Renewed hope in search for lost Mars lander

 作者:枚蹲富     |      日期:2019-02-27 03:13:01
By Kelly Young (Image: NASA/JPL/MSSS) There is renewed hope that an orbiting NASA spacecraft will be able to identify the remnants of the Mars Polar Lander, which was lost after its descent to the Red Planet in December 1999. New images from the Mars Orbiter Camera (MOC) on the Mars Global Surveyor spacecraft may now have pinpointed the 1976 Viking 2 mission, having already spotted Viking 1 and the Mars rovers Spirit and Opportunity. These successes, plus a new technique to improve image resolution, now gives engineers confidence that the Mars Polar Lander (MPL) can be found too. The MPL was lost during descent and a subsequent investigation found that the lander’s legs had deployed before touching down. That may have sent a false signal that the craft had landed, causing the engines to shut down early. The lander may then have plummeted the final 40 metres to the Martian surface. The loss was traumatic for NASA and led to major changes in its exploration strategy. The MPL had no telemetry system for reporting what went wrong and so, even five years on, an image offering clues as to how the failure occurred would be very valuable. After the accident, the MOC searched for the crash site. Scientists looked for a bright parachute within a kilometre of a darkened area that would indicate dirt kicked up by an engine blast. In 2000, the MOC team found one site that met the criteria, but the images were inconclusive because the camera’s resolution was only 1.5 metres per pixel. Since then, MOC has found the rovers, along with their parachutes, heat shields, landing platforms, and the debris that scattered when their engines fired to slow the craft on their descent. Finding the rover parachutes may help the search for the Mars Polar Lander because it used the same type of material for its parachute. “When we saw the Mars rovers’ landing sites in our images, we recognised there were things in common with what we had observed at the candidate MPL site, somewhat supporting our interpretation,” says Michael Malin, of Malin Space Science Systems in San Diego, California, US, which operates the MOC. But now a new technique developed by engineers could take the MOC resolution from 1.5 m per pixel to between 30 and 50 centimetres per pixel. As the spacecraft passes over a target site, the probe will pitch smoothly forward to slow the apparent speed of the ground below, allowing the craft more time to capture a higher resolution image. NASA has not been able to test the new technique on the candidate MPL site because it has been in the dark Martian winter. Mars Global Surveyor project manager Tom Thorpe, at NASA’s Jet Propulsion Laboratory, expects the polar region to come into the light in late July or August 2005. Thorpe says it is still not certain whether the craft landed in one piece or is a trail of wreckage. “The images taken to date are very marginal in terms of identifying it.” The likely identification of the Viking 2 lander was made more difficult because it touched down in a flat region, devoid of major geological features which could be matched to images taken by the probe. But it has accumulated dust over the decades, so it does not stand out like the shinier rovers. Malin said he cannot be absolutely certain that they found Viking 2 because the lander only takes up a pixel or two in the images. More on these topics: