Part 1: OFJ97 has three activities for you and your students
Part 2: Did Jupiter cause a Galileo data loss - - and reflecting on change
Part 3: Problems getting the software to cooperate
Part 4: Subscribing/Unsubscribing: How to do it

The OFJ97 team has put together three excellent activities for you and your students to use and enjoy. They are:

* Study and Interpret New Images of New Worlds

This activity lets students study the most recent pictures from Galileo and make interpretations. Using free software, lessons, and images, your students can simulate the scientific adventure of peering at new worlds. Learners can simulate the work of scientists investigating geological features of the Jovian moon Europa. The students can also attempt to figure out the relative geological age of discreet features in one region of Europa. This qualitative analysis will lead student investigators to experience science using scientific tools.

http://quest.arc.nasa.gov/galileo/features/imaging.html

* Design a Spacecraft to test for Life on Europa

This activity will introduce students to the process involved with designing a spacecraft and testing for life on Europa. The main goal of this activity is to encourage student thinking and to focus on the process not necessarily the results. We are interested in posting any experiences that you and your students have.

-- Send us your results from the Design a Spacecraft activity and we will post them online for all to see --

http://quest.arc.nasa.gov/galileo/features/life.html

* Find Jupiter in the Night Sky

Jupiter is currently visible in the early morning sky and will remain visible throughout OFJ97, however, finding Jupiter is a challenge indeed because of its relative closeness to the Sun. This activity provides information on how to find Jupiter and encourages students to work together and develop a process for observing. We are interested in posting any experiences you might have looking for Jupiter.

-- Send us your results from the Find Jupiter activity and we will post them online for all to see --

http://quest.arc.nasa.gov/galileo/features/findit.html

[Editor's Note: Jim is the Telecom Unit Lead on the Orbital Engineering Team.]

This has not been exactly the day I thought it would be when I went to bed last night. For example the sound from unexpected rain that woke me this morning. And, at work, I followed a path of thought from a report of Galileo data loss to a speculation about the shape of Jupiter.

The first thing I do as I enter my office is to jiggle the mouse on my engineering workstation. That brings up a display of the most current measurements about "my" spacecraft hardware. Those of us who have been on the flight team for long times are very possessive about the health of this object that is now orbiting Jupiter. Just as a person might be concerned about their health from a slight fever, so I'm concerned if any of the measurements aren't quite right. Before I leave for home tonight, I'll jiggle that mouse one last time to make sure all's well.

The other day I explained this to Sue Kientz who is developing a CD-ROM on the Galileo spacecraft and mission. She e-mailed me back:

"Just read your article in Jupiter Online about the Coronal Mass Ejection. Very interesting and informative. Now that I'm involved w/Galileo I know what you mean about getting that feeling in the pit of your stomach when you think something may be wrong w/the spacecraft. I'm getting so *attached* to it, following it and reading its history, that I find myself actually worrying about it up there in space! It's amazing it just keeps on working and giving us all the wonderful information!"

This morning I looked over an e-mail report from Glen Elliott, the Galileo Mission Control Team analyst who keeps track of each "frame" of data sent back from Galileo. The tracking station decodes the data it receives in chunks that are called "frames"). It is part of my job to try to understand why "lost" frames were lost. The communications link could be one such reason, if the amount of noise should overwhelm the signal and prevent the earth receiving station from decoding the data. I wrote about one kind of such noise in my journal page, about the coronal mass ejection.

The e-mail report about yesterday's frame losses said,

"One TF [transfer frame] lost due to early LOS [loss of signal] entering Earth Occultation. The 'Cause' is listed as 'None' because there was not any ground station problem..."

This report struck me as strange. The word "occultation" refers to when one object (in this case, the spacecraft) is occulted or hidden from another (in this case, the earth). An earth occultation of Galileo occurs when Jupiter or one of its satellites gets in the direct path the radio signal takes from the spacecraft to the ground station. Last week we had an occultation caused by Jupiter's satellite Europa, and I was involved in the detailed planning of how to control the radio uplink and the radio downlink. We wanted to give radio science as much information about the occultation as possible. The planning paid off last week, and the occultation started and ended within seconds of the expected times. I learned a couple of new words, "ingress" for enter and "egress" for exit, from that work. But the important thing I remembered was that our ability to predict the path of Galileo and the satellites is so good that we were able to forecast ingress and egress to within seconds!

