370 research outputs found
Janus and Lunar Trailblazer: Lockheed Martin Deep Space SmallSats for NASA SIMPLEx Missions
NASA’s Small Innovative Missions for Planetary Exploration (SIMPLEx) program is a principal investigator-led planetary science program focusing on small spacecraft. In the SIMPLEx-2 opportunity, the cost cap for SIMPLEx missions is approximately 1/10th the cost of the next larger class of planetary exploration missions, the Discovery Program. Unlike Discovery missions, SIMPLEx missions launch as rideshare payloads with other NASA primary missions. Lockheed Martin has developed a science-capable deep space small spacecraft architecture to support two missions selected for the SIMPLEx-2 opportunity: Janus and Lunar Trailblazer. Janus is a two-spacecraft mission to fly by two different binary Near Earth Asteroids, partnered with Dr. Dan Scheeres at the University of Colorado Boulder. Lunar Trailblazer is a lunar orbiter led by Dr. Bethany Ehlmann at Caltech which will map water on the Moon; both have passed PDR and are confirmed for flight. Janus will launch first, in August 2022. A scalable suite of hardware subsystems enables the same low-cost spacecraft architecture to support both missions with a high degree of commonality, despite their disparate mission designs, environments, physical configuration, and science operations. As both missions move through project implementation, the management and engineering teams have learned valuable lessons for developing deep space-capable small spacecraft, adapting from both Earth-orbiting SmallSats and traditional larger planetary exploration missions in the Discovery and New Frontiers program classes. Key lessons learned include the value of early and close coordination between interested science teams and spacecraft providers, the need to tailor the complexity of science investigations to SmallSat spacecraft capabilities, the importance of evaluating component lifetimes against the deep space mission environment, and the challenge of planetary mission design to a rideshare launch. Rideshare missions on planetary launches must meet schedules determined by primary spacecraft with inexorable planetary launch windows and must provide enough propulsion to reach their own destinations which may include planetary orbit insertion or targeting a completely different solar system destination than the primary spacecraft
The Role of Ejecta in the Small Crater Populations on the Mid-Sized Saturnian Satellites
We find evidence that crater ejecta play an important role in the small
crater populations on the Saturnian satellites, and more broadly, on cratered
surfaces throughout the Solar System. We measure crater populations in Cassini
images of Enceladus, Rhea, and Mimas, focusing on image data with scales less
than 500 m/pixel. We use recent updates to crater scaling laws and their
constants to estimate the amount of mass ejected in three different velocity
ranges: (i) greater than escape velocity, (ii) less than escape velocity and
faster than the minimum velocity required to make a secondary crater (v_min),
and (iii) velocities less than v_min. Although the vast majority of mass on
each satellite is ejected at speeds less than v_min, our calculations
demonstrate that the differences in mass available in the other two categories
should lead to observable differences in the small crater populations; the
predictions are borne out by the measurements we have made to date. Rhea,
Tethys, and Dione have sufficient surface gravities to retain ejecta moving
fast enough to make secondary crater populations. The smaller satellites, such
as Enceladus but especially Mimas, are expected to have little or no
traditional secondary populations because their escape velocities are near the
threshold velocity necessary to make a secondary crater. Our work clarifies why
the Galilean satellites have extensive secondary crater populations relative to
the Saturnian satellites. The presence, extent, and sizes of sesquinary craters
(craters formed by ejecta that escape into temporary orbits around Saturn
before re-impacting the surface) is not yet well understood. Finally, our work
provides further evidence for a "shallow" size-frequency distribution (slope
index of ~2 for a differential power-law) for comets a few km diameter and
smaller. [slightly abbreviated]Comment: Submitted to Icarus. 77 double-spaced pages, including 25 figures and
5 table
Receptor for advanced glycation endproducts (RAGE) deficiency protects against MPTP toxicity
Copyright © 2011 Elsevier Inc. All rights reserved.Peer reviewedPublisher PD
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Exploring the seas of Titan: the Titan Mare Eplorer (TiME) mission
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Titan Mare Explorer (TiME): first in situ exploration of an extraterrestrial sea
The lakes and seas of Titan are a sink of products of photolysis in the atmosphere, and a crucial component in Titan's active methane cycle. In situ exploration of the seas is necessary to understand their intriguing prebiotic organic chemistry
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MP3 - A meteorology and physical properties package to explore air-sea interaction on Titan
The exchange of mass, heat and momentum at the air:sea interface are profound influences on the terrestrial environment, affecting the intensity of hurricanes, the size of waves and lake-effect precipitation. Titan presents us with an opportunity to study these processes in a novel physical context, with a different sea, atmosphere and gravity. The MP3 instrument, under development for the proposed Discovery mission TiME (Titan Mare Explorer [1,2]) is an integrated suite of small, simple sensors that combines the function of traditional meteorology packages with liquid physical properties and depth-sounding : these latter functions follow the concept of - and indeed use spare elements from - the Huygens Surface Science Package (SSP,[3]). However, unlike Huygens’ brief and dynamic 3 hours of measurement, in TiME’s 6-Titan-day (96 Earth day) nominal mission enabled by radioisotope power, MP3 will have an unprecedented long-term measurement opportunity in one of the most evocative environments in the solar system, Titan’s sea Ligeia Mare
The global surface roughness of 25143 Itokawa
Surface roughness is an important metric in understanding how the geologic
history of an asteroid affects its small-scale topography and it provides an
additional means to quantitatively compare one asteroid with another. In this
study, we report the first detailed global surface roughness maps of 25143
Itokawa at horizontal scales from 8--32~m. Comparison of the spatial
distribution of the surface roughness of Itokawa with 433 Eros, the other
asteroid for which this kind of analysis has been possible, indicates that the
two asteroids are dominated by different geologic processes. On Itokawa, the
surface roughness reflects the results of down-slope activity that moves fine
grained material into geopotential lows and leaves large blocks in geopotential
highs. On 433 Eros, the surface roughness is controlled by geologically-recent
large impact craters. In addition, large longitudinal spatial variations of
surface roughness could impact the role of YORP on Itokawa
Janus: Launch of a NASA SmallSat Mission to Near-Earth Binary Asteroids
Janus is a two-spacecraft SmallSat mission to fly by two different pairs of binary near Earth asteroids, (175706) 1996 FG3 and (35107) 1991 VH. The two identical Janus spacecraft are scheduled to launch during a launch period opening 1 August 2022 as secondary payloads with the NASA Psyche mission, on a SpaceX Falcon Heavy launch vehicle. Janus is led by principal investigator Dr. Dan Scheeres at the University of Colorado Boulder and managed, built, and operated by Lockheed Martin. These planetary SmallSats share many deep space challenges similar to larger missions: Janus must execute deep space maneuvers to achieve hundreds of meters per second ΔV to reach its destinations, close a telecommunication link at ranges up to 2.4 AU, autonomously manage a several-month-long telecommunications blackout during solar conjunction, operate at a maximum Sun range of 1.62 AU, and survive for approximately four years in interplanetary space before encountering their target asteroids. During the encounters, the spacecraft will return high resolution visible and infra-red images of the asteroids. In getting Janus to the pad, the implementation team successfully managed an aggressive mission schedule despite COVID-19 related supply chain impacts and work environments, all while remaining on target for the SIMPLEx-2 cost cap. Janus is a pathfinder for achievable and affordable SmallSat science missions and demonstrates the valuable partnership between an experienced deep space mission engineering team, the SmallSat commercial component industry, and a forward- looking NASA model for Class-D science missions
Receptor for Advanced Glycation End Products (RAGE) Deficiency Attenuates the Development of Atherosclerosis in Diabetes
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