MISSION TEAM CONSIDER RELAUNCHING NEAR SHOEMAKER FROM EROS >From Space.com, 12 February 2001 http://www.space.com/missionlaunches/missions/nearlanding_preview_010212.html By Leonard David Senior Space Writer LAUREL, MARYLAND - What goes down, may come back up again. Engineers at APL are looking at the prospects for relaunching the NEAR Shoemaker spacecraft from the surface of asteroid Eros. A command is already built into the probe as it rests upon the space rock's surface. The liftoff from the asteroid is on tap for this Wednesday, roughly 2:00 p.m. Eastern time, according to David Dunham, NEAR's mission designer at APL. The launch from Eros would be after nine rotations of the asteroid following today's NEAR Shoemaker landing, Dunham said. "Since we've got a lock on the signal, it's got to be pretty much in the right position" for the liftoff, said Dunham. Dunham said the probe may rise upwards well over 1,300 feet (400 meters) above Eros. "It could sit in the dirt and wiggle a little bit before liftoff. These are weaker thrusters on the spacecraft," he said. Some thought has been given to sequencing a double boost of thrust from the asteroid, hurtling it perhaps as high as a kilometer above the asteroid. Dunham said that if the camera has not been damaged in the first landing, more images above the asteroid could be taken. However, pictures of the first landing spot on Eros are not likely to come into view, he said. The spacecraft would then settle down to a new landing spot. "The whole thing is just more icing on the cake," Dunham said. The NASA probe had already happily surprised scientists earlier today, when it made space history with a successful landing atop an asteroid more than 196 million miles (316 million kilometers) from Earth. "I'm happy to report the near spacecraft has touched down on the surface of Eros. We're still getting some signals, so evidently it's still transmitting from the surface itself. This is the first time that any spacecraft has landed on a small body," said Robert Farquhar, NEAR mission director at The Johns Hopkins University Applied Physics (APL) Laboratory in Laurel, Maryland. NASA Administrator Dan Goldin was among the first to congratulate the team. "I'm just overwhelmed with the courage and talent it took to get to this point," Goldin said shortly after the landing. The car-sized NEAR Shoemaker probe has been orbiting Eros since February 14, 2000. Since it began looping the tumbling space rock almost a year ago -- at a range of high and low-altitudes over Eros -- the craft has amassed an asteroid photo gallery made up of 150,000 snapshots. Touchdown took place shortly after 3:05 p.m. Eastern time. The spacecraft fell onto the dust-laden, cratered, and rock-piled surface of Eros. While the vehicle is a fully equipped science spacecraft, NEAR Shoemaker is without landing legs or airbag. "We're right on the money," cried out mission controllers as the craft drifted closer and closer to Eros. Images relayed on the way down to the surface showed what appears to be ancient craters buried below the thick, dusty face of Eros. "We're seeing things really well," said Joseph Veverka, NEAR's imaging team leader from Cornell University in Ithaca, New York. "The pictures are absolutely fantastic. This is a great experience to just sit here and accompany a spacecraft down to the surface." In one image, a giant boulder could be clearly seen fractured in at least six pieces. As one image after another reached Earth, the spacecraft appeared to be headed toward a smooth landing surface. For over four-and-a-half hours, as engineers and scientists here at The Johns Hopkins University Applied Physics Laboratory (APL) cheered close-up images the probe sent back during its descent, the probe drifted down toward the rock of ages. APL built and managed the NEAR mission for NASA, one of the Discovery-class of probes that signals a cheaper, better, faster approach to space exploration. Price tag for this long-term survey of an asteroid by the econo-class spacecraft: $223 million. NEAR's mission control at The Johns Hopkins University's Applied Physics Laboratory reported the craft blasted its hydrazine-fueled motors for 20 second starting at 10:31 a.m. Eastern time. The burst of rocket thrust moved the NASA probe out of its current orbit 22-miles (35-kilometers) above Eros. The spacecraft immediately began dropping toward Eros. In the next four-and-a-half hours, a series of braking maneuvers led to the spacecraft making contact with Eros. Small body, big