Mars Global Surveyor
Mars Global Surveyor
Mars Global Surveyor is the name given to a small orbiter, to be launched in November 1996, that will recover some of the science goals of the lost Mars Observer mission. MGS will be roughly half the mass and size of Mars Observer.
Click here for the complete Mars Global Surveyor Program list of figures.
Launched with a Delta II expendable vehicle from Cape Canaveral, Fla., in November 1996, the spacecraft will cruise 10 months to Mars, where it will be initially inserted into an elliptical capture orbit. During the following four months, thruster firings and aerobraking techniques will be used to reach the nearly circular mapping orbit over the Martian polar caps. Aerobraking, a technique which uses atmospheric drag to slow the spacecraft into its final mapping orbit, will provide a means of minimizing the amount of fuel required to reach the low Mars orbit. Mapping operations are expected to begin in late January 1998.
The spacecraft will circle Mars once every two hours in an orbit cunningly designed so that it always maintains the same orientation to the martian day-night boundary ("terminator") even as Mars completes its orbit about the Sun. This will put the Sun at a standard angle above the horizon in each image and allow the mid-afternoon lighting to cast shadows in such a way that surface features will stand out. The spacecraft will carry a portion of the Mars Observer instrument payload and will use these instruments to acquire data of Mars for a full martian year. The spacecraft will then be used as a data relay station for signals from U.S. and international landers and low-altitude probes for an additional three years.
The instruments selected for Mars Global Surveyor are the Mars Orbital [previously, Observer] Camera (MSSS/Caltech), the Thermal Emission Spectrometer (Arizona State University/Hughes Santa Barbara Research Center), the Mars Orbiter [previously, Observer] Laser Altimeter (NASA Goddard Space Flight Center), the Magnetometer/Electron Reflectometer (GSFC), and the Mars Relay [previously, Mars Balloon Relay] (French National Center for Space Exploration, CNES). Radio science will also be performed using an Ultrastable Oscillator in the spacecraft's downlink telemetry subsystem. The other two instruments on Mars Observer, the Pressure-Modulator Infrared Radiometer (JPL) and the Gamma Ray Spectrometer (UofA/MMAG), will be flown on small orbiters to be launched in 1998 and 2001 respectively.
The Mars Orbital Camera (Mars Global Surveyor Orbiter Camera), or MOC 2, is the spare instrument fabricated during the Mars Observer mission. The investigation's science objectives, hardware implementation, ground data system, and science analysis plans are essentially identical to those of the Mars Observer investigation. These are described in a series of papers published prior to the loss of Mars Observer.
The Request For Proposals for the spacecraft was issued in early April, and responses were received in mid-May. On 8 July, JPL announced that Martin Marietta Technologies Inc. of Denver, Colorado, had been selected to build Mars Global Surveyor.
More information about Mars Global Surveyor and Mars Observer is available on the JPL www-server at http://mgs-www.jpl.nasa.gov/mgs-home.htm (before you click on this World-Wide-Web address, please make sure you are currently connected to the Internet).
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