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OFJ97 Field Journal from Glenn Orton - 3/24/97

*Europa-6 planning and the final chapter on Europa-4, did we succeed?

Part 1: Time for yet another observing trip in Hawaii!

Our Jupiter atmosphere observation plans for the Europa-6 orbit included taking a good look at some of the large white ovals which "live" just south of Jupiter's Great Red Spot (or GRS, for short). The ovals rotate around the planet at a different speed than the GRS itself, making it more difficult to predict where they will be. The people who plan observations of Jupiter's satellites don't have this problem, since rocky features don't move all over the place!

We needed to use observations from here on Earth (specifically, the Infrared Telescope Facility in Hawaii, or IRTF) to determine where we needed to point Galileo's cameras to "capture" one or more of the white ovals.I was having a problem keeping up with processing the data, and it was beginning to show. In an early December planning session, I gave some tentative locations for the longitudes (or east-west location) for these white ovals. It turned out that those locations were wrong, so now I had to figure out where they would be, using the IRTF data. What you do is look at different images of the white ovals taken over a period of time, and then you can figure out how fast they are moving around Jupiter. It's like predicting how fast a storm system will move into your area. Finding these "drift rates" is usually an easy task, but since I hadn't had time to work with all the data, I never quite got the correct drift rates worked out.

So, we estimated the rates and did what we could, and - sure enough - when we got the rates in, everyone had to make more pointing changes. It was a twofold lesson: (a) there is not enough of me to go around (I didn't know this already? :-), and (b) there really were lots of people counting on my work and I'd better not screw up again. Everyone understood, but it didn't make anyone's workload lighter.

Another question was: where would be find the target hot spot feature, similar to the region where Galileo's atmospheric probe had entered? A bright(when seen at a 5-micron wavelength) feature, while not the brightest on the planet, was sighted near the target hot spot location. It was a chevron- shaped feature with the upper part narrow and dim. The feature's location told us that we were not dealing with an older, "granddaddy"hot spot. The hot spot we targeted originally had disintegrated and a new one formed, or the old one changed and moved substantially in longitude.

We also did some Io observations as payback for some observers who had helped us out earlier; boy, did we owe! But this is one of the ways in which science works: you do someone a favor, they return it.

Another problem that cropped up was the fact that Jupiter was so close to the sun as seen in the sky that our IRTF observations (which were done at a wavelength where Jupiter is very dim and we see sunlight reflected off only the highest particles in Jupiter's atmosphere) were totally swamped by the background sky. So much for being able to look at particular features in Jupiter's northern hemisphere so that we could have Galileo look at them during the Ganymede-7 orbit encounter in early April.

Because of my travel and my observing schedule, I'd have a single night (when I returned, really refreshed - yeah, sure) to buy Christmas gifts AND an anniversary present for my wife AND birthday presents for my son. I ended up getting everything before I left on travel (which meant that the day before I left, I visited 12 stores in 5 hours!). Making life even MORE interesting during the observing run was the fact that one of my teeth lost a filling - ow!

Part 2: Computers and Funding

All this time (yes, the entire journal time frame), I'd been hounded by computer software problems in a very detailed program used to simulate the way in which radiation (e.g. heat) in Jupiter moves up and down in the atmosphere. If our actual data matches up to what we can generate from the computer program, then we know that our computer model is doing a good job of imitating the real Jupiter. But before using the program to test the data, we need to make sure that the program isn't filled with errors.

To make sure that the computer program had no errors, I would check its results against other computer programs, written by other people. If they match up, that means that our programs don't have any obvious bugs. But, my results never quite coincided with those from an apparently simpler program by my colleage and fellow Galileo Probe Net Flux Radiometer co-investigator Andrew Collard. This was especially strange since my model is more complicated, and should do a *better* job! After many changes in my original programming to account for the ways in which he was doing things, our results STILL weren't matching. This continued to be a source of great frustration, as I'd love to be really working on the data - not twiddling bits in a numerical model!

More paperwork was required, too. We were rapidly exhausting the funds in our account to do all this ground-based astronomical support work. The cost of all this equipment shipping and airline travel wasn't trivial! Last year, we'd applied for and gotten a supplement to the budget. Once again, it was time to write letters to the relevant NASA headquarters person for a funding "supplement." which headquarters said they'd consider if it were "moderate." I had no idea what "moderate" was supposed to mean, but the deadline was approaching.

It's sometimes a little tricky asking for support for people who are not associated directly with NASA. For example, we wanted to pay for someone at the University of Wisconsin to work at the Swedish Solar Telscope during the Europa-6 encounter (Hubble and the University of Hawaii telescopes were certainly not capable of handling anything this close to the sun). In addition, we wanted to fund the Mt. Stromlo / Siding Spring Observatory in Australia to monitor Jupiter for us between the Ganymede-8 and Callisto-9 orbit encounters (early May to late June) in order to continue to track various features of interest. The IRTF was scheduled to be down during this entire time for shutter refurbishment, and the Mt. Stromlo / Siding Spring Observatory was one of the few facilities in the world which was capable of doing the type of imaging we needed.



 

 
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