MARS PATHFINDER MISSION STATUS
December 10, 1996
12:00 p.m. Pacific Standard Time
The Mars Pathfinder spacecraft continues to perform nearly flawlessly
on its 203 million kilometer (126 million mile) flight path to Mars. Currently
the spacecraft is 1.8 million kilometers (1.1 million miles) from Earth,
traveling at a speed of 3.2 kilometers per second (7,155 miles per hour).
Temperatures and power utilization of the lander and cruise stage remain
at predicted levels for this early phase of the mission.
The spacecraft's sun sensors are the only issue being watched closely
on an otherwise beautifully performing spacecraft, the flight team reported.
There are five sun sensor heads on board the spacecraft, two pointed along
the craft's spin axis and three that are equally spaced around the circular
cruise stage that look out at about 105 degrees from the spin axis. Of the
five sensor heads, unit #4 on the spin axis is obscured or contaminated
to the point of not being useful. Sensor #5, which is also on the spin axis,
is providing good sun orientation data, but at a lower voltage than was
expected. The other three sensor heads are working fine.
The flight team at JPL uploaded a software modification to the spacecraft
on Saturday, December 7, which allowed the on-board attitude control system
to use the sun sensor data from sensor #5 in its normal calculations of
the spacecraft's orientation. The software patch was successful and the
team was exuberant to see the spacecraft's attitude control estimators operating
The team then began to prepare for turning the spacecraft more toward
Earth to improve the telecommunications link. At the time, Pathfinder was
about 58 degrees from the Earth, which is near the edge of the antenna's
performance. Since this was to be the first time flight controllers used
the propulsion module, they planned a small turn of two degrees to verify
that everything was working properly. Thirty minutes later, they planned
to turn the spacecraft an additional 20 degrees.
"The turn maneuvers were conducted successfully on Monday morning
[December 12]," said Brian Muirhead, Pathfinder flight system manager.
"The propulsion and attitude control systems worked properly and the
spacecraft's spin axis is currently pointed about 44 degrees from the Sun
and 37 degrees from Earth. The downlink performance improved as expected
and we continue to communicate with Pathfinder at 1,185 bits per second."
The flight team is planning its next maneuver to spin the spacecraft
down from 12.3 rpm to 2 rpm. The maneuver will be performed in the next
few days, Muirhead said. Pathfinder's first trajectory correction maneuver
remains on schedule, to take place on January 4, 1997.
Provided courtesy of:
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
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