[meteorite-list] Teaching an Old Spacecraft New Tricks: Astronomer Joe Veverka May Lead New Mission to Comet Tempel 1

[Ron Baalke]

http://www.news.cornell.edu/stories/May07/veverka.stardust.html

Teaching an old spacecraft new tricks: Astronomer Joe Veverka may 
lead new mission to comet Tempel 1

By Lauren Gold
Chronicle Online (Cornell University)
May 23, 2007

PASADENA, Calif. -- It began with two comets (Wild 2 and Tempel 1), 
two spacecraft (Stardust and Deep Impact) and two encounters. But 
before the four objects orbit their separate ways, their dance may 
get more intricate -- with two recombining to form a new couple; one 
pushing forward toward an unfamiliar match, and one left to finish 
solo.

Led by Cornell astronomy professor Joe Veverka, a team of astronomers 
and engineers made a final pitch on May 15 to lead the proposed 
Stardust New Exploration of Tempel 1 (Stardust NExT) mission. Their 
presentation came at an all-day site review at NASA's Jet Propulsion 
Lab (JPL) in Pasadena.

If the mission gets the go-ahead, Stardust NExT will use the 
still-healthy Stardust spacecraft -- which dropped off a capsule of 
dust from the comet Wild 2 in the Utah desert last year -- to observe 
the comet Tempel 1 two years after a probe released by the Deep 
Impact spacecraft carved a crater into that comet's surface.

The mission could provide the first good look at the crater, which 
was obscured by a plume of debris immediately after the collision. 
The crater's size and the amount of ejected material that fell back 
to the surface post-impact offer clues about how porous or cohesive 
the material is -- important considerations for future missions, and 
also for contingency plans in case a rouge comet were to head toward 
Earth.

The new Stardust mission could also offer a unique opportunity to 
compare particle analysis from two comets (Wild 2 and Tempel 1) taken 
with the same instruments -- and to compare two observations of a 
single comet (Tempel 1) taken before and after a single orbit around 
the sun. The latter could help scientists work backward to 
reconstruct what the comet may have looked like just after it was 
formed.

"Every time that comets come close to the sun, material sublimates 
and the surface changes," said Veverka, who chairs Cornell's 
astronomy department. "But what actually happens on the surface -- 
how does the surface change -- that's never been documented because 
no one's ever looked at a comet before and after."

And Stardust NExT is also likely to see new terrain on Tempel 1 -- a 
comet whose surface features, as seen by Deep Impact's cameras, 
already have astronomers puzzled. The images show a pattern of 
layers, as if snow and slush had flowed down the sides of a hill in 
waves -- surprising because particles on the surface experience 
almost no gravity and therefore no sense of downhill.

"These are things that have never been seen on comets," said Veverka. 
"But the hope is, if you see a little bit more of it -- if you can 
see around the corner -- you might get some important clue."

Meanwhile, the Deep Impact spacecraft may also get a second life. 
Michael A'Hearn, Deep Impact's principal investigator and University 
of Maryland astronomer, is proposing a mission called Extrasolar 
Planet Observation and Deep Impact Extended Investigation, or EPOXI. 
It would send the spacecraft to visit the comet Boethin and also use 
it to study planets outside the solar system. (The proposal is the 
melding-together of two other submissions, nicknamed DIXI and EPOCh. 
Hence the geekily clever glue allusion.)

The EPOXI and Stardust NExT teams are both slightly reshuffled and 
added-to versions of the original Stardust and Deep Impact 
scientists. Stardust's principal investigator, University of 
Washington astronomer Don Brownlee, is on the NExT team. Veverka, 
leading NExT, would also play a role in EPOXI.

If one or both missions goes forward, it wouldn't be the first time a 
NASA spacecraft has been granted a new life after completing a 
primary goal. The two Voyager spacecraft, for example, are still 
functional three decades after they were launched on a four-year 
mission to study Jupiter and Saturn. Now the farthest man-made 
objects from Earth, they are busy exploring the edges of the solar 
system and are expected to venture into interstellar space.

A final decision from NASA officials is expected for both missions 
this summer. In the meantime, the NExT team is planning a maneuver 
for later this year that would steer the spacecraft toward its new 
target. Stardust would then fly by Earth in January 2009 and arrive 
at Tempel 1 around Valentine's Day 2011.