[meteorite-list] NEAR Farewell: NASA To Drop Link With Trailblazing Spacecraft Today

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:13 2004
Message-ID: <200102281825.KAA05191_at_zagami.jpl.nasa.gov>

http://www.space.com/missionlaunches/missions/near_finale_010228.html

NEAR Farewell: NASA To Drop Link With Trailblazing Spacecraft Today
By Leonard David
space.com
28 February 2001

WASHINGTON - A Space Age form of electronic euthanasia is about to occur far
from Earth.

On February 28, scientists and engineers are placing the Near Earth Asteroid
Rendezvous (NEAR) Shoemaker probe into deep space slumber. Breaking radio
ties with the spacecraft brings to a close a five year mission to go where
no craft had gone before.

Following a year of orbiting asteroid 433 Eros, NEAR Shoemaker softly
settled down February 12 atop the crusty rock of ages. Subsequently, NASA
granted science teams a two-week extension so the craft could beam back to
Earth quality science data from the space rock's topside.

The giant mountain of a mini-world is over 196 million miles (316 million
kilometers) from Earth.

Over the last 14 days, a NASA Deep Space Network (DSN) radio dish in
Goldstone, California has repeatedly siphoned information from NEAR
Shoemaker as it rests on Eros' dusty and boulder-rich terrain. But with new
surface data in hand, scientists are in a quandary about Eros and the link
between asteroids and known meteorite types.

Extreme silent treatment

"We're putting the spacecraft into hibernation," said Robert Farquhar, NEAR
mission director at The Johns Hopkins University Applied Physics (APL)
Laboratory in Laurel, Maryland. APL designed, built, and is managing the
asteroid mission for NASA.

The last contact with NEAR Shoemaker is to occur late Wednesday night,
Farquhar said.

"It's going into suspended animation," Farquhar said. He added that NEAR
Shoemaker is likely to die a slow death as the solar-powered probe receives
less and less sunlight beginning at the end of March. Total darkness will
descend where the car-sized satellite sits starting August 8.

"NEAR Shoemaker will see no sunlight at all then, and there's going to be
very little before that," Farquhar told SPACE.com.

First glimmers of the sun's rays strike the NEAR Shoemaker landing area in
mid-November. Over those three months, the craft, its electronic innards and
onboard instruments, are not likely to survive. Full sunlight won't fall
upon the probe until August 2002.

"The mission basically ends tomorrow. We got a 14-day extension. So,
roughly, it has been a 5 year mission since we were launched on February 17,
1996," Farquhar said.

The long goodbye

Price tag for the long-term survey of Eros by the econo-class spacecraft is
$223 million. NEAR Shoemaker is a part of NASA's Discovery-class of probes
that are of the cheaper, better and faster variety.

Also offering up a reluctant farewell to NEAR Shoemaker is Jacob Trombka,
team leader for NEAR Shoemaker's gamma-ray spectrometer instrument at NASA's
Goddard Space Flight Center in Greenbelt, Maryland. It is his instrument
that has benefited greatly by the landing and the two-week extension of the
spacecraft's mission.

"We hope to get the last transmission tomorrow before we say goodbye,"
Trombka told SPACE.com in a February 27 interview.

Trombka said the data received so far is excellent, as well as puzzling.

"We're in good shape. The spectra data from the surface has shown us some
very interesting properties of Eros which we were not aware of. You always
learn in situations like this. In order to understand what we're seeing is
what we believe we see, it's going to take a little while for us to convince
ourselves," Trombka said.

The gamma-ray spectrometer is designed to decipher the elemental composition
of Eros.

"We don't want to go too fast. We want to make sure our analysis is correct.
We don't want to do instant data analysis," Trombka said. One curious find
from the probe's magnetometer is that no remnant magnetism has been found on
Eros. Yet the gamma-ray data does show an iron signal, which means that Eros
is loaded with a demagnetized iron of some sort, he said.

"Those two factors are causing us to scratch our head, to try and figure out
what's going on here," Trombka said. "Eros is a very primitive body. The
question is whether this is a primitive body that we haven't seen here on
Earth in terms of meteorites collected to date," he said.

Low and behold!

Gamma-ray data collected so far points to the fact that, indeed, the top
covering of rock and dirt has been churned up from Eros itself. "We may
change our mind, but that's what it looks like," Trombka said.

Clark Chapman, a NEAR Shoemaker science team member at Southwest Research
Institute in Boulder, Colorado, said that the gamma-ray data is a great
outcome of the mission.

Chapman, like Trombka, said that going slow in sifting through the science
data is key. No rush to judgement is necessary.

"Your best situation with the gamma-ray spectrometer is to be buried in the
dirt. And lo and behold, he's apparently got good data. That's a terrific
outcome," Chapman said.

"Science is something that you ponder over for months. The pace of science
has really quickened a lot. It's likely that snapshot views will be
incomplete and turn out to be wrong. That doesn't mean they shouldn't be
talked about, but you've got to be careful," Chapman said.

For Trombka, months of work are ahead to unravel what stories the gamma-ray
spectrometer is telling about Eros.

"We've got quite an interesting picture. The job is for us to understand the
mechanisms which produced such a body," Trombka said.

"It's like meteorites we see on Earth. But there are certain different
things that we're seeing that is causing us to scratch our heads. But that
is what discovery is all about."
Received on Wed 28 Feb 2001 01:25:30 PM PST