earth with minimum mass Msini = 8.2 +/- 1.2 M_Earth, orbital period P = 9.494 +/- 0.005 d, and an orbit that is consistent with circular. Gl 785 b is a Neptune-mass planet with Msini = 21.6 +/- 2.0 M_Earth, P = 74.39 +/- 0.12 d, and orbital eccentricity 0.30 +/- 0.09. Photometric observations with the T12 0.8 m automatic photometric telescope at Fairborn Observatory show that HD 97658 is photometrically constant at the radial velocity period to 0.09 mmag, supporting the existence of the planet.

  5. Preliminary Design Considerations for Access and Operations in Earth-Moon L1/L2 Orbits

    Folta, David C.; Pavlak, Thomas A.; Haapala, Amanda F.; Howell, Kathleen C.

    2013-01-01

    Within the context of manned spaceflight activities, Earth-Moon libration point orbits could support lunar surface operations and serve as staging areas for future missions to near-Earth asteroids and Mars. This investigation examines preliminary design considerations including Earth-Moon L1/L2 libration point orbit selection, transfers, and stationkeeping costs associated with maintaining a spacecraft in the vicinity of L1 or L2 for a specified duration. Existing tools in multi-body trajectory design, dynamical systems theory, and orbit maintenance are leveraged in this analysis to explore end-to-end concepts for manned missions to Earth-Moon libration points.

  6. Near-Earth asteroids orbit propagation with Gaia observations

    Bancelin, D; Thuillot, W

    2016-01-01

    Gaia is an astrometric mission that will be launched in 2013 and set on L2 point of Lagrange. It will observe a large number of Solar System Objets (SSO) down to magnitude 20. The Solar System Science goal is to map thousand of Main Belt asteroids (MBAs), Near Earth Objects (NEOs) (including comets) and also planetary satellites with the principal purpuse of orbital determination (better than 5 mas astrometric precision), determination of asteroid mass, spin properties and taxonomy. Besides, Gaia will be able to discover a few objects, in particular NEOs in the region down to the solar elongation 45{\\deg} which are harder to detect with current ground-based surveys. But Gaia is not a follow-up mission and newly discovered objects can be lost if no ground-based recovery is processed. The purpose of this study is to quantify the impact of Gaia data for the known NEAs population and to show how to handle the problem of these discoveries when faint number of observations and thus very short arc is provided.

  7. Thermodynamic Vent System Test in a Low Earth Orbit Simulation

    VanOverbeke, Thomas J.

    2004-01-01

    A thermodynamic vent system for a cryogenic nitrogen tank was tested in a vacuum chamber simulating oxygen storage in low earth orbit. The nitrogen tank was surrounded by a cryo-shroud at -40 F. The tank was insulated with two layers of multi-layer insulation. Heat transfer into cryogenic tanks causes phase change and increases tank pressure which must be controlled. A thermodynamic vent system was used to control pressure as the location of vapor is unknown in low gravity and direct venting would be wasteful. The thermodynamic vent system consists of a Joule-Thomson valve and heat exchanger installed on the inlet side of the tank mixer-pump. The combination is used to extract thermal energy from the tank fluid, reducing temperature and ullage pressure. The system was sized so that the tank mixer-pump operated a small fraction of the time to limit motor heating. Initially the mixer used sub-cooled liquid to cool the liquid-vapor interface inducing condensation and pressure reduction. Later, the thermodynamic vent system was used. Pressure cycles were performed until steady-state operation was demonstrated. Three test runs were conducted at tank fills of 97, 80, and 63 percent. Each test was begun with a boil-off test to determine heat transfer into the tank. The lower tank fills had time averaged vent rates very close to steady-state boil-off rates showing the thermodynamic vent system was nearly as efficient as direct venting in normal gravity.

  8. Physical Limitations of Nuclear Propulsion for Earth to Orbit

    Blevins, John A.; Patton, Bruce; Rhys, Noah O.; Schafer, Charles F. (Technical Monitor)

    2001-01-01

    An assessment of current nuclear propulsion technology for application in Earth to Orbit (ETO) missions has been performed. It can be shown that current nuclear thermal rocket motors are not sufficient to provide single stage performance as has been stated by previous studies. Further, when taking a systems level approach, it can be shown that NTRs do not compete well with chemical engines where thrust to weight ratios of greater than I are necessary, except possibly for the hybrid chemical/nuclear LANTR (LOX Augmented Nuclear Thermal Rocket) engine. Also, the ETO mission requires high power reactors and consequently large shielding weights compared to NTR space missions where shadow shielding can be used. In the assessment, a quick look at the conceptual ASPEN vehicle proposed in 1962 in provided. Optimistic NTR designs are considered in the assessment as well as discussion on other conceptual nuclear propulsion systems that have been proposed for ETO. Also, a quick look at the turbulent, convective heat transfer relationships that restrict the exchange of nuclear energy to thermal energy in the working fluid and consequently drive the reactor mass is included.

  9. Innovative observing strategy and orbit determination for Low Earth Orbit Space Debris

    Milani, Andrea; Dimare, Linda; Rossi, Alessandro; Bernardi, Fabrizio

    2011-01-01

    We present the results of a large scale simulation, reproducing the behavior of a data center for the build-up and maintenance of a complete catalog of space debris in the upper part of the low Earth orbits region (LEO). The purpose is to determine the performances of a network of advanced optical sensors, through the use of the newest orbit determination algorithms developed by the Department of Mathematics of Pisa (DM). Such a network has been proposed to ESA in the Space Situational Awareness (SSA) framework by Carlo Gavazzi Space SpA (CGS), Istituto Nazionale di Astrofisica (INAF), DM, and Istituto di Scienza e Tecnologie dell'Informazione (ISTI-CNR). The conclusion is that it is possible to use a network of optical sensors to build up a catalog containing more than 98% of the objects with perigee height between 1100 and 2000 km, which would be observable by a reference radar system selected as comparison. It is also possible to maintain such a catalog within the accuracy requirements motivated by collisi...

  10. Innovative observing strategy and orbit determination for Low Earth Orbit space debris

    Milani, A.; Farnocchia, D.; Dimare, L.; Rossi, A.; Bernardi, F.

    2012-03-01

    We present the results of a large scale simulation, reproducing the behavior of a data center for the build-up and maintenance of a complete catalog of space debris in the upper part of the Low Earth Orbits (LEOs) region. The purpose is to determine the performances of a network of advanced optical sensors, through the use of the newest correlation and orbit determination algorithms. This network is foreseen for implementation in a Space Situational Awareness system, such as the future European one. The conclusion is that it is possible to use a network of optical sensors to build up a catalog containing more than 98% of the objects with perigee height between 1100 and 2000 km, which would be observable by a reference radar system selected as comparison. It is also possible to maintain such a catalog within the accuracy requirements motivated by collision avoidance, and to detect catastrophic fragmentation events. The obtained results depend upon specific assumptions on the sensor and on the software technologies.

  11. Optical and photometric studies of Earth orbiting small space objects

    Selim, I. M.; El-Hameed, Afaf M. Abd; Bakhtigaraev, N. S.; Attia, Gamal F.

    2016-03-01

    Variations of light curves for space objects are investigated. Optical observations and photometric measurements for small space debris on highly elliptical orbits (HEO) and geostationary orbits (GEO) are used to determine their orbital parameters. Light curves of small space debris with various area-to-mass ratios and orbital characteristics are discussed. Tracking of some objects shows very rapid brightness variations related to perturbations of the orbital parameters. Changes in brightness and equatorial coordinates of the studied objects are found in observational data. Our results allow improving the accuracy of space debris orbital elements.

  12. Effects of Plasma Drag on Low Earth Orbiting Satellites due to Heating of Earth's Atmosphere by Coronal Mass Ejections

    Nwankwo, Victor U. J.; Chakrabarti, Sandip K.

    2013-01-01

    Solar events, such as coronal mass ejections (CMEs) and solar flares, heat up the upper atmosphere and near-Earth space environment. Due to this heating and expansion of the outer atmosphere by the energetic ultraviolet, X-ray and particles expelled from the sun, the low Earth-Orbiting satellites (LEOS) become vulnerable to an enhanced drag force by the ions and molecules of the expanded atmosphere. Out of various types of perturbations, Earth directed CMEs play the most significant role. The...

  13. Near-earth binaries and triples: Origin and evolution of spin-orbital properties

    J. Fang; Margot, JL

    2012-01-01

    In the near-Earth asteroid population, binary and triple systems have been discovered with mutual orbits that have significant eccentricities as well as large semimajor axes. All known systems with eccentric orbits and all widely separated primary-satellite pairs have rapidly rotating satellites. Here, we study processes that can elucidate the origin of these spin-orbital properties. Binary formation models based on rotational fissioning can reproduce asynchronous satellites on orbits with hi...

  14. Software and hardware implements for tracking low earth orbit (LEO) satellites

    Rahal, Wassila Leila; Banabadji, Noureddine; Belbachir, Ahmed Hafid

    2008-01-01

    In this paper, we present a novel, precise and efficient tracking system for Low Earth Orbit (LEO) Satellites. We have developed a software (LAAR-Track) and a hardware interface for orbit determination based on using orbital elements, which are given by the NORAD (North American Aerospace Defence). Orbital perturbations, such as the atmospheric drag, the influence of the moon and the sun and the geopotential field have been considered for satellites trajectory determination. The LAAR-Track gi...

  15. Effects of Low Earth Orbit on Docking Seal Materials

    Imka, Emily C.; Asmar, Olivia C.; deGroh, Henry C., III; Banks, Bruce A.

    2014-01-01

    Spacecraft docking seals are typically made of silicone elastomers. When such seals are exposed to low Earth orbit (LEO) conditions, they can suffer damage from ultraviolet (UV) radiation and atomic oxygen (AO, or monoatomic oxygen, the predominant oxygen species in LEO). An experiment flew on the International Space Station (ISS) to measure the effects of LEO on seal materials S0383-70 and ELA-SA-401 and various mating counterface materials which included anodized aluminum. Samples flown in different orientations received different amounts of UV and AO. The hypotheses were that most of the damage would be from UV, and 10 days or more of exposure in LEO would badly damage the seals. Eighteen seals were exposed for 543 days in ram (windward), zenith (away from Earth), or wake (leeward) orientations, and 15 control samples (not flown) provided undamaged baseline leakage. To determine post-flight leak rates, each of the 33 seals were placed in an O-ring groove of a leak test fixture and pressure tested over time. Resistance temperature detectors (RTDs), pressure transducers, and LabVIEW (National Instruments) programs were used to measure and analyze the temperature and pressure and calculate leakage. Average leakage of control samples was 2.6 x 10(exp -7) lbs/day. LEO exposure did not considerably damage ELA-SA-401. The S0383-70 flight samples leaked at least 10 times more than ELA-SA-401 in all cases except one, demonstrating that ELA-SA-401 may be a more suitable sealing material in LEO. AO caused greater damage than UV; samples in ram orientation (receiving an AO fluence of 4.3 x 10(exp 21) atoms/(sq cm) and in wake (2.9x 10(exp 20) atoms/(sq cm)) leaked more than those in zenith orientation (1.58 x 10(exp 20) atoms/(sq cm)), whereas variations in UV exposure did not seem to affect the samples. Exposure to LEO did less damage to the seals than hypothesized, and the data did not support the conjecture that UV causes more damage than AO.

  16. Extension of Earth-Moon libration point orbits with solar sail propulsion

    Heiligers, Jeannette; Macdonald, Malcolm; Parker, Jeffrey S.

    2016-07-01

    This paper presents families of libration point orbits in the Earth-Moon system that originate from complementing the classical circular restricted three-body problem with a solar sail. Through the use of a differential correction scheme in combination with a continuation on the solar sail induced acceleration, families of Lyapunov, halo, vertical Lyapunov, Earth-centred, and distant retrograde orbits are created. As the solar sail circular restricted three-body problem is non-autonomous, a constraint defined within the differential correction scheme ensures that all orbits are periodic with the Sun's motion around the Earth-Moon system. The continuation method then starts from a classical libration point orbit with a suitable period and increases the solar sail acceleration magnitude to obtain families of orbits that are parametrised by this acceleration. Furthermore, different solar sail steering laws are considered (both in-plane and out-of-plane, and either fixed in the synodic frame or fixed with respect to the direction of Sunlight), adding to the wealth of families of solar sail enabled libration point orbits presented. Finally, the linear stability properties of the generated orbits are investigated to assess the need for active orbital control. It is shown that the solar sail induced acceleration can have a positive effect on the stability of some orbit families, especially those at the L2 point, but that it most often (further) destabilises the orbit. Active control will therefore be needed to ensure long-term survivability of these orbits.

  17. Comprehensive NASA Cis-Lunar Earth Moon Libration Orbit Reference and Web Application Project

    National Aeronautics and Space Administration — To finalize a comprehensive NASA Cis-Lunar / Earth-Moon Libration Orbit Reference and Web Application begun using FY13 IRAD funding approved in May 2013. This GSFC...

  18. Single Event Effects Testing For Low Earth Orbit Missions with Neutrons

    Reddell, Brandon; O'Neill, Pat; Bailey, Chuck; Nguyen, Kyson

    2015-01-01

    Neutrons can effectively be used to screen electronic parts intended to be used in Low Earth Orbit. This paper compares neutron with proton environments in spacecraft and discusses recent comparison testing.

  19. A model to compare performance of space and ground network support of low-Earth orbiters

    Posner, E. C.

    1992-01-01

    This article compares the downlink performance in a gross average sense between space and ground network support of low-Earth orbiters. The purpose is to assess what the demand for DSN support of future small, low-cost missions might be, if data storage for spacecraft becomes reliable enough and small enough to support the storage requirements needed to enable support only a fraction of the time. It is shown that the link advantage of the DSN over space reception in an average sense is enormous for low-Earth orbiters. The much shorter distances needed to communicate with the ground network more than make up for the speedup in data rate needed to compensate for the short contact times with the DSN that low-Earth orbiters have. The result is that more and more requests for DSN-only support of low-Earth orbiters can be expected.

  20. A Focused Path to Extend Human Presence Beyond Low Earth Orbit

    Robinson, M. S.

    2015-10-01

    Developing a sustainable long-term architecture to move humans out of low Earth orbit and into the solar system requires a focused path built around a series of achievable objectives within a structured time frame.

  1. Rings of earth. [orbiting bands of space debris

    Goldstein, Richard M.; Randolph, L. W.

    1992-01-01

    Small particles moving at an orbital velocity of 7.6 kilometers per second can present a considerable hazard to human activity in space. For astronauts outside of the protective shielding of their space vehicles, such particles can be lethal. The powerful radar at NASA's Goldstone Deep Communications Complex was used to monitor such orbital debris. This radar can detect metallic objects as small as 1.8 mm in diameter at 600 km altitude. The results of the preliminary survey show a flux (at 600 km altitude) of 6.4 objects per square kilometer per day of equivalent size of 1.8 mm or larger. Forty percent of the observed particles appear to be concentrated into two orbits. An orbital ring with the same inclination as the radar (35.1 degrees) is suggested. However, an orbital band with a much higher inclination (66 degrees) is also a possibility.

  2. Probable Spin-Orbit Aligned Super-Earth Planet Candidate KOI-2138.01

    Barnes, Jason W; Seubert, Shayne A; Relles, Howard M

    2015-01-01

    We use rotational gravity darkening in the disk of \\emph{Kepler} star KOI-2138 to show that the orbit of $2.1-R_\\oplus$ transiting planet candidate KOI-2138.01 has a low projected spin-orbit alignment of $\\lambda=1^\\circ\\pm13$. KOI-2138.01 is just the second super-Earth with a measured spin-orbit alignment after 55 Cancri e, and the first to be aligned. With a 23.55-day orbital period, KOI-2138.01 may represent the tip of a future iceberg of solar-system-like terrestrial planets having intermediate periods and low-inclination circular orbits.

  3. The Coverage Analysis for Low Earth Orbiting Satellites at Low Elevation

    Shkelzen Cakaj; Bexhet Kamo; Algenti Lala; Alban Rakipi

    2014-01-01

    Low Earth Orbit (LEO) satellites are used for public networking and for scientific purposes. Communication via satellite begins when the satellite is positioned in its orbital position. Ground stations can communicate with LEO satellites only when the satellite is in their visibility region. The duration of the visibility and the communication vary for each LEO satellite pass over the station, since LEO satellites move too fast over the Earth. The satellite coverage area is defined as a regio...

  4. Tests of general relativity in earth orbit using a superconducting gravity gradiometer

    Paik, H. J.

    1989-01-01

    Interesting new tests of general relativity could be performed in earth orbit using a sensitive superconducting gravity gradiometer under development. Two such experiments are discussed here: a null test of the tracelessness of the Riemann tensor and detection of the Lense-Thirring term in the earth's gravity field. The gravity gradient signals in various spacecraft orientations are derived, and dominant error sources in each experimental setting are discussed. The instrument, spacecraft, and orbit requirements imposed by the experiments are derived.

  5. Optical Orbit Determination of a Geosynchronous Earth Orbit Satellite Effected by Baseline Distances between Various Ground-based Tracking Stations

    Son, Ju Young; Jo, Jung Hyun; Choi, Jin; Kim, Bang-Yeop; Yoon, Joh-Na; Yim, Hong-Suh; Choi, Young-Jun; Park, Sun-Youp; Bae, Young Ho; Roh, Dong-Goo; Park, Jang-Hyun; Kim, Ji-Hye

    2015-09-01

    We estimated the orbit of the Communication, Ocean and Meteorological Satellite (COMS), a Geostationary Earth Orbit (GEO) satellite, through data from actual optical observations using telescopes at the Sobaeksan Optical Astronomy Observatory (SOAO) of the Korea Astronomy and Space Science Institute (KASI), Optical Wide field Patrol (OWL) at KASI, and the Chungbuk National University Observatory (CNUO) from August 1, 2014, to January 13, 2015. The astrometric data of the satellite were extracted from the World Coordinate System (WCS) in the obtained images, and geometrically distorted errors were corrected. To handle the optically observed data, corrections were made for the observation time, light-travel time delay, shutter speed delay, and aberration. For final product, the sequential filter within the Orbit Determination Tool Kit (ODTK) was used for orbit estimation based on the results of optical observation. In addition, a comparative analysis was conducted between the precise orbit from the ephemeris of the COMS maintained by the satellite operator and the results of orbit estimation using optical observation. The orbits estimated in simulation agree with those estimated with actual optical observation data. The error in the results using optical observation data decreased with increasing number of observatories. Our results are useful for optimizing observation data for orbit estimation.

  6. The Orbit of Planet Earth in the Last 150 Million Years

    Noort, van den P.C.

    2011-01-01

    The structure of the world is a construction of philosophers and scientists. It changed all the time. Nowadays we have a chaotic Solar System. The orbit of Earth changes, therefore, on the very long run. With it changed the UV- radiation on the surface of Earth, influencing the number of mutations.

  7. Measuring the Eccentricity of the Earth's Orbit with a Nail and a Piece of Plywood

    Lahaye, Thierry

    2012-01-01

    I describe how to obtain a rather good experimental determination of the eccentricity of the Earth's orbit, as well as the obliquity of the Earth's rotation axis, by measuring, over the course of a year, the elevation of the Sun as a function of time during a day. With a very simple "instrument" consisting of an elementary sundial, first-year…

  8. Scheme of rendezvous mission to lunar orbital station by spacecraft launched from Earth

    Murtazin, R. F.

    2016-05-01

    In recent years, great experience has been accumulated in manned flight astronautics for rendezvous in near-Earth orbit. During flights of Apollo spacecraft with crews that landed on the surface of the Moon, the problem of docking a landing module launched from the Moon's surface with the Apollo spacecraft's command module in a circumlunar orbit was successfully solved. A return to the Moon declared by leading space agencies requires a scheme for rendezvous of a spacecraft launched from an earth-based cosmodromee with a lunar orbital station. This paper considers some ballistic schemes making it possible to solve this problem with minimum fuel expenditures.

  9. Exobiology in Earth orbit: The results of science workshops held at NASA, Ames Research Center

    Defrees, D. (Editor); Brownlee, D. (Editor); Tarter, J. (Editor); Usher, D. (Editor); Irvine, W. (Editor); Klein, H. (Editor)

    1989-01-01

    The Workshops on Exobiology in Earth Orbit were held to explore concepts for orbital experiments of exobiological interest and make recommendations on which classes of experiments should be carried out. Various observational and experimental opportunities in Earth orbit are described including those associated with the Space Shuttle laboratories, spacecraft deployed from the Space Shuttle and expendable launch vehicles, the Space Station, and lunar bases. Specific science issues and technology needs are summarized. Finally, a list of recommended experiments in the areas of observational exobiology, cosmic dust collection, and in situ experiments is presented.

  10. UV Surface Environment of Earth-like Planets Orbiting FGKM Stars Through Geological Evolution

    Rugheimer, S.; Segura, A.; Kaltenegger, L.; Sasselov, D.

    2015-01-01

    The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars at the 1AU equivalent distance for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early Earth atmosphere at 3.9 Gyr ago and three atmo...

  11. The Orbit of Planet Earth in the Last 150 Million Years

    Noort, van den, P.C.

    2011-01-01

    The structure of the world is a construction of philosophers and scientists. It changed all the time. Nowadays we have a chaotic Solar System. The orbit of Earth changes, therefore, on the very long run. With it changed the UV- radiation on the surface of Earth, influencing the number of mutations. This celestial factor plays an important role in the explanation of evolution and extinction which we can see in the fossil record of Earth, and reversed we can reconstruct the orbit of planet Eart...

  12. Access to Mars from Earth-Moon Libration Point Orbits:. [Manifold and Direct Options

    Kakoi, Masaki; Howell, Kathleen C.; Folta, David

    2014-01-01

    This investigation is focused specifically on transfers from Earth-Moon L(sub 1)/L(sub 2) libration point orbits to Mars. Initially, the analysis is based in the circular restricted three-body problem to utilize the framework of the invariant manifolds. Various departure scenarios are compared, including arcs that leverage manifolds associated with the Sun-Earth L(sub 2) orbits as well as non-manifold trajectories. For the manifold options, ballistic transfers from Earth-Moon L(sub 2) libration point orbits to Sun-Earth L(sub 1)/L(sub 2) halo orbits are first computed. This autonomous procedure applies to both departure and arrival between the Earth-Moon and Sun-Earth systems. Departure times in the lunar cycle, amplitudes and types of libration point orbits, manifold selection, and the orientation/location of the surface of section all contribute to produce a variety of options. As the destination planet, the ephemeris position for Mars is employed throughout the analysis. The complete transfer is transitioned to the ephemeris model after the initial design phase. Results for multiple departure/arrival scenarios are compared.

  13. Orbital Properties of the Arecibo Micrometeoroids at Earth Interception

    Janches, D.; Meisel, D. D.; Mathews, J. D.

    2001-04-01

    Using the Arecibo Observatory (AO) 430-MHz Radar we have developed a Doppler technique to measure very precise micrometeor instantaneous velocities directly from the meteor head echo. In addition, a large number of the observed meteoroids show deceleration. With the velocity, the deceleration, and the assumptions of a spherical shape and a mean micrometeoroid mass density, we have obtained estimates of in-atmosphere particle sizes. The size estimate, the MSIS model atmosphere, and the measured deceleration are used to obtain the meteor extra-atmospheric speeds, assuming these particles undergo little mass-loss prior to and during the time we detect them (Janches et al. 2000b, Icarus145, 53-63). Orbital elements at 1 AU are presented and discussed. These results have not been corrected for perturbation effects such as radiation pressure, Poynting-Robertson drag, attraction by the giant planets, and photoelectric charging effects. So far, over 7700 detections obtained during November 1997 and 3500 during the November 1998 observation campaigns have been analyzed. The observing periods included the Leonids meteor shower, but none of the orbits are recently derived from it. Out of these detections, we present details of over 1500 orbits with eccentricities less than unity. These orbits show (a) a depletion of postperihelion particles with small perihelion distance, suggesting the possibility of collisional and thermal destruction, and (b) an enhancement of particles with perihelia in the zone between Mercury and Venus. Also discussed are 40 β-meteoroids (with radii less than 0.5 μm) dynamically related to the elliptical orbit population with q<0.7 AU. We interpret the latter results on the basis of Poynting-Robertson drag and the electromagnetic resonant effects proposed by G. E. Morfill and E. Grün (1979, Planet. Space Sci.27, 1269-1282). Comparison with previous data sets indicates that most of the AO micrometeoroid orbits are well randomized and that association

  14. Comprehensive evaluation of attitude and orbit estimation using real earth magnetic field data

    Deutschmann, Julie; Bar-Itzhack, Itzhack

    1997-01-01

    A single, augmented extended Kalman filter (EKF) which simultaneously and autonomously estimates spacecraft attitude and orbit was developed and tested with simulated and real magnetometer and rate data. Since the earth's magnetic field is a function of time and position, and since time is accurately known, the differences between the computed and measured magnetic field components, as measured by the magnetometers throughout the entire spacecraft's orbit, are a function of orbit and attitude errors. These differences can be used to estimate the orbit and attitude. The test results of the EKF with magnetometer and gyro data from three NASA satellites are presented and evaluated.

