Download UCSD engineers to guide Hubble Telescope to

UCSD engineers to guide Hubble Telescope to first view of stars
April 4, 1990
Contact: Yvonne Baskin, (619) 534-0362
THE FIRST 90 DAYS: UCSD ENGINEERS WILL GUIDE TELESCOPE INSTRUMENT TO ITS FIRST VIEW
OF THE STARS
Five hours and 30 minutes after launch of the space shuttle Discovery, with the Hubble Space Telescope
dangling from the shuttle arm, ground controllers in Maryland will send a signal to activate the heaters on an
instrument called the Faint Object Spectrograph (FOS).
For FOS, designed and built under the direction of University of California, San Diego scientists, it will mark the
beginning of the end of a six-year wait to go into action. But it will be another 90 days before FOS and the other
four instruments aboard the space telescope begin gathering data on the universe.
"We already have 20 million bits of data in the computer about FOS and how it should be operating minute
to minute, day by day," says Lawrence K. Randall, FOS program manager for UCSD's Center for Astrophysics
and Space Sciences. His team of engineers and programmers will remain at their computer consols at Goddard
Space Flight Center in Greenbelt, Maryland, for three months after the launch to complete what NASA calls
"orbital verification."
"Essentially, we turn everything on in a very precise and preprogrammed order and see if it works," says
Randall. "We think we have an instrument that can run for 15 years in space. It's had thousands of hours of
operational time on Earth, and we've done everything we know to do to make it as reliable as possible."
That includes taking the instrument out of the telescope and literally rebuilding it on the floor of a dust-free
"clean room" at Lockheed Missiles and Space Co. in Sunnyvale, Calif., during the years of delay after the
Challenger explosion in 1986.
Every other week since October, Randall's team has been participating in NASA simulations lasting from a
day to a week, trying to anticipate and write a procedure for every possible problem that might arise with the
instrument--a balky heater or entrance shutter or aperture wheel, for instance.
Each of the five instruments aboard the telescope comes with a similar technical team, and all of them must
interact with the controllers at Goddard, Kennedy Space Center in Florida and Johnson Spaceflight Center in
Texas to bring the telescope to full operation.
"FOS initially sits on the cold side of the spacecraft, so turning on the heater is critical," Randall says. "The
next critical point comes at day two, hour eight when we go into a 'hold mode.' That's like flipping a circuit breaker
to a house and checking to see that you have power at all the right places."
Before the high voltage can be turned on, however, the team must make sure the interior of the instrument is a
perfect vacuum. "It's a difficult engineering feat to make an instrument that's sealed to keep out any stray photon
of light, but baffled to let all stray air molecules out once it reaches the perfect vacuum of space," he notes.
On day 20, the team will turn on 23,000 volts.
"It will be a very scary time for us," says William A. Baity, FOS science program manager. "We'll step up the
voltage in 11 steps over 11 orbits, turning it on for two minutes, then off, and sending a bigger jolt each time. If we
don't have a perfect vacuum, we'll see electrical noise bursts on every channel from the arcing (the equivalent of
tiny lightning bolts)."
On day 50, FOS will finally get to look at its first celestial object. The target will be NGC188, a rich star cluster
in the Milky Way.
Toward the end of the telescope's second month in orbit, team members will hold their breaths again as they
test whether the instrument can safely operate at full voltage through a dense cosmic ray area over Brazil called
the South Atlantic Anomaly.
"We believe we can operate through it, but we're not sure we can do science there because of the cosmic rays
hitting our detectors and messing up the photon counts," says Baity.
If the voltage must be turned off and on again during every 90-minute orbit as the telescope moves through the
South Atlantic Anomaly, it will eliminate more of the telescope's precious viewing time. Observing time is already
limited to about 35 percent of each orbit by the need to keep the telescope from pointing too directly toward the
sun; the time it takes to slew and point the telescope and lock it onto "guide stars" for each new target; and the
fact that the Earth will partially or fully block the view about 40 percent of the time.
At three months after launch, the phase NASA calls "science verification" will begin and continue, if all goes
well, into the eighth month.
"During this phase, we'll test all the different modes the instrument can be in," says Baity. "But we want to
get some science out of this, so we'll be targeting FOS on some of the most interesting objects on our list--radio
galaxy M87 and quasar 3C273, which have radiation jets coming out of them, and the Crab Nebula, a supernova
remnant."
The UCSD team will have certain guaranteed observing time on FOS during its first three years in orbit. All of
the non-allocated time on the space telescope's five instruments is apportioned to astronomers throughout the
world by the Space Telescope Science Institute in Baltimore.
(April 4, 1990)