With fingers flying across calculator keypads as new guidance data flowed in, JPL space navigators yesterday used fast math, and lots of it, to help carefully nudge NASA's NEAR Shoemaker spacecraft to its historic touchdown on the surface of asteroid Eros.
The success of the landing, and the spacecraft's continuing communications with controllers via NASA's JPL- managed Deep Space Network, astounded even the most optimistic of scientists and engineers associated with the mission.
"Unbelievable," was how deputy navigation team chief Jim Miller of JPL described the landing and the fact that the spacecraft is still alive and communicating with Earth.
NEAR Shoemaker project managers at Johns Hopkins University's Applied Physics Lab (APL) in Laurel, Md., reported today that the team is assessing the overall health and performance of the spacecraft and evaluating ways to gather additional information from the craft. A decision on how to do that could be reached as early as today, mission managers said.
Eros is about the size of Manhattan Island. NEAR Shoemaker landed on a rock-strewn plain of the asteroid at 12:02:10 Pacific Standard Time (3:02:10 EST) on Monday, Feb. 12. It had slowed to a gentle 1.9 meters per second (4 miles per hour) just before finally coming to rest after a journey of 3.2 billion kilometers (2 billion miles).
Cheers and congratulations filled the NEAR Shoemaker mission operations center at Maryland's APL yesterday as images and engineering data arrived from the spacecraft. APL built the spacecraft and manages the mission for NASA.
The NEAR Shoemaker navigation team at JPL is headed by Bobby Williams and includes Miller, Bill Owen, Mike Wang, Cliff Helfrich, Peter Antreasian, Eric Carranza, John Bordi and Steve Chesley. JPL's Dr. Donald Yeomans serves as the mission's radio science principal investigator, and JPLers Jon Giorgini and Alex Konopliv are team members.
The last image from NEAR Shoemaker was snapped a mere 120 meters (394 feet) from the asteroid's surface and covers an area 6 meters (20 feet) wide. As NEAR Shoemaker touched down, it began sending a beacon, assuring the team that the small spacecraft had landed gently. The signal was identified by radar science data, and about an hour later was locked onto by NASA's Deep Space Network antennas, which will monitor the spacecraft until Feb. 14.
NEAR Shoemaker's final descent started with an engine firing at 7:31 a.m. PST (10:31 a.m. EST), which nudged the spacecraft toward Eros from about 16 miles (26 kilometers) away. Then four braking maneuvers brought the spacecraft to rest on the asteroid's surface in an area just outside a saddle-shaped depression, Himeros. When it touched down, NEAR Shoemaker became the first spacecraft ever to land, or even attempt to land, on an asteroid. The success was sweetened by the fact that it was not designed as a lander.
The spacecraft spent the last year in a close-orbit study of asteroid 433 Eros, a near-Earth asteroid that is currently 316 million kilometers (196 million miles) from Earth. During that time it collected 10 times more data than originally planned and completed all its science goals before attempting its descent to the asteroid.
JPL, a NASA center, is a division of the California Institute of Technology in Pasadena.