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OFJ Field Journal from Claudia Alexander - 12/20/95


I cancelled my Christmas vacation today! I will fly up on Christmas day, and fly back again that night. Mom will hate it, but this year I just can't do it. Even my brother is working, so I know I'm not the only one.

Sometimes when you work for a living, Christmas vacation just doesn't come at a good time for the job. For us on Galileo, the schedule has been squeezed and squeezed until there is no room left to postpone things. For example when we had the problem with the tape recorder, everybody on Galileo had to drop what they were doing in order to work on all the tape recorder issues, and put other things aside for "later." But the deadline for Galileo's first flyby of Jupiter's moon Ganymede cannot be postponed. The spacecraft is going by Ganymede in June whether we are ready or not. There is no more room for doing things "later."

We are trying to test one of our spacecraft computer sequences (the testing is done on equipment here on lab, not on the spacecraft itself). This is the first time that we've tried running the test with all the instruments "on." The test was supposed to be in December, right around arrival day. That wouldn't have interfered with Christmas vacation at all. But one of the engineers who we *had* to have present during the test had to help with another test on the tape recorder at the same time, and that couldn't be rescheduled. So the sequence test was postponed until Jan 8.

Now normally the testbed engineers like to get the sequence of commands 2 weeks early, so that they can "massage" it and make sure it is correct. That would mean that we would need have the commands to be tested ready on Christmas Day! (That meant we were sure to have a "slip" of at least one day!)

We have already found problems which have to be fixed before the computer sequence will run, even before getting the test started. One of my instrument's commands was not working properly. My instrument engineer fixed it. The computer software engineer fixed his portion. But the SEQGEN writers cannot be ready on time.

SEQGEN, which stands for SEQuence GENerator, is like a giant complex spellchecker for the sequence of commands that are written by people like me. Galileo is a very complicated spacecraft, and the commands that run it are also very complicated. It's easy to make a mistake that would mean a command wouldn't work (for example, not allowing enough time for the command to do everything it has to do). Plus all of the other science teams and the engineering people are also putting in *their* commands, which means that one instrument might try to do something during a time when the spacecraft can't handle that much activity. SEQGEN catches all of these possible mistakes before they can be sent on to the spacecraft where they could do serious damage. Then you clean up your mistakes and send the sequence back for another run through SEQGEN until SEQGEN says that you've passed inspection.

My instrument engineer fixed the portion of our instrument's software that didn't work. That means that our commands are now different from what SEQGEN expects to see. If I run the test sequence through SEQGEN, it will tell me there are errors, when they are not really there, but it will also not give me the "OK" on my sequence. A new version of SEQGEN was supposed to be ready in time for the test, but it won't be. It's like one of those machines that automatically grade tests; I KNOW that the answer key has been changed to something new, but SEQGEN doesn't know it yet.

So I have to bypass SEQGEN, and grade this exam by hand. I have to write the subcommands, by hand, that SEQGEN would generate if SEQGEN could read my sequence. This will be very complicated and will take a couple of days to do. (Since I work half-time on Galileo, it will actually take me more than a couple of days). Then I have to make sure I did not make a mistake -- and since I can't use SEQGEN to catch my mistakes, this will be harder than usual. My instrument engineer back at the University of Iowa will help me by reviewing what I do. That'll probably be a day or two after Christmas. Then we have to give the new sequence to the testbed engineers so they can make sure it will work properly. They really want to have it the day after Christmas (they aren't taking Christmas off either). If they make any changes, my instrument engineer at the University of Iowa and I have to review them and make sure we agree.

They are supposed to generate the "bits and bytes" version -- the actual 1's and 0's that would get sent to the testbed -- on or about Jan 3, 1996. We will also begin doing some preliminary testing on the 3, 4, and 5th. So I have to be here to review the sequence as it comes out from the various teams. (I still haven't reviewed the final product that the sequence team helped us put together! - yiiipes, naughty me. This is what I get for going away for a week to work on other things). Then, since I'm new at this testbed stuff, I have to learn how to read the data that the testbed will send to us, etc. AAAAck. And I still have to finish my paper and deliver pages for my Windows project. This is why I have to cancel my Christmas vacation. I'm not sure I can explain all this to my mother, though.



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