This file artist rendering of the Stardust spacecraft encountering the bright halo of dust and gas surrounding a shimmering comet released by NASA. After eyeing a comet for the past four years, a NASA spacecraft will finally make its move. NASA on Thursday, March 24, 2011 ordered its comet-hunting Stardust probe to burn its remaining fuel, setting off a series of events that will shut down the spacecraft after a 12-year career (AP Photo/NASA, File) |
DENVER
(AP) — With the click of a mouse, Sandy Freund Kasper sent a command to
NASA’s comet-hunting Stardust space probe to burn all its fuel,
starting a sequence that would shut the spacecraft down after a 12-year
run.
“Like
saying goodbye to a friend,” said Allan Cheuvront, the Stardust program
manager for Lockheed Martin, who has worked on the probe since 1996,
when it was still in the design stage.
“It’s been an amazing spacecraft,” he said Thursday. “It’s done everything we asked, it’s done it perfectly.”
Launched
in 1999, Stardust finished its main mission in 2006, sending a tiny
sample of particles from the Wild 2 comet to Earth via a
parachute-equipped canister. NASA then recycled the probe, sending it
past a comet last month to photograph a crater left by a projectile
launched by another space probe.
It
accomplished one last experiment on Thursday, firing its thrusters
until its last hydrazine fuel was gone. The length of that burn, a
little under 2 1/2 minutes, will tell engineers exactly how much fuel
was left so they can see how accurate their calculations were.
That in turn will help with the design and operation of future probes.
It
will take a few days to analyze the fuel data, said Jim Neuman, a
mission operations manager for Lockheed Martin Corp., which built and
operated the probe for NASA.
Freund
Kasper was serving as the Stardust “ace” Thursday, sending commands to
the spacecraft from a big room in Lockheed Martin’s Denver complex that
looked more like a set from “The Office” than a 21st century mission
control.
A
dozen or so engineers peered at computer screens in low-walled
cubicles. Tape dispensers, beige telephones and three-ring binders lined
the work stations. There was a dollar-a-head office pool, with 60 or so
names scrawled on a whiteboard with their best guesses on how much fuel
Stardust had left.
Before
Freund Kasper sent Stardust its final instruction, Cheuvront polled
eight or nine other engineers at work stations labeled “Power,”
”Thermal,” ”Propulsion” and other roles, asking each in turn if the
probe was ready.
Then
he turned to Don Brownlee of the University of Washington, the lead
scientist on Stardust’s primary mission to take samples from the Wild 2
comet.
In this Jan. 11, 1999 file photo, workers at Kennedy Space Center in Florida watch as the Stardust spacecraft is lowered. (AP Photo/NASA, File) |
“It’s been a wonderful and overwhelming experience,” Brownlee said.
At
4:41 p.m. MDT, Freund Kasper sent a command instructing Stardust to
begin executing a set of instructions that had been transmitted to the
probe earlier in the day.
About
42 minutes later — the time it took the command to travel the roughly
93 million miles to Stardust, and for Stardust’s reply to reach Earth —
the engineers’ computer screens showed the burn was under way.
Once
the fuel was gone, Stardust lost its ability to keep its antennas
pointed toward Earth, and the control room lost radio contact at 5:33
p.m.
If
the probe executed all of its final orders as expected, it put itself
in “safe mode,” turning most of its systems off, at 6:13 p.m., about 1
1/2 hours after the last command was sent.
With
no fuel, Stardust can’t keep its solar panels aimed at the sun, and
once its batteries are drained it will shut down for good.
Stardust
will be left in an orbit around the sun. Engineers project that in the
next 100 years, Stardust won’t get any closer than 1.7 million miles of
Earth’s orbit or 13 million miles of Mars’ orbit.
SOURCE: The Associated Press
