The tough little NEAR Shoemaker spacecraft made its last call from asteroid Eros on Feb. 28, as NASA's Deep Space Network antennas pulled down their last bits of NEAR data and the first close-up study of an asteroid came to a quiet end.
NEAR, the first in NASA's Discovery Program of low-cost, scientifically focused space missions and the first to land on an asteroid, delighted scientists and stargazers alike.
"NEAR has been successful far beyond its original mission plan," said Robert Farquhar, NEAR mission director at the Applied Physics Laboratory, which managed NEAR for NASA. "We got the first images of a C-class asteroid when we added a flyby of asteroid Mathilde in 1997; we added two low-altitude series of passes over the ends of Eros this past October and January that gave us spectacular images from 2.7 kilometers above the surface; and we achieved the first landing of a spacecraft on an asteroid on Feb. 12, all at no extra cost. When you talk about 'faster, cheaper, better,' this is what 'better' means."
Though it was never designed to land, NEAR Shoemaker survived its touchdown on Eros last month and continued to operate and communicate with Earth. Jumping at the chance to get "bonus science" from the spacecraft--which had already collected 10 times more data than originally planned--NEAR managers requested and received mission extensions from NASA that enabled NEAR Shoemaker's gamma-ray spectrometer to collect elemental composition readings through Feb. 28.
"This is the first gamma-ray experiment that has ever been done on the surface of a body other than Earth," said gamma-ray spectrometer team leader Jacob Trombka, of NASA's Goddard Space Flight Center. "In fact, we can say it's the first feasibility study of how to design an instrument to be used on a rover that could select samples from the surface, look for water or map the surface for the purpose of future mining."
The gamma-ray spectrometer team retrieved seven days' worth of data after the landing. "We have good data with strong signatures, but it will take months to scrutinize what we've collected," Trombka said. "We're looking for information that will help us more precisely classify Eros and determine the relationship between the asteroid and meteorites that have fallen to Earth."
NEAR Shoemaker now rests silently to the south of the saddle-shaped feature Himeros as the asteroid twists farther from the sun with each rotation, moving the southern hemisphere into its winter season and temperatures as low as minus 238 degrees Fahrenheit.
Mission scientists will now start to dig into a large data set, which includes more than 160,000 pictures snapped by the spacecraft. "We solved mysteries and we unveiled more mysteries," said NEAR project scientist Andrew Cheng of APL. "We're sharing the amazing amount of data that we collected with scientists all over the world, to sort through and debate and hopefully to help us discover new facts about Eros and our solar system."