  15. Low-Thrust Transfers from Distant Retrograde Orbits to L2 Halo Orbits in the Earth-Moon System

    Parrish, Nathan L.; Parker, Jeffrey S.; Hughes, Steven P.; Heiligers, Jennette

    2016-01-01

    Enable future missions Any mission to a DRO or halo orbit could benefit from the capability to transfer between these orbits Chemical propulsion could be used for these transfers, but at high propellant cost Fill gaps in knowledge A variety of transfers using SEP or solar sails have been studied for the Earth-Moon system Most results in literature study a single transfer This is a step toward understanding the wide array of types of transfers available in an N-body force model.

  16. Biofilms On Orbit and On Earth: Current Methods, Future Needs

    Vega, Leticia

    2013-01-01

    Biofilms have played a significant role on the effectiveness of life support hardware on the Space Shuttle and International Space Station (ISS). This presentation will discuss how biofilms impact flight hardware, how on orbit biofilms are analyzed from an engineering and research perspective, and future needs to analyze and utilize biofilms for long duration, deep space missions.

  17. Low earth orbit infrastructure to accommodate manned lunar missions

    Cirillo, William M.; Troutman, Patrick A.; Brender, Karen D.; Dahlstrom, Eric L.; Ayers, J. Kirk; Waters, Laura M.

    1990-01-01

    In order to establish bases on the lunar and Mars surfaces, a significant amount of orbital infrastructure including assembly platforms, cryogenic fluids depots, and Space Station Freedom, will be required in LEO. These facilities will be required to perform a myriad of functions ranging from orbital demonstration of advanced technology systems and establishment of life science capabilities to servicing and refurbishment of reusable lunar transfer vehicles. This paper addresses the requirements levied on these facilities and provides an overview of potetial LEO infrastructure elements that satisfy various advanced manned missions. Of key importance to the success of the manned lunar mission are (1) the evolutionary growth of Space Station Freedom to serve as a transportation node and (2) the development of a Shuttle-derived launch vehicle to deliver mission elements to LEO.

  18. Microarcsecond radio imaging using earth-orbit synthesis

    Macquart, JP; Jauncey, DL

    2002-01-01

    The observed interstellar scintillation pattern of an intraday variable radio source is influenced by its source structure. If the velocity of the interstellar medium responsible for the scattering is comparable to the Earths, the vector sum of these allows an observer to probe the scintillation pat

  19. Dynamical sequestration of the Moon-forming impactor in co-orbital resonance with Earth

    Kortenkamp, Stephen J.; Hartmann, William K.

    2016-09-01

    Recent concerns about the giant impact hypothesis for the origin of the Moon, and an associated "isotope crisis" may be assuaged if the impactor was a local object that formed near Earth. We investigated a scenario that may meet this criterion, with protoplanets assumed to originate in 1:1 co-orbital resonance with Earth. Using N-body numerical simulations we explored the dynamical consequences of placing Mars-mass companions in various co-orbital configurations with a proto-Earth of 0.9 Earth-masses (M⊕). We modeled 162 different configurations, some with just the four terrestrial planets and others that included the four giant planets. In both the 4- and 8-planet models we found that a single Mars-mass companion typically remained a stable co-orbital of Earth for the entire 250 million year (Myr) duration of our simulations (59 of 68 unique simulations). In an effort to destabilize such a system we carried out an additional 94 simulations that included a second Mars-mass co-orbital companion. Even with two Mars-mass companions sharing Earth's orbit about two-thirds of these models (66) also remained stable for the entire 250 Myr duration of the simulations. Of the 28 2-companion models that eventually became unstable 24 impacts were observed between Earth and an escaping co-orbital companion. The average delay we observed for an impact of a Mars-mass companion with Earth was 102 Myr, and the longest delay was 221 Myr. In 40% of the 8-planet models that became unstable (10 out of 25) Earth collided with the nearly equal mass Venus to form a super-Earth (loosely defined here as mass ≥1.7 M⊕). These impacts were typically the final giant impact in the system and often occurred after Earth and/or Venus has accreted one or more of the other large objects. Several of the stable configurations involved unusual 3-planet hierarchical co-orbital systems.

  20. Earth Observing System (EOS) real-time onboard orbit determination

    Folta, David C.; Muller, Ron

    1993-01-01

    The paper describes the TDRSS Onboard Navigation System (TONS) selected by NASA/GSFC for the EOS-AM1 spacecraft as the baseline navigation system for real-time onboard orbit determination. Particular attention is given to the TONS algorithms and environmental models, the general design considerations, the algorithm implementation, and the required hardware. Results are presented of the covariance analysis for the nominal onboard and instrument requirements.

  1. Orbiting.

    Halford, Sarah Juliette

    2013-01-01

    I always knew I was from another planet. Earth was my home, yes, I liked hamburgers and roller coasters, but there was still an orbit in me that seemed out of place. My imaginative orbit felt like it didn't to spin the "normal" way. As a performer I spent more time alienating myself and judging how different I felt, rather than owning the creative space I lived in and applying it to my craft. My past three years at UC San Diego have been the perfect atmosphere for my artist self. I have been ...

  2. How the inclination of Earth's orbit affects incoming solar irradiance

    Vieira, L. E. A.; Norton, A; Dudok de Wit, T.; M. Kretzschmar; Schmidt, G. A.; Cheung, M.C.M.

    2012-01-01

    International audience [1] The variability in solar irradiance, the main external energy source of the Earth's system, must be critically studied in order to place the effects of human-driven climate change into perspective and allow plausible predictions of the evolution of climate. Accurate measurements of total solar irradiance (TSI) variability by instruments onboard space platforms during the last three solar cycles indicate changes of approximately 0.1% over the sunspot cycle. Physic...

  3. UV Surface Environment of Earth-like Planets Orbiting FGKM Stars Through Geological Evolution

    Rugheimer, S; Kaltenegger, L; Sasselov, D

    2015-01-01

    The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars at the 1AU equivalent distance for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early Earth atmosphere at 3.9 Gyr ago and three atmospheres covering the rise of oxygen to present day levels at 2.0 Gyr ago, 0.8 Gyr ago and modern Earth (Following Kaltenegger et al. 2007). In addition to calculating the UV flux on the surface of the planet, we model the biologically effective irradiance, using DNA damage as a proxy for biological damage. We find that a pre-biotic Earth (3.9 Gyr ago) orbiting an F0V star receives 6 times the biologically effective radiation as around the early Sun and 3520 times the modern Earth-Sun levels. A pre-biotic Earth orbiting GJ...

  4. Solar dynamic heat receiver thermal characteristics in low earth orbit

    Wu, Y. C.; Roschke, E. J.; Birur, G. C.

    1988-01-01

    A simplified system model is under development for evaluating the thermal characteristics and thermal performance of a solar dynamic spacecraft energy system's heat receiver. Results based on baseline orbit, power system configuration, and operational conditions, are generated for three basic receiver concepts and three concentrator surface slope errors. Receiver thermal characteristics and thermal behavior in LEO conditions are presented. The configuration in which heat is directly transferred to the working fluid is noted to generate the best system and thermal characteristics. as well as the lowest performance degradation with increasing slope error.

  5. GNSS/INS/Star Tracker Integrated Navigation System for Earth-Moon Transfer Orbit

    Capuano, Vincenzo; Botteron, Cyril; Wang, Yanguang; Tian, Jia; Leclère, Jérôme; Farine, Pierre-André

    2014-01-01

    Over the last few years, new Global Navigation Satellite System (GNSS) applications have emerged that go far beyond the original objectives of GNSS which was providing position, velocity and timing (PVT) services for land, maritime, and air applications. Indeed, today, GNSS is used in Low Earth Orbit (LEO) for a wide range of applications such as real-time navigation, formation flying, precise time synchronization, orbit determination and atmospheric profiling. GNSS, in fact, can maximize the...

  6. Tidal heating of Earth-like exoplanets around M stars: Thermal, magnetic, and orbital evolutions

    Driscoll, P E; Barnes, R.

    2015-01-01

    Abstract The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the “tidal zone,” where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbita...

  7. ADCS controllers comparison for small satellitess in Low Earth Orbit

    Calvo, Daniel; Laverón-Simavilla, Ana; Lapuerta, Victoria

    2016-07-01

    Fuzzy logic controllers are flexible and simple, suitable for small satellites Attitude Determination and Control Subsystems (ADCS). In a previous work, a tailored Fuzzy controller was designed for a nanosatellite. Its performance and efficiency were compared with a traditional Proportional Integrative Derivative (PID) controller within the same specific mission. The orbit height varied along the mission from injection at around 380 km down to 200 km height, and the mission required pointing accuracy over the whole time. Due to both, the requirements imposed by such a low orbit, and the limitations in the power available for the attitude control, an efficient ADCS is required. Both methodologies, fuzzy and PID, were fine-tuned using an automated procedure to grant maximum efficiency with fixed performances. The simulations showed that the Fuzzy controller is much more efficient (up to 65% less power required) in single manoeuvres, achieving similar, or even better, precision than the PID. The accuracy and efficiency improvement of the Fuzzy controller increase with orbit height because the environmental disturbances decrease, approaching the ideal scenario. However, the controllers are meant to be used in a vast range of situations and configurations which exceed those used in the calibration process carried out in the previous work. To assess the suitability and performance of both controllers in a wider framework, parametric and statistical methods have been applied using the Monte Carlo technique. Several parameters have been modified randomly at the beginning of each simulation: the moments of inertia of the whole satellite and of the momentum wheel, the residual magnetic dipole and the initial conditions of the test. These parameters have been chosen because they are the main source of uncertainty during the design phase. The variables used for the analysis are the error (critical for science) and the operation cost (which impacts the mission lifetime and

  8. Earth-to-Geostationary Orbit Transportation for Space Solar Power System Development

    Martin, James A.; Donahue, Benjamin B.; Lawrence, Schuyler C.; McClanahan, James A.; Carrington, Connie K. (Technical Monitor)

    2000-01-01

    Space solar power satellites have the potential to provide abundant quantities of electricity for use on Earth. One concept, the Sun Tower, can be assembled in geostationary orbit from pieces transferred from Earth. The cost of transportation is one of the major hurdles to space solar power. This study found that autonomous solar-electric transfer is a good choice for the transportation from LEO to GEO.

  9. Conceptual design and flight simulation of space station missions beyond low earth orbit

    Yazdi, Kian

    2006-01-01

    Humans will live and work in space for the exploration and development of the solar system. A wide range of space infrastructure elements will be required in low Earth orbit and beyond. Besides new transfer and re-entry vehicles as well as planetary surface installations, space stations in the Earth-Moon system can be a crucial element of forthcoming exploration missions. This dissertation documents an investigation on conceptual design and flight simulation of such space station missions ...

  10. Spacecraft orbit/earth scan derivations, associated APL program, and application to IMP-6

    Smith, G. A.

    1971-01-01

    The derivation of a time shared, remote site, demand processed computer program is discussed. The computer program analyzes the effects of selected orbit, attitude, and spacecraft parameters on earth sensor detections of earth. For prelaunch analysis, the program may be used to simulate effects in nominal parameters which are used in preparing attitude data processing programs. After launch, comparison of results from a simulation and from satellite data will produce deviations helpful in isolating problems.

  11. Free Space Laser Communication Experiments from Earth to the Lunar Reconnaissance Orbiter in Lunar Orbit

    Sun, Xiaoli; Skillman, David R.; Hoffman, Evan D.; Mao, Dandan; McGarry, Jan F.; Zellar, Ronald S.; Fong, Wai H; Krainak, Michael A.; Neumann, Gregory A.; Smith, David E.

    2013-01-01

    Laser communication and ranging experiments were successfully conducted from the satellite laser ranging (SLR) station at NASA Goddard Space Flight Center (GSFC) to the Lunar Reconnaissance Orbiter (LRO) in lunar orbit. The experiments used 4096-ary pulse position modulation (PPM) for the laser pulses during one-way LRO Laser Ranging (LR) operations. Reed-Solomon forward error correction codes were used to correct the PPM symbol errors due to atmosphere turbulence and pointing jitter. The signal fading was measured and the results were compared to the model.

  12. Aerodynamic Stability of Satellites in Elliptic Low Earth Orbits

    Bailey, Matthew; Mancas, Stefan C; Udrea, Bogdan; Umeadi, Uchenna

    2013-01-01

    Topical observations of the thermosphere at altitudes below $200 \\, km$ are of great benefit in advancing the understanding of the global distribution of mass, composition, and dynamical responses to geomagnetic forcing, and momentum transfer via waves. The perceived risks associated with such low altitude and short duration orbits has prohibited the launch of Discovery-class missions. Miniaturization of instruments such as mass spectrometers and advances in the nano-satellite technology, associated with relatively low cost of nano-satellite manufacturing and operation, open an avenue for performing low altitude missions. The time dependent coefficients of a second order non-homogeneous ODE which describes the motion have a double periodic shape. Hence, they will be approximated using Jacobi elliptic functions. Through a change of variables the original ODE will be converted into Hill's ODE for stability analysis using Floquet theory. We are interested in how changes in the coefficients of the ODE affect the ...

  13. Targeting Ballistic Lunar Capture Trajectories Using Periodic Orbits in the Sun-Earth CRTBP

    Cooley, D.S.; Griesemer, Paul Ricord; Ocampo, Cesar

    2009-01-01

    A particular periodic orbit in the Earth-Sun circular restricted three body problem is shown to have the characteristics needed for a ballistic lunar capture transfer. An injection from a circular parking orbit into the periodic orbit serves as an initial guess for a targeting algorithm. By targeting appropriate parameters incrementally in increasingly complicated force models and using precise derivatives calculated from the state transition matrix, a reliable algorithm is produced. Ballistic lunar capture trajectories in restricted four body systems are shown to be able to be produced in a systematic way.

  14. Extrasolar Giant Planet in Earth-like Orbit

    1999-07-01

    Discovery from a Long-term Project at La Silla A new extrasolar planet has been found at the ESO La Silla Observatory as a companion to iota Horologii (iota Hor) . This 5.4-mag solar-type star is located at a distance of 56 light-years and is just visible to the unaided eye in the southern constellation Horologium (The Pendulum Clock). The discovery is the result of a long-term survey of forty solar-type stars that was begun in November 1992. It is based on highly accurate measurements of stellar radial velocities, i.e. the speed with which a star moves along the line of sight. The presence of a planet in orbit around a star is inferred from observed, regular changes of this velocity, as the host star and its planet revolve around a common center of gravity. Since in all cases the star is much heavier than the planet, the resulting velocity variations of the star are always quite small. The team that found the new planet, now designated iota Hor b , consists of Martin Kürster , Michael Endl and Sebastian Els (ESO-Chile), Artie P. Hatzes and William D. Cochran (University of Texas, Austin, USA), and Stefan Döbereiner and Konrad Dennerl (Max-Planck-Institut für extraterrestrische Physik, Garching, Germany). Iodine cell provides very accurate velocity measurements iota Hor b represents the first discovery of an extrasolar planet with an ESO instrument [1]. The finding is based on data obtained with ESO's highest-resolution spectrograph, the Coudé Echelle Spectrometer (CES) at the 1.4-m Coudé Auxiliary Telescope (CAT). While this telescope has recently been decommissioned, the CES instrument is now coupled via an optical fiber link to the larger ESO 3.6-m telescope, thus permitting the continuation of this survey. The high precision radial velocity measurements that are necessary for a study of this type were achieved by means of a special calibration technique. It incorporates an iodine gas absorption cell and sophisticated data modelling. The cell is used like

  15. Probable Rotation States of Rocket Bodies in Low Earth Orbit

    Ojakangas, G.; Anz-Meador, P.; Cowardin, H.

    2012-09-01

    In order for Active Debris Removal to be accomplished, it is critically important to understand the probable rotation states of orbiting, spent rocket bodies (RBs). However, rotational dynamics is non-intuitive and misconceptions are common. Determinations of rotation and precession rates from light curves have been published that are inconsistent with the theory presented here. In a state of free precession, the total angular momentum of the object is constant, while kinetic energy decreases due to internal friction, approaching rotation about the axis of maximum inertia. For solid internal friction the timescale is hundreds to thousands of years for quality factors of ~100 and assuming metallic rigidities, but for friction in partially-filled liquid fuel tanks we predict that the preferred rotational state is approached rapidly, within days to months. However, history has shown that theoretical predictions of the timescale have been notoriously inaccurate. In free precession, the 3-1-3 Euler angle rates dphi/dt (precession rate of long axis about fixed angular momentum with cone angle theta) and dpsi/dt (roll rate around long axis) have comparable magnitudes until very close to theta=pi/2, so that otherwise the true rotation period is not simply twice the primary light curve period. Furthermore dtheta/dt, nonzero due to friction, becomes asymptotically smaller as theta=pi/2 is approached, so that theta can linger within several degrees of flat spin for a relatively long time. Such a condition is likely common, and cannot be distinguished from the wobble of a cylinder with a skewed inertia tensor unless the RB has non-axisymmetric reflectivity characteristics. For an RB of known dimensions, a given value of theta fixes the relative values of dpsi/dt and dphi/dt. In forced precession, the angular momentum precesses about a symmetry axis defined by the relevant torque. However, in LEO, only gravity gradient and magnetic eddy current torques are dominant, and these

  16. Tidal Heating of Earth-like Exoplanets around M Stars: Thermal, Magnetic, and Orbital Evolutions.

    Driscoll, P E; Barnes, R

    2015-09-01

    The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the "tidal zone," where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a viscoelastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within 0.07 AU circularize before 10 Gyr, independent of initial eccentricity. Once circular, these planets cool monotonically and maintain dynamos similar to that of Earth. Planets forced into eccentric orbits can experience a super-cooling of the core and rapid core solidification, inhibiting dynamo action for planets in the habitable zone. We find that tidal heating is insignificant in the habitable zone around 0.45 (or larger) solar-mass stars because tidal dissipation is a stronger function of orbital distance than stellar mass, and the habitable zone is farther from larger stars. Suppression of the planetary magnetic field exposes the atmosphere to stellar wind erosion and the surface to harmful radiation. In addition to weak magnetic fields, massive melt eruption rates and prolonged magma oceans may render eccentric planets in the habitable zone of low-mass stars inhospitable for life. PMID:26393398

  17. Exobiology experiments for Earth-orbital platforms. [Abstract only

    Huntington, J. L.; Stratton, D. M.; Scattergood, T. W.; Marshall, J. R.

    1994-01-01

    Low-gravity (microgravity) studies relevant to prebiotic evolution and the history of the biogenic elements (C, H, N, O, P, S) are particularly suited to orbital platforms. Relevant to these topics are phenomena such as gas-particle interactions (e.g., formation of organic aerosols via photolytic reactions) including nucleation, condensation, evaporation, adsorption, and catalytic reactions on surfaces; and, small-particle or grain interactions (e.g., growth of interstellar dust particles and planetesimals) including processes such as aggregation (or coagulation), scavenging, and collisions. Both gas-particle and grain (i.e., dust, crystals, organic aerosols, etc.) interactions studies can benefit from microgravity and are pertinent to studies in the areas of chemical evolution in the solar nebula, the interstellar medium, and planetary atmospheres; growth of planetesimals; and prebiotic evolution. In general, the microgravity environment allows for long duration and controlled simulations of processes occurring in exobiologically significant systems such as Titan's atmosphere, interstellar dust clouds, and the solar nebula in which gas-particle or particle-particle interactions play a significant role.

  18. Multiprocessor DSP for real-time data processing on Earth orbiting scatterometers

    Bachmann, A.; Clark, D.; Lux, J.; Steffke, R.

    2000-01-01

    The implementation of a Multi DSP radar signal processor for a Ku-Band Earth orbiting scatterometer is discussed. A testbed has been assembled using a combination of commercial DSP hardware and spaceflight components to evaluate the proposed multiprocessing approaches. Test results of real-time radar echo processing are presented, as well as proposed designs for future investigation.

  19. The Coverage Analysis for Low Earth Orbiting Satellites at Low Elevation

    Shkelzen Cakaj

    2014-07-01

    Full Text Available Low Earth Orbit (LEO satellites are used for public networking and for scientific purposes. Communication via satellite begins when the satellite is positioned in its orbital position. Ground stations can communicate with LEO satellites only when the satellite is in their visibility region. The duration of the visibility and the communication vary for each LEO satellite pass over the station, since LEO satellites move too fast over the Earth. The satellite coverage area is defined as a region of the Earth where the satellite is seen at a minimum predefined elevation angle. The satellite’s coverage area on the Earth depends on orbital parameters. The communication under low elevation angles can be hindered by natural barriers. For safe communication and for savings within a link budget, the coverage under too low elevation is not always provided. LEO satellites organized in constellations act as a convenient network solution for real time global coverage. Global coverage model is in fact the complementary networking process of individual satellite’s coverage. Satellite coverage strongly depends on elevation angle. To conclude about the coverage variation for low orbiting satellites at low elevation up to 10º, the simulation for attitudes from 600km to 1200km is presented through this paper.

  20. MALEO: Modular Assembly in Low Earth Orbit. A strategy for an IOC lunar base

    Thangavelu, M.; Schierle, G. G.

    1990-01-01

    Modular Assembly in Low Earth Orbit (MALEO) is a new strategy for building an initial operational capability lunar habitation base. In this strategy, the modular lunar base components are brought up to Low Earth Orbit by the Space Transportation System/Heavy Lift Launch Vehicle fleet, and assembled there to form a complete lunar base. Modular propulsion systems are then used to transport the MALEO lunar base, complete and intact, all the way to the moon. Upon touchdown on the lunar surface, the MALEO lunar habitation base is operational. An exo-skeletal truss superstructure is employed in order to uniformly absorb and distribute the rocket engine thrusting forces incurred by the MALEO lunar base during translunar injection, lunar orbit insertion, and lunar surface touchdown. The components, configuration, and structural aspects of the MALEO lunar base are discussed. Advantages of the MALEO strategy over conventional strategies are pointed out. It is concluded that MALEO holds promise for lunar base deployment.

  1. Earth observation mission operation of COMS during in-orbit test

    Cho, Young-Min

    2011-11-01

    Communication Ocean Meteorological Satellite (COMS) for the hybrid mission of meteorological observation, ocean monitoring, and telecommunication service was launched onto Geostationary Earth Orbit on June 27, 2010 and it is currently under normal operation service after the In-Orbit Test (IOT) phase. The COMS is located on 128.2° East of the geostationary orbit. In order to perform the three missions, the COMS has 3 separate payloads, the meteorological imager (MI), the Geostationary Ocean Color Imager (GOCI), and the Ka-band antenna. Each payload is dedicated to one of the three missions, respectively. The MI and GOCI perform the Earth observation mission of meteorological observation and ocean monitoring, respectively. During the IOT phase the functionality and the performance of many aspects of the COMS satellite and ground station have been checked through the Earth observation mission operation for the observation of the meteorological phenomenon over several areas of the Earth and the monitoring of marine environments around the Korean peninsula. The Earth observation mission operation of COMS during the IOT phase is introduced in terms of mission operation characteristics, mission planning, and mission operation results for the missions of meteorological observation and ocean monitoring, respectively.

  2. Tidal heating of Earth-like exoplanets around M stars: Thermal, magnetic, and orbital evolutions

    Driscoll, Peter

    2015-01-01

    The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low mass M stars whose radiative habitable zone overlaps with the "tidal zone". We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a visco-elastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within $0.07$ AU circularize before 10 G...

  3. 3D climate modeling of Earth-like extrasolar planets orbiting different types of host stars

    Godolt, M; Hamann-Reinus, A; Kitzmann, D; Kunze, M; Langematz, U; von Paris, P; Patzer, A B C; Rauer, H; Stracke, B

    2015-01-01

    The potential habitability of a terrestrial planet is usually defined by the possible existence of liquid water on its surface. The potential presence of liquid water depends on many factors such as, most importantly, surface temperatures. The properties of the planetary atmosphere and its interaction with the radiative energy provided by the planet's host star are thereby of decisive importance. In this study we investigate the influence of different main-sequence stars upon the climate of Earth-like extrasolar planets and their potential habitability by applying a 3D Earth climate model accounting for local and dynamical processes. The calculations have been performed for planets with Earth-like atmospheres at orbital distances where the total amount of energy received from the various host stars equals the solar constant. In contrast to previous 3D modeling studies, we include the effect of ozone radiative heating upon the vertical temperature structure of the atmospheres. The global orbital mean results o...

  4. The rotational motion of an earth orbiting gyroscope according to the Einstein theory of general relativity

    Hoots, F. R.; Fitzpatrick, P. M.

