NEAR Shoemaker's Silent Treatment
12 Dec 2002
(Source: Johns Hopkins University Applied Physics Laboratory)
NEAR Mission News
Even though the NEAR Shoemaker spacecraft had exceeded every mission expectation, the NEAR team asked for one more spectacular addition to the mission's legacy: Talk to us one more time.
But NEAR Shoemaker - the first spacecraft to orbit, land on and send data from the surface of an asteroid - kept mum despite a 12-hour effort to communicate with it.
"The exercise was an experiment to see how robust the spacecraft and its instrumentation and subsystems were given the extremely cold temperature it has been in for nearly two years," says NEAR Mission Director Robert Farquhar. "We didn't hold out much hope but we had an opportunity to establish an important data point and didn't want to lose the chance."
The attempt was initiated at 2:40 p.m. EST, Tuesday, Dec. 10, by the NEAR mission operations team at the Johns Hopkins University Applied Physics Laboratory, which managed the mission and built the spacecraft, and the Deep Space Network team, which supported the effort through their 70-meter Goldstone antenna. With asteroid Eros only about 86 million miles (138 million kilometers) from Earth - less than half the distance it was when NEAR Shoemaker landed on it in February 2001 - and NEAR Shoemaker's solar panels basking in sunlight for the past three months, the timing was ideal.
First, operators listened passively for a carrier signal from the spacecraft. Then they sent commands asking NEAR Shoemaker to transmit data indicating it had survived the last 22 months on the asteroid's surface, despite temperatures that dipped as low as minus 170 degrees Celsius (-274 degrees Fahrenheit) and long periods of total darkness.
Not knowing which of NEAR Shoemaker's two computers had access to its transmitter, mission operators tried sending commands to one, then the other. Then they waited - in vain - to receive data.
Farquhar says the team will probably never know precisely why NEAR Shoemaker did not respond and they do not expect to try again.
The first in NASA's Discovery Program of low-cost, scientifically focused planetary missions, NEAR conducted a yearlong orbit study of asteroid 433 Eros. The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., designed and built the NEAR Shoemaker spacecraft and managed the NEAR mission for NASA. For more information and images visit the NEAR Web site at http://near.jhuapl.edu.
For more on NASA's Discovery Program visit http://discovery.nasa.gov.