Mars Observer

artist concept of Mars Observer orbiting Mars

* Mission Overview

The Mars Observer mission spacecraft was primarily designed for exploring Mars and the Martian environment. However, in addition to its planetary payload, Mars Observer carried some high energy astrophysics instruments, including a gamma ray spectrometer.

Mars Observer was launched on September 25, 1992 from Kennedy Space Center aboard a Titan III rocket. The spacecraft was lost in the vicinity of Mars after (most probably) an explosion of the fuel and oxidizer elements on August 21, 1993 when the spacecraft began its maneuvering sequence for Martian orbital insertion.

* Instrumentation

While intended as a gamma-ray spectrometer (GRS) for mapping the Martian surface composition from orbit, the GRS was also capable of suspending this function in order to make detailed observations of cosmic gamma-ray bursts. The n-type Ge detector was 5.5 cm in diameter and length. Passive cooling kept the crystal at less that 100K. A combined anti-coincidence shield and neutron system surrounding the Ge crystal rejected cosmic-ray and neutron events when a burst mode had been triggered. The energy range covered for bursts was 0.5 - 2.0 MeV, with some 1024 energy channels available. Energy resolution of 2.7 keV at 1.333 MeV was achieved. During a burst trigger, data could be accumulated into a minimum of 16 ms intervals.

* Science

The Mars Observer spacecraft did very little science during its cruise phase to Mars to save on costs, but approximately two months of total data from the gamma ray spectrometer were successfully collected, including spectral observations of one burst, GB930706, for which the VLA obtained radio observations approximately eight days later. Preliminary analysis of the Mars Observer data also shows some information for approximately twenty other burst sources detected by Ulysses and Compton Observatory, though none triggered the Gamma Ray Spectrometer to interrupt its mapping functions to observe the source directly.

*Other information

  • Laros, J.G. et al 1994, AIP 307, Gamma Ray Bursts, Second Workshop,32.


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