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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Mars Observer orbital accuracy analysis

Attention is given to the orbital accuracy of the Mars Observer (MO) spacecraft throughout its 687 days of mapping (scheduled to commence in 1991). The MO's short period and near circular orbit necessitate a multiorbit analysis in which the spacecraft's motion is strongly perturbed by the local and global gravity field of Mars. This analysis attests to the feasibility of achieving an orbital position accuracy at the level of 2-3 km within the data interval. It is found that Very Long Baseline Interferometric data can rectify a situation in which the position accuracy degrades significantly.

Esposito, P. B.↗
NASA NTRS1987

A Ka-band (32 GHz) beacon link experiment (KABLE) with Mars Observer

A proposal for a Ka-Band (32 GHz) Link Experiment (KABLE) with the Mars Observer mission was submitted to NASA. The experiment will rely on the fourth harmonic of the spacecraft X-band transmitter to generate a 33.6 GHz signal. The experiment will rely also on the Deep Space Network (DSN) receiving station equipped to simultaneously receive X- and Ka-band signals. The experiment will accurately measure the spacecraft-to-Earth telecommunication link performance at Ka-band and X-band (8.4 GHz).

Riley, A. L.↗
NASA NTRS1990

Mars observer - Orbital evolution, accuracy and control

The orbital phase and the major factors controlling the Mars Observer orbital evolution and accuracy are studied. Particular attention is given to the gravity field and atmospheric density. It is found that gravity field errors are reduced by the implementation of a gravity calibration period. A typical set of ground tracks corresponding to the optional mapping orbit definition is given.

Esposito, Pasquale B.↗
NASA NTRS1993

Optical Chopper Assembly for the Mars Observer

This paper describes the Honeywell-developed Optical Chopper Assembly (OCA), a component of Mars Observer spacecraft's Pressure Modulator Infrared Radiometer (PMIRR) science experiment, which will map the Martian atmosphere during 1993 to 1995. The OCA is unique because of its constant accurate rotational speed, low electrical power consumption, and long-life requirements. These strict and demanding requirements were achieved by use of a number of novel approaches.

Allen, Terry↗
NASA NTRS1993

DSN support of Mars Observer

This article provides a summary of the DSN prelaunch, launch, and cruise support of the Mars Observer through Trajectory Correction Maneuver 2 (TCM-2) on 8 Feb. 1993. This summary includes planning, implementation, testing, DSN special configurations and DSN operational problems, and successes and challenges to date.

Traxler, M. R.↗
NASA NTRS1992

Martian volatiles determined using the Mars observer gamma ray spectrometer

The relative abundances of H2O and CO2 and their latitude, longitude, and depth profiles on Mars sensitively reflect, as well as help control, past and present Martian climate patterns. Seasonal variations of their distributions at high latitudes also reflect and help control global weather patterns and erosion through surface weathering. A combined analysis of gamma ray line and neutron flux maps constructed from data measured using the Mars Observer Gamma Ray Spectrometer (MOGRS) should allow a determination of seasonal changes in both the horizontal and vertical structure of CO2 ice that covers the north polar cap during winter and the south polar cap throughout the year and both the horizontal and vertical structure of residual H2O ice within the top meter of the surface that was predicted from Viking observations to exist primarily at high latitudes. Particularly important in this regard will be maps of thermal and epithermal neutron fluxes measured using the MOGRS anticoincidence shield, the intensity of the hydrogen, neutron capture gamma ray line at 2.223 MeV, the intensity of a capture gamma ray line as 1.725 MeV from iron, and the intensity of an inelastic scatter gamma ray line as 1.779 MeV from silicon.

Feldman, W. C.↗
NASA NTRS2004

Participation of D.O. Muhleman as a Co-Investigator on the Mars Observer Laser Altimeter (MOLA) Team

The Co-I has been a principle member of the MOLA Team since the beginning of the Mars Observer Project and the MOLA Team formation. The basic area of research for the Co-I involved the interactions of the MOLA laser beam with the Mars atmosphere, ice fields and surface in general. The Co-I was assisted by one graduate student, and later a research assistant, Anton Ivanov, throughout the reporting period. Dr. Ivanov received a PhD from Caltech in 2000 from research involving the MOLA project. Dr. Ivanov continued with the MOLA project after receiving his degree as a research assistant to Professor Muhleman. Most of the funding from this grant was used to support Dr. Ivanov during the later years. The primary results of these investigations included the measurement of Mars atmospheric opacity at the 1 micron wavelength of the laser, the effects of dust within the craters and canyons of Mars, and a detailed study of the North Polar Ice Cap in terms of ice sublimation and the current structure of that ice cap. We were able to show that the sublimation of the ice on the polar cap would create the current average shape of the norther cap. Extensive data collection and study were made of the Mars surface 1 micron reflectivity until the laser mechanically failed during the reporting period. Reflectivity maps of Mars were produced although there were serious problems of the laser echo signal strength calibration. After that event the efforts were mainly to complete the older investigations. All of the work supported by this grant was theoretical in nature and did not lead to any patents.

Muhleman, Duane O.↗
NASA NTRS1989

Hardware impacts to software development strategies - The history of the development of the Mars Observer Payload Data Subsystem embedded real-time software

Ways in which parallel hardware development and high level requirements changes have influenced Mars Observer Payload Data Subsystem (PDS) flight software development are discussed. Particular attention is given to ways in which the evolving hardware product and changing requirements have led to repeated modification to software requirements, design, code, and test tools and a delay in the closure of corresponding phases of the software development life cycle. Design and implementation problems which were encountered during the PDS software development effort are described.