    1979-01-01

    The classical Poisson equations of rotational motion are used to study the attitude motions of an earth orbiting, rapidly spinning gyroscope perturbed by the effects of general relativity (Einstein theory). The center of mass of the gyroscope is assumed to move about a rotating oblate earth in an evolving elliptic orbit which includes all first-order oblateness effects produced by the earth. A method of averaging is used to obtain a transformation of variables, for the nonresonance case, which significantly simplifies the Poisson differential equations of motion of the gyroscope. Long-term solutions are obtained by an exact analytical integration of the simplified transformed equations. These solutions may be used to predict both the orientation of the gyroscope and the motion of its rotational angular momentum vector as viewed from its center of mass. The results are valid for all eccentricities and all inclinations not near the critical inclination.

  5. Mission Preparation Program for Exobiological Experiments in Earth Orbit

    Panitz, Corinna; Reitz, Guenther; Horneck, Gerda; Rabbow, Elke; Rettberg, Petra

    The ESA facilities EXPOSE-R and EXPOSE-E on board of the the International Space Station ISS provide the technology for exposing chemical and biological samples in a controlled manner to outer space parameters, such as high vacuum, intense radiation of galactic and solar origin and microgravity. EXPOSE-E has been attached to the outer balcony of the European Columbus module of the ISS in Febraury 2008 and will stay for about 1 year in space, EXPOSE-R will be attached to the Russian Svezda module of the ISS in fall 2008. The EXPOSE facilities are a further step in the study of the Responses of Organisms to Space Environment (ROSE concortium). The results from the EXPOSE missions will give new insights into the survivability of terrestrial organisms in space and will contribute to the understanding of the organic chemistry processes in space, the biological adaptation strategies to extreme conditions, e.g. on early Earth and Mars, and the distribution of life beyond its planet of origin.To test the compatibility of the different biological and chemical systems and their adaptation to the opportunities and constraints of space conditions a profound ground support program has been developed. It resulted in several experiment verification tests EVTs and an experiment sequence test EST that were conducted in the carefully equipped and monitored planetary and space simulation facilities PSI of the Institute of Aerospace Medicine at DLR in Cologne, Germany. These ground based pre-flight studies allow the investigation of a much wider variety of samples and the selection of the most promising organisms for the flight experiment. The procedure and results of these EVT tests and EST will be presented. These results are an essential prerequisite for the success of the EXPOSE missions and have been done in parallel with the development and construction of the final hardware design of the facility. The results gained during the simulation experiments demonstrated mission

  6. THE SYNERGY OF DIRECT IMAGING AND ASTROMETRY FOR ORBIT DETERMINATION OF EXO-EARTHS

    The holy grail of exoplanet searches is an exo-Earth, an Earth mass planet in the habitable zone (HZ) around a nearby star. Mass is one of the most important characteristics of a planet and can only be measured by observing the motion of the star around the planet-star center of gravity. The planet's orbit can be measured either by imaging the planet at multiple epochs or by measuring the position of the star at multiple epochs by space-based astrometry. The measurement of an exoplanet's orbit by direct imaging is complicated by a number of factors. One is the inner working angle (IWA). A space coronagraph or interferometer imaging an exo-Earth can separate the light from the planet from the light from the star only when the star-planet separation is larger than the IWA. Second, the apparent brightness of a planet depends on the orbital phase. A single image of a planet cannot tell us whether the planet is in the HZ or distinguish whether it is an exo-Earth or a Neptune-mass planet. Third is the confusion that may arise from the presence of multiple planets. With two images of a multiple planet system, it is not possible to assign a dot to a planet based only on the photometry and color of the planet. Finally, the planet-star contrast must exceed a certain minimum value in order for the planet to be detected. The planet may be unobservable even when it is outside the IWA, such as when the bright side of the planet is facing away from us in a 'crescent' phase. In this paper we address the question: 'Can a prior astrometric mission that can identify which stars have Earth-like planets significantly improve the science yield of a mission to image exo-Earths?' In the case of the Occulting Ozone Observatory, a small external occulter mission that cannot measure spectra, we find that the occulter mission could confirm the orbits of ∼4 to ∼5 times as many exo-Earths if an astrometric mission preceded it to identify which stars had such planets. In the case of an

  7. The Synergy of Direct Imaging and Astrometry for Orbit Determination of exo-Earths

    Shao, Michael; Pan, Xiaopei

    2010-01-01

    The holy grail of exoplanet searches is an exo-Earth, an Earth mass planet in the habitable zone around a nearby star. Mass is the most important parameter of a planet and can only be measured by observing the motion of the star around the planet-star center of mass. A single image of a planet, however, does not provide evidence that the planet is Earth mass or that it is in a habitable zone orbit. The planet's orbit, however, can be measured either by imaging the planet at multiple epochs or by measuring the position of the star at multiple epochs by space-based astrometry. The measurement of an exo-planet's orbit by direct imaging is complicated by a number of factors: (1) the inner working angle (IWA); (2) the apparent brightness of the planet depending on the orbital phase; (3) confusion arising from the presence of multiple planets; and (4) the planet-star contrast. In this paper we address the question: "Can a prior astrometric mission that can identify which stars have Earthlike planets significantly i...

  8. Autonomous optical navigation for orbits around Earth-Moon collinear libration points

    Virgili Llop, Josep

    2013-05-01

    The analysis of optical navigation in an Earth-Moon libration point orbit is examined. Missions to libration points have been winning momentum during the last decades. Its unique characteristics make it suitable for a number of operational and scientific goals. Literature aimed to study dynamics, guidance and control of unstable orbits around collinear libration points is vast. In particular, several papers deal with the optimisation of the Δv budget associated to the station-keeping of these orbits. One of the results obtained in literature establishes the critical character of the Moon-Earth system in this aspect. The reason for this behaviour is twofold: high Δv cost and short optimal manoeuvre spacing. Optical autonomous navigation can address the issue of allowing a more flexible manoeuvre design. This technology has been selected to overcome similar difficulties in other critical scenarios. This paper analyses in detail this solution. A whole GNC system is defined to meet the requirements imposed by the unstable dynamic environment. Finally, a real simulation of a spacecraft following a halo orbit of the L2 Moon-Earth system is carried out to assess the actual capabilities of the optical navigation in this scenario.

  9. Orbital Simulations on Deflecting Near-Earth Objects by Directed Energy

    Zhang, Qicheng; Melis, Carl; Hughes, Gary B; Lubin, Philip M

    2016-01-01

    Laser ablation of a Near-Earth Object (NEO) on a collision course with Earth produces a cloud of ejecta which exerts a thrust on the NEO, deflecting it from its original trajectory. Ablation may be performed from afar by illuminating an Earth-targeting asteroid or comet with a stand-off "DE- STAR" system consisting of a large phased-array laser in Earth orbit. Alternatively, a much smaller stand-on "DE-STARLITE" system may travel alongside the target, slowly deflecting it from nearby over a long period. This paper presents orbital simulations comparing the effectiveness of both systems across a range of laser and NEO parameters. Simulated parameters include magnitude, duration and, for the stand-on system, direction of the thrust, as well as the type, size and orbital characteristics of the target NEO. These simulations indicate that deflection distance is approximately proportional to the magnitude of thrust and to the square of the duration of ablation, and is inversely proportional to the mass. Furthermore...

  10. Prevalence of Earth-size planets orbiting Sun-like stars

    Petigura, Erik A; Marcy, Geoffrey W

    2013-01-01

    Determining whether Earth-like planets are common or rare looms as a touchstone in the question of life in the universe. We searched for Earth-size planets that cross in front of their host stars by examining the brightness measurements of 42,000 stars from National Aeronautics and Space Administration's Kepler mission. We found 603 planets, including 10 that are Earth size (1-2 Earth-radii) and receive comparable levels of stellar energy to that of Earth (within a factor of four). We account for Kepler's imperfect detectability of such planets by injecting synthetic planet-caused dimmings into the Kepler brightness measurements and recording the fraction detected. We find that $11\\pm4%$ of Sun-like stars harbor an Earth-size planet receiving between one and four times the stellar intensity as Earth. We also find that the occurrence of Earth-size planets is constant with increasing orbital period (P), within equal intervals of logP up to $\\sim200$ d. Extrapolating, one finds $5.7^{+1.7}_{-2.2}%$ of Sun-like s...

  11. Application of X-Ray Pulsar Navigation: A Characterization of the Earth Orbit Trade Space

    Yu, Wayne

    2016-01-01

    The potential for pulsars as a navigation source has been studied since their discovery in 1967. X-ray pulsar navigation (XNAV) is a celestial navigation system that uses the consistent timing nature of x-ray photons from milli-second pulsars (MSP) to perform space navigation. By comparing the detected arrival of x-ray photons to a reference database of expected pulsar lightcurve timing models, one can infer a range and range rate measurement based on light time delay. Much of the challenge of XNAV comes from the faint signal, availability, and distant nature of pulsars. This is a study of potential pulsar XNAV measurements to measure extended Kalman filter (EKF) tracking performance with a wide trade space of bounded Earth orbits, using a simulation of existing x-ray detector space hardware. An example of an x-ray detector for XNAV is the NASA Station Explorer for X-ray Timing and Navigation (SEXTANT) mission, a technology demonstration of XNAV set to perform on the International Space Station (ISS) in late 2016early 2017. XNAV hardware implementation is driven by trajectory and environmental influences which add noise to the x-ray pulse signal. In a closed Earth orbit, the radiation environment can exponentially increase the signal noise from x-ray pulsar sources, decreasing the quality and frequency of measurements. The SEXTANT mission in particular improves on the signal to noise ratio by focusing an array of 56 x-ray silicon drift detectors at one pulsar target at a time. This reduces timing glitches and other timing noise contributions from ambient x-ray sources to within a 100 nanosecond resolution. This study also considers the SEXTANT scheduling challenges inherent in a single target observation. Finally, as the navigation sources are now relatively inertial targets, XNAV measurements are also subject to periods of occultation from various celestial bodies. This study focuses on the characterization of these drivers in closed Earth orbits and is not a

  12. Galileo view of Moon orbiting the Earth taken from 3.9 million miles

    1992-01-01

    Eight days after its encounter with the Earth, the Galileo spacecraft was able to look back and capture this remarkable view of the Moon in orbit about the Earth, taken from a distance of about 6.2 million kilometers (3.9 million miles). The picture was constructed from images taken through the violet, red, and 1.0-micron infrared filters. The Moon is in the foreground, moving from left to right. The brightly-colored Earth contrasts strongly with the Moon, which reflects only about one-third as much sunlight as the Earth. Contrast and color have been computer-enhanced for both objects to improve visibility. Antarctica is visible through clouds (bottom). The Moon's far side is seen; the shadowy indentation in the dawn terminator is the south-Pole/Aitken Basin, one of the largest and oldest lunar impact features. Alternate Jet Propulsion Laboratory (JPL) number is P-41508.

  13. Design Concepts for a Small Space-Based GEO Relay Satellite for Missions Between Low Earth and near Earth Orbits

    Bhasin, Kul B.; Warner, Joseph D.; Oleson, Steven; Schier, James

    2014-01-01

    The main purpose of the Small Space-Based Geosynchronous Earth orbiting (GEO) satellite is to provide a space link to the user mission spacecraft for relaying data through ground networks to user Mission Control Centers. The Small Space Based Satellite (SSBS) will provide services comparable to those of a NASA Tracking Data Relay Satellite (TDRS) for the same type of links. The SSBS services will keep the user burden the same or lower than for TDRS and will support the same or higher data rates than those currently supported by TDRS. At present, TDRSS provides links and coverage below GEO; however, SSBS links and coverage capability to above GEO missions are being considered for the future, especially for Human Space Flight Missions (HSF). There is also a rising need for the capability to support high data rate links (exceeding 1 Gbps) for imaging applications. The communication payload on the SSBS will provide S/Ka-band single access links to the mission and a Ku-band link to the ground, with an optical communication payload as an option. To design the communication payload, various link budgets were analyzed and many possible operational scenarios examined. To reduce user burden, using a larger-sized antenna than is currently in use by TDRS was considered. Because of the SSBS design size, it was found that a SpaceX Falcon 9 rocket could deliver three SSBSs to GEO. This will greatly reduce the launch costs per satellite. Using electric propulsion was also evaluated versus using chemical propulsion; the power system size and time to orbit for various power systems were also considered. This paper will describe how the SSBS will meet future service requirements, concept of operations, and the design to meet NASA users' needs for below and above GEO missions. These users' needs not only address the observational mission requirements but also possible HSF missions to the year 2030. We will provide the trade-off analysis of the communication payload design in terms of

  14. Use and Protection of GPS Sidelobe Signals for Enhanced Navigation Performance in High Earth Orbit

    Parker, Joel J. K.; Valdez, Jennifer E.; Bauer, Frank H.; Moreau, Michael C.

    2016-01-01

    GPS (Global Positioning System) Space Service Volume (SSV) signal environment is from 3,000-36,000 kilometers altitude. Current SSV specifications only capture performance provided by signals transmitted within 23.5(L1) or 26(L2-L5) off-nadir angle. Recent on-orbit data lessons learned show significant PNT (Positioning, Navigation and Timing) performance improvements when the full aggregate signal is used. Numerous military civil operational missions in High Geosynchronous Earth Orbit (HEOGEO) utilize the full signal to enhance vehicle PNT performance

  15. Geosynchronous earth orbit/low earth orbit space object inspection and debris disposal: A preliminary analysis using a carrier satellite with deployable small satellites

    Crockett, Derick

    Detailed observations of geosynchronous satellites from earth are very limited. To better inspect these high altitude satellites, the use of small, refuelable satellites is proposed. The small satellites are stationed on a carrier platform in an orbit near the population of geosynchronous satellites. A carrier platform equipped with deployable, refuelable SmallSats is a viable option to inspect geosynchronous satellites. The propellant requirement to transfer to a targeted geosynchronous satellite, perform a proximity inspection mission, and transfer back to the carrier platform in a nearby orbit is determined. Convex optimization and traditional optimization techniques are explored, determining minimum propellant trajectories. Propellant is measured by the total required change in velocity, delta-v. The trajectories were modeled in a relative reference frame using the Clohessy-Wiltshire equations. Mass estimations for the carrier platform and the SmallSat were determined by using the rocket equation. The mass estimates were compared to the mass of a single, non-refuelable satellite performing the same geosynchronous satellite inspection missions. From the minimum delta-v trajectories and the mass analysis, it is determined that using refuelable SmallSats and a carrier platform in a nearby orbit can be more efficient than using a single non-refuelable satellite to perform multiple geosynchronous satellite inspections.

  16. Returning an Entire Near-Earth Asteroid in Support of Human Exploration Beyond Low-Earth Orbit

    Brophy, John R.; Friedman, Louis

    2012-01-01

    This paper describes the results of a study into the feasibility of identifying, robotically capturing, and returning an entire Near-Earth Asteroid (NEA) to the vicinity of the Earth by the middle of the next decade. The feasibility of such an asteroid retrieval mission hinges on finding an overlap between the smallest NEAs that could be reasonably discovered and characterized and the largest NEAs that could be captured and transported in a reasonable flight time. This overlap appears to be centered on NEAs roughly 7 m in diameter corresponding to masses in the range of 250,000 kg to 1,000,000 kg. The study concluded that it would be possible to return a approx.500,000-kg NEA to high lunar orbit by around 2025. The feasibility is enabled by three key developments: the ability to discover and characterize an adequate number of sufficiently small near-Earth asteroids for capture and return; the ability to implement sufficiently powerful solar electric propulsion systems to enable transportation of the captured NEA; and the proposed human presence in cislunar space in the 2020s enabling exploration and exploitation of the returned NEA. Placing a 500-t asteroid in high lunar orbit would provide a unique, meaningful, and affordable destination for astronaut crews in the next decade. This disruptive capability would have a positive impact on a wide range of the nation's human space exploration interests. It would provide a high-value target in cislunar space that would require a human presence to take full advantage of this new resource. It would offer an affordable path to providing operational experience with astronauts working around and with a NEA that could feed forward to much longer duration human missions to larger NEAs in deep space. It represents a new synergy between robotic and human missions in which robotic spacecraft would retrieve significant quantities of valuable resources for exploitation by astronaut crews to enable human exploration farther out into

  17. The Use Of In-Orbit Data For Assessing The Loss In Solar Panel Performance Due To Orbital Debris In A Low Earth Orbit

    Kimber, Rick

    2011-10-01

    This paper studies how the growing issue of orbital debris in Low Earth Orbit is having an apparent effect on the solar panel electrical performance of satellites. Using the solar panel data from a micro-satellite Beijing-1, which has body mounted solar panels, it is able to discern that the solar cells of the leading panel in the ram direction are experiencing a higher rate of degradation than the cells on the other two panels. All panels will receive the same amount of ultra-violet radiation loss, particulate radiation degradation and natural micrometeroid loss, regardless of their orientation. This difference in degradation is most likely explained by the leading panel receiving a lot more man-made orbital debris impacts onto the coverglass and cells which will degrade the optical performance. It is therefore recommended that for body mounted panels the design loss factors due to orbital debris may have to be varied in the future depending on the position on the spacecraft.

  18. Trapped proton fluxes at low Earth orbits measured by the PAMELA experiment

    Adriani, O; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bruno, A; Cafagna, F; Campana, D; Carbone, R; Carlson, P; Casolino, M; Castellini, G; Danilchenko, I A; De Donato, C; De Santis, C; De Simone, N; Di Felice, V; Formato, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N; Zverev, V G

    2014-01-01

    We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above > 70 MeV performed by the PAMELA mission at low Earth orbits (350-610 km). Data were analyzed in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.

  19. Measuring the eccentricity of the Earth orbit with a nail and a piece of plywood

    Lahaye, Thierry

    2012-01-01

    I describe how to obtain a rather good experimental determination of the eccentricity of the Earth orbit, as well as the obliquity of the Earth rotation axis, by measuring, over the course of a year, the elevation of the Sun as a function of time during a day. With a very simple "instrument" consisting of an elementary sundial, first-year students can carry out an appealing measurement programme, learn important concepts in experimental physics, see concrete applications of kinematics and changes of reference frames, and benefit from a hands-on introduction to astronomy.

  20. Low earth orbit environmental effects on the space station photovoltaic power generation systems

    A summary of the Low Earth Orbital Environment, its impact on the photovoltaic power systems of the space station and the solutions implemented to resolve the environmental concerns or issues are described. Low Earth Orbital Environment (LEO) presents several concerns to the photovoltaic power systems of the space station. These concerns include atomic oxygen interaction with the polymeric substrate of the solar arrays, ionized environment effects on the array operating voltage, the effects of the meteoroids and debris impacts and penetration through the different layers of the solar cells and their circuits, and the high energy particle and radiation effects on the overall solar array performance. Potential solutions to some of the degrading environmental interactions that will provide the photovoltaic power system of the space station with the desired life are also summarized

  1. Improved model for solar cosmic ray exposure in manned Earth orbital flights

    Wilson, John W.; Nealy, John E.; Atwell, William; Cucinotta, Francis A.; Shinn, Judy L.; Townsend, Lawrence W.

    1990-01-01

    A calculational model is derived for use in estimating Solar cosmic ray exposure to critical body organs in low-Earth orbit at the center of a large spherical shield of fixed thickness. The effects of the Earth's geomagnetic field and the astronauts' self-shielding are evaluated explicitly. The geomagnetic field model is an approximate tilted eccentric dipole with geomagnetic storms represented as a uniform-impressed field. The storm field is related to the planetary geomagnetic index K(sub p). The code is applied to the Shuttle geometry using the Shuttle mass distribution surrounding two locations on the flight deck. The Shuttle is treated as pure aluminum and the astronaut as soft tissue. Short-term, average fluence over a single orbit is calculated as a function of the location of the lines of nodes or long-term averages over all lines of nodes for a fixed inclination.

  2. Analytical investigation of the dynamics of tethered constellations in Earth orbit, phase 2

    Lorenzini, Enrico C.; Gullahorn, Gordon E.; Cosmo, Mario L.; Estes, Robert D.; Grossi, Mario D.

    1994-01-01

    This final report covers nine years of research on future tether applications and on the actual flights of the Small Expendable Deployment System (SEDS). Topics covered include: (1) a description of numerical codes used to simulate the orbital and attitude dynamics of tethered systems during station keeping and deployment maneuvers; (2) a comparison of various tethered system simulators; (3) dynamics analysis, conceptual design, potential applications and propagation of disturbances and isolation from noise of a variable gravity/microgravity laboratory tethered to the Space Station; (4) stability of a tethered space centrifuge; (5) various proposed two-dimensional tethered structures for low Earth orbit for use as planar array antennas; (6) tethered high gain antennas; (7) numerical calculation of the electromagnetic wave field on the Earth's surface on an electrodynamically tethered satellite; (8) reentry of tethered capsules; (9) deployment dynamics of SEDS-1; (10) analysis of SEDS-1 flight data; and (11) dynamics and control of SEDS-2.

  3. The BioSentinel Bioanalytical Microsystem: Characterizing DNA Radiation Damage in Living Organisms Beyond Earth Orbit

    Ricco, A. J.; Hanel, R.; Bhattacharya, S.; Boone, T.; Tan, M.; Mousavi, A.; Rademacher, A.; Schooley, A.; Klamm, B.; Benton, J.; Padgen, M.; Gentry, D.; Friedericks, C.; Defouw, G.; Parra, M.; Santa Maria, S.; Marina, D.; Swan, B. G.; Wheeler, S.; Gavalas, S.; Lewis, B.; Sanchez, H.; Chartres, J.; Lusby, T.

    2016-01-01

    We will present details and initial lab test results from an integrated bioanalytical microsystem designed to conduct the first biology experiments beyond low Earth orbit (LEO) since Apollo 17 (1972). The 14-kg, 12x24x37-cm BioSentinel spacecraft (Figure 1) assays radiation-responsive yeast in its science payload by measuring DNA double-strand breaks (DSBs) repaired via homologous recombination, a mechanism common to all eukaryotes including humans. S. cerevisiae (brewer's yeast) in 288 microwells are provided with nutrient and optically assayed for growth and metabolism via 3-color absorptimetry monthly during the 18-month mission. BioSentinel is one of several secondary payloads to be deployed by NASA's Exploration Mission 1 (EM-1) launch vehicle into approximately 0.95 AU heliocentric orbit in July 2018; it will communicate with Earth from up to 100 million km.

  4. FLUKA Calculation of the Neutron Albedo Encountered at Low Earth Orbits

    Claret, Arnaud; Combier, Natacha; Ferrari, Alfredo; Laurent, Philippe

    2014-01-01

    This paper presents Monte-Carlo simulations based on the Fluka code aiming to calculate the contribution of the neutron albedo at a given date and altitude above the Earth chosen by the user. The main input parameters of our model are the solar modulation affecting the spectra of cosmic rays, and the date of the Earth’s geomagnetic fi eld. The results consist in a two-parameter distribution, the neutron energy and the angle to the tangent plane of the sphere containing the orbi t of interest, and are provided by geographical position above the E arth at the chosen altitude. This model can be used to predict the te mporal variation of the neutron fl ux encountered along the orbit, and thus constrain the determination of the instrumental backg round noise of space experiments in low earth orbit.

  5. Possible Effect of the Earth's Inertial Induction on the Orbital Decay of LAGEOS

    Dey, Ujjal; Kar, Samanwita; Ghosh, Amitabha

    2016-09-01

    The theory of velocity dependent inertial induction, based upon extended Mach's principle, has been able to generate many interesting results related to celestial mechanics and cosmological problems. Because of the extremely minute magnitude of the effect its presence can be detected through the motion of accurately observed bodies like Earth satellites. LAGEOS I and II are medium altitude satellites with nearly circular orbits. The motions of these satellites are accurately recorded and the past data of a few decades help to test many theories including the general theory of relativity. Therefore, it is hoped that the effect of the Earth's inertial induction can have any detectable effect on the motion of these satellites. It is established that the semi-major axis of LAGEOS I is decreasing at the rate of 1.3 mm/d. As the atmospheric drag is negligible at that altitude, a proper explanation of the secular change has been wanting, and, therefore, this paper examines the effect of the Earth's inertial induction effect on LAGEOS I. Past researches have established that Yarkovsky thermal drag, charged and neutral particle drag might be the possible mechanisms for this orbital decay. Inertial induction is found to generate a perturbing force that results in 0.33 mm/d decay of the semi major axis. Some other changes are also predicted and the phenomenon also helps to explain the observed changes in the orbits of a few other satellites. The results indicate the feasibility of the theory of inertial induction i.e. the dynamic gravitation phenomenon of the Earth on its satellites as a possible partial cause for orbital decay.

  6. Do slow orbital periodicities appear in the record of earth's magnetic reversals?

    Stothers, Richard B.

    1987-01-01

    Time-series spectral analysis has been performed on the dates of geomagnetic reversals of the last 20 Myr BP and earlier. Possible evidence is found from the presence of high spectral peaks for two very long periodicities, 0.4 Myr and 1.3 Myr, that may be associated with slow variations of the earth's orbital eccentricity as predicted by Berger. However, statistical significance tests and a number of other arguments do not confirm the two detections.

