When the Mars Exploration Rover (MER-A), Spirit, was landing on 4 January 2004 (3 January 2004, PST), Mars Global Surveyor (MGS) was in position above the region to receive the critical entry, descent, and landing data via ultra high frequency (UHF) radio transmission to the MGS Mars Relay (MR) system. Data from the MR antenna are stored in the Mars Orbiter Camera (MOC) computer until they are transmitted to Earth. The transmission from Spirit on 4 January 2004 occurred in real time, as the rover descended, bounced, and rolled to a stop.
At the same time that MGS was receiving data during Spirit's landing, the MGS MOC obtained this oblique wide angle view looking east across the martian surface toward Gusev Crater, the site where the MER-A landed. The image on the right is labeled to show the location of Gusev Crater; the arrow points approximately to the place that Spirit touched down. The 165 km (103 mi) diameter Gusev Crater and the Spirit landing site are located near 14.7°S, 184.6°W. In this view, sunlight is coming from the bottom (west).For additional information about the Spirit landing site, see:
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, California. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, California and Denver, Colorado.