HR: 14:30h
AN: P23A-03    [Abstracts]
TI: Mars Reconnaissance Orbiter Accelerometer Experiment Results
AU: * Keating, G M
EM: g.m.keating@larc.nasa.gov
AF: The George Washington University, Mechanical and Aerospace Engineering, Newport News, VA , United States
AU: Bougher, S W
EM: bougher@umich.edu
AF: The University of Michigan, Atmospheric, Oceanic and Space Sciences, Ann Arbor, MI , United States
AU: Theriot, M E
EM: m.e.theriot@larc.nasa.gov
AF: The George Washington University, Mechanical and Aerospace Engineering, Newport News, VA , United States
AU: Zurek, R W
EM: Richard.W.Zurek@jpl.nasa.gov
AF: California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA , United States
AU: Blanchard, R C
EM: r.c.blanchard@larc.nasa.gov
AF: The George Washington University, Mechanical and Aerospace Engineering, Newport News, VA , United States
AU: Tolson, R H
EM: r.h.tolson@larc.nasa.gov
AF: North Carolina State University, National Institute of Aerospace, Hampton, VA , United States
AU: Murphy, J R
EM: murphy@nmsu.edu
AF: New Mexico State University, Astronomy, Las Cruces, NM , United States
AB: The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005, designed for aerobraking, achieved Mars Orbital Insertion (MOI), March 10, 2006. Atmospheric density decreases exponentially with increasing height. By small propulsive adjustments of the apoapsis orbital velocity, periapsis altitude is fine tuned to the density surface that safely used the atmosphere of Mars to aerobrake over 400 orbits. MRO periapsis precessed from the South Pole at 6pm LST to near the equator at 3am LST. Meanwhile, apoapsis was brought dramatically from 40,000km at MOI to 460 km at aerobraking completion (ABX) August 30, 2006. After ABX, a few small propulsive maneuvers established the Primary Science Orbit (PSO), which without aerobraking would have required an additional 400 kg of fuel. Each of the 400 plus aerobraking orbits provided a vertical structure and distribution of density, scale heights, and temperatures, along the orbital path, providing key in situ insight into various upper atmosphere (greater than 100 km) processes. One of the major questions for scientists studying Mars is: "Where did the water go?" Honeywell's substantially improved electronics package for its IMU (QA-2000 accelerometer, gyro, electronics) maximized accelerometer sensitivities at the requests of The George Washington University, JPL, and Lockheed Martin. The improved accelerometer sensitivities allowed density measurements to exceed 200km, at least 40 km higher than with Mars Odyssey (MO). This extended vertical structures from MRO into the neutral lower exosphere, a region where various processes may allow atmospheric gasses to escape. Over the eons, water may have been lost in both near the surface and in the upper atmosphere. Thus the water balance throughout the entire atmosphere from subsurface to exosphere may both be critical. Comparisons of data from Mars Global Surveyor (MGS), MO and MRO help characterize key temporal and spatial cycles including: winter polar warming, planetary scale gravity waves, latitudinal, seasonal, and diurnal variations, and variations from perihelion to aphelion. This will validate and constrain both upper atmospheric circulation models used to understand the nature of high-altitude variability and transport processes, and engineering models used to plan future missions.
DE: 0343 Planetary atmospheres (5210, 5405, 5704)
DE: 0350 Pressure, density, and temperature
DE: 3369 Thermospheric dynamics (0358)
DE: 5405 Atmospheres (0343, 1060)
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Joint Assembly