  7. Characteristic of the radiation field in low Earth orbit and in deep space.

    Reitz, Guenther

    2008-01-01

    The radiation exposure in space by cosmic radiation can be reduced through careful mission planning and constructive measures as example the provision of a radiation shelter, but it cannot be completely avoided. The reason for that are the extreme high energies of particles in this field and the herewith connected high penetration depth in matter. For missions outside the magnetosphere ionizing radiation is recognized as the key factor through its impact on crew health and performance. In absence of sporadic solar particle events the radiation exposure in Low Earth orbit (LEO) inside Spacecraft is determined by the galactic cosmic radiation (protons and heavier ions) and by the protons inside the South Atlantic Anomaly (SAA), an area where the radiation belt comes closer to the earth surface due to a displacement of the magnetic dipole axes from the Earth's center. In addition there is an albedo source of neutrons produced as interaction products of the primary galactic particles with the atoms of the earth atmosphere. Outside the spacecraft the dose is dominated by the electrons of the horns of the radiation belt located at about 60" latitude in Polar Regions. The radiation field has spatial and temporal variations in dependence of the Earth magnetic field and the solar cycle. The complexity of the radiation field inside a spacecraft is further increased through the interaction of the high energy components with the spacecraft shielding material and with the body of the astronauts. In interplanetary missions the radiation belt will be crossed in a couple of minutes and therefore its contribution to their radiation exposure is quite small, but subsequently the protection by the Earth magnetic field is lost, leaving only shielding measures as exposure reduction means. The report intends to describe the radiation field in space, the interaction of the particles with the magnetic field and shielding material and give some numbers on the radiation exposure in low earth

  8. Packet switching for mobile earth stations via low-orbit satellite network

    Brayer, K.

    1984-11-01

    An autonomous adaptive protocol for spaceborne computer communication in a self-configuring network is presented. The key concept is survivability, which could be achieved with a satellite ring located at orbits of 1000-4000 mi altitude. Each spacecraft would carry an on-board computer with algorithms which would guide automated reconfiguring of nodes should one satellite fail or be destroyed. Transmissions would then be uninterrupted for link between land and mobile stations. It is recommended that the orbits be at 50-60 deg inclinations. The spacecraft, boosted from the Orbiter, would be three-axis stabilized and would carry antennas pointing forward and backward along the ring and downward to earth. Message routing schemes based on ARPANET confirm that acceptable routes are attainable. The associated algorithm has been validated by experiments with routing data between six computers.

  9. Tidal Heating of Earth-like Exoplanets around M Stars: Thermal, Magnetic, and Orbital Evolutions

    Barnes, R.

    2015-01-01

    Abstract The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the “tidal zone,” where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a viscoelastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within 0.07 AU circularize before 10 Gyr, independent of initial eccentricity. Once circular, these planets cool monotonically and maintain dynamos similar to that of Earth. Planets forced into eccentric orbits can experience a super-cooling of the core and rapid core solidification, inhibiting dynamo action for planets in the habitable zone. We find that tidal heating is insignificant in the habitable zone around 0.45 (or larger) solar-mass stars because tidal dissipation is a stronger function of orbital distance than stellar mass, and the habitable zone is farther from larger stars. Suppression of the planetary magnetic field exposes the atmosphere to stellar wind erosion and the surface to harmful radiation. In addition to weak magnetic fields, massive melt eruption rates and prolonged magma oceans may render eccentric planets in the habitable zone of low-mass stars inhospitable for life. Key Words

  10. Prevalence of Earth-size Planets Orbiting Sun-like Stars

    Petigura, Erik Ardeshir

    2015-01-01

    In this thesis, I explore two topics in exoplanet science. The first is the prevalence of Earth-size planets in the Milky Way Galaxy. To determine the occurrence of planets having different sizes, orbital periods, and other properties, I conducted a survey of extrasolar planets using data collected by NASA's Kepler Space Telescope. This project involved writing new algorithms to analyze Kepler data, finding planets, and conducting follow-up work using ground-based telescopes. I found that most stars have at least one planet at or within Earth's orbit and that 26% of Sun-like stars have an Earth-size planet with an orbital period of 100 days or less. The second topic is the connection between the properties of planets and their host stars. The precise characterization of exoplanet hosts helps to bring planet properties like mass, size, and equilibrium temperature into sharper focus and probes the physical processes that form planets. I studied the abundance of carbon and oxygen in over 1000 nearby stars using ...

  11. Transverse and Longitudinal Doppler Effects of the Sunbeam Spectra and Earth-Self Rotation and Orbital Velocities, the Mass of the Sun and Others

    Nam, Sang Boo

    2009-01-01

    The transverse and longitudinal Doppler effects of the sunbeam spectra are shown to result in the earth parameters such as the earth-self rotation and revolution velocities, the earth orbit semi-major axis, the earth orbital angular momentum, the earth axial tilt, the earth orbit eccentricity, the local latitude and the mass of the sun. The sunbeam global positioning scheme is realized, including the earth orbital position. PACS numbers: 91.10.Fc, 95.10.Km, 91.10.Da, 91.10.Jf.

  12. THE OCCURRENCE RATE OF EARTH ANALOG PLANETS ORBITING SUN-LIKE STARS

    Kepler is a space telescope that searches Sun-like stars for planets. Its major goal is to determine ηEarth, the fraction of Sun-like stars that have planets like Earth. When a planet 'transits' or moves in front of a star, Kepler can measure the concomitant dimming of the starlight. From analysis of the first four months of those measurements for over 150,000 stars, Kepler's Science Team has determined sizes, surface temperatures, orbit sizes, and periods for over a thousand new planet candidates. In this paper, we characterize the period probability distribution function of the super-Earth and Neptune planet candidates with periods up to 132 days, and find three distinct period regimes. For candidates with periods below 3 days, the density increases sharply with increasing period; for periods between 3 and 30 days, the density rises more gradually with increasing period, and for periods longer than 30 days, the density drops gradually with increasing period. We estimate that 1%-3% of stars like the Sun are expected to have Earth analog planets, based on the Kepler data release of 2011 February. This estimate of ηEarth is based on extrapolation from a fiducial subsample of the Kepler planet candidates that we chose to be nominally 'complete' (i.e., no missed detections) to the realm of the Earth-like planets, by means of simple power-law models. The accuracy of the extrapolation will improve as more data from the Kepler mission are folded in. Accurate knowledge of ηEarth is essential for the planning of future missions that will image and take spectra of Earth-like planets. Our result that Earths are relatively scarce means that a substantial effort will be needed to identify suitable target stars prior to these future missions.

  13. Two Transiting Earth-size Planets Near Resonance Orbiting a Nearby Cool Star

    Petigura, Erik A; Crossfield, Ian J M; Howard, Andrew W; Deck, Katherine M; Ciardi, David R; Sinukoff, Evan; Allers, Katelyn N; Best, William M J; Liu, Michael C; Beichman, Charles A; Isaacson, Howard; Hansen, Brad M S; Lépine, Sébastien

    2015-01-01

    Discoveries from the prime Kepler mission demonstrated that small planets (< 3 Earth-radii) are common outcomes of planet formation. While Kepler detected many such planets, all but a handful orbit faint, distant stars and are not amenable to precise follow up measurements. Here, we report the discovery of two small planets transiting EPIC-206011691, a bright (K = 9.4) M0 dwarf located 65$\\pm$6 pc from Earth. We detected the transiting planets in photometry collected during Campaign 3 of NASA's K2 mission. Analysis of transit light curves reveals that the planets have small radii compared to their host star, 2.60 $\\pm$ 0.14% and 3.15 $\\pm$ 0.20%, respectively. We obtained follow up NIR spectroscopy of \\epic to constrain host star properties, which imply planet sizes of 1.59 $\\pm$ 0.43 Earth-radii and 1.92 $\\pm$ 0.53 Earth-radii, respectively, straddling the boundary between high-density, rocky planets and low-density planets with thick gaseous envelopes. The planets have orbital periods of 9.32414 days and...

  14. An isoflux antenna for a low earth orbit satellite mobile communication system

    Tsao, C.-H. A.; Jung, P.; Raguenet, G.

    1992-03-01

    In this paper a satellite antenna for a low earth orbit satellite mobile communication system is described. The proposed communication system employs TDD-FD-CDMA (time division duplexing-frequency division-code division multiple access) technique which imposes certain constraints on the antenna design. The antenna discussed in this paper employs six spot beams in conjunction with the CDMA technology to allow the frequency spectrum reuse. The antenna radiation pattern in each beam is shaped to compensate for the path loss differences caused by the slant range differences from the spacecraft to different points on earth. This design provides an isometric radiation flux density on earth within each beam to mitigate the potential near/far problems in a CDMA system. Additional constraints on the antenna design include low profile, light weight and easy deployment to meet the requirements of small satellite implementation of the system.

  15. Orbital Simulations on Deflecting Near-Earth Objects by Directed Energy

    Zhang, Qicheng; Walsh, Kevin J.; Melis, Carl; Hughes, Gary B.; Lubin, Philip M.

    2016-04-01

    Laser ablation of a near-Earth object (NEO) on a collision course with Earth produces a cloud of ejecta that exerts a thrust on the NEO, deflecting it from its original trajectory. Ablation may be performed from afar by illuminating an Earth-targeting asteroid or comet with a stand-off “DE-STAR” system consisting of a large phased-array laser in Earth orbit. Alternatively, a much smaller stand-on “DE-STARLITE” system may travel alongside the target, slowly deflecting it from nearby over a long period. This paper presents orbital simulations comparing the effectiveness of both systems across a range of laser and NEO parameters. Simulated parameters include magnitude, duration and, for the stand-on system, direction of the thrust, as well as the type, size, and orbital characteristics of the target NEO. These simulations indicate that deflection distance is approximately proportional to the magnitude of thrust and to the square of the duration of ablation, and is inversely proportional to the mass. Furthermore, deflection distance shows strong dependence on thrust direction with the optimal direction of thrust varying with the duration of laser activity. As one example, consider a typical 325 m asteroid: beginning 15 years in advance, just 2 N of thrust from a ∼20 kW stand-on DE-STARLITE system is sufficient to deflect the asteroid by 2 {R}\\oplus . Numerous scenarios are discussed as is a practical implementation of such a system consistent with current launch vehicle capabilities.

  16. Trapped Proton Environment in Medium-Earth Orbit (2000-2010)

    This report describes the method used to derive fluxes of the trapped proton belt along the GPS orbit (i.e., a Medium-Earth Orbit) during 2000 - 2010, a period almost covering a solar cycle. This method utilizes a newly developed empirical proton radiation-belt model, with the model output scaled by GPS in-situ measurements, to generate proton fluxes that cover a wide range of energies (50keV- 6MeV) and keep temporal features as well. The new proton radiation-belt model is developed based upon CEPPAD proton measurements from the Polar mission (1996 - 2007). Comparing to the de-facto standard empirical model of AP8, this model is not only based upon a new data set representative of the proton belt during the same period covered by GPS, but can also provide statistical information of flux values such as worst cases and occurrence percentiles instead of solely the mean values. The comparison shows quite different results from the two models and suggests that the commonly accepted error factor of 2 on the AP8 flux output over-simplifies and thus underestimates variations of the proton belt. Output fluxes from this new model along the GPS orbit are further scaled by the ns41 in-situ data so as to reflect the dynamic nature of protons in the outer radiation belt at geomagnetically active times. Derived daily proton fluxes along the GPS ns41 orbit, whose data files are delivered along with this report, are depicted to illustrate the trapped proton environment in the Medium-Earth Orbit. Uncertainties on those daily proton fluxes from two sources are evaluated: One is from the new proton-belt model that has error factors < ~3; the other is from the in-situ measurements and the error factors could be ~ 5.

  17. Trapped Proton Environment in Medium-Earth Orbit (2000-2010)

    Chen, Yue [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Friedel, Reinhard Hans [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kippen, Richard Marc [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-31

    This report describes the method used to derive fluxes of the trapped proton belt along the GPS orbit (i.e., a Medium-Earth Orbit) during 2000 – 2010, a period almost covering a solar cycle. This method utilizes a newly developed empirical proton radiation-belt model, with the model output scaled by GPS in-situ measurements, to generate proton fluxes that cover a wide range of energies (50keV- 6MeV) and keep temporal features as well. The new proton radiation-belt model is developed based upon CEPPAD proton measurements from the Polar mission (1996 – 2007). Comparing to the de-facto standard empirical model of AP8, this model is not only based upon a new data set representative of the proton belt during the same period covered by GPS, but can also provide statistical information of flux values such as worst cases and occurrence percentiles instead of solely the mean values. The comparison shows quite different results from the two models and suggests that the commonly accepted error factor of 2 on the AP8 flux output over-simplifies and thus underestimates variations of the proton belt. Output fluxes from this new model along the GPS orbit are further scaled by the ns41 in-situ data so as to reflect the dynamic nature of protons in the outer radiation belt at geomagnetically active times. Derived daily proton fluxes along the GPS ns41 orbit, whose data files are delivered along with this report, are depicted to illustrate the trapped proton environment in the Medium-Earth Orbit. Uncertainties on those daily proton fluxes from two sources are evaluated: One is from the new proton-belt model that has error factors < ~3; the other is from the in-situ measurements and the error factors could be ~ 5.

  18. Determination of Eros Physical Parameters for Near Earth Asteroid Rendezvous Orbit Phase Navigation

    Miller, J. K.; Antreasian, P. J.; Georgini, J.; Owen, W. M.; Williams, B. G.; Yeomans, D. K.

    1995-01-01

    Navigation of the orbit phase of the Near Earth steroid Rendezvous (NEAR) mission will re,quire determination of certain physical parameters describing the size, shape, gravity field, attitude and inertial properties of Eros. Prior to launch, little was known about Eros except for its orbit which could be determined with high precision from ground based telescope observations. Radar bounce and light curve data provided a rough estimate of Eros shape and a fairly good estimate of the pole, prime meridian and spin rate. However, the determination of the NEAR spacecraft orbit requires a high precision model of Eros's physical parameters and the ground based data provides only marginal a priori information. Eros is the principal source of perturbations of the spacecraft's trajectory and the principal source of data for determining the orbit. The initial orbit determination strategy is therefore concerned with developing a precise model of Eros. The original plan for Eros orbital operations was to execute a series of rendezvous burns beginning on December 20,1998 and insert into a close Eros orbit in January 1999. As a result of an unplanned termination of the rendezvous burn on December 20, 1998, the NEAR spacecraft continued on its high velocity approach trajectory and passed within 3900 km of Eros on December 23, 1998. The planned rendezvous burn was delayed until January 3, 1999 which resulted in the spacecraft being placed on a trajectory that slowly returns to Eros with a subsequent delay of close Eros orbital operations until February 2001. The flyby of Eros provided a brief glimpse and allowed for a crude estimate of the pole, prime meridian and mass of Eros. More importantly for navigation, orbit determination software was executed in the landmark tracking mode to determine the spacecraft orbit and a preliminary shape and landmark data base has been obtained. The flyby also provided an opportunity to test orbit determination operational procedures that will be

  19. The Near-Earth Orbital Debris Problem and the Challenges for Environment Remediation

    Liou, Jer-Chyi

    2012-01-01

    The near-Earth space environment has been gradually polluted with orbital debris (OD) since the beginning of space activities 55 years ago. Although this problem has been known to the research community for decades, the public was, in general, unaware of the issue until the anti-satellite test conducted by China in 2007 and the collision between Cosmos 2251 and the operational Iridium 33 in 2009. The latter also underlined the potential of an ongoing collision cascade effect (the "Kessler Syndrome") in the low Earth orbit (LEO, the region below 2000 km altitude). Recent modeling results have indicated that mitigation measures commonly adopted by the international space community will be insufficient to stabilize the LEO debris population. To better limit the OD population increase, more aggressive actions must be considered. There are three options for OD environment remediation-removal of large/massive intact objects to address the root cause of the OD population growth problem, removal of 5-mm-to-1 cm debris to mitigate the main mission-ending threats for the majority of operational spacecraft, and prevention of major debris-generating collisions as a temporary means to slow down the OD population increase. The technology, engineering, and cost challenges to carry out any of these three options are monumental. It will require innovative ideas, game-changing technologies, and major collaborations at the international level to address the OD problem and preserve the near-Earth environment for future generations.

  20. THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

    Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for ∼8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 102 (104) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M☉ white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

  1. THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

    Fossati, L.; Haswell, C. A.; Patel, M. R.; Busuttil, R. [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Bagnulo, S. [Armagh Observatory, College Hill, Armagh BT61 9DG (United Kingdom); Kowalski, P. M. [GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam (Germany); Shulyak, D. V. [Institute of Astrophysics, Georg-August-University, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Sterzik, M. F., E-mail: l.fossati@open.ac.uk, E-mail: C.A.Haswell@open.ac.uk, E-mail: M.R.Patel@open.ac.uk, E-mail: r.busuttil@open.ac.uk, E-mail: sba@arm.ac.uk, E-mail: kowalski@gfz-potsdam.de, E-mail: denis.shulyak@gmail.com, E-mail: msterzik@eso.org [European Southern Observatory, Casilla 19001, Santiago 19 (Chile)

    2012-09-20

    Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for {approx}8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 10{sup 2} (10{sup 4}) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M{sub Sun} white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

  2. A real-time guidance algorithm for aerospace plane optimal ascent to low earth orbit

    Calise, A. J.; Flandro, G. A.; Corban, J. E.

    1989-01-01

    Problems of onboard trajectory optimization and synthesis of suitable guidance laws for ascent to low Earth orbit of an air-breathing, single-stage-to-orbit vehicle are addressed. A multimode propulsion system is assumed which incorporates turbojet, ramjet, Scramjet, and rocket engines. An algorithm for generating fuel-optimal climb profiles is presented. This algorithm results from the application of the minimum principle to a low-order dynamic model that includes angle-of-attack effects and the normal component of thrust. Maximum dynamic pressure and maximum aerodynamic heating rate constraints are considered. Switching conditions are derived which, under appropriate assumptions, govern optimal transition from one propulsion mode to another. A nonlinear transformation technique is employed to derived a feedback controller for tracking the computed trajectory. Numerical results illustrate the nature of the resulting fuel-optimal climb paths.

  3. Measured force on elongated bodies in a simulated low-Earth orbit environment

    An overview of the development of a magnetically filtered atomic oxygen plasma source and the application of the source to study low-Earth orbit drag on elongated bodies is presented. Plasma diagnostics show that the magnetic filter plasma source produces atomic oxygen ions (O+) with streaming energies equivalent to the relative orbital environment of approximately 5eV and can supply the appropriate density for LEO simulation. Previous research has demonstrated that momentum transfer between ions and metal surfaces is equivalent to the momentum transfer expected for neutral molecules with similar energy, due to charge exchange occurring prior to momentum transfer. Total drag measurements of aluminum cuboid geometries of varying length to diameter ratios immersed in the extracted plasma plume are presented as a function of streaming ion energy

  4. Highly stable evolution of Earth's future orbit despite chaotic behavior of the Solar System

    Zeebe, Richard E

    2015-01-01

    Due to the chaotic nature of the Solar System, the question of its dynamic long-term stability can only be answered in a statistical sense, e.g. based on numerical ensemble integrations of nearby orbits. Destabilization, including catastrophic encounters and/or collisions involving the Earth, has been suggested to be initiated through a large increase in Mercury's eccentricity (eM), with an estimated probability of ~1%. However, it has recently been shown that the statistics of numerical Solar System integrations are sensitive to the accuracy and type of numerical algorithm. Here I report results from computationally demanding ensemble integrations (N=1,600 with slightly different initial conditions) at unprecedented accuracy based on the full equations of motion of the eight planets and Pluto over 5Gyr, including contributions from general relativity. The standard symplectic algorithm produced spurious results for highly eccentric orbits and during close encounters, which were hence integrated with a suitabl...

  5. Measured force on elongated bodies in a simulated low-Earth orbit environment

    Maldonado, C. A.; Ketsdever, A. D. [University of Colorado, Colorado Springs, CO 80918 (United States); Gimelshein, S. F. [University of Southern California, Los Angeles, CA 90033 (United States)

    2014-12-09

    An overview of the development of a magnetically filtered atomic oxygen plasma source and the application of the source to study low-Earth orbit drag on elongated bodies is presented. Plasma diagnostics show that the magnetic filter plasma source produces atomic oxygen ions (O{sup +}) with streaming energies equivalent to the relative orbital environment of approximately 5eV and can supply the appropriate density for LEO simulation. Previous research has demonstrated that momentum transfer between ions and metal surfaces is equivalent to the momentum transfer expected for neutral molecules with similar energy, due to charge exchange occurring prior to momentum transfer. Total drag measurements of aluminum cuboid geometries of varying length to diameter ratios immersed in the extracted plasma plume are presented as a function of streaming ion energy.

  6. Measured force on elongated bodies in a simulated low-Earth orbit environment

    Maldonado, C. A.; Ketsdever, A. D.; Gimelshein, S. F.

    2014-12-01

    An overview of the development of a magnetically filtered atomic oxygen plasma source and the application of the source to study low-Earth orbit drag on elongated bodies is presented. Plasma diagnostics show that the magnetic filter plasma source produces atomic oxygen ions (O+) with streaming energies equivalent to the relative orbital environment of approximately 5eV and can supply the appropriate density for LEO simulation. Previous research has demonstrated that momentum transfer between ions and metal surfaces is equivalent to the momentum transfer expected for neutral molecules with similar energy, due to charge exchange occurring prior to momentum transfer. Total drag measurements of aluminum cuboid geometries of varying length to diameter ratios immersed in the extracted plasma plume are presented as a function of streaming ion energy.

  7. Application of Spaceborne Infrared Atmospheric Sounder for Geosynchronous Earth Orbit (SIRAS-G) technology to future Earth science missions

    Kampe, Thomas U.

    2008-04-01

    The Spaceborne Infrared Sounder for Geosynchronous Earth Orbit (SIRAS-G) was developed by Ball Aerospace & Technologies Corp (BATC) under NASA's 2002 Instrument Incubator Program. SIRAS-G was a technology development program focused on next-generation IR imaging spectrometers for sounding of the atmosphere. SIRAS-G demonstrated that the dispersive grating spectrometer is a suitable instrument architecture for this application. In addition to providing atmospheric temperature and water vapor profiles, SIRAS-G can provide trace gases concentrations, land and ocean surface temperatures and the IR mineral dust aerosol signature from satellite. The 3-year SIRAS-G IIP development effort included the successful cryogenic testing of the SIRAS-G laboratory demonstration spectrometer operating in the 2083 to 2994 cm -1 frequency range. The performance of the demonstration instrument has been quantified including measurement of keystone distortion, spectral smile, MTF, and the spectral response function (SRF). Development efforts associated with this advanced infrared spectrometer technology provides the basis for instrumentation to support future Earth science missions.

  8. A Framework for Orbital Performance Evaluation in Distributed Space Missions for Earth Observation

    Nag, Sreeja; LeMoigne-Stewart, Jacqueline; Miller, David W.; de Weck, Olivier

    2015-01-01

    Distributed Space Missions (DSMs) are gaining momentum in their application to earth science missions owing to their unique ability to increase observation sampling in spatial, spectral and temporal dimensions simultaneously. DSM architectures have a large number of design variables and since they are expected to increase mission flexibility, scalability, evolvability and robustness, their design is a complex problem with many variables and objectives affecting performance. There are very few open-access tools available to explore the tradespace of variables which allow performance assessment and are easy to plug into science goals, and therefore select the most optimal design. This paper presents a software tool developed on the MATLAB engine interfacing with STK, for DSM orbit design and selection. It is capable of generating thousands of homogeneous constellation or formation flight architectures based on pre-defined design variable ranges and sizing those architectures in terms of predefined performance metrics. The metrics can be input into observing system simulation experiments, as available from the science teams, allowing dynamic coupling of science and engineering designs. Design variables include but are not restricted to constellation type, formation flight type, FOV of instrument, altitude and inclination of chief orbits, differential orbital elements, leader satellites, latitudes or regions of interest, planes and satellite numbers. Intermediate performance metrics include angular coverage, number of accesses, revisit coverage, access deterioration over time at every point of the Earth's grid. The orbit design process can be streamlined and variables more bounded along the way, owing to the availability of low fidelity and low complexity models such as corrected HCW equations up to high precision STK models with J2 and drag. The tool can thus help any scientist or program manager select pre-Phase A, Pareto optimal DSM designs for a variety of science

  9. Confirming the transit of the Earth-mass planet orbiting Alpha Centauri B

    Demory, Brice-Olivier

    2013-10-01

    One of the most fascinating exoplanet findings of the past years is undoubtedly the discovery of an Earth-mass exoplanet orbiting Alpha Centauri B. Alpha Cen Bb orbits one component of the closest stellar system to the Earth and has the potential to become a true Rosetta stone in exoplanet science, if its transiting nature were revealed. In 2013, we observed Alpha Centauri B during 16 orbits with HST/STIS to search for the transit of Alpha Cen Bb. We recently carried out in-depth photometric analyses of this dataset that resulted in the clear detection of a transit-shaped pattern. Several factors, however, prevent us from securing the planetary nature of the signal found in the STIS time-series. Now that we know where and when to look for, we propose to confirm the repeatability of this signal and to firmly establish Alpha Cen Bb's existence and tighten its physical and orbital properties. We base our observing strategy on the successful approach employed just one year ago with the same instrument. Until Aug 9th 2014, combination of HST available roll angles, Alpha Cen binary separation and position angle will match the nearly-ideal configuration we had in July 2013. It would even be possible to benefit from CVZ status from 24/7/2014 to 28/7/2014, in which one transit of Alpha Centauri Bb is expected. HST/STIS is the only facility able to confirm a transit from such a small planet at a high confidence level.

