Astronomers On Kitt Peak Join In Observing Deep Space 1 Encounter With Comet
When the first U.S. spacecraft to carry a camera close to a comet
successfully flew by comet Borrelly Saturday afternoon, Tucson astronomers
supported the scientific milestone with observations from Kitt Peak.
University of Arizona astronomers using the university’s 90-inch Bok
telescope collaborated with National Optical Astronomy Observatory (NOAO)
astronomers using the NOAO 84-inch telescope.
“We had excellent weather every night for observing this comet,” said
Humberto Campins, a senior research scientist at the UA Lunar and Planetary
Lab and a program officer at the Tucson-based Research Corp.
“We are looking at the extended structure of the comet’s dust coma and tail
to help the NASA mission science team interpret their close-up images,” said
Beatrice Mueller, a research associate with NOAO and leader of the NOAO
comet observations. Mueller also observed the comet several months ago to
obtain information about its rotation in space to help NASA plan the flyby
encounter.
Campins and UA Steward Observatory astronomer Donald McCarthy Jr. used
PISCES, a broad-field infrared camera that McCarthy built, to photograph
comet Borrelly before dawn last Thursday, Friday and Saturday. They took
infrared images 12 hours before and 12 hours after NASA’s Deep Space 1
spacecraft passed within about 1,250 miles of the comet on Sept.22.
The UA and NOAO teams are part of a NASA-funded network of observers in
Arizona, Hawaii, California and elsewhere helping gather a detailed picture
of the comet. While the Deep Space 1 spacecraft took up-close snapshots of
comet Borrelly, ground-based astronomers took wide-view photographs of the
whole comet before, during and after flyby.
NASA will release Deep Space 1 images of comet Borrelly tomorrow at a 1 p.m.
EDT (10 a.m. MST) news conference from the Jet Propulsion Laboratory in
Pasadena, Calif. The news conference will be carried on NASA television and
it will be available on the internet at
http://www.jpl.nasa.gov/webcast/ds1_webcast.html
“The spacecraft flew by the comet around 3:30 p.m. Tucson time on Saturday,”
Campins said. “The comet is visible for us between 3:30 a.m. and 5:30 a.m.,
after the comet has risen on the horizon and before the sky gets too bright
at dawn.”
Comet Borrelly cannot be seen with the naked eye, he added, but small
telescopes may pick it up.
“The fact that Nalin Samarasinha of NOAO was simultaneously observing at
visible light wavelengths on the 84-inch telescope was a godsend,” Campins
added.
Samarasinha was not scheduled to observe the comet with the NOAO Kitt Peak
telescope at this time. But disrupted national air travel forced a change in
the observing plans of a colleague, who swapped telescope time with
Samarasinha and Mueller.
“It is a important to work in tandem in both wavelengths because the
structure of these objects can change on short time scales. They can be
completely unpredictable. Having simultaneous observations helps us
determine what is happening with the comet at that moment. Both views give
us a better look at the actual distribution of dust around the comet through
time,” Campins said.
“We could check with each on whether ‘seeing’ was poor or whether something
needed adjusting on our telescopes,” he added. “Simultaneous observations
allowed us to make a number of decisions that allowed us to make much more
efficient use of our time.”
Launched in October 1998, Deep Space 1 completed its primary mission of
flight-testing an ion engine and other advanced technologies two years ago.
It was not designed for a comet flyby. Despite comet Borrelly’s dense dust,
the spacecraft took more than two dozen comet images that JPL finished
downloading yesterday.
Observations of and from the encounter are important in planetary science
and also will help researchers assess the hazards to future spacecraft
during comet flybys, Campins said.
Until now, “The only detailed spacecraft picture of a comet we have is a
1986 picture of comet Halley from the European Space Agency’s Giotto
mission,” he said. The Russians and French used the Vega 1 and 2 spacecraft
to get less detailed, but still helpful, pictures of comet Halley that same
year, he added.
“The Europeans and Russians deserve a lot of credit. If it weren’t for them,
we wouldn’t know half as much about comets as we do now.”
NOAO will release a black-and-white image of comet Borrelly taken with the
84-inch telescope tomorrow, Sept. 25, at its website,
http://www.noao.edu/news/. NOAO is operated by the Association of
Universities for Research in Astronomy (AURA), Inc., under cooperative
agreement with the National Science Foundation.
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Contact Information
Humberto Campins
520-571-1111 campins@lpl.arizona.edu
Beatrice Mueller, Nalin Samarasinha
C/o Doug Isbell, NOAO Public Information
520-318-8214, disbell@noao.edu
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