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"Saturday" Means Nothing to a Spacecraftby David Mittman
Saturday, February 22, 1997
08:30 PST -- It's Saturday morning and I've just kissed the wife and kids goodbye for the morning. It's off to work! Today I get to do the flight controller part of my job. I haven't had flight control duty for about three weeks now because we are no longer tracking Mars Pathfinder 24 hours a day. Since the spacecraft is behaving so well, we no longer need to monitor it around the clock. So, although Saturday duty is not great, at least I get to work during the daylight hours. During around-the-clock monitoring, we all had some pretty rough shifts, for instance, 11:15 pm to 7:30 am for four days in a row.
Today we expect to hear from the spacecraft that all is well. No one has been listening to the spacecraft since Thursday morning. If all is well, we will command the spacecraft to perform what's called an HRS Pump Cycle. Some explanation: There are two pumps which move freon (a coolant similar to that used in household air-conditioners) through the spacecraft, picking up heat inside the lander and dumping it outside the cruise stage. Usually we only use one of the pumps. To make sure the second, or backup, pump remains in good working condition we are required to periodically switch it on for an hour. After turning on the second pump, the thermal control analysts watch the temperatures inside the lander for a small but noticeable drop...about one degree Celsius. If the temperature drops and the power analysts report that the pump is drawing the right amount of power, then we can assume that the pump is in good working order. The backup pump is then turned off until the next pump cycle activity or until the first pump fails.
As flight controller, I have to be at the JPL Mars Pathfinder Project Operations Control Center before everyone else in order to set up the communications link with the spacecraft. Actually, what I really do is tell the engineers at the Deep Space Network (DSN) some key information and they make sure that the antennas are set up properly. Today's tracking pass will use the 34-meter antenna at Madrid, Spain. If there is a problem with the communications link, I can help them figure it out. If there seem to be no problems with either the spacecraft or the DSN antennas, then the JPL staff all get to go home and leave the communications link unattended for the rest of the eight-hour shift. If a problem occurs, we'll all get paged and have to come back to work. I'm glad about unattended operations today because tomorrow is my son's fourth birthday party and I have to go home to help set up the house.
12:00 PST -- Well, everything went very nicely and the JPL staff is going to an unattended operations mode. I'll secure our spacecraft commanding workstation, make sure that the spacecraft data are still flowing smoothly to our database here at JPL, and go home!
Tuesday, March 4, 1997
22:00 PST -- It's 10 o'clock in the evening, and I'm just getting in to work to set up for another flight controller duty shift. There seems to be a problem with our spacecraft command computer as I can't communicate with another computer located one floor above me.
Wednesday, March 5, 1997
01:00 PST -- The 34-meter DSN antenna in Canberra, Australia is up and running, sending information about Mars Pathfinder's health to JPL. At JPL, however, the problems continue. It's after midnight (now it's Wednesday morning), and not only can't I send commands to the spacecraft, I can't see the data that are coming our way from Australia. The data seem to make it to our data control center upstairs, but I'm not seeing it. It looks like we have a broken connection of some kind between our project control room and the data control room one floor up. Since this kind of problem is not my area of expertise, I'll wake up some of our computer network experts to help diagnose the problem.
02:00 PST -- Well I've awakened two of my coworkers at home and we've found the problem. A computer device called a "router" has died, taking out our communications link with our data control center upstairs. Our network expert is coming in to fix the problem. For now, there is nothing to do but go home and get some sleep. If needed, we can always have our data control team replay the data to us at a later time.