  10. Space Network IP Services (SNIS): An Architecture for Supporting Low Earth Orbiting IP Satellite Missions

    Israel, David J.

    2005-01-01

    The NASA Space Network (SN) supports a variety of missions using the Tracking and Data Relay Satellite System (TDRSS), which includes ground stations in White Sands, New Mexico and Guam. A Space Network IP Services (SNIS) architecture is being developed to support future users with requirements for end-to-end Internet Protocol (IP) communications. This architecture will support all IP protocols, including Mobile IP, over TDRSS Single Access, Multiple Access, and Demand Access Radio Frequency (RF) links. This paper will describe this architecture and how it can enable Low Earth Orbiting IP satellite missions.

  11. An optimum organizational structure for a large earth-orbiting multidisciplinary Space Base

    Ragusa, J. M.

    1973-01-01

    The purpose of this exploratory study was to identify an optimum hypothetical organizational structure for a large earth-orbiting multidisciplinary research and applications (R&A) Space Base manned by a mixed crew of technologists. Since such a facility does not presently exist, in situ empirical testing was not possible. Study activity was, therefore, concerned with the identification of a desired organizational structural model rather than the empirical testing of it. The essential finding of this research was that a four-level project type 'total matrix' model will optimize the efficiency and effectiveness of Space Base technologists.

  12. BioSentinel: Monitoring DNA Damage Repair Beyond Low Earth Orbit on a 6U Nanosatellite

    Lewis, Brian; Hanel, Robert; Bhattacharya, Sharmila; Ricco, Antonio; Agasid, Elwood; Reiss-Bubenheim, Debra; Straume, Tore; Parra, Macarena; Boone, Travis; Santa Maria, Sergio; Tan, Ming; Bowman, Robert; Sorgenfrei, Matthew; Nehrenz, Matthew; Gandlin, Marina

    2014-01-01

    We are designing and developing a “6U” nanosatellite as a secondary payload to fly aboard NASA’s Space Launch System (SLS) Exploration Mission (EM) 1, scheduled for launch in late 2017. For the first time in over forty years, direct experimental data from biological studies beyond low Earth orbit (LEO) will be obtained during BioSentinel’s 12 to 18-month mission. BioSentinel will measure the damage and repair of DNA in a biological organism and compare that to information from onboard physica...

  13. Hyperbolic orbits of Earth flybys and effects of ungravity-inspired conservative potentials

    Bertolami, O.; Francisco, F.; Gil, P. J. S.

    2016-06-01

    In this work we take a critical look at the available data on the flyby anomaly and on the current limitations of attempts to develop an explanation. We aim to verify how conservative corrections to gravity could affect the hyperbolic trajectories of Earth flybys. We use ungravity-inspired potentials as illustrative examples and show how the resulting orbital simulations differ from the observed anomaly. We also get constraints on the model parameters from the observed flyby velocity shifts. The conclusion is that no kind of conservative potential can be the cause of the flyby anomaly.

  14. Capturing asteroids into bound orbits around the earth: Massive early return on an asteroid terminal defense system

    Nuclear explosives may be used to capture small asteroids (e.g., 20--50 meters in diameter) into bound orbits around the earth. The captured objects could be used for construction material for manned and unmanned activity in Earth orbit. Asteroids with small approach velocities, which are the ones most likely to have close approaches to the Earth, require the least energy for capture. They are particularly easy to capture if they pass within one Earth radius of the surface of the Earth. They could be intercepted with intercontinental missiles if the latter were retrofit with a more flexible guiding and homing capability. This asteroid capture-defense system could be implemented in a few years at low cost by using decommissioned ICMs. The economic value of even one captured asteroid is many times the initial investment. The asteroid capture system would be an essential part of the learning curve for dealing with larger asteroids that can hit the earth

  15. TRAPPED PROTON FLUXES AT LOW EARTH ORBITS MEASURED BY THE PAMELA EXPERIMENT

    Adriani, O.; Bongi, M. [Department of Physics and Astronomy, University of Florence, I-50019 Sesto Fiorentino, Florence (Italy); Barbarino, G. C. [Department of Physics, University of Naples " Federico II," I-80126 Naples (Italy); Bazilevskaya, G. A. [Lebedev Physical Institute, RU-119991 Moscow (Russian Federation); Bellotti, R.; Bruno, A. [Department of Physics, University of Bari, I-70126 Bari (Italy); Boezio, M.; Bonvicini, V.; Carbone, R. [INFN, Sezione di Trieste, I-34149 Trieste (Italy); Bogomolov, E. A. [Ioffe Physical Technical Institute, RU-194021 St. Petersburg (Russian Federation); Bottai, S. [INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy); Cafagna, F. [INFN, Sezione di Bari, I-70126 Bari (Italy); Campana, D. [INFN, Sezione di Naples, I-80126 Naples (Italy); Carlson, P. [KTH, Department of Physics, and the Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691 Stockholm (Sweden); Casolino, M.; De Donato, C.; De Santis, C.; De Simone, N.; Felice, V. Di [INFN, Sezione di Rome " Tor Vergata," I-00133 Rome (Italy); Castellini, G., E-mail: alessandro.bruno@ba.infn.it [IFAC, I-50019 Sesto Fiorentino, Florence (Italy); and others

    2015-01-20

    We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above ∼70 MeV performed by the PAMELA mission at low Earth orbits (350 ÷ 610 km). Data were analyzed in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra, and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes, placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.

  16. A demonstration of the conservation of the orbital angular momentum of Earth

    Pellizza, Leonardo J.; Mayochi, Mariano G.; Ciocci Brazzano, Ligia; Pedrosa, Susana E.

    2015-12-01

    We describe a simple but quantitative experiment to demonstrate the conservation of angular momentum. We measure the correlation of the apparent radius and angular velocity of the Sun with respect to the stars, due to the conservation of the angular momentum of Earth in its orbit. We also determine the direction of Earth's angular momentum vector and show that it is conserved. The experiment can be performed using a small telescope and a digital camera. It is conceptually simple, allowing students to get direct physical insight from the data. The observations are performed near the resolution limit imposed by the atmosphere, and in the presence of strong competing effects. These effects necessitate a careful experimental setup and allow students to improve their skills in experimentation.

  17. Effect of rare earth metal on the spin-orbit torque in magnetic heterostructures

    Ueda, Kohei; Pai, Chi-Feng; Tan, Aik Jun; Mann, Maxwell; Beach, Geoffrey S. D.

    2016-06-01

    We report the effect of the rare earth metal Gd on current-induced spin-orbit torques (SOTs) in perpendicularly magnetized Pt/Co/Gd heterostructures, characterized using harmonic measurements and spin-torque ferromagnetic resonance (ST-FMR). By varying the Gd metal layer thickness from 0 nm to 8 nm, harmonic measurements reveal a significant enhancement of the effective fields generated from the Slonczewski-like and field-like torques. ST-FMR measurements confirm an enhanced effective spin Hall angle and show a corresponding increase in the magnetic damping constant with increasing Gd thickness. These results suggest that Gd plays an active role in generating SOTs in these heterostructures. Our finding may lead to spin-orbitronics device application such as non-volatile magnetic random access memory, based on rare earth metals.

  18. Preparation, analysis, and release of simulated interplanetary grains into low earth orbit

    Astronomical observations which reflect the optical and dynamical properties of interstellar and interplanetary grains are the primary means of identifying the shape, size, and the chemistry of extraterrestrial grain materials and is a major subject of this workshop. Except for recent samplings of extraterrestrial particles in near-Earth orbit and in the stratosphere, observations have been the only method of deducing the properties of extraterrestrial particles. Terrestrial laboratory experiments typically seek not to reproduce astrophysical conditions but to illuminate fundamental dust processes and properties which must be extrapolated to interesting astrophysical conditions. In this report, we discuss the formation and optical characterization of simulated interstellar and interplanetary dust with particular emphasis on studying the properties on irregularly shaped particles. We also discuss efforts to develop the techniques to allow dust experiments to be carried out in low-Earth orbit, thus extending the conditions under which dust experiments may be performed. The objectives of this study are threefold: (1) Elucidate the optical properties, including scattering and absorption, of simulated interstellar grains including SiC, silicates, and carbon grains produced in the laboratory. (2) Develop the capabilities to release grains and volatile materials into the near-Earth environment and study their dynamics and optical properties. (3) Study the interaction of released materials with the near-Earth environment to elucidate grain behavior in astrophysical environments. Interaction of grains with their environment may, for example, lead to grain alignment or coagulation, which results in observable phenomena such as polarization of lighter or a change of the scattering properties of the grains

  19. Effect of UV Radiation on the Spectral Fingerprints of Earth-like Planets Orbiting M dwarfs

    Rugheimer, S; Segura, A; Linsky, J; Mohanty, S

    2015-01-01

    We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with $T_{eff}$ = 2300K to $T_{eff}$ = 3800K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1AU equivalent distance and show spectra from the VIS to IR (0.4$\\mu$m - 20$\\mu$m) to compare detectability of features in different wavelength ranges with JWST and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely: H$_2$O, O$_3$, CH$_4$, N$_2$O and CH$_3$Cl. To observe signatures of life - O$_2$/O$_3$ in combination with reducing species like CH$_4$, we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O$_2$ spectral feature at 0.76$\\mu$m is increasingly difficult to detect in reflected light of later M dwarfs due to low stellar flux in ...

  20. A vector method for synthesis of orbits and the structure of satellite constellations for multiswath periodic coverage of the Earth

    Saulskiy, V. K.

    2016-07-01

    Single satellites and multisatellite constellations for the periodic coverage of the Earth are considered. The main feature is the use of several cameras with different swath widths. A vector method is proposed which makes it possible to find orbits minimizing the periodicities of coverage of a given area of Earth uniformly for all swaths. Their number is not limited, but the relative dimensions should satisfy the Fibonacci series or some new numerical sequences. The results apply to constellations of any number of satellites. Formulas were derived for calculating their structure, i.e., relative position in the constellation. Examples of orbits and the structure of constellations for the Earth's multiswath coverage are presented.

  1. The problems of cosmic ray particle simulation for the near-Earth orbital and interplanetary flight conditions

    A wide range of the galactic cosmic ray and SEP event flux simulation problems for the near-Earth satellite and manned spacecraft orbits and for the interplanetary mission trajectories are discussed. The models of the galactic cosmic ray and SEP events in the Earth orbit beyond the Earth's magnetosphere are used as a basis. The particle fluxes in the near-Earth orbits should be calculated using the transmission functions. To calculate the functions, the dependences of the cutoff rigidities on the magnetic disturbance level and on magnetic local time have to be known. In the case of space flights towards the Sun and to the boundary of the solar system, particular attention is paid to the changes in the SEP event occurrence frequency and size. The particle flux gradients are applied in this case to galactic cosmic ray fluxes

  2. Low-Earth-Orbiter resource allocation and capacity planning for the DSN using LEO4CAST

    Fox, G.; Borden, C.

    1994-01-01

    The Deep Space Network provides tracking and communication services for a number of U.S. and international low-Earth-orbiting (LEO) and near-Earth missions. This service is supplied by the 26-m subnet (located at each of the DSN complexes), the 9-m and the 34-m Antenna Research System antennas at Goldstone, and the 11-m antennas (following the orbital VLBI mission). An increasing number of LEO missions are planned for DSN support, which will result in increasingly complex ground resource allocation and mission support trades. To support TDA decision making on mission support and cost-effective ground system evolution for this 26-m subnet, LEO4CAST has been developed. LEO4CAST is a tool that uses statistical approaches to provide useful information for long-term ground system capacity planning and near-term resource allocation (prior to detailed time-of-day scheduling). LEO4CAST is currently beta-test software and is being exercised by both the Office of Telecommunications and Data Acquisition (TDA) and the JPL Systems Division.

  3. Observation and modeling of the South Atlantic Anomaly in low Earth orbit using photometric instrument data

    Schaefer, R. K.; Paxton, L. J.; Selby, C.; Ogorzalek, B.; Romeo, G.; Wolven, B.; Hsieh, S.-Y.

    2016-05-01

    We present a new model of the South Atlantic Anomaly (SAA) particle flux intensity for low Earth orbit, based a new data set, i.e., particle noise pulses in an ultraviolet photomultiplier. The data set is unique in that it provides daily monitoring of the strength of the particle radiation at a fixed altitude and local time and provides a consistent set of observations across the deep solar minimum. The observations show the following: (1) a development over the decline of solar cycle 23 into a deep solar minimum and the subsequent rise of cycle 24, (2) the slow motion drift of the SAA centroid with time at the rate—longitude drift =0.36 ± 0.06°W/yr, and latitude drift =0.16 ± 0.09°N/yr, (3) a higher particle flux at solar minimum than at solar maximum, and (4) a yearly cyclical variation. These particle rates are deduced from electric noise pulses generated in the photometers when an energetic charged particle hits the detector and causes an electron to be liberated from the detector material. The model described here can be used to monitor and even spatially predict the changes in particle fluxes seen by instruments in contemporaneous low Earth orbits through the SAA.

  4. Fractal Structure of the Heliospheric Plasma Sheet at the Earth's Orbit

    M. V. Eselevich; V. G. Eselevich

    2005-01-01

    An analysis of the data from the Wind and IMP-8 spacecraft revealed that a slow solar wind,flowing in the heliospheric plasma sheet, represents a set of magnetic tubes with plasma of increased density(N > 10cm-3 at the Earth's orbit). They have a fine structure at several spatial scales (fractality), from2°-3° (at the Earth's orbit, it is equivalent to 3.6-5.4 h, or(5.4-8.0) × 106 km) to the minimum about0.025°, i.e. the angular siz.e of the nested tubes is changed nearly by two orders of magnitude. The magnetic tubes at each observed spatial scale are diamagnetic, i.e. their surface sustains a flow of diamagnetic (or drift)current that decreases the magnetic field within the tube itself and increases it outside the tube. Furthermore,the value of β = 8π[N(Te + Tp)]/B2 within the tube exceeds the value of β outside the tube. In many cases total pressure P = N(Te + Tp) + B2/8π is almost constant within and outside the tubes at any one of the aforementioned scales.

  5. The aphelion distribution of the Near Earth meteoroid orbits with larger eccentricities

    Kolomiyets, Svitlana; Voloshchuk, Yury

    2015-08-01

    The question of the stability of the Solar System has always sparked urgency to research. In some cases, larger values of eccentricity and/or inclination can be a sign of the instability. The time has now come to extend this question to a larger number of planetary systems. The discovery of extrasolar planets systems has raised many similar questions on their formation and dynamical evolution. The origin of the surprisingly large eccentricities and/or inclinations (relative to the stellar equator) of many extrasolar planets remains elusive: planet instabilities, planet-disk interactions, external perturbations from eccentric or inclined stars remain viable options. The understanding of our own planetary system and extrasolar planets systems can leap forward only with the combination of mutual research. The time has now come to the golden years of the space exploration on the distant Solar System bodies. At the same time every day the meteoric matter penetrates in the Earth atmosphere and carries information about the various locations of the Solar system. The meteoroid orbits with large eccentricities and large aphelion distances associated with the distant locations of the Solar system. We used the data of the ground-based radar observations in Kharkiv (Ukraine) to obtain the distribution of aphelion distances for the near Earth meteoroid orbits (100341) with large eccentricities (e>0.5). We analyzed the orbital inclinations too. We obtained the complicated structure of the sporadic meteoroid complex. It is the consequence of the plurality of parent bodies and origin mechanisms of meteoroids. In addition the perturbing action of the planets, non-gravitational forces affect on the stracture of meteoroid complex. Our experimental results in 1972-1978 demonstrated meteoroid masses 10^-3 -10^-6 g. The aphelion distance of orbits for these investigated meteoroids has the range from near 1 till 2 000 AU. Undoubtedly, the meteoric matter contains key information about

  6. A low earth orbit dynamic model for the proton anisotropy validation

    Badavi, Francis F.

    2011-11-01

    Ionizing radiation measurements at low earth orbit (LEO) form the ideal tool for the experimental validation of radiation environmental models, nuclear transport code algorithms and nuclear reaction cross sections. Indeed, prior measurements on the space transportation system (STS; shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the LEO environment. Previous studies using computer aided design (CAD) models of the international space station (ISS) have demonstrated that the dosimetric prediction for a spacecraft at LEO requires the description of an environmental model with accurate anisotropic as well as dynamic behavior. This paper describes such a model for the trapped proton. The described model is a component of a suite of codes collectively named GEORAD (GEOmagnetic RADiation) which computes cutoff rigidity, trapped proton and trapped electron environments. The web version of GEORAD is named OLTARIS (On-line Tool for the Assessment of Radiation in Space). GEORAD suite is applicable to radiation environment prediction at LEO, medium earth orbit (MEO) and geosynchronous earth orbit (GEO) at quiet solar periods. GEORAD interest is in the study of long term effect of the trapped environment and therefore it does not account for any short term external field contribution due to solar activity. With the concentration of the paper on the LEO protons only, the paper presents the validation of the trapped proton model within GEORAD with reported measurements from the compact environment anomaly sensor (CEASE) science instrument package, flown onboard the tri-service experiment-5 (TSX-5) satellite during the period of June 2000 to July 2006. The spin stabilized satellite was flown in a 410 × 1710 km, 69° inclination elliptical orbit, allowing it to be exposed to a broad range of the LEO regime. The paper puts particular emphasize on the validation of the

  7. A low earth orbit dynamic model for the proton anisotropy validation

    Badavi, Francis F., E-mail: francis.f.badavi@nasa.gov [Christopher Newport University, OSP, 1 University Place, Newport News, VA 23606 (United States)

    2011-11-01

    Ionizing radiation measurements at low earth orbit (LEO) form the ideal tool for the experimental validation of radiation environmental models, nuclear transport code algorithms and nuclear reaction cross sections. Indeed, prior measurements on the space transportation system (STS; shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the LEO environment. Previous studies using computer aided design (CAD) models of the international space station (ISS) have demonstrated that the dosimetric prediction for a spacecraft at LEO requires the description of an environmental model with accurate anisotropic as well as dynamic behavior. This paper describes such a model for the trapped proton. The described model is a component of a suite of codes collectively named GEORAD (GEOmagnetic RADiation) which computes cutoff rigidity, trapped proton and trapped electron environments. The web version of GEORAD is named OLTARIS (On-line Tool for the Assessment of Radiation in Space). GEORAD suite is applicable to radiation environment prediction at LEO, medium earth orbit (MEO) and geosynchronous earth orbit (GEO) at quiet solar periods. GEORAD interest is in the study of long term effect of the trapped environment and therefore it does not account for any short term external field contribution due to solar activity. With the concentration of the paper on the LEO protons only, the paper presents the validation of the trapped proton model within GEORAD with reported measurements from the compact environment anomaly sensor (CEASE) science instrument package, flown onboard the tri-service experiment-5 (TSX-5) satellite during the period of June 2000 to July 2006. The spin stabilized satellite was flown in a 410 x 1710 km, 69{sup o} inclination elliptical orbit, allowing it to be exposed to a broad range of the LEO regime. The paper puts particular emphasize on the validation of the

  8. A low earth orbit dynamic model for the proton anisotropy validation

    Ionizing radiation measurements at low earth orbit (LEO) form the ideal tool for the experimental validation of radiation environmental models, nuclear transport code algorithms and nuclear reaction cross sections. Indeed, prior measurements on the space transportation system (STS; shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the LEO environment. Previous studies using computer aided design (CAD) models of the international space station (ISS) have demonstrated that the dosimetric prediction for a spacecraft at LEO requires the description of an environmental model with accurate anisotropic as well as dynamic behavior. This paper describes such a model for the trapped proton. The described model is a component of a suite of codes collectively named GEORAD (GEOmagnetic RADiation) which computes cutoff rigidity, trapped proton and trapped electron environments. The web version of GEORAD is named OLTARIS (On-line Tool for the Assessment of Radiation in Space). GEORAD suite is applicable to radiation environment prediction at LEO, medium earth orbit (MEO) and geosynchronous earth orbit (GEO) at quiet solar periods. GEORAD interest is in the study of long term effect of the trapped environment and therefore it does not account for any short term external field contribution due to solar activity. With the concentration of the paper on the LEO protons only, the paper presents the validation of the trapped proton model within GEORAD with reported measurements from the compact environment anomaly sensor (CEASE) science instrument package, flown onboard the tri-service experiment-5 (TSX-5) satellite during the period of June 2000 to July 2006. The spin stabilized satellite was flown in a 410 x 1710 km, 69o inclination elliptical orbit, allowing it to be exposed to a broad range of the LEO regime. The paper puts particular emphasize on the validation of the

  9. Investigating fundamental physics and space environment with a dedicated Earth-orbiting spacecraft

    Peron, Roberto

    The near-Earth environment is a place of first choice for performing fundamental physics experiments, given its proximity to Earth and at the same time being relatively quiet dynamically for particular orbital arrangements. This environment also sees a rich phenomenology for what concerns gravitation. In fact, the general theory of relativity is an incredibly accurate description of gravitational phenomenology. However, its overall validity is being questioned by the theories that aim at reconciling it with the microscopic domain. Challenges come also from the ‘mysteries’ of Dark Matter and Dark Energy, though mainly at scales from the galactic up to the cosmological. It is therefore important to precisely test the consequences of the theory -- as well as those of competing ones -- at all the accessible scales. At the same time, the development of high-precision experimental space techniques, which are needed for tests in fundamental physics, opens the way to complementary applications. The growth of the (man-made) orbital debris population is creating problems to the future development of space. The year 2009 witnessed the first accidental collision between two satellites in orbit (Iridium and Cosmos) that led to the creation of more debris. International and national agencies are intervening by issuing and/or adopting guidelines to mitigate the growth of orbital debris. A central tenet of these guidelines requires a presence in space shorter than 25 years to satellites in low Earth orbit (LEO) after the conclusion of their operational lives. However, the determination of the natural lifetime of a satellite in LEO is very uncertain due to a large extent to the short-term and long-term variability of the atmospheric density in LEO and the comparatively low-accuracy of atmospheric density models. Many satellites orbiting in the 500-1200 km region with circular or elliptical orbits will be hard pressed to establish before flight whether or not they meet the 25

  10. Object Image Linking of Earth Orbiting Objects in the Presence of Cosmics

    Früh, Carolin

    2011-01-01

    In survey series of unknown Earth orbiting objects, no a priori orbital elements are available. In surveys of wide field telescopes possibly many nonresolved object images are present on the single frames of the series. Reliable methods have to be found to associate the object images stemming from the same object with each other, so-called linking. The presence of cosmic ray events, so-called Cosmics, complicates reliable linking of non-resolved images. The tracklets of object images allow to extract exact positions for a first orbit determination. A two step method is used and tested on observation frames of space debris surveys of the ESA Space Debris Telescope, located on Tenerife, Spain: In a first step a cosmic filter is applied in the single observation frames. Four different filter approaches are compared and tested in performance. In a second step, the detected object images are linked on observation series based on the assumption of a linear accelerated movement of the objects over the frame during t...

