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FIELD JOURNAL FIELD JOURNAL FIELD JOURNAL FIELD JOURNAL

The Spacecraft Arrives

by Guy Beutelschies

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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