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  • 1
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    Fast Attitude Maneuvers for the Lunar Reconnaissance Orbiter (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: This paper describes a new operational capability for fast attitude maneuvering that is being developed for the Lunar Reconnaissance Orbiter (LRO). The LRO hosts seven scientific instruments. For some instruments, it is necessary to per-form large off-nadir slews to collect scientific data. The accessibility of off-nadir science targets has been limited by slew rates and/or occultation, thermal and power constraints along the standard slew path. The new fast maneuver (FastMan) algorithm employs a slew path that autonomously avoids constraint violations while simultaneously minimizing the slew time. The FastMan algo-rithm will open regions of observation that were not previously feasible and improve the overall science return for LRO's extended mission. The design of an example fast maneuver for LRO's Lunar Orbiter Laser Altimeter that reduc-es the slew time by nearly 40% is presented. Pre-flight, ground-test, end-to-end tests are also presented to demonstrate the readiness of FastMan. This pioneer-ing work is extensible and has potential to improve the science data collection return of other NASA spacecraft, especially those observatories in extended mission phases where new applications are proposed to expand their utility.
    Keywords: Spacecraft Design, Testing and Performance
    Type: AAS 19-053 , GSFC-E-DAA-TN65209 , Annual AAS Guidance, Navigation, and Control Conference; Feb 01, 2019 - Feb 06, 2019; Breckenridge, CO; United States
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  • 2
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    Solar System Expansion and Strong Equivalence Principle as Seen by the NASA MESSENGER Mission (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NASA MESSENGER mission explored the innermost planet of the solar system and obtained a rich dataset of range measurements for the determination of Mercury's ephemeris. Here we use these precise data collected over seven years to estimate parameters related to General Relativity and the evolution of the Sun. These results confirm the validity of the Strong Equivalence Principle with a significantly refined uncertainty of the Nordtvedt parameter eta=(-6.6 plus or minus 7.2)x10(exp -5) By assuming a metric theory of gravitation, we retrieved the Post-Newtonian parameter beta = 1 + (-1.6 plus or minus 1.8)x10(exp -5) and the Sun's gravitational oblateness, J(sub 2 solar)=(2.246 plus or minus 0.022)x10(exp -7). Finally, we obtain an estimate of the time variation of the Sun gravitational parameter, G (raised dot)solar mass/G solar mass =(-6.13 plus or minus 1.47)x10(exp -14), which is consistent with the expected solar mass loss due to the solar wind and interior processes. This measurement allows us to constrain |G(raised dot)|/G to be less than 4 x 10(exp -14) yr(exp -1).
    Keywords: Solar Physics; Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN50758 , GSFC-E-DAA-TN51570 , Nature Communications (e-ISSN 2041-1723); 9; 289
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  • 3
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    Small and Lightweight Laser Retro-Reflector Arrays for Lunar Landers (2019)
    In:  Other Sources
    Details
    Publication Date: 2020-01-01
    Description: A set of small and lightweight laser retro-reflector arrays (LRAs) was fabricated and tested for use on lunar landersunder NASA's Commercial Lunar Payload Service program. Each array contains eight 1.27-cm-diameter cornercube retro-reflectors mounted on a dome-shaped aluminum structure. The arrays are 5.0cmin diameter at the base,1.6 cm in height, and 20 g in mass. They can be tracked by an orbiting laser altimeter, such as the Lunar OrbiterLaser Altimeter, froma distance of a few hundred kilometers or by a landing lidar on future lunar landers. TheLRAsdemonstrated a diffraction-limited optical performance. They were designed and tested to survive and function ontheMoon for decades,well after the lander missions are completed.
    Keywords: Spacecraft Design, Testing and Performance
    Type: GSFC-E-DAA-TN75773 , Applied Optics (ISSN 1559-128X) (e-ISSN 2155-3165); 58; 33; 9259-9266
    Format: text
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  • 4
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    Trilogy, A Planetary Geodesy Mission Concept for Measuring the Expansion of the Solar System (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The scale of the solar system is slowly changing, likely increasing as a result of solar mass loss, with additional change possible if there is a secular variation of the gravitational constant, G. The measurement of the change of scale could provide insight into the past and the future of the solar system, and in addition a better understanding of planetary motion and fundamental physics. Estimates for the expansion of the scale of the solar system are of order 1.5 cm year(exp -1) AU(exp -1), which over several years is an observable quantity with present-day laser ranging systems. This estimate suggests that laser measurements between planets could provide an accurate estimate of the solar system expansion rate. We examine distance measurements between three bodies in the inner solar system -- Earth's Moon, Mars and Venus -- and outline a mission concept for making the measurements. The concept involves placing spacecraft that carry laser ranging transponders in orbit around each body and measuring the distances between the three spacecraft over a period of several years. The analysis of these range measurements would allow the co-estimation of the spacecraft orbit, planetary ephemerides, other geophysical parameters related to the constitution and dynamics of the central bodies, and key geodetic parameters related to the solar system expansion, the Sun, and theoretical physics.
    Keywords: Solar Physics; Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN52817 , Planetary and Space Science (ISSN 0032-0633); 153; 127-133
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