  11. The spaceborne infrared atmospheric sounder for geosynchronous earth orbit (SIRAS-G): pathfinder to space

    Kampe, Thomas U.; Chase, Holden

    2007-09-01

    The Spaceborne Infrared Sounder for Geosynchronous Earth Orbit (SIRAS-G) was developed by Ball Aerospace and Technologies Corp (BATC) under NASA's 2002 Instrument Incubator Program. SIRAS-G is a technology development program focused on next-generation IR imaging spectrometers for sounding of the atmosphere. SIRAS-G is ideally suited for measuring atmospheric temperature and water vapor profiles, trace gases concentrations, land and ocean surface temperatures and the IR mineral dust aerosol signature from satellite, providing high-spectral resolution imaging spectroscopy over a broad IR spectral range and extended field of view. Instrument concepts for future mission in LEO and GEO are discussed, including an instrument concept to be flown in low earth orbit having the potential to provide high spatial resolution, comparable to that of MODIS, along with the high spectral resolution currently being demonstrated by the Atmospheric Infrared Sounder (AIRS). This capability would dramatically improve the yield of cloud-free pixels scenes that can be assimilated into Numerical Weather Prediction (NWP) models. The SIRAS-G dispersive spectrometer module is readily adaptable for missions in LEO, GEO and MEO orbits and can be optimized for spectral resolution over subsets of the total spectral range. We have completed the 3-year SIRAS-G IIP development effort, including successful testing of the SIRAS-G laboratory demonstration spectrometer that utilized the Hawaii 1RG MWIR FPA. Performance testing was conducted at cryogenic temperatures and the performance of the demo instrument has been quantified including measurement of keystone distortion, spectral smile, MTF, and the spectral response function (SRF) to high accuracy. We present the results of the laboratory instrument development including characterization of the demonstration instrument performance. We discuss instrument concepts utilizing SIRAS-G technology for potential future missions including an anticipated

  12. A Wide Field Auroral Imager (WFAI for low Earth orbit missions

    N. P. Bannister

    2007-03-01

    Full Text Available A comprehensive understanding of the solar wind interaction with Earth's coupled magnetosphere-ionosphere system requires an ability to observe the charged particle environment and auroral activity from the same platform, generating particle and photon image data which are matched in time and location. While unambiguous identification of the particles giving rise to the aurora requires a Low Earth Orbit satellite, obtaining adequate spatial coverage of aurorae with the relatively limited field of view of current space bourne auroral imaging systems requires much higher orbits. A goal for future satellite missions, therefore, is the development of compact, wide field-of-view optics permitting high spatial and temporal resolution ultraviolet imaging of the aurora from small spacecraft in low polar orbit. Microchannel plate optics offer a method of achieving the required performance. We describe a new, compact instrument design which can observe a wide field-of-view with the required spatial resolution. We report the focusing of 121.6 nm radiation using a spherically-slumped, square-pore microchannel plate with a focal length of 32 mm and an F number of 0.7. Measurements are compared with detailed ray-trace simulations of imaging performance. The angular resolution is 2.7±0.2° for the prototype, corresponding to a footprint ~33 km in diameter for an aurora altitude of 110 km and a spacecraft altitude of 800 km. In preliminary analysis, a more recent optic has demonstrated a full width at half maximum of 5.0±0.3 arcminutes, corresponding to a footprint of ~1 km from the same spacecraft altitude. We further report the imaging properties of a convex microchannel plate detector with planar resistive anode readout; this detector, whose active surface has a radius of curvature of only 100 mm, is shown to meet the spatial resolution and sensitivity requirements of the new wide field auroral imager (WFAI.

  13. Sunlight effects on the 3D polar current system determined from low Earth orbit measurements

    Laundal, Karl M.; Finlay, Christopher C.; Olsen, Nils

    2016-08-01

    Interaction between the solar wind and the Earth's magnetosphere is associated with large-scale currents in the ionosphere at polar latitudes that flow along magnetic field lines (Birkeland currents) and horizontally. These current systems are tightly linked, but their global behaviors are rarely analyzed together. In this paper, we present estimates of the average global Birkeland currents and horizontal ionospheric currents from the same set of magnetic field measurements. The magnetic field measurements, from the low Earth orbiting Swarm and CHAMP satellites, are used to co-estimate poloidal and toroidal parts of the magnetic disturbance field, represented in magnetic apex coordinates. The use of apex coordinates reduces effects of longitudinal and hemispheric variations in the Earth's main field. We present global currents from both hemispheres during different sunlight conditions. The results show that the Birkeland currents vary with the conductivity, which depends most strongly on solar EUV emissions on the dayside and on particle precipitation at pre-midnight magnetic local times. In sunlight, the horizontal equivalent current flows in two cells, resembling an opposite ionospheric convection pattern, which implies that it is dominated by Hall currents. By combining the Birkeland current maps and the equivalent current, we are able to calculate the total horizontal current, without any assumptions about the conductivity. We show that the total horizontal current is close to zero in the polar cap when it is dark. That implies that the equivalent current, which is sensed by ground magnetometers, is largely canceled by the horizontal closure of the Birkeland currents.

  14. A SUPER-EARTH ORBITING THE NEARBY SUN-LIKE STAR HD 1461

    We present precision radial velocity (RV) data that reveal a Super-Earth mass planet and two probable additional planets orbiting the bright nearby G0V star HD 1461. Our 12.8 years of Keck High Resolution Echelle Spectrometer precision RVs indicate the presence of a 7.4 M+ planet on a 5.77 day orbit. The data also suggest, but cannot yet confirm, the presence of outer planets on low-eccentricity orbits with periods of 446.1 and 5017 days, and projected masses (Msin i) of 27.9 and 87.1 M+, respectively. Test integrations of systems consistent with the RV data suggest that the configuration is dynamically stable. We present a 12.2 year time series of photometric observations of HD 1461, which comprise 799 individual measurements, and indicate that it has excellent long-term photometric stability. However, there are small amplitude variations with periods comparable to those of the suspected second and third signals in the RVs near 5000 and 446 days, thus casting some suspicion on those periodicities as Keplerian signals. If the 5.77 day companion has a Neptune-like composition, then its expected transit depth is of order d∼0.5 mmag. The geometric a priori probability of transits is ∼8%. Phase folding of the ground-based photometry shows no indication that transits of the 5.77 day companion are occurring, but high-precision follow-up of HD 1461 during upcoming transit phase windows will be required to definitively rule out or confirm transits. This new system joins a growing list of solar-type stars in the immediate galactic neighborhood that are accompanied by at least one Neptune (or lower) mass planets having orbital periods of 50 days or less.

  15. Real-time Sub-cm Differential Orbit Determination of two Low-Earth Orbiters with GPS Bias Fixing

    Wu, Sien-Chong; Bar-Sever, Yoaz E.

    2006-01-01

    An effective technique for real-time differential orbit determination with GPS bias fixing is formulated. With this technique, only real-time GPS orbits and clocks are needed (available from the NASA Global Differential GPS System with 10-20 cm accuracy). The onboard, realtime orbital states of user satellites (few meters in accuracy) are used for orbit initialization and integration. An extended Kalman filter is constructed for the estimation of the differential orbit between the two satellites as well as a reference orbit, together with their associating dynamics parameters. Due to close proximity of the two satellites and of similar body shapes, the differential dynamics are highly common and can be tightly constrained which, in turn, strengthens the orbit estimation. Without explicit differencing of GPS data, double-differenced phase biases are formed by a transformation matrix. Integer-valued fixing of these biases are then performed which greatly strengthens the orbit estimation. A 9-day demonstration between GRACE orbits with baselines of approx.200 km indicates that approx.80% of the double-differenced phase biases can successfully be fixed and the differential orbit can be determined to approx.7 mm as compared to the results of onboard K-band ranging.

  16. SALSA: a tool to estimate the stray light contamination for low-Earth orbit observatories

    Kuntzer, Thibault; Fortier, Andrea; Benz, Willy

    2014-08-01

    Stray light contamination reduces considerably the precision of photometric of faint stars for low altitude spaceborne observatories. When measuring faint objects, the necessity of coping with stray light contamination arises in order to avoid systematic impacts on low signal-to-noise images. Stray light contamination can be represented by a flat offset in CCD data. Mitigation techniques begin by a comprehensive study during the design phase, followed by the use of target pointing optimisation and post-processing methods. We present a code that aims at simulating the stray-light contamination in low-Earth orbit coming from reflexion of solar light by the Earth. StrAy Light SimulAtor (SALSA) is a tool intended to be used at an early stage as a tool to evaluate the effective visible region in the sky and, therefore to optimise the observation sequence. SALSA can compute Earth stray light contamination for significant periods of time allowing missionwide parameters to be optimised (e.g. impose constraints on the point source transmission function (PST) and/or on the altitude of the satellite). It can also be used to study the behaviour of the stray light at different seasons or latitudes. Given the position of the satellite with respect to the Earth and the Sun, SALSA computes the stray light at the entrance of the telescope following a geometrical technique. After characterising the illuminated region of the Earth, the portion of illuminated Earth that affects the satellite is calculated. Then, the flux of reflected solar photons is evaluated at the entrance of the telescope. Using the PST of the instrument, the final stray light contamination at the detector is calculated. The analysis tools include time series analysis of the contamination, evaluation of the sky coverage and an objects visibility predictor. Effects of the South Atlantic Anomaly and of any shutdown periods of the instrument can be added. Several designs or mission concepts can be easily tested and

  17. The Effect of Lunar-like Satellites on the Orbital Infrared Light Curves of Earth-analog Planets

    Moskovitz, Nicholas A.; Gaidos, Eric; Williams, Darren

    2008-01-01

    We investigate the influence of lunar-like satellites on the infrared orbital light curves of Earth-analog extra-solar planets. Such light curves will be obtained by NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin missions as a consequence of repeat observations to confirm the companion status of a putative planet. We use an energy balance model to calculate disk-averaged infrared (bolometric) fluxes from planet-satellite systems over a full orbital period (one year). The satellites a...

  18. Investigation of Teflon FEP Embrittlement on Spacecraft in Low-Earth Orbit

    deGroh, Kim K.; Banks, Bruce A.

    1997-01-01

    Teflon fluorinated ethylene propylene (FEP) (DuPont) is commonly used on exterior spacecraft surfaces for thermal control in the low-Earth orbit environment. Silverized or aluminized Teflon FEP is used for the outer layers of the thermal control blanket because of its high reflectance, low solar absorptance, and high thermal emittance. Teflon FEP is also desirable because, compared with other spacecraft polymers (such as Kapton), it has relatively high resistance to atomic oxygen erosion. Because of its comparably low atomic oxygen erosion yield, Teflon FEP has been used unprotected in the space environment. Samples of Teflon FEP from the Long Duration Exposure Facility (LDEF) and the Hubble Space Telescope (retrieved during its first servicing mission) were evaluated for solar-induced embrittlement and for synergistic effects of solar degradation and atomic oxygen.

  19. Changes in the Optical Properties of Materials Are Observed After 18 Months in Low Earth Orbit

    Jaworske, Donald A.

    1999-01-01

    Materials located on the exterior of spacecraft in low Earth orbit are subjected to a number of environmental threats, including atomic oxygen, ultraviolet radiation, thermal cycling, and micrometeroid and debris impact. Atomic oxygen attacks materials vulnerable to oxidation. Ultraviolet radiation can break chemical bonds and cause undesirable changes in optical properties. Thermal cycling can cause cracking, and micrometeroid and debris impacts can damage protective coatings. Another threat is contamination. The outgassing of volatile chemicals can contaminate nearby surfaces, changing their thermal control properties. Contaminated surfaces may undergo further change as a result of atomic oxygen and ultraviolet radiation exposure. The Passive Optical Sample Assembly (POSA) experiment was designed as a risk mitigation experiment for the International Space Station. Samples were characterized before launch, exposed for 18 months on the exterior of Mir, and characterized upon their return. Lessons learned from POSA about the durability of material properties can be applied to the space station and other long-duration missions.

  20. Sunsynchronous low Earth orbit spacecraft concepts and technology requirements for global change monitoring

    Garrett, L. Bernard; Butterfield, Ansel J.; Taback, Israel; Garn, Paul A.; Burrowbridge, Donald R., Jr.

    1991-01-01

    The Global Change Technology Initiative listing of instruments for operation in low Earth, sunsynchronous orbits contain 21 entries, of which 20 are carried aboard multi-instrument spacecraft. This list identifies the temporal requirements for repetition of measurements and also includes groups of instruments that make complementing measurements. Definitions for individual spacecraft follows the temporal and grouping requirements to establish constellations which will provide the measurement data. The definitions of constellations for multi-instrument spacecraft show two alternatives: a constellation of 10 spacecraft, each compatible with launch by a Delta booster; a constellation of 4 spacecraft, each requiring a Titan booster. Operating subsystems for the individual spacecraft can use modular concepts that are adaptations based upon current plans for improving the performance of the NASA-Goddard Multimission Modular units. The descriptions of the spacecraft and constellations begins with a compilation of instrument related requirements that define the principal system performance parameters and operating capabilities.

  1. The effects of low earth orbit atomic oxygen on the properties of Polytetrafluoroethylene

    Hooshangi, Zhila; Hossein Feghhi, Seyed Amir; Saeedzadeh, Rezgar

    2016-02-01

    Polymers are widely used in space systems as the structural materials. The low earth orbit (LEO) space environment includes hazards such as atomic oxygen. Exposure of polymeric materials to atomic oxygen results in destructive effects on the chemical, electrical, thermal, optical and mechanical properties as well as surface degradation. In the present work, the effects of atomic oxygen on the mechanical, thermal, and optical properties of Polytetrafluoroethylene film have been investigated. The atomic oxygen density was calculated by SPENVIS tool. After the atomic oxygen exposure by using radio-frequency (RF) plasma source, the appearance of the samples changed, and the mass of the samples reduced because of outgassing. The results of thermal analysis showed that atomic oxygen flux does not affect thermal degradation of samples regarding TGA diagrams. By increasing the atomic oxygen flux, the amount of absorbance increased showing that atomic oxygen had damaged the surface of Polytetrafluoroethylene, and it had oxidized the surface of the polymer.

  2. Operation of commercial R3000 processors in the low earth orbit (LEO) space environment

    Spacecraft processors must operate with minimal degradation of performance in the Low Earth Orbit (LEO) radiation environment, which includes the effects of total accumulated ionizing dose and Single Event Phenomena (SEP) caused by protons and cosmic rays. Commercially available microprocessors can offer a number of advantages relative to radiation-hardened devices, including lower cost, reduced development and procurement time, extensive software support, higher density and performance. However, commercially available systems are not normally designed to tolerate effects induced by the LEO environments. Lawrence Livermore National Laboratory (LLNL) and others have extensively tested the MIPS R3000 Reduced Instruction Set Computer (RISC) microprocessor family for operation in LEO environments. In this paper the authors characterize total dose and SEP effects for altitudes and inclinations of interest to systems operating in LEO, and the authors postulate techniques for detection and alleviation of SEP effects based on experimental results

  3. Evaluation of Bulk Charging in Geostationary Transfer Orbit and Earth Escape Trajectories Using the Numit 1-D Charging Model

    Minow, Joseph I.; Coffey, Victoria N.; Parker, Linda N.; Blackwell, William C., Jr.; Jun, Insoo; Garrett, Henry B.

    2007-01-01

    The NUMIT 1-dimensional bulk charging model is used as a screening to ol for evaluating time-dependent bulk internal or deep dielectric) ch arging of dielectrics exposed to penetrating electron environments. T he code is modified to accept time dependent electron flux time serie s along satellite orbits for the electron environment inputs instead of using the static electron flux environment input originally used b y the code and widely adopted in bulk charging models. Application of the screening technique ts demonstrated for three cases of spacecraf t exposure within the Earth's radiation belts including a geostationa ry transfer orbit and an Earth-Moon transit trajectory for a range of orbit inclinations. Electric fields and charge densities are compute d for dielectric materials with varying electrical properties exposed to relativistic electron environments along the orbits. Our objectiv e is to demonstrate a preliminary application of the time-dependent e nvironments input to the NUMIT code for evaluating charging risks to exposed dielectrics used on spacecraft when exposed to the Earth's ra diation belts. The results demonstrate that the NUMIT electric field values in GTO orbits with multiple encounters with the Earth's radiat ion belts are consistent with previous studies of charging in GTO orb its and that potential threat conditions for electrostatic discharge exist on lunar transit trajectories depending on the electrical proper ties of the materials exposed to the radiation environment.

  4. International Space Station as a base camp for exploration beyond low Earth orbit

    Raftery, Michael; Hoffman, Jeffrey

    2013-04-01

    The idea for using the International Space Station (ISS) as a platform for exploration has matured in the past few years and the concept continues to gain momentum. ISS provides a robust infrastructure which can be used to test systems and capabilities needed for missions to the Moon, Mars, asteroids and other potential destinations. International cooperation is a critical enabler and ISS has already demonstrated successful management of a large multi-national technical endeavor. Systems and resources needed for expeditions can be aggregated and thoroughly tested at ISS before departure thus providing wide operational flexibility and the best assurance of mission success. A small part of ISS called an Exploration Platform (ISS-EP) can be placed in cislunar space providing immediate benefits and flexibility for future exploration missions. We will show how ISS and the ISS-EP can be used to reduce risk and improve the operational flexibility for missions beyond low Earth orbit. Life support systems and other technologies developed for ISS can be evolved and adapted to the ISS-EP and other exploration spacecrafts. New technology, such as electric propulsion and advanced life support systems can be tested and proven at ISS as part of an incremental development program. Commercial companies who are introducing transportation and other services will benefit with opportunities to contribute to the mission since ISS will serve as a focal point for the commercialization of low earth orbit services. Finally, we will show how the use of ISS provides immediate benefits to the scientific community because its capabilities are available today and certain critical aspects of exploration missions can be simulated.

  5. Foundational Methane Propulsion Related Technology Efforts, and Challenges for Applications to Human Exploration Beyond Earth Orbit

    Brown, Thomas; Klem, Mark; McRight, Patrick

    2016-01-01

    Current interest in human exploration beyond earth orbit is driving requirements for high performance, long duration space transportation capabilities. Continued advancement in photovoltaic power systems and investments in high performance electric propulsion promise to enable solar electric options for cargo delivery and pre-deployment of operational architecture elements. However, higher thrust options are required for human in-space transportation as well as planetary descent and ascent functions. While high thrust requirements for interplanetary transportation may be provided by chemical or nuclear thermal propulsion systems, planetary descent and ascent systems are limited to chemical solutions due to their higher thrust to weight and potential planetary protection concerns. Liquid hydrogen fueled systems provide high specific impulse, but pose challenges due to low propellant density and the thermal issues of long term propellant storage. Liquid methane fueled propulsion is a promising compromise with lower specific impulse, higher bulk propellant density and compatibility with proposed in-situ propellant production concepts. Additionally, some architecture studies have identified the potential for commonality between interplanetary and descent/ascent propulsion solutions using liquid methane (LCH4) and liquid oxygen (LOX) propellants. These commonalities may lead to reduced overall development costs and more affordable exploration architectures. With this increased interest, it is critical to understand the current state of LOX/LCH4 propulsion technology and the remaining challenges to its application to beyond earth orbit human exploration. This paper provides a survey of NASA's past and current methane propulsion related technology efforts, assesses the accomplishments to date, and examines the remaining risks associated with full scale development.

  6. Concepts for AutomatedPrecise Low Earth Orbiter Navigation With the Global Positioning System

    Lichten, S. M.; Thornton, C. L.; Young, L. E.; Yunck, T. P.

    1998-01-01

    The Global Positioning System (GPS) is widely used for satellite positioning and navigation and for numerous geolocation activities. Real-time, onboard positioning accuracies for low Earth orbiters (LEOs) currently vary from 50 to 100 m for stand-alone conventional GPS tracking to somewhat better than 10 m with sophisticated onboard data filtering. Wide-area differential techniques, such as those supported by the Wide Area Augmentation System (WAAS) under development by the U.S. Federal Aviation Administration, offer real-time, kinematic positioning accuracies ranging from a few meters to better than a meter over well-defined local regions. This article describes a concept for extending the wide-area differential GPS techniques to achieve global, real-time positioning of LEOs at submeter accuracies. GPS design and operation policy issues that currently limit real-time, onboard precision positioning are discussed. The article then examines a number of proposed system design enhancements under consideration by the U.S. Department of Defense for the next-generation GPS, termed GPS III. These potential enhancements, if implemented, would enable global real-time, stand-alone position accuracies of a few decimeters for kinematic users and better than 10 cm for LEOs. Such capabilities could dramatically impact NASA missions by greatly lowering ground operations costs, as well as navigation and orbit determination costs in general.

  7. International Space Station as a Platform for Exploration Beyond Low Earth Orbit

    Raftery, Michael; Woodcock, Gordon

    2010-01-01

    The International Space Station (ISS) has established a new model for the achievement of the most difficult engineering goals in space: international collaboration at the program level with competition at the level of technology. This strategic shift in management approach provides long term program stability while still allowing for the flexible evolution of technology needs and capabilities. Both commercial and government sponsored technology developments are well supported in this management model. ISS also provides a physical platform for development and demonstration of the systems needed for missions beyond low earth orbit. These new systems at the leading edge of technology require operational exercise in the unforgiving environment of space before they can be trusted for long duration missions. Systems and resources needed for expeditions can be aggregated and thoroughly tested at ISS before departure thus providing wide operational flexibility and the best assurance of mission success. We will describe representative mission profiles showing how ISS can support exploration missions to the Moon, Mars, asteroids and other potential destinations. Example missions would include humans to lunar surface and return, and humans to Mars orbit as well as Mars surface and return. ISS benefits include: international access from all major launch sites; an assembly location with crew and tools that could help prepare departing expeditions that involve more than one launch; a parking place for reusable vehicles; and the potential to add a propellant depot.

  8. Thermally induced vibration of composite solar array with honeycomb panels in low earth orbit

    Solar arrays are critical appendages that provide primary power sources for spacecrafts. This paper presents a numerical method to characterize the thermal response of a composite solar array subjected to space heat flux. Thermally induced vibration is investigated based on this method. The thermally induced vibrations of a solar array using two commonly used materials are also compared. Thermally induced vibrations in different thermal environments, incident angles of solar radiation, and material properties of honeycomb panel are discussed to reveal the causes of thermally induced vibration. Simulation results reveal the dynamic response of the solar array in low earth orbit under transient temperature, which could provide guidance for designers to optimize the structure utilized in minimizing the influence of the space thermal environment. - Highlights: • A method to characterize the thermal response of a rigid solar array is presented. • Composite material and orbital thermal environments are considered in the model. • Thermally induced vibration is investigated based on this model. • The effects of different parameters are discussed. • Incident angle and parameters of honeycomb composite have significant influence

  9. Orbital, spin state and thermophysical characterization of near-Earth asteroid (3200) Phaethon

    Hanus, J; Vokrouhlicky, D; Pravec, P; Emery, J P; Ali-Lagoa, V; Bolin, B; Devogele, M; Dyvig, R; Galad, A; Jedicke, R; Kornos, L; Kusnirak, P; Licandro, J; Reddy, V; Rivet, J-P; Vilagi, J; Warner, B D

    2016-01-01

    The near-Earth asteroid (3200) Phaethon is an intriguing object: its perihelion is only at 0.14 au and is associated with the Geminid meteor stream. We aim to use all available disk-integrated optical data to derive reliable convex shape model of Phaethon. By interpreting the available space- and ground-based thermal infrared data and Spitzer spectra using a thermophysical model, we also aim to further constrain its size, thermal inertia, and visible geometric albedo. We apply the convex inversion method to the new optical data obtained by six instruments together with the already existing observations. The convex shape model is then used as an input for the thermophysical modeling. We also study the long-term stability of Phaethon's orbit and spin axis by a numerical orbital and rotation-state integrator. We present a new convex shape model and rotational state of Phaethon - sidereal rotation period of 3.603958(2) h and ecliptic coordinates of the preferred pole orientation of (319$^{\\circ}$, $-$39$^{\\circ}$...

  10. Full simulation of the LUCID experiment in the Low Earth Orbit radiation environment

    The Langton Ultimate Cosmic ray Intensity Detector (LUCID) experiment is a satellite-based device that uses five Timepix hybrid silicon pixel detectors to make measurements of the radiation environment at an altitude of approximately 630 km, i.e. in Low Earth Orbit (LEO) . The experiment launched aboard Surrey Satellite Technology Limited's (SSTL's) TechDemoSat-1 on Tuesday the 8th of July 2014. The Timepix detectors, developed by the Medipix2 Collaboration, are arranged to form the five sides of a cube enclosed by a 0.7 mm thick aluminium covering, and are operated in Time-over-Threshold (ToT) mode to allow the flux, energy and directionality of incident ionising radiation to be measured. To understand the expected detector performance with respect to these measurements, the LUCID experiment has been modelled using the Allpix software package, a generic simulation toolkit for silicon pixel detectors built upon the GEANT4 framework. The work presented here summarises studies completed using the GridPP Collaboration's computing grid infrastructure to perform the simulations, store the resultant datasets, and share that data with the LUCID Collaboration. The analysis of these datasets has given an indication of the expected performance in differing space radiation environments (for example, during passes of the polar regions or the South Atlantic Anomaly), and has allowed the LUCID Collaboration to prepare for when data is transmitted back to Earth in late 2014

  11. Physics of man-made extended magnetic structures in low earth orbit

    Recently there have been proposals to place high field magnets aboard the Space Station. The introduction of such an extended magnetic field structure into low earth orbit raises a number of interesting plasma physics issues. For example, the ASTROMAG magnet would create an extended magnet field whose strength drops to the ambient level of .3 G over a scale length of approximately 10 m. The combined field from the cusp magnet and the earth produces a complex extended configuration with ring nulls which separate open from closed field lines. This configuration will move through the ambient 1 x 10/sup 5/ cm/sup -3/ plasma at a velocity of approximately 7 km/sec, a velocity slow compared to the Alfven speed, but fast compared to ion sound speed. The ambient plasma crosses the field structure in a time short compared to an ion Larmor period in the ambient field, but long compared to an electron Larmor period. Thus, electrons behave as a magnetized fluid while ions move ballistically until they approach and reflect from the higher fields near the cusp. Since the ambient plasma Debye length is short compared to the field scale length, an electrostatic shock structure forms to equilibrate the flows in order to achieve quasi-neutrality. The authors conjecture based on previous laboratory experiments that the ambient plasma will be excluded from a cavity surrounding the magnet

  12. Orbital and mission planning constraints for the deflection of NEOs impacting on Earth

    Carusi, Andrea; D'Abramo, Germano; Valsecchi, Giovanni B.

