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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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This paper presents orbit determination work conducted at JPL for the purpose of refining the Mars gravity field as part of the radio science investigation.
In this analysis we invert global models of Mars' topography from Mars Orbiter Laser Altimeter (MOLA) and gravity from Doppler tracking obtained during the mapping mission of Mars Global Surveyor (MGS). We analyze the distribution of Martian crust and discuss implications for Mars' thermal history.
The global redistribution of dust by the atmosphere is geologically and climatologically important. Dust deposition and removal at the surface represents ongoing sedimentary geology: a vestige of aeolian processes responsible for the concentration of vast dustsheets and potentially for ancient layered units at various locations on Mars. The varying amount of dust on the surface has also long been hypothesized as a factor in determining whether regional or global dust storms occur in a given year. Indeed, the atmosphere has a very short, sub-seasonal time-scale (or memory) and as such, any inter-annual variability in the climate system that is not simply ascribable to stochastic processes, must involve changing conditions on the surface. An excellent, multi-year dataset is provided by the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) and the Mars Orbiter Camera Wide Angle imager (MOC-WA). This dataset allows investigation into the degree to which surface dust deposits on Mars really change: over decadal time scales, over the course of the annual cycle, and as a result of global and regional dust storms. The MGS mapping orbit data set extends over almost 3 Martian years at the time of writing. These data sets include one global dust storm and smaller regional storms (one in the first TES mapping year and two in the third).
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We will present our latest results in providing access to the Mars Global Surveyor Data through the Planetary Image Atlas. This work is a prototype for future Internet based data distribution systems. Additional information is contained in the original extended abstract.
Observations of the gravity field of Mars reveal a planet that has responded differently in its northern and southern hemispheres to major impacts and volcanic processes. The rough, elevated southern hemisphere has a relatively featureless gravitational signature indicating a state of near-isostatic compensation, whereas the smooth, low northern plains display a wider range of gravitational anomalies that indicates a thinner but stronger surface layer than in the south. The northern hemisphere shows evidence for buried impact basins, although none large enough to explain the hemispheric elevation difference. The gravitational potential signature of Tharsis is approximately axisymmetric and contains the Tharsis Montes but not the Olympus Mons or Alba Patera volcanoes. The gravity signature of Valles Marineris extends into Chryse and provides an estimate of material removed by early fluvial activity.
Due to a post launch failure of a part a new plan for the Mars Global Surveyor was developed. This new plan involved the addition of many deep thermal cycles to the Power Shunt Assemblies (PSA's). This new plan exceeds the previous acceptance cold level, and fatigue life on packaging design. This presentation reviews the experiments that were used to test the capabilities of the PSA to function in the new situation. It also reviews the analyses preformed to verify the most likely failure mechanism, and the likelihood that these failures would impact the new mission requirements.
Two planetary spacecraft have been successfully aerobraked from elliptical initial orbits to nearly circular final orbits. This paper will compare the aerobraking phases of the Magellan and Mars Global Surveyor missions.
A recent study (Desai, 2008) has shown that the actual landing sites of Mars Pathfinder, the Mars Exploration Rovers (Spirit and Opportunity) and the Phoenix Mars Lander have been further downrange than predicted by models prior to landing Desai's reconstruction of their entries into the Martian atmosphere showed that the models consistently predicted higher densities than those found upon entry, descent and landing. Desai's results have raised a question as to whether there is a systemic problem within Mars atmospheric models. Proposal is to compare Mars atmospheric density estimates from Mars atmospheric models to measurements made by Mars Global Surveyor (MGS). Comparison study requires the completion of several tasks that would result in a greater understanding of reasons behind the discrepancy found during recent landings on Mars and possible solutions to this problem.
The martian exosphere and upper atmosphere exert measurable drag on the Mars Global Surveyor (MGS) spacecraft. Using the Goddard Space Flight Center's GEODYN orbit determination software, the science phasing orbits (SPO) were analyzed to determine the atmospheric drag and hence, measure the average density near the orbits' perifocus (170-180 km altitude above high northern latitudes). Future work will include the gravity calibration and mapping periods as well. Additional information is contained in the original extended abstract.
The spacecraft testbed is a crucial part of the spacecraft development and operations phase. Given the aggressive schedule of the Mars Global Surveyor spacecraft, the Spacecraft Test Laboratory will play a crucial part during the MGS development phase in support of flight software testing, fault protection testing, sequence testing, and other areas to meet the November, 1996 launch date.
This grant supported various data analysis projects involving calibration and analysis of observations of the Martian polar caps and of condensate and dust clouds by Mars Global Surveyor.
The calibration and validation of satellite soundings of atmospheric variables is always a difficult prospect, but this difficulty is greatly magnified when the measurements are made at a different planet, whose meteorology is poorly known and poorly constrained, and for which there are virtually no prospects of obtaining ground truth. The Mars Global Surveyor which has been circling Mars in its mapping orbit since early 1999 includes a variety of instruments capable of making atmospheric observations: the Thermal Emission Spectrometer (TES) which takes more than 100,000 nadir-view infrared spectra per day (although these observations are confined to the 2am - 2pm time of the sun-fixed orbit); much less frequent TES limb scans (still only at 2am and 2pm); the Mars Horizon Sensor Assembly measures side-looking broadband 15 micrometer radiation; Radio Science occultations at favorable seasons give high resolution temperature profiles; the Mars orbiter Camera and Mars Orbiter Laser Altimeter have made water, dust, and carbon dioxide cloud detections. These observations are now being supplemented by high-resolution 15 micron measurements by THEMIS on Mars Odyssey. Thus, all of these observations are made at different times and places. Data assimilation techniques are being used to fuse this vast array of observations into a single dataset that best represents our understanding of the Martian atmosphere, its current meteorological state, and the relevant instrumental properties.
The design and performance of a highly reliable, 20 volt nickel hydrogen battery compatible with existing NiCad Mars observer based spacecraft components and an 800 psi, zirconium wall wick Common Pressure Vessel (CPV) are discussed. The objectives of the design process are: to meet or exceed all PD requirements by using existing technologies; to have high reliability hardware and parallel fabrication of components; and low schedule risk configurations. This paper discusses the tests performed on the batteries (capacity, charge retention, random vib., pyro shock, energy density, and packing factor) and the results of the tests. In addition to the design discussion, a brief introduction on Mars Global Surveyor (MGS) Satellite objectives (NASA's next interplanetary mission) is also presented.
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An Engineering-of-Failure approach to designing and executing an accelerated product qualification test was performed to support a risk assessment of a "work-around" necessitated by an on-orbit failure of another piece of hardware on the Mars Global Surveyor spacecraft. The proposed work-around involved exceeding the previous qualification experience both in terms of extreme cold exposure level and in terms of demonstrated low cycle fatigue life for the power shunt assemblies. An analysis was performed to identify potential failure sites, modes and associated failure mechanisms consistent with the new use conditions. A test was then designed and executed which accelerated the failure mechanisms identified by analysis. Verification of the resulting failure mechanism concluded the effort.
An Engineering-of-Failure approach to designing and executing an accelerated product qualification test was performed to support a risk assessment of a work-around necessitated by an on-orbit failure of another piece of hardware on the Mars Global Surveyor spacecraft.