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 An ad hoc team of engineers and scientists won permission from
NASA to try to take control of the International Sun-Earth
Explorer-3, or ISEE-3. The spacecraft was launched in 1978 to study
the solar wind, a continuous stream of charged particles flowing
from the sun.
A second mission to study comets followed in 1981, after which the
satellite entered a graveyard orbit around the sun.
As ISEE-3 neared Earth’s orbit this spring, a volunteer team
launched a crowd-funding campaign to raise money, eventually ending
up with nearly $160,000. The group also petitioned NASA to let it
try to redirect the probe into a stable orbit around Earth so it
could resume science operations.
The Arecibo Observatory in Puerto Rico offered free telescope time
and the group made two-way radio contact with ISEE-3 on May 29. More
than a month of painstaking checkouts followed. Last week, flight
controllers finally coaxed a tiny thruster burn out of ISEE-3, which
made it spin slightly faster, steadying it for the long series of
engine firings needed to change its orbit.
The trajectory shift began on Tuesday but the joy was short-lived.
“We didn’t see the accelerometer moving,” Keith Cowing, one of the
organizers of the ISEE-3 Reboot project, told Reuters.
Initially, the team thought the spacecraft had a stuck valve, but
additional troubleshooting on Tuesday and Wednesday pointed to a
more serious problem: no more nitrogen to pressurize the fuel
system.
"We think there is a chance that the nitrogen … may have been
depleted," the team wrote in a status report on the project’s
website on Tuesday.
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Without a course change, ISEE-3 will fly around the moon on Aug. 10
and resume its trek around the sun. The thruster burns were intended
to put ISEE-3 in a gravitationally stable orbit about 932,000 miles
(1.5 million km) from Earth, from where it could resume its original
mission to observe the solar wind hit the planet’s magnetic field.
Flight controllers hope to get more information about ISEE-3’s
condition during their next radio communications session on Friday.
Even if the optimal orbit is no longer possible, the team hopes to
use ISEE-3 for science while it is still within the inner solar
system, Cowing said.
(Reporting and writing by Irene Klotz; Editing by Bill Trott)
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