    2008-04-01

    This paper is the third in a series. Paper 1 presented the results of numerical modeling of deflections of NEOs in route of collision with the Earth. The model was applied to a variety of dynamical cases including both asteroidal and cometary NEOs. Paper 2 introduced the concept of "distributed deflection," i.e., the possibility to provide the Δ V necessary to deflect an object with a succession of maneuvers each of which would have been insufficient per se to obtain the desired result. In both papers no assumptions were made on the physical composition and structure of the NEO, nor on the details of the possible deflection maneuvers from the point of view of mission analysis. Moreover, Δ V-plots were computed assuming only along-track impulses (both in the positive and negative directions), because it is easy to demonstrate that in general this is energetically the most favorable configuration. Also in the present paper no assumptions were made on the physical composition and structure of the NEO, even if order of magnitude considerations are made on the physical feasibility of a deflection, in terms of the internal strength of the NEO. We present here the results of an investigation on the mission requirements necessary to deflect an object (or contribute to a succession of deflecting maneuvers) in terms of accessibility of the spacecraft terminal orbit from Earth with the current launchers.

  13. Preliminary investigations on a NTP cargo shuttle for earth to moon orbit payload transfer based on a particle bed reactor

    MAPS, a 3-year study program on NTP has recently been launched at CEA following the conclusions of a preliminary scoping study of an NTP system for earth to moon orbit cargo shuttle missions. This paper presents the main results of this scoping study, and gives an outline of the MAPS program. (authors). 5 figs., 11 tabs., 7 refs

  14. Observations on the reliability of COTS-device-based solid state data recorders operating in low-earth orbit

    This paper presents the results of Surrey Space Centre's experience in using different coding schemes and hardware configurations to protect data and protect data and software stored in COTS-device (Commercial-Off-The-Shelf) based memories on-board operational spacecraft in low Earth orbit. (author)

  15. Jupiter family comets in near-Earth orbits: Are some of them interlopers from the asteroid belt?

    Fernández, Julio A.; Sosa, Andrea

    2015-12-01

    We analyze a sample of 58 Jupiter family comets (JFCs) in near-Earth orbits, defined as those whose perihelion distances at the time of discovery were qdisc clones for each one of them, for 104 yr in the past and in the future. We find that most of them move on highly unstable orbits, having fallen in their current near-Earth orbits in the recent past, going from less than one hundred years to a few thousands years. They experience frequent close encounters with Jupiter down to distances ≲ 0.1 au. This is the expected behavior for comets whose limited physical lifetimes in the near-Earth region make them unlikely to survive there for more than about a few hundred revolutions. In this sense the orbits of most JFCs are typically "cometary", and they should be regarded as newcomers in the near-Earth region. Yet, a minor fraction of JFCs (less than about one third) are found to move on stable orbits for the past ∼ 104 yr, and in some cases are found to continue to be stable at 5 × 104 yr in the past. They also avoid very close encounters with Jupiter. Their orbital behavior is very similar to that of NEAs in cometary orbits. While "typical" JFCs in unstable orbits probably come from the trans-Neptunian region, the minor group of JFCs in asteroidal orbits may come from the main asteroid belt, like the NEAs. The asteroidal JFCs may have a more consolidated structure and a higher mineral content than that of comets coming from the trans-Neptunian belt or the Oort cloud, which could explain their much longer physical lifetimes in the near-Earth region. In particular, we mention comets 66P/du Toit, 162P/Siding Spring, 169P/NEAT, 182P/LONEOS, 189P/NEAT, 249P/LINEAR, 300P/Catalina, and P/2003 T12 (SOHO) as the most likely candidates to have an origin in the main asteroid belt. Another interesting case is 207P/NEAT, which stays near the 3:2 inner mean motion resonance with Jupiter, possibly evolving from the Hilda asteroid zone.

  16. The Low Earth Orbit validation of a dynamic and anisotropic trapped radiation model through ISS measurements

    Badavi, Francis F.; Nealy, John E.; Wilson, John W.

    2011-10-01

    The International Space Station (ISS) provides the proving ground for future long duration human activities in space. Ionizing radiation measurements in ISS form the ideal tool for the experimental validation of radiation environmental models, nuclear transport code algorithms and nuclear reaction cross sections. Indeed, prior measurements on the Space Transportation System (STS; Shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the Low Earth Orbit (LEO) environment. Previous studies using Computer Aided Design (CAD) models of the evolving ISS configurations with Thermo-Luminescent Detector (TLD) area monitors, demonstrated that computational dosimetry requires environmental models with accurate non-isotropic as well as dynamic behavior, detailed information on rack loading, and an accurate six degree of freedom (DOF) description of ISS trajectory and orientation. It is imperative that we understand ISS exposures dynamically for crew career planning, and insure that the regulatory requirements of keeping exposure as low as reasonably achievable (ALARA) are adequately implemented. This is especially true as ISS nears some form of completion with increasing complexity, resulting in a larger drag coefficient, and requiring operation at higher altitudes with increased exposure rates. In this paper ISS environmental model is configured for 11A (circa mid 2005), and uses non-isotropic and dynamic geomagnetic transmission and trapped proton models. ISS 11A and LEO model validations are important steps in preparation for the design and validation for the next generation manned vehicles. While the described cutoff rigidity, trapped proton and electron formalisms as coded in a package named GEORAD (GEOmagnetic RADiation) and a web interface named OLTARIS (On-line Tool for the Assessment of Radiation in Space) are applicable to the LEO, Medium Earth Orbit (MEO) and

  17. Near-Earth asteroid (3200) Phaethon: Characterization of its orbit, spin state, and thermophysical parameters

    Hanuš, J.; Delbo', M.; Vokrouhlický, D.; Pravec, P.; Emery, J. P.; Alí-Lagoa, V.; Bolin, B.; Devogèle, M.; Dyvig, R.; Galád, A.; Jedicke, R.; Kornoš, L.; Kušnirák, P.; Licandro, J.; Reddy, V.; Rivet, J.-P.; Világi, J.; Warner, B. D.

    2016-07-01

    Context. The near-Earth asteroid (3200) Phaethon is an intriguing object: its perihelion is at only 0.14 au and is associated with the Geminid meteor stream. Aims: We aim to use all available disk-integrated optical data to derive a reliable convex shape model of Phaethon. By interpreting the available space- and ground-based thermal infrared data and Spitzer spectra using a thermophysical model, we also aim to further constrain its size, thermal inertia, and visible geometric albedo. Methods: We applied the convex inversion method to the new optical data obtained by six instruments and to previous observations. The convex shape model was then used as input for the thermophysical modeling. We also studied the long-term stability of Phaethon's orbit and spin axis with a numerical orbital and rotation-state integrator. Results: We present a new convex shape model and rotational state of Phaethon: a sidereal rotation period of 3.603958(2) h and ecliptic coordinates of the preferred pole orientation of (319°, -39°) with a 5° uncertainty. Moreover, we derive its size (D = 5.1 ± 0.2 km), thermal inertia (Γ = 600 ± 200 J m-2 s-1/2 K-1), geometric visible albedo (pV = 0.122 ± 0.008), and estimate the macroscopic surface roughness. We also find that the Sun illumination at the perihelion passage during the past several thousand years is not connected to a specific area on the surface, which implies non-preferential heating.

  18. Radiation measurements in low Earth orbit: U.S. and Russian results

    Badhwar, G. D.

    2000-01-01

    The radiation environment in low-Earth orbital flights is complex. It is strongly influenced by altitude, orbital inclination, time within a given solar cycle, flight duration, and shielding configuration. At any specified shielded location, both primary and secondary particles generated by nuclear interactions of primary particles with spacecraft structure are present. In addition, there are atmospheric secondary albedo protons and neutrons. No single detector can adequately measure this complex radiation field, and measurements of very high linear energy transfer target fragmentation products are particularly difficult. Crew radiation exposure have exclusively been measured using passive thermoluminescent detectors (TLDs). The cosmonaut exposures on the Mir station, uncorrected for the TLD inefficiency and neutron contribution, have varied from a low of 2.43 cGy to a high of 8.70 cGy. These correspond to dose rates of 144 microGy d(-1) to 468 microGy d(-1). These are consistent with rates observed by the D2 ion-chamber. Using the rates measured by the D1 chamber, dose rates under 4 cm of water vary from about 60 microGy d-1 to about 350 microGy d(-1). There is variation of about a factor of two between the dose rates at various locations in the same module. There is also a variation of dose rates of about a factor two between various modules. The highest astronaut dose for a Shuttle flight (STS-82) was 3.205 cGy with a dose rate of 3,221 microGy d(-1). Neutron contribution could be 36 +/- 15% of the astronaut charged particle dose equivalent. East-West asymmetry of dose rate is significant for spacecrafts that fly in an fixed altitude, such as the International Space Station.

  19. High energy-intensity atomic oxygen beam source for low earth orbit materials degradation studies

    A high intensity (1019O-atoms/s-sr) high energy (5 eV) source of oxygen atoms has been developed that produces a total fluence of 1022 O-atoms/cm2 in less than 100 hours of continuous operation at a distance of 15 cm from the source. The source employs a CW CO2 laser sustained discharge to form a high temperature (15,000 K) plasma in the throat of a 0.3-mm diameter nozzle using 3--8 atmospheres of rare gas/O2 mixtures. Visible and infrared photon flux levels of 1 watt/cm2 have been measured 15 cm downstream of the source while vacuum UV (VUV) fluxes are comparable to that measured in low earth orbit. The reactions of atomic oxygen with kapton, Teflon, silver, and various coatings have been studied. The oxidation of kapton (reaction efficiency = 3 /times/ 10/sup /minus/24/ cm /+-/ 50%) has an activation energy of 0.8 Kcal/mole over the temperature range of 25/degree/C to 100/degree/C at a beam energy of 1.5 eV and produces low molecular weight gas phase reaction products (H2O, NO, CO2). Teflon reacts with ∼0.1--0.2 efficiency to that of kapton at 25/degree/C and both surfaces show a rug-like texture after exposure to the O-atom beam. Angular scattering distribution measurements of O-atoms show a near cosine distribution from reactive surfaces indicating complete accommodation of the translational energy with the surface while a nonreactive surface (nickel oxide) shows specular-like scattering with 50% accommodation of the translational energy with the surface. A technique for simple on orbit chemical experiments using resistance measurements of coated silver strips is described. 9 figs

  20. NASA's Space Launch System: A Flagship for Exploration Beyond Earth's Orbit

    May, Todd A.

    2012-01-01

    The National Aeronautics and Space Administration's (NASA) Space Launch System (SLS) Program, managed at the Marshall Space Flight Center, is making progress toward delivering a new capability for exploration beyond Earth orbit in an austere economic climate. This fact drives the SLS team to find innovative solutions to the challenges of designing, developing, fielding, and operating the largest rocket in history. To arrive at the current SLS plan, government and industry experts carefully analyzed hundreds of architecture options and arrived at the one clear solution to stringent requirements for safety, affordability, and sustainability over the decades that the rocket will be in operation. This paper will explore ways to fit this major development within the funding guidelines by using existing engine assets and hardware now in testing to meet a first launch by 2017. It will explain the SLS Program s long-range plan to keep the budget within bounds, yet evolve the 70 metric ton (t) initial lift capability to 130-t lift capability after the first two flights. To achieve the evolved configuration, advanced technologies must offer appropriate return on investment to be selected through a competitive process. For context, the SLS will be larger than the Saturn V that took 12 men on 6 trips for a total of 11 days on the lunar surface over 4 decades ago. Astronauts train for long-duration voyages on the International Space Station, but have not had transportation to go beyond Earth orbit in modern times, until now. NASA is refining its mission manifest, guided by U.S. Space Policy and the Global Exploration Roadmap. Launching the Orion Multi-Purpose Crew Vehicle s (MPCV s) first autonomous certification flight in 2017, followed by a crewed flight in 2021, the SLS will offer a robust way to transport international crews and the air, water, food, and equipment they need for extended trips to asteroids, Lagrange Points, and Mars. In addition, the SLS will accommodate

  1. Technology Development to Support Human Health and Performance in Exploration Beyond Low Earth Orbit

    Kundrot, C.E.; Steinberg, S. L.; Charles, J. B.

    2011-01-01

    In the course of defining the level of risks and mitigating the risks for exploration missions beyond low Earth orbit, NASA s Human Research Program (HRP) has identified the need for technology development in several areas. Long duration missions increase the risk of serious medical conditions due to limited options for return to Earth; no resupply; highly limited mass, power, volume; and communication delays. New space flight compatible medical capabilities required include: diagnostic imaging, oxygen concentrator, ventilator, laboratory analysis (saliva, blood, urine), kidney stone diagnosis & treatment, IV solution preparation and delivery. Maintenance of behavioral health in such an isolated, confined and extreme environment requires new sensory stimulation (e.g., virtual reality) technology. Unobtrusive monitoring of behavioral health and treatment methods are also required. Prolonged exposure to weightlessness deconditions bone, muscle, and the cardiovascular system. Novel exercise equipment or artificial gravity are necessary to prevent deconditioning. Monitoring of the degree of deconditioning is required to ensure that countermeasures are effective. New technologies are required in all the habitable volumes (e.g., suit, capsule, habitat, exploration vehicle, lander) to provide an adequate food system, and to meet human environmental standards for air, water, and surface contamination. Communication delays require the crew to be more autonomous. Onboard decision support tools that assist crew with real-time detection and diagnosis of vehicle and habitat operational anomalies will enable greater autonomy. Multi-use shield systems are required to provide shielding from solar particle events. The HRP is pursuing the development of these technologies in laboratories, flight analog environments and the ISS so that the human health and performance risks will be acceptable with the available resources.

  2. An Automated Optical Fiber Puller for Use in Low-Earth Orbit

    Tucker, Dennis S.; Smith, W. Scott (Technical Monitor)

    2002-01-01

    With the slowdown in space station construction, limiting astronaut time for scientific experiments, an effort is being made to automate certain experiments. One such experiment is production of heavy metal fluoride fibers in the microgravity environment. Previous work by this author and others have shown that microgravity inhibits crystallization of ZBLAN glass. Thus an automated experiment has been designed. This experiment will consist of several elements, one which includes the use of an autonomous robot to initiate fiber pulling. The first element will be to melt the preform to eliminate crystals. The preform tip will then be heated to the viscosity necessary for fiber drawing. The robot will initiate the draw and attach the fiber end to the take-up reel. Once fiber pulling has commenced, sensors will be used to detect a fiber break, whereupon the robot can re-initiate the pulling process. The fiber will be coated with a polymer and the polymer cured with ultraviolet light. A laser micrometer will be used to monitor fiber diameter. The experiment is designed so that up to 10 preforms can be pulled into fiber during one flight. The apparatus will be mounted on a free-flying carrier which will be placed into low-earth orbit from the cargo bay of the space shuttle by the shuttle robot arm. The experiment can be started by a signal from the shuttle or from the ground via telescience. The experiment will proceed automatically using specially designed algorithms and will be monitored from the ground. The carrier will be picked up by the shuttle before return to earth.

  3. Next generation earth-to-orbit space transportation systems: Unmanned vehicles and liquid/hybrid boosters

    Hueter, Uwe

    1991-01-01

    The United States civil space effort when viewed from a launch vehicle perspective tends to categorize into pre-Shuttle and Shuttle eras. The pre-Shuttle era consisted of expendable launch vehicles where a broad set of capabilities were matured in a range of vehicles, followed by a clear reluctance to build on and utilize those systems. The Shuttle era marked the beginning of the U.S. venture into reusable space launch vehicles and the consolidation of launch systems used to this one vehicle. This led to a tremendous capability, but utilized men on a few missions where it was not essential and compromised launch capability resiliency in the long term. Launch vehicle failures, between the period of Aug. 1985 and May 1986, of the Titan 34D, Shuttle Challenger, and the Delta vehicles resulted in a reassessment of U.S. launch vehicle capability. The reassessment resulted in President Reagan issuing a new National Space Policy in 1988 calling for more coordination between Federal agencies, broadening the launch capabilities and preparing for manned flight beyond the Earth into the solar system. As a result, the Department of Defense (DoD) and NASA are jointly assessing the requirements and needs for this nations's future transportation system. Reliability/safety, balanced fleet, and resiliency are the cornerstone to the future. An insight is provided into the current thinking in establishing future unmanned earth-to-orbit (ETO) space transportation needs and capabilities. A background of previous launch capabilities, future needs, current and proposed near term systems, and system considerations to assure future mission need will be met, are presented. The focus is on propulsion options associated with unmanned cargo vehicles and liquid booster required to assure future mission needs will be met.

  4. Wind and Temperature Spectrometry of the Upper Atmosphere in Low-Earth Orbit

    Herrero, Federico

    2011-01-01

    Wind and Temperature Spectrometry (WATS) is a new approach to measure the full wind vector, temperature, and relative densities of major neutral species in the Earth's thermosphere. The method uses an energy-angle spectrometer moving through the tenuous upper atmosphere to measure directly the angular and energy distributions of the air stream that enters the spectrometer. The angular distribution gives the direction of the total velocity of the air entering the spectrometer, and the energy distribution gives the magnitude of the total velocity. The wind velocity vector is uniquely determined since the measured total velocity depends on the wind vector and the orbiting velocity vector. The orbiting spectrometer moves supersonically, Mach 8 or greater, through the air and must point within a few degrees of its orbital velocity vector (the ram direction). Pointing knowledge is critical; for example, pointing errors 0.1 lead to errors of about 10 m/s in the wind. The WATS method may also be applied without modification to measure the ion-drift vector, ion temperature, and relative ion densities of major ionic species in the ionosphere. In such an application it may be called IDTS: Ion-Drift Temperature Spectrometry. A spectrometer-based coordinate system with one axis instantaneously pointing along the ram direction makes it possible to transform the Maxwellian velocity distribution of the air molecules to a Maxwellian energy-angle distribution for the molecular flux entering the spectrometer. This implementation of WATS is called the gas kinetic method (GKM) because it is applied to the case of the Maxwellian distribution. The WATS method follows from the recognition that in a supersonic platform moving at 8,000 m/s, the measurement of small wind velocities in the air on the order of a few 100 m/s and less requires precise knowledge of the angle of incidence of the neutral atoms and molecules. The same is true for the case of ion-drift measurements. WATS also

  5. A trio of horseshoes: past, present and future dynamical evolution of Earth co-orbital asteroids 2015 XX169, 2015 YA and 2015 YQ1

    Marcos, C. de la Fuente; Marcos, R. de la Fuente

    2016-01-01

    It is widely accepted that a quasi-steady-state flux of minor bodies moving in and out of the co-orbital state with the Earth may exist. Some of these objects are very good candidates for future in situ study due to their favourable dynamical properties. In this paper, we show that the recently discovered near-Earth asteroids 2015 XX169, 2015 YA and 2015 YQ1 are small transient Earth co-orbitals. These new findings increase the tally of known Earth co-orbitals to 17. The three of them current...

  6. The Expose-R2 mission: astrobiology and astrochemistry in low Earth orbit

    Demets, René

    EXPOSE is an exposure platform developed by ESA which permits scientists to install test samples for 1 to 2 years at the outer surface of the ISS. In that way, the impact of the open space environment on biological and biochemical sample materials can be explored. This environment, featuring full-spectrum solar light, near-vacuum, cosmic radiation, wide temperature variations and near-weightlessness, is impossible to reproduce in its entirety in the lab. As such, EXPOSE offers astrochemists and astrobiologists a chance to acquire novel scientific data. Astrochemists are interested in Low Earth Orbit conditions due to the fact that photochemistry in space is quite different from photochemistry on Earth, where the high-energy UV compounds of the solar spectrum are filtered away by our atmosphere. As for the astro biologists, EXPOSE offers an attractive opportunity to expand earlier results obtained during short-duration LEO flights, which have shown that particular microbes and, amazingly, even some multi-cellular macroscopic organisms were able to cope with a two-week exposure to space. The open space environment, often described as harsh and hostile, can apparently be tolerated by some robust inhabitants of our Earth - unprotected, in the absence of a space suit! The first mission of EXPOSE, as an external payload on the European Columbus module, happened during 2008-2009 with the test samples provided by five separate research teams. Three additional teams were involved in the monitoring of space environment. The results were published collectively in 2012 in a special issue of the monthly journal Astrobiology. Several organisms survived, having spent 1.5 years in space. The second mission was called EXPOSE-R, the R referring to ‘Russian segment’, the location where the EXPOSE instrument was installed this time. The EXPOSE-R mission took place in 2009-2011, ten science teams were involved. The publication of the results, again as a collection, is currently in

  7. Atmospheric effects of stellar cosmic rays on Earth-like exoplanets orbiting M-dwarfs

    Tabataba-Vakili, F; Grießmeier, J -M; Rauer, H

    2016-01-01

    M-dwarf stars are generally considered favourable for rocky planet detection. However, such planets may be subject to extreme conditions due to possible high stellar activity. The goal of this work is to determine the potential effect of stellar cosmic rays on key atmospheric species of Earth-like planets orbiting in the habitable zone of M-dwarf stars and show corresponding changes in the planetary spectra. We build upon the cosmic rays model scheme of Grenfell et al. (2012), who considered cosmic ray induced NOx production, by adding further cosmic ray induced production mechanisms (e.g. for HOx) and introducing primary protons of a wider energy range (16 MeV - 0.5 TeV). Previous studies suggested that planets in the habitable zone that are subject to strong flaring conditions have high atmospheric methane concentrations, while their ozone biosignature is completely destroyed. Our current study shows, however, that adding cosmic ray induced HOx production can cause a decrease in atmospheric methane abundanc...

  8. Orbital modulation of millennial-scale climate variability in an earth system model of intermediate complexity

    T. Friedrich

    2009-07-01

    Full Text Available The effect of orbital variations on simulated millennial-scale variability of the Atlantic Meridional Overturning Circulation (AMOC is studied using the earth system model of intermediate complexity LOVECLIM. It is found that for present-day topographic boundary conditions low obliquity values (~22.1° favor the triggering of internally generated millennial-scale variability in the North Atlantic region. Reducing the obliquity leads to changes of the pause-pulse ratio of the corresponding AMOC oscillations. Stochastic excitations of the density-driven overturning circulation in the Nordic Seas can create regional sea-ice anomalies and a subsequent reorganization of the atmospheric circulation. The resulting remote atmospheric anomalies over the Hudson Bay can release freshwater pulses into the Labrador Sea leading to a subsequent reduction of convective activity. The millennial-scale AMOC oscillations disappear if LGM bathymetry (with closed Hudson Bay is prescribed. Furthermore, our study documents the marine and terrestrial carbon cycle response to millennial-scale AMOC variability. Our model results support the notion that stadial regimes in the North Atlantic are accompanied by relatively high levels of oxygen in thermocline and intermediate waters off California – in agreement with paleo-proxy data.

  9. Low Earth orbital atomic oxygen environmental simulation facility for space materials evaluation

    Simulation of low Earth orbit atomic oxygen for accelerated exposure in ground-based facilities is necessary for the durability evaluation of space power system component materials for Space Station Freedom (SSF) and future missions. A facility developed at the National Aeronautics and Space Administrations's (NASA) Lewis Research Center provides accelerated rates of exposure to a directed or scattered oxygen beam, vacuum ultraviolet (VUV) radiation, and offers in-situ optical characterization. The facility utilizes an electron-cyclotron resonance (ECR) plasma source to generate a low energy oxygen beam. Total hemispherical spectral reflectance of samples can be measured in situ over the wavelength range of 250 to 2500 nm. Deuterium lamps provide VUV radiation intensity levels in the 115 to 200 nm range of three to five equivalent suns. Retarding potential analyses show distributed ion energies below 30 electron volts (eV) for the operating conditions most suited for high flux, low energy testing. Peak ion energies are below the sputter threshold energy (approximately 30 eV) of the protective coatings on polymers that are evaluated in the facility, thus allowing long duration exposure without sputter erosion. Neutral species are expected to be at thermal energies of approximately .04 eV to .1 eV. The maximum effective flux level based on polyimide Kapton mass loss is 4.4 x 10 exp 6 atoms/((sq. cm)*s), thus providing a highly accelerated testing capability

  10. Advanced Earth-to-orbit propulsion technology program overview: Impact of civil space technology initiative

    Stephenson, Frank W., Jr.

    1988-01-01

    The NASA Earth-to-Orbit (ETO) Propulsion Technology Program is dedicated to advancing rocket engine technologies for the development of fully reusable engine systems that will enable space transportation systems to achieve low cost, routine access to space. The program addresses technology advancements in the areas of engine life extension/prediction, performance enhancements, reduced ground operations costs, and in-flight fault tolerant engine operations. The primary objective is to acquire increased knowledge and understanding of rocket engine chemical and physical processes in order to evolve more realistic analytical simulations of engine internal environments, to derive more accurate predictions of steady and unsteady loads, and using improved structural analyses, to more accurately predict component life and performance, and finally to identify and verify more durable advanced design concepts. In addition, efforts were focused on engine diagnostic needs and advances that would allow integrated health monitoring systems to be developed for enhanced maintainability, automated servicing, inspection, and checkout, and ultimately, in-flight fault tolerant engine operations.