hopes The craft has relayed a bounty of scientific data about the asteroid, including some 160,000 images that covered all of the 21-mile-long (34-kilometers) asteroid's surface. Eros is moving in a clockwise direction as it spins on its axis. NEAR Shoemaker drifted onto the surface of Eros, softly touching down in an area bordering Himeros - a distinctive saddle-shaped depression. On the way down to the landing zone, the highest-resolution images ever taken of Eros' boulder-strewn, cratered terrain were transmitted to Earth. NEAR Shoemaker was not designed specifically for the touchdown, with the daring dive called for as the mission drew to a successful close on February 14. "It's a very nice way to end this mission," Louise Prockter, a member of the NEAR imaging team at the Applied Physics Laboratory (APL) told SPACE.com. "At least we'll know exactly where the spacecraft is and what happened to it. So if there's a future mission out that way, we'll be able to look for it," Prockter said. Remaining fuel a question When the spacecraft was launched February 17, 1996, its fuel tanks were filled with 715 pounds (325 kilograms) of fuel. After five years, exactly how much propellant remains is unknown. Precious bursts of fuel were needed to prod NEAR Shoemaker lower and lower to the surface of Eros and mission director Robert Farquhar was not sure the probe would have enough gas to the end. "The primary thing is to get high-resolution images. The closer we get the more success we have," Farquhar said. After plopping down on Eros, the spacecraft was healthy enough to transmit science data. Over the next two days, ground stations on Earth will keep an active ear to transmissions from NEAR Shoemaker. Roundtrip communications time between NEAR and Earth is 35 minutes. At Goldstone, California, a Jet Propulsion Laboratory (JPL) Deep Space Network antenna is to keep a lock on NEAR, with another big dish in Madrid, Spain also at the ready. Landing on an asteroid is no cakewalk, Farquhar said, particularly when the spacecraft is not built for such a task. Any number of things could have gone wrong. Engines could misfire; the camera could be pointed the wrong way; or the landing site terrain could have proved impossible for NEAR to navigate successfully. >From a distance Scientists are delighted that the spacecraft relayed high-quality, close-up images of Eros. The telescopic camera, built for remote distance viewing, stayed in focus down to an altitude of about 0.3 mile (0.5 kilometer) above the surface. "The camera should reveal things on the surface, down to as small as a tea cup," said Clark Chapman, member of the NEAR Shoemaker science team from Southwest Research Institute in Boulder, Colorado. "The close-up images are what we're after," said Lucy McFadden, NEAR science team member from the University of Maryland in College Park. "We're going to microscopic views relative to where we started. It's just tremendous." Prockter said the spacecraft's last in-focus snapshots may help quell considerable debate between scientists working on the project. The nature of the regolith -- broken up bits of rock and dirt that cover the asteroid -- as well as how deep and how much is there, and the origin of that material, are all questions being argued. "Looking close up might help us answer some of those questions," Prockter said. Chapman said a head-scratcher for him is understanding why so many giant boulders populate Eros. "We've been arguing between ourselves about what it means geologically," Chapman said. "Why is it so different than the Moon? I've just got to believe that the higher resolution images are going to give us a whole bunch of additional clues as to what's really going on. There's lots of speculation." Survivor for science? Now that the craft has touched down on the surface of Eros, hopes run high that NEAR's onboard magnetometer can relay measurements directly from the asteroid. To date, the magnetometer has not seen anything that can be attributed to Eros. Why that's the case is a little puzzling, said Andrew Cheng, NEAR project scientist, because most of the meteorites that are thought to be related to Eros are magnetized. But whether or not the magnetometer ever picks up data from Eros, researchers are still constrained by finances. Money for mission operations runs out on February 14, 2001. Prior to the landing, McFadden was wistful. "It's really sad the whole thing is going to end Monday," she said. == You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
