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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Pointing Control System Architecture for the Eclipse Mission

This paper describes the high performance pointing control system used to point the Eclipse telescope. Eclipse is a new mission under study at Jet Propulsion Laboratory for a proposal as a discovery mission. Eclipse is a space telescope for high-contrast optical astronomy. It will be used to investigate the planetary bodies and environments. The main objective of the Eclipse mission is to study planets around nearby stars. Eclipse is designed to reveal planets or dust structures by reducing the scattered and diffracted light within a few arcseconds of a star to a level three orders of magnitude lower than any instrument on the Hubble Space Telescope (HST). Eclipse achieves this high contrast using a 1.8 meter diameter telescope, a coronagraphic system for control of diffracted light, and active wavefront correction using a Precision Deformable Mirror (DM) for the suppression of scattered light. The observatory will be launched into a Sun-synchronous 690 Km, 98.2(deg) Earth Orbit in 2012.

architecture↗
NASA NTRS2006

The Kepler Mission and Eclipsing Binaries

The Kepler Mission is a photometric mission with a precision of 14 ppm (at R=12) that is designed to continuously observe a single field of view (FOV) of greater 100 sq deg in the Cygnus-Lyra region for four or more years. The primary goal of the mission is to monitor greater than 100,000 stars for transits of Earth-size and smaller planets in the habitable zone of solar-like stars. In the process, many eclipsing binaries (EB) will also be detected and light curves produced. To enhance and optimize the mission results, the stellar characteristics for all the stars in the FOV with R less than 16 will have been determined prior to launch. As part of the verification process, stars with transit candidates will have radial velocity follow-up observations performed to determine the component masses and thereby separate eclipses caused by stellar companions from transits caused by planets. The result will be a rich database on EBs. The community will have access to the archive for further analysis, such as, for EB modeling of the high-precision light curves. A guest observer program is also planned to allow for photometric observations of objects not on the target list but within the FOV, since only the pixels of interest from those stars monitored will be transmitted to the ground.

Koch, David↗
NASA NTRS2005

The Effects of Instrumental Elliptical Polarization on Stellar Point Spread Function Fine Structure

We present procedures and preliminary results from a study on the effects of instrumental polarization on the fine structure of the stellar point spread function (PSF). These effects are important to understand because the the aberration caused by instrumental polarization on an otherwise diffraction-limited will likely have have severe consequences for extreme high contrast imaging systems such as NASA's planned Terrestrial Planet Finder (TPF) mission and the proposed NASA Eclipse mission. The report here, describing our efforts to examine these effects, includes two parts: 1) a numerical analysis of the effect of metallic reflection, with some polarization-specific retardation, on a spherical wavefront; 2) an experimental approach for observing this effect, along with some preliminary laboratory results. While the experimental phase of this study requires more fine-tuning to produce meaningful results, the numerical analysis indicates that the inclusion of polarization-specific phase effects (retardation) results in a point spread function (PSF) aberration more severe than the amplitude (reflectivity) effects previously recorded in the literature.

high angular resolution↗
NASA NTRS2020

Operational Techniques for Dealing with Long Eclipses During the MMS Extended Mission

Launch window design for the Magnetospheric Multiscale (MMS) mission ensured that no excessive eclipses would be encountered during the prime mission. However, no orbit solutions exist that satisfy the eclipse constraints indefinitely: most extended mission years contain 1-3 eclipses long enough to potentially damage either the spacecraft or its scientific instruments. Two steps were taken to improve the situation. Firstly, raising apogee radius from 25 to 29.34 Earth radii altered the Sun-Earth-MMS phasing, so efficiently achieving reductions in the long eclipse durations. These maneuvers were performed early this year, in preparation for the first pair of long eclipses in August 2019. Secondly, a set of operational steps were taken around the time of the eclipses to help maintain spacecraft and instrument temperatures while preventing power load shedding. These operational steps included raising key onboard temperatures through adjusting the spacecraft attitude to tilt the instrument deck towards the Sun, and engaging select heaters prior to going into eclipses. In addition, all scientific instruments were turned off, as well as high-power, non-critical spacecraft systems, to conserve energy.These steps each came with trade-offs which will be discussed in the paper. Finally, the results that were obtained when the spacecraft experienced the first extremely long eclipses will be discussed, as will lessons learned for future long eclipses.

