A NASA spacecraft circling Mars has spied, for the first time, two of its fellow probes orbiting the Red Planet.
Mars Global Surveyor successfully photographed NASA’s Mars Odyssey probe and the European-built Mars Express spacecraft during a series of observations released Thursday.
From its polar orbit around Mars, Global Surveyor found Mars Express first as the two spacecraft flew over the Red Planet on April 20. Separated from its orbital target by a distance of 155 miles (249 kilometers), Global Surveyor turned its Mars Orbiter Camera lens toward the passing spacecraft to snap the first two images of a Red Planet orbiter.
Because of the distance between Global Surveyor and Mars Express, the European orbiter appears as little more than a narrow blur in the final composite image. But astronomers analyzing the image said the Express probe appeared to be about 1.5 meters by 15 meters (5 by 50 feet) in dimensions, which is consistent with what they would expect from the Global Surveyor spacecraft’s vantage point.
Just one day after its Mars Express encounter, Mars Global Surveyor found NASA's Mars Odyssey probe.
Odyssey and Global Surveyor share similar near-polar orbits, sometimes passing within 9 miles (15 kilometers) of each other. Odyssey orbits higher than MGS to prevent collision.
During the recent pass, Global Surveyor compiled two views of the Odyssey orbiter — in which a distinct spacecraft profile can be seen — in images taken 7.5 seconds apart. In the first view, Global Surveyor was just 56 miles (90 kilometers) away from its NASA-built relative, but a few seconds later the two spacecraft were separated by about 84 miles (135 kilometers). Because of the additional distance, Odyssey appeared to move more slowly.
Built by San Diego-based Malin Space Science Systems, the Mars Orbiter Camera has been a key tool for the for Global Surveyor, which entered orbit around the Red Planet in 1997. Mars Odyssey arrived at the planet in 2001, with Mars Express following suit in late 2003.
From a distance of 62 miles (100 kilometers), Global Surveyor's camera has a field of view 830 yards (758 meters) across, so any mismatch in timing during its orbiter photography would have yielded only blank space. But the orbiter managed to photograph its fellow Red Planet probes while all three circled Mars at 7,000 miles an hour (11,265 kilometers an hour).
The images of both Mars Express and Mars Odyssey from Global Surveyor were obtained by the Mars Global Surveyor operations teams at Denver’s Lockheed Martin Space Systems, as well as NASA’s Jet Propulsion Laboratory and Malin Space Science Systems.