  11. Requirements for Designing Life Support System Architectures for Crewed Exploration Missions Beyond Low-Earth Orbit

    Howard, David; Perry,Jay; Sargusingh, Miriam; Toomarian, Nikzad

    2016-01-01

    NASA's technology development roadmaps provide guidance to focus technological development on areas that enable crewed exploration missions beyond low-Earth orbit. Specifically, the technology area roadmap on human health, life support and habitation systems describes the need for life support system (LSS) technologies that can improve reliability and in-situ maintainability within a minimally-sized package while enabling a high degree of mission autonomy. To address the needs outlined by the guiding technology area roadmap, NASA's Advanced Exploration Systems (AES) Program has commissioned the Life Support Systems (LSS) Project to lead technology development in the areas of water recovery and management, atmosphere revitalization, and environmental monitoring. A notional exploration LSS architecture derived from the International Space has been developed and serves as the developmental basis for these efforts. Functional requirements and key performance parameters that guide the exploration LSS technology development efforts are presented and discussed. Areas where LSS flight operations aboard the ISS afford lessons learned that are relevant to exploration missions are highlighted.

  12. Near-Earth asteroid satellite spins under spin-orbit coupling

    Naidu, Shantanu P.; Margot, Jean-Luc [Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095 (United States)

    2015-02-01

    We develop a fourth-order numerical integrator to simulate the coupled spin and orbital motions of two rigid bodies having arbitrary mass distributions under the influence of their mutual gravitational potential. We simulate the dynamics of components in well-characterized binary and triple near-Earth asteroid systems and use surface of section plots to map the possible spin configurations of the satellites. For asynchronous satellites, the analysis reveals large regions of phase space where the spin state of the satellite is chaotic. For synchronous satellites, we show that libration amplitudes can reach detectable values even for moderately elongated shapes. The presence of chaotic regions in the phase space has important consequences for the evolution of binary asteroids. It may substantially increase spin synchronization timescales, explain the observed fraction of asychronous binaries, delay BYORP-type evolution, and extend the lifetime of binaries. The variations in spin rate due to large librations also affect the analysis and interpretation of light curve and radar observations.

  13. Electric propulsion systems for small satellites: the low earth orbit mission perseus

    Bock, D.; Herdrich, G.; Lau, M.; Lengowski, M.; Schönherr, T.; Steinmetz, F.; Wollenhaupt, B.; Zeile, O.; Röser, H.-P.

    2011-10-01

    The Institute of Space Systems, Universität Stuttgart, launched a "Small a Satellite Program" in 2002. The first two of the four planed small satellites, Flying Laptop and PERSEUS, are both Low Earth Orbit (LEO) missions. The third mission Cermit is a reentry satellite and the last of the small satellites - Lunar Mission BW1 - is a mission to the Moon. For this purpose, different propulsion systems are mandatory. The propulsion system for Lunar Mission BW1 will consist of two different types of thruster systems: a cluster of pulsed magnetoplasmadynamic (MPD) thrusters (SIMP-LEX) using solid polytetrafluoroethylene (PTFE) as propellant and a thermal arcjet thruster (TALOS) using gaseous ammonia as propellant. Both thruster systems are currently under development at IRS. They are planned to be tested on board the small satellite mission PERSEUS, one of the precursor missions of Lunar Mission BW1. The thruster systems have been investigated intensely in the past and, furthermore, optimization of the thrusters with respect to the mission requirements of Lunar Mission BW1 has been started. The test procedures for the technology demonstration on the PERSEUS satellite are under development at present.

  14. Radiation Protection Effectiveness of Polymeric Based Shielding Materials at Low Earth Orbit

    Badavi, Francis F.; Stewart-Sloan, Charlotte R.; Wilson, John W.; Adams, Daniel O.

    2008-01-01

    Correlations of limited ionizing radiation measurements onboard the Space Transportation System (STS; shuttle) and the International Space Station (ISS) with numerical simulations of charged particle transport through spacecraft structure have indicated that usage of hydrogen rich polymeric materials improves the radiation shielding performance of space structures as compared to the traditionally used aluminum alloys. We discuss herein the radiation shielding correlations between measurements on board STS-81 (Atlantis, 1997) using four polyethylene (PE) spheres of varying radii, and STS-89 (Endeavour, 1998) using aluminum alloy spheres; with numerical simulations of charged particle transport using the Langley Research Center (LaRC)-developed High charge (Z) and Energy TRaNsport (HZETRN) algorithm. In the simulations, the Galactic Cosmic Ray (GCR) component of the ionizing radiation environment at Low Earth Orbit (LEO) covering ions in the 1Radiation (AIR) measurements. With the validity of numerical simulations through correlation with PE and aluminum spheres measurements established, we further present results from the expansion of the simulations through the selection of high hydrogen content commercially available polymeric constituents such as PE foam core and Spectra fiber(Registered TradeMark) composite face sheet to assess their radiation shield properties as compared to generic PE.

  15. The Cost of Jointness: Insights from Environmental Monitoring Systems in Low-Earth Orbit

    Dwyer, Morgan Maeve [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-09-01

    This report summarizes the results of doctoral research that explored the cost impact of acquiring complex government systems jointly. The report begins by reviewing recent evidence that suggests that joint programs experience greater cost growth than non-joint programs. It continues by proposing an alternative approach for studying cost growth on government acquisition programs and demonstrates the utility of this approach by applying it to study the cost of jointness on three past programs that developed environmental monitoring systems for low-Earth orbit. Ultimately, the report concludes that joint programs' costs grow when the collaborating government agencies take action to retain or regain their autonomy. The report provides detailed qualitative and quantitative data in support of this conclusion and generalizes its findings to other joint programs that were not explicitly studied here. Finally, it concludes by presenting a quantitative model that assesses the cost impacts of jointness and by demonstrating how government agencies can more effectively architect joint programs in the future.

  16. Analytical investigation of the dynamics of tethered constellations in earth orbit

    Lorenzini, Enrico C.; Gullahorn, Gordon E.; Estes, Robert D.

    1988-01-01

    This Quarterly Report on Tethering in Earth Orbit deals with three topics: (1) Investigation of the propagation of longitudinal and transverse waves along the upper tether. Specifically, the upper tether is modeled as three massive platforms connected by two perfectly elastic continua (tether segments). The tether attachment point to the station is assumed to vibrate both longitudinally and transversely at a given frequency. Longitudinal and transverse waves propagate along the tethers affecting the acceleration levels at the elevator and at the upper platform. The displacement and acceleration frequency-response functions at the elevator and at the upper platform are computed for both longitudinal and transverse waves. An analysis to optimize the damping time of the longitudinal dampers is also carried out in order to select optimal parameters. The analytical evaluation of the performance of tuned vs. detuned longitudinal dampers is also part of this analysis. (2) The use of the Shuttle primary Reaction Control System (RCS) thrusters for blowing away a recoiling broken tether is discussed. A microcomputer system was set up to support this operation. (3) Most of the effort in the tether plasma physics study was devoted to software development. A particle simulation code has been integrated into the Macintosh II computer system and will be utilized for studying the physics of hollow cathodes.

  17. Environmental Durability Issues for Solar Power Systems in Low Earth Orbit

    Degroh, Kim K.; Banks, Bruce A.; Smith, Daniela C.

    1994-01-01

    Space solar power systems for use in the low Earth orbit (LEO) environment experience a variety of harsh environmental conditions. Materials used for solar power generation in LEO need to be durable to environmental threats such as atomic oxygen, ultraviolet (UV) radiation, thermal cycling, and micrometeoroid and debris impact. Another threat to LEO solar power performance is due to contamination from other spacecraft components. This paper gives an overview of these LEO environmental issues as they relate to space solar power system materials. Issues addressed include atomic oxygen erosion of organic materials, atomic oxygen undercutting of protective coatings, UV darkening of ceramics, UV embrittlement of Teflon, effects of thermal cycling on organic composites, and contamination due to silicone and organic materials. Specific examples of samples from the Long Duration Exposure Facility (LDEF) and materials returned from the first servicing mission of the Hubble Space Telescope (HST) are presented. Issues concerning ground laboratory facilities which simulate the LEO environment are discussed along with ground-to-space correlation issues.

  18. Earth as diode: monsoon source of the orbital ~100 ka climate cycle

    R. Y. Anderson

    2010-08-01

    Full Text Available A potential source for Earth's enigmatic ~100 ka climate cycle, which is found in many ancient geological records at low latitudes and also in the pacing of glaciation during the late Pleistocene, is traced to a climatic rectifying process inherent in the monsoon. Seasonal information needed to identify the rectifying mechanism is preserved within varves of a continuous, 200 ka recording of annual maximum surface temperature (Tmax from the equator of Western Pangea. Specific seasonal reactions recorded in varves show how the monsoon reacted to seasonal differences in insolation at equinox to produce a 11.7 ka semi-precession cycle in Tmax. At solstice, anti-phasing of insolation in the Northern and Southern Hemispheres, intensified and focused by a highly asymmetric Pangea relative to the equator, produced a strong equatorial maritime monsoon that performed a nonlinear rectifying function similar to that of a simple rectifying diode. Expressed in the resulting varve series are substantial cycles in Tmax of 100 ka, 23.4 ka, and 11.7 ka. Importantly, any external or internal forcing of the tropical (monsoon climate system at higher-than-orbital frequencies (e.g. solar, ENSO should also be amplified at Milankovitch frequencies by the monsoon.

  19. Use and Protection of GPS Sidelobe Signals for Enhanced Navigation Performance in High Earth Orbit

    Parker, Joel J. K.; Valdez, Jennifer E.; Bauer, Frank H.; Moreau, Michael C.

    2016-01-01

    The application of the Global Positioning System (GPS) for navigation of spacecraft in High and Geosynchronous Earth Orbit (HEO/GEO) has crossed a threshold and is now being employed in operational missions. Utilizing advanced GPS receivers optimized for these missions, space users have made extensive use of the sidelobe transmissions from the GPS satellites to realize navigation performance that far exceeds that predicted by pre-launch simulations. Unfortunately, the official specification for the GPS Space Service Volume (SSV), developed in 2006, assumes that only signals emanating from the main beam of the GPS transmit antenna are useful for navigation, which greatly under-estimates the number of signals available for navigation purposes. As a result, future high-altitude space users may be vulnerable to any GPS design changes that suppress the sidelobe transmissions, beginning with Block III space vehicles (SVs) 11-32. This paper presents proposed changes to the GPS system SSV requirements, as informed by data from recent experiments in the SSV and new mission applications that are enabled by GPS navigation in HEO/GEO regimes. The NASA/NOAA GOES-R series satellites are highlighted as an example of a mission that relies on this currently-unspecified GPS system performance to meet mission requirements.

  20. Space Radiation: The Number One Risk to Astronaut Health beyond Low Earth Orbit

    Jeffery C. Chancellor

    2014-09-01

    Full Text Available Projecting a vision for space radiobiological research necessitates understanding the nature of the space radiation environment and how radiation risks influence mission planning, timelines and operational decisions. Exposure to space radiation increases the risks of astronauts developing cancer, experiencing central nervous system (CNS decrements, exhibiting degenerative tissue effects or developing acute radiation syndrome. One or more of these deleterious health effects could develop during future multi-year space exploration missions beyond low Earth orbit (LEO. Shielding is an effective countermeasure against solar particle events (SPEs, but is ineffective in protecting crew members from the biological impacts of fast moving, highly-charged galactic cosmic radiation (GCR nuclei. Astronauts traveling on a protracted voyage to Mars may be exposed to SPE radiation events, overlaid on a more predictable flux of GCR. Therefore, ground-based research studies employing model organisms seeking to accurately mimic the biological effects of the space radiation environment must concatenate exposures to both proton and heavy ion sources. New techniques in genomics, proteomics, metabolomics and other “omics” areas should also be intelligently employed and correlated with phenotypic observations. This approach will more precisely elucidate the effects of space radiation on human physiology and aid in developing personalized radiological countermeasures for astronauts.

  1. The viscoelastic characterization of polymer materials exposed to the low-Earth orbit environment

    Strganac, Thomas; Letton, Alan

    1992-01-01

    Recent accomplishments in our research efforts have included the successful measurement of the thermal mechanical properties of polymer materials exposed to the low-earth orbit environment. In particular, viscoelastic properties were recorded using the Rheometrics Solids Analyzer (RSA 2). Dynamic moduli (E', the storage component of the elastic modulus, and E'', the loss component of the elastic modulus) were recorded over three decades of frequency (0.1 to 100 rad/sec) for temperatures ranging from -150 to 150 C. Although this temperature range extends beyond the typical use range of the materials, measurements in this region are necessary in the development of complete viscoelastic constitutive models. The experimental results were used to provide the stress relaxation and creep compliance performance characteristics through viscoelastic correspondence principles. Our results quantify the differences between exposed and control polymer specimens. The characterization is specifically designed to elucidate a constitutive model that accurately predicts the change in behavior of these materials due to exposure. The constitutive model for viscoelastic behavior reflects the level of strain, the rate of strain, and the history of strain as well as the thermal history of the material.

  2. Spacecraft plume interactions with the magnetosphere plasma environment in geostationary Earth orbit

    Stephani, K. A.; Boyd, I. D.

    2016-02-01

    Particle-based kinetic simulations of steady and unsteady hydrazine chemical rocket plumes are presented in a study of plume interactions with the ambient magnetosphere in geostationary Earth orbit. The hydrazine chemical rocket plume expands into a near-vacuum plasma environment, requiring the use of a combined direct simulation Monte Carlo/particle-in-cell methodology for the rarefied plasma conditions. Detailed total and differential cross sections are employed to characterize the charge exchange reactions between the neutral hydrazine plume mixture and the ambient hydrogen ions, and ion production is also modeled for photoionization processes. These ionization processes lead to an increase in local plasma density surrounding the spacecraft owing to a partial ionization of the relatively high-density hydrazine plume. Results from the steady plume simulations indicate that the formation of the hydrazine ion plume are driven by several competing mechanisms, including (1) local depletion and (2) replenishing of ambient H+ ions by charge exchange and thermal motion of 1 keV H+ from the ambient reservoir, respectively, and (3) photoionization processes. The self-consistent electrostatic field forces and the geostationary magnetic field have only a small influence on the dynamics of the ion plume. The unsteady plume simulations show a variation in neutral and ion plume dissipation times consistent with the variation in relative diffusion rates of the chemical species, with full H2 dissipation (below the ambient number density levels) approximately 33 s after a 2 s thruster burn.

  3. ORBITS OF NEAR-EARTH ASTEROID TRIPLES 2001 SN263 AND 1994 CC: PROPERTIES, ORIGIN, AND EVOLUTION

    Three-body model fits to Arecibo and Goldstone radar data reveal the nature of two near-Earth asteroid triples. The triple-asteroid system 2001 SN263 is characterized by a primary of ∼1013 kg, an inner satellite ∼1% as massive orbiting at ∼3 primary radii in ∼0.7 days, and an outer satellite ∼2.5% as massive orbiting at ∼13 primary radii in ∼6.2 days. 1994 CC is a smaller system with a primary of mass ∼2.6 x1011 kg and two satellites ∼2% and ∼-1; 1994 CC inner body: dpiv/dt∼ -0.2 deg day-1), which is in agreement with analytical predictions of the secular evolution due to mutually interacting orbits and primary oblateness. Nonzero mutual inclinations between the orbital planes of the satellites provide the best fits to the data in both systems (2001 SN263: ∼ 14 deg; 1994 CC: ∼16 deg). Our best-fit orbits are consistent with nearly circular motion, except for 1994 CC's outer satellite which has an eccentric orbit of e ∼ 0.19. We examine several processes that can generate the observed eccentricity and inclinations, including the Kozai and evection resonances, past mean-motion resonance crossings, and close encounters with terrestrial planets. In particular, we find that close planetary encounters can easily excite the eccentricities and mutual inclinations of the satellites' orbits to the currently observed values.

  4. Jupiter family comets in near-Earth orbits: Are some of them interlopers from the asteroid belt?

    Fernández, Julio A.; Sosa, Andrea

    2015-12-01

    We analyze a sample of 58 Jupiter family comets (JFCs) in near-Earth orbits, defined as those whose perihelion distances at the time of discovery were qdisc newcomers in the near-Earth region. Yet, a minor fraction of JFCs (less than about one third) are found to move on stable orbits for the past ∼ 104 yr, and in some cases are found to continue to be stable at 5 × 104 yr in the past. They also avoid very close encounters with Jupiter. Their orbital behavior is very similar to that of NEAs in cometary orbits. While "typical" JFCs in unstable orbits probably come from the trans-Neptunian region, the minor group of JFCs in asteroidal orbits may come from the main asteroid belt, like the NEAs. The asteroidal JFCs may have a more consolidated structure and a higher mineral content than that of comets coming from the trans-Neptunian belt or the Oort cloud, which could explain their much longer physical lifetimes in the near-Earth region. In particular, we mention comets 66P/du Toit, 162P/Siding Spring, 169P/NEAT, 182P/LONEOS, 189P/NEAT, 249P/LINEAR, 300P/Catalina, and P/2003 T12 (SOHO) as the most likely candidates to have an origin in the main asteroid belt. Another interesting case is 207P/NEAT, which stays near the 3:2 inner mean motion resonance with Jupiter, possibly evolving from the Hilda asteroid zone.

  5. Perihelion advances for the orbits of Mercury, Earth and Pluto from Extended Theory of General Relativity (ETGR)

    Ridao, Luis Santiago; De Cicco, Martín Daniel; Bellini, Mauricio

    2014-01-01

    We explore the geodesic movement on a effective 4D hypersurface which is embedded in a 5D Ricci-flat Manifold described by a canonical metric, in order to applying to planetary orbits in our solar system. Some important solutions are given, which provide the standard solutions of General Relativity without any extra force component. We study the perihelion advances of Mercury, the Earth and Pluto using the Extended Theory of General Relativity (ETGR). Our results are in very good agreement with observations and show how the foliation is determinant to the value of the perihelion's advances. The possible applications are not limited to these kinds of orbits.

  6. Contribution of the Earth's gravitational potential to variations in orbital motion of short-period comets

    We present simulation results on evolution development of orbital motion of short-period comets with the revolution period not exceeding 6–7 years, namely comets 21P/Giacobini–Zinner, 26P/Grigg–Skjellerup and 7P/Pons–Winnecke. The calculations cover the range from the date of the object's discovery to 2100. Variations in the objects' orbital elements under the action of gravity disturbances, taking Earth's gravitational potential into account when the small body approaches, are analyzed. Corrected dates of perihelion passages can be used for scheduling observations. (paper)

  7. 太阳帆绕地球周期轨道研究%Solar Sail Periodical Orbits around Earth

    龚胜平; 李俊峰; 宝音贺西; 罗镇

    2012-01-01

    Earth-synchronous orbits and Sun-synchronous orbits can be applied in all kinds of fields. Geostationary orbit is a special Earth-synchronous orbit and geostationary orbit resource is limited. Utilization of chemical propulsion or electrical propulsion can generate stationary orbits of different orbit altitudes, which will consume unbearable propellant in engineer practice. A solar sail is proposed to implement Earth-synchronous orbits and Sun-synchronous orbits in this paper. The solar sail is aligned to guarantee that the orbit plane rotates synchronously with the sunlight. The results show that this is possible by designing the solar sail and selecting the orbit parameters. With the assumption that the sunlight is in the Earth equator, the solar sail can evolve in a quasi-stationary orbit with its ground track moving around a point. In fact, the sunlight is in the ecliptic plane. Considering the angle included between the Earth equator and ecliptic plane, the ground track of solar sail will be an area suitable for long time observation.%地球同步和太阳同步卫星在各个领域有着广泛的应用.静止轨道是一种特殊的地球同步轨道,轨道资源有限.利用化学推进或电推进可以实现轨道高度不同的同步轨道,如悬挂轨道,但需要消耗较多的燃料,工程上无法承受.本文考虑利用太阳帆实现地球同步和太阳同步轨道.太阳光压力在轨道平面内沿拱线方向,选择光压力与平面的夹角使得轨道平面的旋转速率与太阳光同步.研究表明,设计合适的半长轴和偏心率可以使得轨道旋转速率与地球自转速率一致.假设太阳光与赤道平面平行,可以得到准静止轨道,太阳帆将在传统静止轨道的附近运动,星下点的经度将在一个固定值附近振动.实际上太阳光是与黄道面平行,黄道面与赤道面之间存在夹角.考虑黄赤交角的情况下,太阳帆将在一定纬度和经度范围内运动.适合于对某个区域进行长期观测任务.

  8. Development of Multifunctional Radiation Shielding Materials for Long Duration Human Exploration Beyond the Low Earth Orbit

    Sen, S.; Bhattacharya, M.; Schofield, E.; Carranza, S.; O'Dell, S.

    2007-01-01

    One of the major challenges for long duration human exploration beyond the low Earth orbit and sustained human presence on planetary surfaces would be development of materials that would help minimize the radiation exposure to crew and equipment from the interplanetary radiation environment, This radiation environment consists primarily of a continuous flux of galactic cosmic rays (GCR) and transient but intense fluxes of solar energetic particles (SEP). The potential for biological damage by the relatively low percentage of high-energy heavy-ions in the GCR spectrum far outweigh that due to lighter particles because of their ionizing-power and the quality of the resulting biological damage. Although the SEP spectrum does not contain heavy ions and their energy range is much lower than that for GCRs, they however pose serious risks to astronaut health particularly in the event of a bad solar storm The primary purpose of this paper is to discuss our recent efforts in development and evaluation of materials for minimizing the hazards from the interplanetary radiation environment. Traditionally, addition of shielding materials to spacecrafts has invariably resulted in paying a penalty in terms of additional weight. It would therefore be of great benefit if materials could be developed not only with superior shielding effectiveness but also sufficient structural integrity. Such a multifunctional material could then be considered as an integral part of spacecraft structures. Any proposed radiation shielding material for use in outer space should be composed of nuclei that maximize the likelihood of projectile fragmentation while producing the minimum number of target fragments. A modeling based approach will be presented to show that composite materials using hydrogen-rich epoxy matrices reinforced with polyethylene fibers and/or fabrics could effectively meet this requirement. This paper will discuss the fabrication of such a material for a crewed vehicle. Ln addition

  9. From horseshoe to quasi-satellite and back again: the curious dynamics of Earth co-orbital asteroid 2015 SO2

    Marcos, C de la Fuente

    2015-01-01

    Earth co-orbitals of the horseshoe type are interesting objects to study for practical reasons. They are relatively easy to access from our planet and that makes them attractive targets for sample return missions. Here, we show that near-Earth asteroid (NEA) 2015 SO2 is a transient co-orbital to the Earth that experiences a rather peculiar orbital evolution characterised by recurrent, alternating horseshoe and quasi-satellite episodes. It is currently following a horseshoe trajectory, the ninth asteroid known to do so. Besides moving inside the 1:1 mean motion resonance with the Earth, it is subjected to a Kozai resonance with the value of the argument of perihelion librating around 270 degrees. Contrary to other NEAs, asteroid 2015 SO2 may have remained in the vicinity of Earth's co-orbital region for a few hundreds of thousands of years.

  10. Atomic Oxygen Interactions With Silicone Contamination on Spacecraft in Low Earth Orbit Studied

    Banks, Bruce A.

    2001-01-01

    Silicones have been widely used on spacecraft as potting compounds, adhesives, seals, gaskets, hydrophobic surfaces, and atomic oxygen protective coatings. Contamination of optical and thermal control surfaces on spacecraft in low Earth orbit (LEO) has been an ever-present problem as a result of the interaction of atomic oxygen with volatile species from silicones and hydrocarbons onboard spacecraft. These interactions can deposit a contaminant that is a risk to spacecraft performance because it can form an optically absorbing film on the surfaces of Sun sensors, star trackers, or optical components or can increase the solar absorptance of thermal control surfaces. The transmittance, absorptance, and reflectance of such contaminant films seem to vary widely from very transparent SiOx films to much more absorbing SiOx-based films that contain hydrocarbons. At the NASA Glenn Research Center, silicone contamination that was oxidized by atomic oxygen has been examined from LEO spacecraft (including the Long Duration Exposure Facility and the Mir space station solar arrays) and from ground laboratory LEO simulations. The findings resulted in the development of predictive models that may help explain the underlying issues and effects. Atomic oxygen interactions with silicone volatiles and mixtures of silicone and hydrocarbon volatiles produce glassy SiOx-based contaminant coatings. The addition of hydrocarbon volatiles in the presence of silicone volatiles appears to cause much more absorbing (and consequently less transmitting) contaminant films than when no hydrocarbon volatiles are present. On the basis of the LDEF and Mir results, conditions of high atomic oxygen flux relative to low contaminant flux appear to result in more transparent contaminant films than do conditions of low atomic oxygen flux with high contaminant flux. Modeling predictions indicate that the deposition of contaminant films early in a LEO flight should depend much more on atomic oxygen flux than