January 22, 2004
Rover Problem
Called 'Very Serious'
Flight-team engineers for NASA's Mars Exploration
Rover Mission are trying to diagnose the cause of earlier communications
difficulties that have prevented any data being returned from
Spirit since early Wednesday.
"We have a very serious situation,"
Pete Theisinger of NASA's Jet Propulsion Laboratory said.
Spirit did send a radio signal via NASA's
Mars Global Surveyor orbiter Wednesday evening, but the transmission
did not carry any data. Spirit did not make radio contact with
NASA's Mars Odyssey during a scheduled session two hours later
or during another one Thursday morning. It also did not respond
to the first two attempts Thursday to elicit an acknowledgment
signal with direct communications between Earth and the rover,
and it did not send a signal at a time pre-set for doing so when
its computer recognizes certain communication problems. The successful
attempt to get a response signal came shortly before 9 a.m. Pacific
Standard Time.
No single explanation considered so far
fits all of the events observed, Theisinger said. When the team
tried to replicate the situation in its testing facility at JPL,
the testbed rover did not have any trouble communicating. Two
of the possibilities under consideration are a corruption of
flight software or corruption of computer memory, either of which
could leave Spirit's power supply healthy and allow adequate
time for recovering control of the rover.
Engineers will continue efforts to understand
the situation in preparation for scheduled communication relay
sessions using Mars Global Surveyor at 7:10 p.m. PST and Mars
Odyssey at 10:35 PST. Efforts to resume direct communications
between Spirit and antennas of NASA's Deep Space Network will
resume after the rover's expected wake-up at about 3 a.m. PST
Friday.
Meanwhile, mission leaders decided to skip
an optional trajectory correction maneuver today for Opportunity,
the other Mars Exploration Rover. Opportunity is on course to
land halfway around Mars from Spirit, in a region called Meridiani
Planum, on Jan. 25 (Universal Time and EST; Jan. 24 at 9:05 p.m.
PST).
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