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MUSES-C Takes Tiny Rover To Tiny World
By Andrew Bridges
Pasadena Bureau Chief
posted: 07:06 am ET
03 August 2000
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hopping_rover_000803 PASADENA, Calif. A launch delay has forced the selection of a new target for a joint Japanese-U.S. mission that will make an unprecedented docking with an asteroid, where the probe will gather rock samples for return to Earth and release a tiny rover to roam its surface.The launch date for the Muses C mission has now slipped to November or December 2002, prompting planners to fix their sights on the asteroid 1998 SF 36 as the spacecrafts new target destination. | The Rover and the Asteroid | | How will the little rover get around the rough terrain of the asteroid? Watch the video . | 
How close to Earth does asteroid 1998 S36 come? Watch the video . | "The change is significant, in the sense the arrival date also slips to September 2005 and well stay not six months but just three months," said Donald Yeomans, of NASAs Jet Propulsion Laboratory (JPL), project manager for the NASA portion of the mission. Small rover for a small world NASAs contribution to the mission, called Muses CN, includes a 2.2-pound (1-kilogram), hopping-and-rolling nanorover. The tiny rover will be the smallest such robot ever sent to another planetary body once the Muses C spacecraft drops it onto the asteroids surface for a one-month tour.
NASA's Muses-CN nanorover will be the smallest rover ever sent into space. Japan will contribute the main spacecraft itself, as well as the launch vehicle. Rocket problems The entire $180 million mission as originally planned was to visit the asteroid (10302) 1989 ML, also known as Nereus. However, problems with the Japanese M 5 rocket which failed in a February attempt to hoist that nations Astro E X-ray observatory into orbit and was to launch the Muses C spacecraft forced the delay.~ "They think they are going to need some additional time to study the problem and make the necessary corrections," Yeomans said of the Japanese Institute of Space and Astronautical Science (ISAS). Look out, Australia The mission is but one of several spacecraft that have, or soon will, visit asteroids or comets, but it will be the first to robotically return asteroid samples to Earth.After arriving at 1998 SF 36, Muses C will first map the asteroid in full. The spacecraft will then bump into the tiny world which is perhaps just one-half mile (1 kilometer) across as many as three times, each time firing a pellet into its surface. A funnel-like device will capture the ejecta kicked up by the pellets, packaging them for eventual return to Earth. Because of the change in timing, the sample capsule will not land in Utah in June 2006, as originally planned. Instead, the capsule will return to Earth for recovery somewhere in the Southern Hemisphere Australia is the most likely target a full year later, Yeomans said. One small step into space During one of its three bump-and-grab maneuvers, the spacecraft will gently drop the nanorover onto the asteroids surface. Since the asteroids gravity is only one-one hundred thousandth as strong as the Earths, the rovers behavior will be literally unworldly. "It will float to the surface and land there and then bounce. And bounce. And bounce," Yeomans said. Builders of the tiny rover will rely on the microgravity environment to help negotiate the stony world, using a delicate scissors-kick motion to prompt the rover to hop."With this rover it takes such a little force, it should actually jump into the sky," said Ross Jones, the Muses CN project manager at NASAs JPL. "Its pretty cool." 
An artist's rendering of the nanorover at work on a distant asteroid. Since too high a jump could send the rover into orbit around the asteroid, Jones said mission planners would hold off on the hops until late in the mission. "Itd be possible to jump off the asteroid," said Jones, adding that engineers hoped to perform simulated microgravity experiments with the rover at JPL this fall. More time for study The delay will allow scientists to gain more knowledge about the missions new target, however. 1998 SF 36 will pass by Earth twice, on March 29, 2001 and again on June 25, 2004, allowing even amateur astronomers to catch a peek of the space rock. The asteroid is officially classified as a "potentially hazardous object" since its orbit brings it within 4.7 million miles (7.5 million kilometers) of that of Earth. Scientists hope the two close approaches will allow them to determine the asteroids size, shape and rotation to aid them in the further planning of the Muses C mission. "The hope is well have this object well characterized before we arrive to make things easier," Yeomans said.
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