Losing that data frame means that we missed calculating something by several *minutes*! I knew that yesterday's major event was an earth occultation by Jupiter itself. I looked at the log kept by the Mission Controller as he monitored the loss of radio signal at the start of the occultation. The time was nearly 6 minutes earlier than was predicted. I e-mailed our radio science coordinator, Randy Herrera, to ask how this could be. Randy wrote back that this was the first time the spacecraft had passed behind Jupiter (as seen from the earth) near to Jupiter's equator. He speculated on two reasons that "ingress" on an equatorial occultation might occur earlier than predicted. Can you think about simple properties of Jupiter or its atmosphere that might be the cause? (The answer is at the bottom of this journal.)

Oh, by the way, it turned out the lost frame occurred as part of the planned preparation for the occultation. I figured out this much less interesting reason simply by comparing the loss time with the published time for each part of the preparation sequence. But, even though the result ended up routine, I had relished the chance to learn about something a little outside my ordinary work experience.

With the resolution of the data loss issue, and a few other technical problems like it, my mind turned to another matter. The main Galileo mission is nearly over. What I mean by this is that we are relatively much closer to the end of the mission in December of this year than to launch in October of 1989. I saw an electronically posted newspaper article this morning that an "extended" mission has been approved for Galileo. That means the spacecraft, its continued good health willing, has been budgeted by NASA to continue to return valuable scientific data for two years beyond the main mission, to December 7, 1999.

Why, with this good news, would some members of the flight team wear worried expressions on their faces or feel anxious for the future? The budget for conducting the extended mission means that we have to fly this spacecraft with just 50 people, down seven-fold from the current staff. Some are anxious because it's clear that not everyone who wants to stay faithful to Galileo will be able to. To them, it may feel like leaving their family. Others, their positions assured, worry about how to conduct a mission just as challenging as it is right now, but with a relatively tiny staff! In telecom, as in the rest of the flight team, we'll automate our essential processes to a greater extent, and we'll have to choose carefully the problems that we look at in detail.

A telecom colleague, Wade Mayo, went with me this afternoon to listen to the JPL Director talk about "Operations Plan 2000", of which the changes in Galileo flight operations is one small part. We reflected on "change" as we left. Wade is an evening class teacher. He said in the schools, the common concept now is that job security, even career security, is a thing of the past. That's very different from my 35-year experience, of being in one kind of career (telecommunications analysis), and with only two employers the whole time, AND on a single project for half that time!

Nonetheless, I felt invigorated from what I heard our Director Ed Stone tell us about the JPL vision for the future. These are not his exact words, but the vision is we will *develop* the systems we need to, in order to *conduct* our voyages of exploration, and *continue* to "push the envelope" in space exploration. It reminded me, I remarked to Wade, of what I remember about the Chinese word for "crisis". As I recall, the word is made up of the forms for both "danger" and "opportunity." I am really looking forward to meeting the challenges of planning to fly Galileo safely through the next 2-3/4 years and continuing to be involved in the design of efficient deep space telecommunications systems.

P.S. - I promised you a couple of possible reasons (courtesy of Randy Herrera of the Galileo Radio Science team) why the occultation by Jupiter might occur at a different time than predicted. Most engineering and scientific predictions are based on mathematical models. (1) The occultation prediction assumes that Jupiter has a atmospheric thickness, below which radio signals can't penetrate. (2) It also assumes that Jupiter has a particular shape, that of a slightly flattened sphere. Randy reminded me that this occultation was the first one to "test" the Jupiter atmospheric thickness and planet shape models near the equator.

P.P.S. - my wife Barbara and I did go see the movie "Hamlet". We knew the movie would be four hours long plus an intermission. I only fell asleep once. 8-) And my Galileo beeper didn't go off.

[Editor's Note: Tal Brady designs and programs the flight software for the Control and Data Subsystem (CDS) computer.]

