Navigation and the Mars Global Surveyor Mission
The Mars Global Surveyor was successfully launched from Cape Kennedy on November 7, 1996. This paper discusses the details of the various navigation phases of the mission.
navigation↗
Engineering topics
Demcak, S.
Publications and source records attributed to Demcak, S..
Navigating Mars Observer: Launch Through Encounter and Response to the Spacecraft's Pre-Encounter and Response to the Spacecraft's Pre-Encounter Anomaly
This paper provides an in-depth review of the Mars Observer Navigation Team's activities throughout interplanetary cruise to Mars and our response to the spacecraft's anomaly which occurred approximately 68 hours before encounter.
Navigating Mars Observe↗
Mars Observer Interplanetary Cruise Orbit Determination
The Mars Observer orbit determination activity extending from launch to loss of contact is summarized, and includes quantitative results and conclusions derived from mission experience.
Mars↗
Mars Gravity Field From Dual Satellite Observations
Two strategies are examined in this paper to improve the spherical harmonic representations of the Martian gravitational field. Continous observation over a week-long data arc and a 30th degree gravitational field are assumed for analysis.
Mars↗
Atmospheric drag perturbations on the Mars Observer Orbiter
The nominal launch date of the Mars Observer spacecraft is 09 - 16 - 02, with Mars encounter on 08 - 19 - 93 and the mapping orbit established on 12 - 06 - 93. Because this orbit is nearly circular at low altitude (361 km), both gravity and atmospheric drag will dominate the orbital evolution and are also the major error sources. This paper provides: (1) a summary of atmospheric density and errors for the Mars Observer orbit and time frame, (2) an assessment of spacecraft-position errors using current density estimates, and (3) an estimate of atmospheric density modeling improvement directly from the Doppler data acquired during flight operations. With an improved gravity field model, reconstructed spacecraft-position errors are at the level of 0.5 km (1sigma). However, when predicting the spacecraft's position over 14 days, the density error (at the 90-percent confidence level) dominates, yielding a down-track error of almost 70 km. By modeling the mean atmospheric density, this error can be reduced by at least a factor of two.
Esposito, P. B.↗
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.↗
Orbit determination study results for the Venus Radar Mapper orbiter
The Venus Radar Mapper (VRM), to be launched by the U.S. in July 1988 is described and Doppler-only and Doppler plus N-Delta-VLBI data analyses are contrasted in order to evaluate the importance of VLBI data to VRM orbit determination (OD). VRM OD study results are summarized by showing the accuracy of various orbital parameters for ten cases selected over a 243-day primary mission. It is concluded that VLBI data were responsible for improving the knowledge of the longitude of the ascending node with respect to the plane of the sky by a factor of 5 to 10 throughout (excluding superior conjunction) this primary mission. It is noted that there is a certain sensitivity to where along the orbit the VLBI data are acquired.
Esposito, P. B.↗