[meteorite-list] NEAR Collects Data From Asteroid's Surface

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:11 2004
Message-ID: <200102201808.KAA14865_at_zagami.jpl.nasa.gov>

http://space.com/missionlaunches/missions/near_data_010219.html

NEAR Collects Data From Asteroid's Surface
By Leonard David
space.com
19 February 2001

Data is being received from NASA's Near Earth Asteroid Rendezvous (NEAR)
Shoemaker spacecraft sitting on the dusty surface of asteroid 433 Eros.

NEAR Shoemaker's gamma-ray spectrometer was commanded by ground controllers
to turn itself on February 15. The instrument dutifully began collecting
science data about Eros.

Information gleaned by the device was received by the NEAR scientists and
engineers on Sunday, February 18.

"It's working and we got reasonably good looking spectra...the spectra we
have received looks very good," Jacob Trombka, NEAR team leader for the
X-ray Gamma Ray Spectrometer at NASA's Goddard Space Flight Center in
Greenbelt, Maryland, told SPACE.com.

The gamma-ray spectrometer appears to be running at higher temperatures than
in the past. This is due, apparently, to the spacecraft's new location on
the asteroid, rather than orbiting above the giant space rock.

"When we're up in orbit we can radiate the heat. On the surface, you can't
radiate all the thermal heat due to the power we're using for transmitting
and operating. If we could arrange an atmosphere on Eros, then we could get
some convection. But I think that costs too much," Trombka said with a
laugh.

On track

Precious time is being found on the heavily used Deep Space Network (DSN) of
radio dishes to make contact with NEAR Shoemaker, said Robert Farquhar, NEAR
mission director at the Johns Hopkins University Applied Physics Laboratory
(APL). On Monday, as well as Thursday of this week, additional "tracks" of
time on the DSN will allow for more data to be gleaned from the gamma-ray
spectrometer, he said.

The DSN is operated for NASA by the Jet Propulsion Laboratory in Pasadena,
California.

Trombka said it takes as much as 8 hours of DSN time, and sometimes multiple
passes to get all the data downlinked to Earth.

To the delight and surprise of many involved in the project, NEAR Shoemaker
successful soft-landed on Eros February 12. A decision was made two days
later to have the probe make the first on-the-spot measurements of an
asteroid using the craft's gamma ray spectrometer.

NASA extended the mission for up to 10 days. A further extension is
possible, to assure that enough listening time from ground stations is found
to receive quality science data.

"Once we've got good data, then maybe we can ask for more tracking time,"
Trombka said. A link between and Earth and NEAR Shoemaker might be
maintained until the end of the month, he said.

Gawking at gamma-rays

Trombka said the instrument is resting on or slightly above the asteroid's
topside of rock and dirt.

The equipment, mounted on NEAR Shoemaker structure, is focused on a small
circular patch of Eros. By using gamma rays, Trombka said, the device
detects specific elements in the asteroid's surface.

Measurements taken by the gamma-ray spectrometer are expected to be ten
times more sensitive than what was possible when the spacecraft began
orbiting Eros on February 14, 2000.

Signals from the equipment on Eros are being relayed by the DSN to mission
controllers at APL in Laurel, Maryland.

APL designed, built, and is managing the asteroid surveying craft for NASA.

"I'm looking at the spectra and they are looking very nice," Trombka said,
saluting his engineering colleague at APL, John Goldsten, who has worked
hard to get the gamma-ray spectrometer working and interpreting the data, he
said.

"It's going to take a number of months for us to get a good answer out of
the data, and it'll also help us interpret the orbital data much better now
too," Trombka said.

Data has been sent back from Eros' surface utilizing both the gamma ray
spectrometer, as well as an onboard magnetometer, although the latter
instrument has now been turned off.

Information from the magnetometer found no intrinsic magnetic field at Eros
as it circled the celestial body for a year at various altitudes. No word
yet as to whether or not the instrument detected magnetism at surface level.
Finding a magnetic field would have important implications about the space
rock's thermal and geologic history.

Long and winding road

NEAR Shoemaker made a journey of more than 2 billion miles (3.2 kilometers),
and performed a year-long observational campaign around Eros.

As the first asteroid orbiter, the probe was not built for landing.
Scientists and engineers made a go-for-broke decision to attempt a touchdown
on the rocky mini-world. They succeeded in soft-landing the probe onto Eros,
with the craft plopping down on the asteroid at less than 4 miles per hour
(between 1.5 and 1.8 meters per second).

The science data from the asteroid's surface was received almost five years
to the day after NEAR Shoemaker was launched on February 17, 1996.
Received on Tue 20 Feb 2001 01:08:46 PM PST