Mars Observer was launched September 25, 1992 from Cape Canaveral on a Titan III built by Martin Marietta Corporation, with an upper Transfer Orbit Stage from Orbital Sciences Corporation. On August 21, 1993, flight controllers lost contact with the Mars Observer spacecraft when an expected transmission that was part of the pre-Mars-Orbit-Insertion sequence failed to occur. Subsequent attempts to re-establish communication with the spacecraft proved unsuccessful. After the 11-month transit the spacecraft was to be injected into an elliptical orbit around Mars with periapsis near the north pole. The orbit would then be adjusted through a series of maneuvers to a near-circular, sun-synchronous (2 am/pm), low altitude, near-polar orbit. Due to the non-uniformity of the gravity field, the altitude was to vary from 376 km near the south pole to 430 km near the north pole. During the Martian year in this mapping orbit the instruments were to acquire data in a systematic program of global mapping. At the end of the mission the spacecraft could have been boosted to a permanent quarantine orbit. The Mars orbit insertion (MOI) period was to end one month before solar conjunction and the beginning of the dust storm period. The playback data rate for a 10-hour link would vary by a factor of 4 with Earth-Mars distance during the mission. The continuous data rate to the tape recorders was about one fifth the playback rate for a 10-hour link to a 34 m NASA Deep Space Network tracking station. The normal sequence of collecting scientific data would be to record continuously for 24 hours and then to play the data back in one 10-hour link. The mapping orbit would be a 117-minute orbit with a 7-day repeat cycle. As a result, the planet would be repeatedly mapped in 26-day cycles with a 58.6 km nominal path separation. Orbit trim adjustments would make it possible to obtain uniform coverage during the course of the mission with an ultimate spacing of ground tracks at the equator or 3.1 km. The Mars Observer spacecraft provided a three-axis stabilized, nadir-oriented platform for the continuous observations of Mars by the science instruments. The spacecraft was built by the General Electric Astro-Space Division. The Gamma Ray Spectrometer and Magnetometer sensor assemblies were mounted on individual booms on the spacecraft. All other instruments were rigidly mounted to the spacecraft structure. No movable scan platform was provided; the spacecraft was to be continuously nadir pointed, rotating at the orbital rate. Those instruments that required scanning or multiple fields of view had internal scanning mechanisms.

extracted metadata from PDS3 catalog and
                    modified to comply with PDS4 Information Model

Mars Observer

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