Elson, Anne B.↗
NASA NTRS1992

The interannual variability of polar cap recessions as a measure of Martian climate and weather: Using Earth-based data to augment the time line for the Mars observer mapping mission

The recessions of the polar ice caps are the most visible and most studied indication of seasonal change on Mars. Circumstantial evidence links these recessions to the seasonal cycles of CO2, water, and dust. The possible advent of a planet encircling storm during the Mars Observer (MO) mission will provide a detailed correlation with a cap recession for that one Martian year. That cap recession will then be compared with other storm and nonstorm years. MO data will also provide a stronger link between cap recessions and the water and CO2 cycles. Cap recession variability might also be used to determine the variability of these cycles. After nearly a century of valiant attempts at measuring polar cap recessions, including Mariner 9 and Viking data, MO will provide the first comprehensive dataset. In contrast to MO, the older data are much less detailed and precise and could be forgotten, except that it will still be the only information on interannual variability. By obtaining simultaneous Earth-based observations (including those from Hubble) during the MO mission, direct comparisons can be made between the datasets.

Martin, L. J.↗
NASA NTRS1992

Burst detection capability of the Mars Observer gamma-ray spectrometer

This paper describes the gamma-ray burst detection capability of the gamma-ray spectrometer on board the Mars Observer spacecraft. The instrument is designed to respond to significant bursts by suspending its observation of the Martian surface in favor of optimizing the collection of pre-burst, burst, and post-burst data. The results are expected to contribute to our understanding of gamma-ray bursts through a high energy resolution search for line emission, by the examination of spectral shapes and by comprising one leg of an arrival time network to determine the direction of origin.

Metzger, Albert E.↗
NASA NTRS2016

Plasma Clouds and Snowplows: Bulk Plasma Escape from Mars Observed by MAVEN

We present initial Mars Atmosphere and Volatile EvolutioN (MAVEN) observations and preliminary interpretation of bulk plasma loss from Mars. MAVEN particle and field measurements show that planetary heavy ions derived from the Martian atmosphere can escape in the form of discrete coherent structures or "clouds." The ions in these clouds are unmagnetized or weakly magnetized, have velocities well above the escape speed, and lie directly downstream from magnetic field amplifications, suggesting a "snowplow" effect. This postulated escape process, similar to that successfully used to explain the dynamics of active gas releases in the solar wind and terrestrial magnetosheath, relies on momentum transfer from the shocked solar wind protons to the planetary heavy ions, with the electrons and magnetic field acting as intermediaries. Fluxes of planetary ions on the order of 10(exp 7)/sq cm/s can escape by this process, and if it operates regularly, it could contribute 10-20% of the current ion escape from Mars.

Halekas, J. S.↗
NASA NTRS1999

Mars Observer: Planetary Constants and Model

The value of EOT in degrees is usually converted to solar-minutes to give the correction to mean solar time to obtain true solar time. The value of EOT for Mars over the Mars Observer mapping phase is plotted.

Mars Planetary Constants Models↗
NASA NTRS1994

The Mars Observer differential one-way range demonstration

Current methods of angular spacecraft positioning using station differenced range data require an additional observation of an extragalactic radio source (quasar) to estimate the timing offset between the reference clocks at the two Deep Space Stations. The quasar observation is also used to reduce the effects of instrumental and media delays on the radio metric observable by forming a difference with the spacecraft observation (delta differential one-way range, delta DOR). An experiment has been completed using data from the Global Positioning System satellites to estimate the station clock offset, eliminating the need for the quasar observation. The requirements for direct measurement of the instrumental delays that must be made in the absence of a quasar observation are assessed. Finally, the results of the 'quasar-free' differential one-way range, or DOR, measurements of the Mars Observer spacecraft are compared with those of simultaneous conventional delta DOR measurements.

Kroger, P. M.↗
NASA NTRS1990

Bipropellant engine plume analyses for the Mars Observer scientific spacecraft

This paper discusses the methodology utilized to characterize exhaust plume expansion of the 490 N bipropellant engine and provides an analysis of exhaust plune impingement effects on the Mars Observer oxidizer tank structure. Nozzle and plume continuum flowfields are computed with a method of characteristics solution while transitional and rarefied regions of the exhaust gas flow were defined by a direct simulation Monte Carlo method. Results of this study provide sufficient data for an assessment of spacecraft thermal impacts due to plume heating effects and thrust losses from exhaust plume impingement.

Rattenni, L., Jr.↗
NASA NTRS1994

The Mars Observer Ka-band link experiment

The Ka-Band Link Experiment was the first demonstration of a deep-space communications link in the 32- to 35-GHz band (Ka-band). It was carried out using the Mars Observer spacecraft while the spacecraft was in the cruise phase of its mission and using a 34-meter beam-waveguide research and development antenna at the Goldstone complex of the DSN. The DSN has been investigating the performance benefits of a shift from X-band (8.4 GHz) to Ka-band (32 GHz) for deep-space communications. The fourfold increase in frequency is expected to offer a factor of 3 to 10 improvement (5 to 10 dB) in signal strength for a given spacecraft transmitter power and antenna size. Until recently, the expected benefits were based on performance studies, with an eye to implementing such a link, but theory was transformed to reality when a 33.7-GHz Ka-band signal was received from the spacecraft by DSS 13. This article describes the design and implementation of the Ka-Band Link Experiment from the spacecraft to the DSS-13 system, as well as results from the Ka-band telemetry demonstration, ranging demonstration, and long-term tracking experiment. Finally, a preliminary analysis of comparative X- and Ka-band tracking results is included. These results show a 4- to 7-dB advantage for Ka-band using the system at DSS 13, assuming such obstacles as antenna pointing loss and power conversion loss are overcome.

Rebold, T. A.↗