Weather reports from Mars, global mapping, inspection of potential landing sites, more data about the red planet than from all previous missions - no problem for the hardworking Mars Global Surveyor spacecraft.

In fact, the Global Surveyor has been so successful that it earned an extension following conclusion of its prime mapping mission early in 2001. The second extension began in April 2002 and will continue the mission into late 2004.

Thorpe looks forward to Surveyor's second extension.

"Things are going well," said Tom Thorpe, Mars Global Surveyor project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We've accomplished all of our primary mission objectives to date and the science instruments have returned a tremendous amount of data. Now we're looking forward to all the science to come in the second extension."

In addition to mapping operations, the spacecraft is targeting images of potential landing sites for the 2003 Mars Exploration Rovers. In its extended mission, the Surveyor has been given latitude to take pictures at different angles and target areas missed in the prime mission.

A Beautiful View

Artist's concept of the Mars Global Surveyor in a downward-pointing nadir position and an off-nadir slightly backward-pointing position.

One of the tasks that scientists want to do is obtain stereo (three-dimensional) images of some areas already covered. To do this, the spacecraft has to be pointed off-nadir. Nadir is the point directly below the observer; hence if the spacecraft is "tipped," the target can be imaged up to 30 degrees away from the original ground track. When a place imaged from one angle is pictured again from another angle, the images can be overlaid to create a stereo picture.

This technique is useful for providing dramatic views of the planet's surface and to study the vertical profile of its atmosphere. For example, scientists want as complete a picture as possible of potential landing sites for the 2003 Mars Exploration Rovers. The stereo images taken by Global Surveyor will help substantially in the final site selection.

"There is still so much to learn about Mars," said Mars scientist Dr. Ken Edgett, Malin Space Science Systems, San Diego, Calif. "Our high-resolution camera is testing hypotheses formulated over the past two decades using Mariner 9 and Viking data and even new theories from Surveyor and Mars Odyssey images. We're seeking to understand previous observations, and to monitor changes that are taking place due to weather and changes in polar frost."