The Mars Global Surveyor is a pretty complicated satellite, to say the least -- there are six different instruments on it, all completing different kinds of tasks. Although this MAG/ER site focuses on, as you can tell from the name, the Magnetometer/Electron Reflectometer, all of the instruments have interesting histories. So sit back, relax, and get ready to learn about the instruments on Mars Global Surveyor.
The Magnetometer/Electron Reflectometer instrument measures the magnetic fields on Mars. Scientists hope that data from this instrument will allow them to learn about the interior composition of Mars and the history of Mars' magnetic field. MAG/ER is different from all of the other instruments because it is not attached to the main body of the spacecraft; the two sensors sit on opposite sides of the craft, at the ends of the Mars Global Surveyor's solar arrays. Why? So that the magnetic signal generated by the craft itself will not pollute MAG/ER data. Magnetometers like the one on the Mars Global Surveyor have flown on Voyager, International Solar Polar Mission, and many other spacecraft.
MGS's Thermal Emission spectrometer originally flew aboard the Mars Observer; now rebuilt, it flies with the new craft with the purpose of measuring the thermal infrared energy coming from Mars' surface and atmosphere. By using thermal emission spectroscopy (creating a spectrum of detected infrared light, then measuring it), scientists will be able to tell what minerals are on the surface of Mars, what gases are in its atmosphere, and what kinds of ice are in Mars' polar regions. The TES concept was first introduced by Dr. Phil Christensen in 1983 for the Mars Observer. Want to learn more about TES, its science, and its construction? Try Arizona State University's TES page.
The Mars Orbiter Laser Altimeter is a descendant of the laser altimeter on board the Mars Observer. Its purpose? To calculate the height of surface features on Mars. The laser altimeter works by measuring the amount of time it takes for a pulse of light to get from the spacecraft, to the ground, and bounced back to the collecting mirror. Scientists can then multiply the reflection time by the speed of light and receive a quite accurate value for the craft's height above Mars' surface (which changes, of course, over mountains or valleys). Then, topographic maps can be made of Mars. For more information on MOLA, go to the MOLA Science Investigation home page.
The Mars Orbiter Camera has returned over 200,000 images of Mars and continues to operate. The camera has two modes, narrow-angle (which allows the camera to take pictures of things as small as five feet across), and wide-angle (which takes huge panoramic views). The panoramic views can be put together in an animation so scientists can study weather on Mars and look at surface features blown by the wind. To find out more about this camera, look at the resources at the Preparing the MOC 2 for Mars and MOC pages.
Using the Ultra-Stable Oscillator on the Mars Global Surveyor, scientists
will be able to study the electrical strength and tone of radio transmissions
coming from MGS because the USO allows signals to be broadcast at an extremely
precise frequency. Changes in the radio signal as the spacecraft orbits Mars
will allow scientists to accurately determine its shape. When the spacecraft
is behind Mars, changes in the radio signal may be caused by the Martian
atmosphere. Studying these changes will allow knowledge of Mars' atmospheric
pressure at a certain point. If you would like to learn more, take a look at
Stanford's MGS WWW pages.
Mars Relay is the only one of Mars Global Surveyor's six main instruments that does not measure something about Mars; its job is to collect data sent by spacecraft on the Martian surface, then transmit it back to Earth. This means that future Mars landers do not have to carry huge antennae to send their data to Earth; they can send it to MGS and use the space for more experiments. It is sometimes used to relay data from the Mars Exploration Rovers, Spirit and Opportunity, to Earth.