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Avoiding lunar hazards
With a rocky surface, hills and craters covering the moon’s vast landscape, astronauts approaching a landing will have to be particularly careful. But thanks to a technology developed by JPL, it should be easier for future explorers to achieve a safe touchdown.
JPL’s Autonomous Landing and Hazard Avoidance Technology (ALHAT) Project -- developed predominantly for the Altair lunar lander, part of the Constellation Program -- is funded by NASA to develop an integrated autonomous guidance, navigation and control hardware and software system capable of detecting and avoiding surface hazards and guiding humans and cargo safely and precisely to selected lunar landing areas.
The technology uses sensors to look at the ground and compare that data to a reference map to determine the lander’s location. The main sensor used to find safe landing zones is the Light Detection and Radar (LIDAR) sensor, which takes pictures of the shapes of an area rather than the color, essentially providing an elevation map. NASA’s Langley Research Center builds the actual sensors, and JPLers are developing the software and algorithms that process the sensor data, with Johnson Space Center as the project lead.
JPL is also responsible for conducting the field tests for the project, having just completed the third out of a planned series of seven. In this most recent test, sensors were put on an airplane to test the terrain-relative navigation capabilities of the system. Thirty-two flight hours were logged during seven days of testing at various altitudes and lighting conditions for about 10 different flights over the Nevada test site and Death Valley, both of which resemble the lunar surface because of craters created by nuclear testing in the 1950s and ’60s and a general lack of vegetation, respectively. The combination of a flat desert floor, mountainous terrain, and cratered landscape provided the perfect mock lunar surface for the field test team to test their equipment. “We’re trying to make the field tests as much like the actual landing situation as possible,” said Johnson.
The first two field tests focused more on hazard detection and avoidance rather than precision landing, and used helicopters to house the sensors.
So far the tests have been very successful, according to Sohrab Mobasser, the field-test lead, although the Lab is still in the stage of processing the data. While it’s still to be decided how much of this technology will be used in Altair, Johnson is optimistic. “In general, we are working very closely with Altair,” said Johnson. “We have representatives from Altair at our meetings and our field tests. They’re expecting to use significant parts of what ALHAT is providing.”