Williams, Trevor↗
NASA NTRS2005

A Case Study in High Contrast Coronagraph for Planet Discovery: The Eclipse Concept and Support Laboratory Experience

Eclipse is a proposed NASA Discovery mission to perform a sensitive imaging survey of nearby planetary systems, including a survey for jovian-sized planets orbiting Sun-like stars to distances of 15 pc. We outline the science objectives of the Eclipse mission and review recent developments in the key enabling technologies. Eclipse is a space telescope concept for high-contrast visible-wavelength imaging and spectrophotometry. Its design incorporates a telescope with an unobscured aperture of 1.8 meters, a coronographic camera for suppression of diffracted light, and precise active wavefront correction for the suppression of scattered background light. For reference, Eclipse is designed to reduce the diffracted and scattered starlight between 0.33 and 1.5 arcseconds from the star by three orders of magnitude compared to any HST instrument. The Eclipse mission provides precursor science exploration and technology experience in support of NASA's Terrestrial Planet Finder (TPF) program.

coronagraphic imaging testbed↗
NASA NTRS2005

Eclipsing Binaries from the Kepler Mission

The Kepler Mission is a photometric space mission that will continuously observe a single 100 sq deg field of view (FOV) of greater than 100,000 stars in the Cygnus-Lyra region for 4 or more years with a precision of 14 ppm (R=12). The primary goal of the mission is to detect Earth-size planets in the habitable zone of solar-like stars. In the process, many eclipsing binaries (EB) will also be detected. Prior to launch, the stellar characteristics will have been detennined for all the stars in the FOV with R<16. As part of the verification process, stars with transits ~<5% will need to have follow-up radial velocity observations performed to determine the component masses and thereby separate transits caused by stellar companions from those caused by planets. The result will be a rich database on EBs. The community will have access to the archive for uses such as for EB modeling of the high-precision light curves. A guest observer program is also planned for objects not already on the target list.

Koch, David↗
NASA NTRS1995

Ground-Based and Space-Based Laser Beam Power Applications

A space power system based on laser beam power is sized to reduce mass, increase operational capabilities, and reduce complexity. The advantages of laser systems over solar-based systems are compared as a function of application. Power produced from the conversion of a laser beam that has been generated on the Earth's surface and beamed into cislunar space resulted in decreased round-trip time for Earth satellite electric propulsion tugs and a substantial landed mass savings for a lunar surface mission. The mass of a space-based laser system (generator in space and receiver near user) that beams down to an extraterrestrial airplane, orbiting spacecraft, surface outpost, or rover is calculated and compared to a solar system. In general, the advantage of low mass for these space-based laser systems is limited to high solar eclipse time missions at distances inside Jupiter. The power system mass is less in a continuously moving Mars rover or surface outpost using space-based laser technology than in a comparable solar-based power system, but only during dust storm conditions. Even at large distances for the Sun, the user-site portion of a space-based laser power system (e.g., the laser receiver component) is substantially less massive than a solar-based system with requisite on-board electrochemical energy storage.

Bozek, John M.↗
NASA NTRS2001

Design of the Thermal Control System for the Space Technology 5 Microsatellite

The New Millennium Program's (NMP) Space Technology 5 (ST-5) Project, currently in Phase B of the design process, is slated to launch three 20-kg class spin stabilized microsatellites in late 2003. The proposed orbit is highly elliptical and could result in an earth shadow eclipse of almost 2 hours. Although ST-5's maximum eclipse is only 2 hours, future missions could involve eclipses as long as 8 hours. As spacecraft size, mass, and available resources decrease and eclipse duration increases, thermal engineers will be challenged to design simple but robust thermal control systems that meet temperature requirements for all phases of the mission. This paper presents the results of a study of three design concepts and preliminary analysis of the design selected for ST-5.

Douglas, Donya↗
NASA NTRS2019

Libration Orbit Eclipse Avoidance Maneuver Study for the James Webb Space Telescope Mission

Mission analysis of libration orbit trajectories at Sun-Earth/Moon L2 typically includes predictions of lunar and Earth eclipses during the mission life-time. The NASA James Webb Space Telescope (JWST) trajectory, by design, avoids these eclipses by pruning its launch window. In an off-nominal scenario where an eclipse is predicted, a maneuver strategy is needed. In this paper, trade studies are examined for JWST that characterize the burn magnitude, location, and epochs of multiple maneuver plans to avoid an eclipse. The results enable analysts to explore the space of feasible maneuver strategies during routine operations.

Maneuver design↗
NASA NTRS2016

Monte Carlo Analysis as a Trajectory Design Driver for the TESS Mission

The Transiting Exoplanet Survey Satellite (TESS) will be injected into a highly eccentric Earth orbit and fly 3.5 phasing loops followed by a lunar flyby to enter a mission orbit with lunar 2:1 resonance. Through the phasing loops and mission orbit, the trajectory is significantly affected by lunar and solar gravity. We have developed a trajectory design to achieve the mission orbit and meet mission constraints, including eclipse avoidance and a 30-year geostationary orbit avoidance requirement. A parallelized Monte Carlo simulation was performed to validate the trajectory after injecting common perturbations, including launch dispersions, orbit determination errors, and maneuver execution errors. The Monte Carlo analysis helped identify mission risks and is used in the trajectory selection process.

trajectory↗
NASA NTRS2016

Monte Carlo Analysis as a Trajectory Design Driver for the Transiting Exoplanet Survey Satellite (TESS) Mission

The Transiting Exoplanet Survey Satellite (TESS) will be injected into a highly eccentric Earth orbit and fly 3.5 phasing loops followed by a lunar flyby to enter a mission orbit with lunar 2:1 resonance. Through the phasing loops and mission orbit, the trajectory is significantly affected by lunar and solar gravity. We have developed a trajectory design to achieve the mission orbit and meet mission constraints, including eclipse avoidance and a 30-year geostationary orbit avoidance requirement. A parallelized Monte Carlo simulation was performed to validate the trajectory after injecting common perturbations, including launch dispersions, orbit determination errors, and maneuver execution errors. The Monte Carlo analysis helped identify mission risks and is used in the trajectory selection process.

monte carlo↗
NASA NTRS1998

AXAF-I Low Intensity-Low Temperature (LILT) Testing of the Development Verification Test (DVT) Solar Panel

The planned orbit of the AXAF-I spacecraft will subject the spacecraft to both short, less than 30 minutes for solar and less than 2 hours for lunar, and long earth eclipses and lunar eclipses with combined conjunctive duration of up to 3 to 4 hours. Lack of proper Electrical Power System (EPS) conditioning prior to eclipse may cause loss of mission. To avoid this problem, for short eclipses, it is necessary to off-point the solar array prior to or at the beginning of the eclipse to reduce the battery state of charge (SOC). This yields less overcharge during the high charge currents at sun entry. For long lunar eclipses, solar array pointing and load scheduling must be tailored for the profile of the eclipse. The battery SOC, loads, and solar array current-voltage (I-V) must be known or predictable to maintain the bus voltage within acceptable range. To address engineering concerns about the electrical performance of the AXAF-I solar array under Low Intensity and Low Temperature (LILT) conditions, Marshall Space Flight Center (MSFC) engineers undertook special testing of the AXAF-I Development Verification Test (DVT) solar panel in September-November 1997. In the test the DVT test panel was installed in a thermal vacuum chamber with a large view window with a mechanical "flapper door". The DVT test panel was "flash" tested with a Large Area Pulse Solar Simulator (LAPSS) at various fractional sun intensities and panel (solar cell) temperatures. The testing was unique with regards to the large size of the test article and type of testing performed. The test setup, results, and lessons learned from the testing will be presented.

Alexander, Doug↗
NASA NTRSDate not supplied

Eclipse Mitigation Strategies in P/2 Lunar Resonant Orbits

Lunar resonant orbits present several important challenges in terms of trajectory design, insertion, stability and eclipse mitigation. For some mission concepts, the placement of the initial orbital elements is fundamental to overcoming show-stopping performance values such as eclipse duration and orbit lifetime. Lunar resonant orbits need to maintain specific alignments in order to avoid undesired flybys or even recontact with Earth or GEO satellites. This paper presents methods to mitigate long eclipses while preserving achievable lunar resonant orbits that persist in the long term.

Eclipse Mitigation↗
NASA NTRS2012

Heliophysics from and of the Moon - the Solar Occultation Explorer (SOX)

The fundamental processes of the inner corona of the Sun at 1.1 to 3 solar radii can occasionally be investigated in detail by ground-based solar eclipse observations at quasi-yearly intervals. The combination of portable ground-based telescopes and the distant occulting edge provided by the lunar limb allows imaging of coronal structure and ion excitation emission lines at the highest available spatial and spectral resolution. These observations are limited to the visible eastern and western coronal regions and cannot view the intervening region over the central disk in the hemisphere towards Earth. A comparable configuration for continuous coronal observations from a spacecraft, e.g. with an external occulter disk on a 100-meter boom, is conceivable and could generate 3-D data models of the corona via tomographic reconstruction from time series measurements but may not now be technically or economically feasible. The faster and cheaper approach would be to make high cadence eclipse observations from one or more small satellites in lunar orbit. The Solar Occultation Explorer (SOX) is suggested as an explorer-class NASA mission that would conduct eclipse observations at daily to hourly cadence depending on the orbit. This smallsat would carry two principal instrument suites: (1 ) spectroscopic imaging telescope with sub-nm resolution for selected coronal emission lines diagnostic of coronal plasma charge state, denSity, and temperature, and (2) in-situ field & particle instrument suite for measurements of the solar wind and local lunar environments. The most comparable flight heritage instrument, the LASCO C1 spectrometer on the Solar and Heliospheric Observatory (SOHO) mission, did achieve high visible-band spectral resolution with a Fabry-Perot interferometer but was limited in brightness sensitivity by usage of an internal occulter system and has not been operational since June 1998 The SOX mission concept is undergoing initial study by the Lunar Solar Origins Exploration (LunaSOX) project of the NASA Lunar Advanced Science and Exploration Research (LASER) program. This mission would offer high complementarity with the planned Solar Probe Plus spacecraft, designed to investigate.

Cooper, John F.↗