:: NASA Quest > Archives ::

OFJ97 Field Journal from Laura Barnard - 2/13/97

This morning our team chief wanted to double check the Europa 6 (E6) sequence before it is sent to the spacecraft later tonight. The problem is the tape recorder. It has four "tracks" (the tapes that you are used to have two tracks: one going forward, one going backward. Galileo's tape recorder has two going forward, and two backward). Whenever the tape is switching direction, it can't record any data. Our software lets us check when the tape will turn around. Usually we tend to trust our models, but with the differences between the command software and our planning software we get concerned about WHEN the tape will change to the next track. If the tape turns too early or too late we will lose our timed observations that we are recording during the encounter. Europa has so much good stuff that we don't want to lose anything if we can help it! So once again I loaded up the current sequence and ran it through our planning software MIRAGE. Do you see a trend here? Everyday I am working with my computer and different pieces of software modeling different things. Small wonder I don't use my computer at home!

With the completion of one sequence (E6, the one that's currently running on the spacecraft), it means that we need to start working on the next. We are constantly rolling off one sequence and starting another. In actual fact the entire science team is actually working on four plus sequences at any one time (or more if you are behind schedule!). For instance: Right now, the spacecraft is in the Europa 6 (E6) sequence. We just finished getting back the data on the tape from the Europa 4 (E4) orbit. We also have plans in place for Ganymede 7 (G7) that are now going to the sequence team for iteration and final checks. The science teams are also working on the Ganymede 8 (G8) sequence. Whew! If you are someone like me that also does archiving for the team as well, you are working on so many sequences that you have to ask what sequence they want to look at!

For the rest of the afternoon I looked at the predictions of the tape movement for the next (G7) sequence. I found some disturbing things that will have to fixed. Near the beginning of the G7 sequence, the tape is supposed to slew (kind of a fast forward). However, my model shows that it will stick (which was exactly what caused our big problems with the tape recorder before), so we have to make sure we make that slew earlier. There isn't much time to make that change, so everyone has to hurry a little to make sure that the commands get rearranged properly.