Deep Space Network

The last data from the overachieving Near Earth Asteroid Rendezvous (NEAR Shoemaker) mission to asteroid Eros will be received today via NASA's Deep Space Network telecommunications system.

A group of engineers at NASA's Jet Propulsion Laboratory stands by, monitoring final telemetry from this successful extended mission to map and understand the asteroid. NEAR Shoemaker was directed to a successful landing on the asteroid on Feb. 12. Today, the Deep Space Network, Earth's phone line to Eros, will hang up, marking the probable conclusion to the historic mission, which is managed by the Johns Hopkins University's Applied Physics Laboratory in Laurel, Md, for NASA.

The Deep Space Network, managed by JPL for NASA, consists of large antennas at three complexes located in Goldstone, Calif., near Canberra, Australia, and near Madrid, Spain. Each complex houses several radio antennas of different sizes, including giant 70-meter (230-foot) telescopes, used to communicate with interplanetary spacecraft.

Antennas at Goldstone today received science data from the last NEAR experiment, spectrometry from the spacecraft's gamma ray instrument. This data will tell scientists about the surface and subsurface composition of asteroid Eros. NEAR's position on the asteroid precludes it from using its largest communications antenna, called the high-gain antenna. To receive the weaker signal from the low-gain antenna, the Deep Space Network is using its own largest antenna, the 70-meter dish.

"The pass is going fine, we're locked on to the spacecraft's signal and we're getting good data back." said JPL's Allen Berman, the telecommunications and mission systems manager for NEAR. Telecommunications support of the mission were scheduled to end at 4 p.m Pacific Standard Time today, he said.

Throughout NEAR's five-year mission, controllers at the Deep Space Network have provided every link between the spacecraft and Earth. The Deep Space Network has transferred information about the size, shape and gravity of the asteroid from the spacecraft to Earth, sent commands to make changes in the spacecraft's course, and maintained the contact for the exciting landing on Feb. 12.

"We're the vehicle of getting those commands from the mission controllers at Applied Physics Lab to the spacecraft," said Berman. "Then we receive the science and engineering data from the spacecraft to Earth. We also generate navigational data -- the Deep Space Network continuously measures the velocity of the spacecraft through the Doppler shift imprinted in the signal. We extract that data, and send it to the JPL navigation team so that they can determine the orbit and develop maneuvers."

The antennas rotate toward certain portions of the sky where engineers predict the signal will come from the spacecraft. Data, in the form of radio signals, is intercepted by the antennas, and sent via data processing equipment at the facility to the Jet Propulsion Laboratory, where navigators determine the exact position of the spacecraft.

The Deep Space Network also provided all the ground communications for the NEAR mission between the Applied Physics Lab, JPL and worldwide Deep Space Network stations via voice and data networks.

The NEAR spacecraft spent the last year in a low-altitude orbit 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.

The Deep Space Network is managed and operated for NASA by the Jet Propulsion Laboratory. NEAR is managed by Applied Physics Laboratory of the Johns Hopkins University for NASA. For mission updates, images and other information, see . JPL, a NASA center, is a division of the California Institute of Technology in Pasadena.

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