Mars Global
Surveyor is the first mission of a new, decade-long program of robotic exploration of
Mars, called the Mars Exploration Program. This will be an aggressive series of orbiters
and landers to be launched every 26 months, as Mars moves into alignment with Earth. The
program will be affordable, costing about $100 million per year; engaging to the public,
providing fresh new global and close-up images of Mars; and have high scientific value
obtained with the development of leading-edge space technologies.
The Mars Global Surveyor is designed to orbit Mars over a two year period and collect data on the surface morphology, topography, composition, gravity, atmospheric dynamics, and magnetic field. This data will be used to investigate the surface processes, geology, distribution of material, internal properties, evolution of the magnetic field, and the weather and climate of Mars. After launch and a 10 month cruise phase, the Mars Global Surveyor will be inserted into an elliptical capture orbit on 12 September 1997. During the year, thruster firings and aerobraking techniques will be used to reach the nearly circular mapping orbit over the Martian polar caps, an 117.65 minute polar orbit with an index altitude of 378 km, an inclination of 92.9 degrees, and an eccentricity of 0.0072. Aerobraking, a technique pioneered by the Magellan mission, which uses the forces of 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. Limited data will be returned during this time. The spacecraft will circle Mars once every two hours, maintaining a "sun synchronous" orbit that 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 be orbiting from north to south on these dayside passes. This orbit will allow complete imaging coverage of the martian surface (video) every 7.2 earth days. The spacecraft will collect preliminary data from this mapping orbit beginning in January, 1998. The primary mission begins in March, 1998, and will last one martian year (687 Earth days) until January, 2000. After this time, the orbiter will act as a relay until January of 2003 in support of the other missions of the Mars Surveyor program.
The spacecraft itself is a rectangular box approximately 1.17 x 1.17 x 1.7 meters in size, made up of two parts, the equipment module and the propulsion module. All instruments except the magnetometer are stored on the nadir equipment deck, on one of the 1.17 x 1.17 meter surfaces. This is the top of the equipment module, which is 0.735 m high. The main thruster and propulsion tanks are on the opposite side from the instruments, on the propulsion module, which is approximately 1 meter high. Two solar panels, each 6 square meters in area, extend out from opposite sides of the craft. A 1.5 meter diameter parabolic high gain dish antenna is mounted on an adjacent side, and attached to a 2 meter boom, which is extended for mapping operations so the antenna is held away from the body of the spacecraft. 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 equivalent of about two Earth years. 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 on the nadir equipment deck that will be used to carry out the experiments consist of a camera, thermal emission spectrometer, laser altimeter, and a radio transmission relay. A magnetometer/electron reflectometer sensor will be attached to the end of each solar array, and an ultra-stable oscillator will be used for tracking and gravity determination. An 8086 processor will be used for the payload data subsystem, and 1750A processors for the standard controls processor and the engineering data formatter. Data will be stored on four 0.75 Gb solid state recorders.
International participation, collaboration and coordination will enhance all missions of the program. Landers in future years -- 1998, 2001, 2003 and 2005 -- will capitalize on the experience of the Mars Pathfinder lander mission launched in 1996. Small orbiters launched in the 1998 and 2003 opportunities will carry other instruments from the Mars Observer payload and will serve as data relay stations for international missions of the future.
The Mars Global Surveyor spacecraft will be acquired from industry through a competitive procurement. The science payload will be provided as government-furnished equipment that was built to duplicate the instruments flown on Mars Observer. The payload includes the Mars orbital camera, thermal emission spectrometer, ultra-stable oscillator, laser altimeter, magnetometer/electron reflectometer and Mars relay system.
The Jet Propulsion Laboratory will manage the project for NASA's Solar System Exploration Division and will provide the mission design, navigation, and conduct mission operations. Tracking and data acquisition will be provided by a 34-meter subnetwork of the worldwide Deep Space Network.
Project costs for the Mars Global Surveyor through 30 days after launch will be approximately $155 million.
VRML