"The Spacecraft Arrives" Guy Beutelschies - August 12, 1996 Mars Pathfinder Test Director Currently on assignment at the Kennedy Space Center, Florida |
Week of August 12, 1996
The spacecraft arrived at Kennedy Space Center. It was pouring rain. We waited until
the rain stopped to roll the container that the spacecraft is in into the airlock. We
then wiped down the exterior of the container with alcohol to clean off any dirt and to
kill any biological material. Mars Pathfinder has to be very clean from a biological
standpoint so it does not contaminate Mars. Spores from Earth life are actually hardy
enough to withstand the flight through space. After the container is cleaned, the top was
taken off and the spacecraft was moved to a workstand using an overhead crane.
Meanwhile, the rest of the electronic equipment used to test the spacecraft was craned
up to the test complex, which is on the second floor. It is very nerve-racking to watch
million dollar equipment swinging in the air 20 feet from the ground. This equipment is
used to create commands, process telemetry and provide power to the spacecraft. It is
connected via long cables which pass through the wall and down into the cleanroom. This
allows us to do most of our electrical testing without having to put on cleanroom
clothing, which are called bunny suits (because they make you look like a big bunny
without ears).
Week of August 19
Testing started. We found several problems with the flight software during our testing
at the Jet Propulsion Laboratory (JPL) so we decided to repeat our complete mission mode
test down here in Florida. This test started with launch, went through the cruise to
Mars, the descent to the surface, and then the Day 1 activities. This went pretty
smoothly until the (simulated) entry to the Mars atmosphere. We were feeding data into
the accelerometers to make the spacecraft think that it was entering the atmosphere and
slowing down. There is software onboard that is supposed to read these data and figure '
out when to fire the parachute. This software never produced an answer. The telemetry
showed that the parachute fire signal was sent based on the backup timers and not the
software algorithm. We spent a couple of days (and nights) troubleshooting this before we
found the bug in the software. The rest of the test went smoothly.
Week of August 25
The mechanics then opened up the lander and took the petals off. We are doing this so
that we can install fresh batteries for launch. We also have to put in the radioisotope
heater units on the rover. These devices contain a very small amount of plutonium, which
gives off heat to keep the rover warm. We also installed a small amount of radioactive
curium in the alpha-proton x-ray spectrometer instrument on the rover. This instrument
uses the radioactivity in the curium to give off alpha particles. When placed against a
rock, these particles will hit the molecules in the rock, which in turn will release
x-rays, protons and other alpha particles. The instrument looks at all three of these and
determines what elements are in the rock.
We also took off the thermal enclosure on the lander so that we could replace an
antenna switch. During one of the last tests at JPL, we broke it due to a bug in the
software which applied power to it for much longer than it was designed for. We had a
spare so we swapped it for the broken one. We then ran a series of tests to make sure
that everything under the thermal enclosure was working properly before we put the
enclosure back on.
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