[meteorite-list] Prepping WISE to Pop Its Lens Cap

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 23 Dec 2009 11:26:36 -0800 (PST)
Message-ID: <200912231926.nBNJQa60018260_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/features.cfm?feature=2418
  
Prepping WISE to Pop Its Lens Cap
Jet Propulsion Laboratory
December 22, 2009

All systems are behaving as expected on NASA's Wide-field Infrared
Survey Explorer (WISE), which rocketed into the sky just before dawn on
Dec. 14 from Vandenberg Air Force Base in California. The mission will
undergo a one-month checkout before beginning the most detailed survey
yet of the entire sky in infrared light. Hundreds of millions of objects
will populate its vast catalog, including dark asteroids, the closest
"failed" stars and tremendously energetic galaxies.

Shortly after the space telescope reached its polar orbit around Earth
on Dec. 14, it acquired the sun's position and lined up with its solar
panels facing the sun. Engineers and scientists continue to check out
the spacecraft's pointing-control system in preparation for jettisoning
the instrument's cover, an event now scheduled for Dec. 29. With the
cover off, WISE will get its first look at the sky.

The cover serves as the top to a Thermos-like bottle, called a cryostat,
which chills the heat-sensitive infrared instrument. The instrument
consists of a 40-centimeter (16-inch) telescope and four detectors, each
with one million pixels. Just as a Thermos bottle keeps your coffee warm
or your iced tea cold with a thin vacuum layer, a vacuum inside WISE's
cryostat kept the instrument cold while it was on the ground.

The cover also prevented light from reaching the detectors, and
protected the chilly interior of the instrument from heat that could
have come about from unintentional pointing at Earth or the sun during
launch. After WISE was pushed away from its rocket, it wobbled around
slightly before stabilizing (a process that took surprisingly little
time -- only 3 minutes). Without the cover, the heat from Earth or the
sun would have shortened the time the cryostat kept the instrument cold,
and possibly damaged the detectors.

Now that WISE is steadily perched in the vacuum of space, it will no
longer need the instrument cover; in fact, space will provide an even
better vacuum. Engineers are preparing to pop the cover by making sure
the pointing-control system is functioning properly. Once everything has
been checked out, they will send a signal to fire pyrotechnic devices,
releasing nuts that are clamping the cover shut. Three springs will then
push the lid away and into an orbit closer to Earth than that of the
spacecraft.

The WISE team has also verified that the instrument is as cold as
planned. The cryostat's outer shell is slightly below the planned 190
Kelvin (minus 83 degrees Celsius, or minus 117 degrees Fahrenheit), and
the coldest of the detectors is less than 8 Kelvin (minus 265 degrees
Celsius, or minus 447 degrees Fahrenheit).

All spacecraft systems are functioning normally, and both the low- and
high-rate data links are working properly. The instrument's detectors
are turned on, and though they are currently staring into the backside
of the instrument cover, they will soon see the light of stars. WISE's
first images will be released within one month after its one-month
checkout.

JPL manages the Wide-field Infrared Survey Explorer for NASA's Science
Mission Directorate, Washington. The principal investigator, Edward
Wright, is at UCLA. The mission was competitively selected under NASA's
Explorers Program managed by the Goddard Space Flight Center, Greenbelt,
Md. The science instrument was built by the Space Dynamics Laboratory,
Logan, Utah, and the spacecraft was built by Ball Aerospace &
Technologies Corp., Boulder, Colo. Science operations and data
processing take place at the Infrared Processing and Analysis Center at
the California Institute of Technology in Pasadena. Caltech manages JPL
for NASA. More information is online at http://www.nasa.gov/wise,
http://wise.astro.ucla.edu and http://www.jpl.nasa.gov/wise.
Received on Wed 23 Dec 2009 02:26:36 PM PST