The encounter with Europa is still moving along OK. Talked to some of the science team about the realtime science data results, which is the non-image science (e.g. information about the magnetic field). The realtime data is slowly coming in and looks good, but some analysis time will be required before they can tell if the data shows any surprises. The operations monitors had a display of the "Doppler" data, which shows the spacecraft's velocity change at the point of Europa closest approach. I was there watching and it looked really fine as it tracked the actual change against the predicted. (Readers might want to look up the Doppler effect on electromagnetic radiation to see how the radio telemetry received from the Galileo can be used to track spacecraft velocity changes.) I think some of this display was on the web page. [ed. note: yes, it was; "Doppler" data during each encounter is often broadcast "live" to the Galileo Countdown pages]

Now that we've done the Europa closest approach, the schedule says there will be Jupiter and Ganymede science tonight and tomorrow, then Jupiter and Callisto science Saturday. This encounter seems to have a little of each major science objective. Sort of a casserole; put in some Europa and some Jupiter, then add a little Ganymede, Callisto and Io for spice. Playback of the recorded image and approach science should start late Saturday night (PST). Looks like another good encounter. Maybe the most trouble free yet. It's a good sign for the mission lifetime if there are fewer problems past the halfway point. It means that things are pretty stable on the spacecraft.

As far as my own work goes, we had to restart the Phase-3A software testing on the testbed again this morning. Yesterday's test found that the new camera software didn't "load" the right way. Today's test has both of the new software loads running correctly. However, it looks like testing is showing that the CDS software and the camera software are having some problems working together--exactly what I was worried about. The problems may be fairly small because the test is still running and is producing telemetry packets containing image data. Since the test hasn't crashed, and since we are actually getting data, this indicates that most of the software is working properly. Still, it definitely looks like we will have to make some changes to the flight software based on these results. We should have more complete results by Monday, and then we can get started on any required changes to the software.

2-21-97

Noticed in the operations schedule that they took an image last night of Amalthea (one of Jupiter's smaller moons) later than expected. But, it looks like it got recorded OK. I'll have to remember to keep an eye out during playback for that image showing up on the web [ed. note: you might have to watch for awhile: it can sometimes take months before images are ready to show up on the web!]. The encounter "record" period, during which image data are recorded onto the tape player for later playback of the data to Earth, looks to finish about 6:00 PM Saturday and Playback to start about 7:00 PM (PST). I wonder if there will be anything from the new playback on the Web by Monday or Tuesday. The people who put images on the web page will probably kill me for that thought. That's probably way too early. Oh well, off to see 'The Empire Strikes Back' with some friends tonight.

2-24-96

Playback has started and it's going fine, Yaaah! I was right, it's way too early for new pictures, but there is a nice Galileo Today article that talks about what is happening about now. The Empire Strikes Back was great; big crowd, lots of fun.

Got some bad news today. The Magnetometer instrument software seems to have stopped running prior to the encounter and so their realtime science data from the encounter is probably not good. Their recorded data may be OK. We'll just have to wait and see. Fortunately, the problem is most likely to be a temporary memory error caused by the high radiation environment around Jupiter; Europa's pretty close in to Jupiter, so it sits in a lot of radiation. Although we use special "radiation hard" (i.e. resistant to radiation damage) memory on Galileo to protect against this kind of problem, we expect to have this kind of failure every once in a while,and we have seen a similar problem on one other instrument in the earlier encounter with Europa last December. If the problem is temporary, we can read out the Magnetometer's memory, send it back to Earth, compare it to the copy of the program that we have at JPL, find the bad part, and send up commands to the spacecraft to write a copy of good code over the bad part. Then we can just restart their computer with a command; a lot like rebooting a home computer after a crash. If we do the extended mission, there will be several more Europa passes, so if we were going to lose any science, this encounter is not the worst place to do so. Though I doubt that the magnetometer people would agree with me!

In the CDS Flight software development area the system test results from the new Phase-3 software do, as I expected, indicate errors in the way the CDS software interfaces (talks to) the camera software. There are two, I think, and one will require another system test later this week in order to determine if the problem is best fixed in my Control and Data Subsystem software or in the camera software. Also, both in the system test and in our development integration tests a small number of errors were found. The software is being changed to fix these errors during the first few days of this week. The changes required look pretty straight- forward. Only the one needing the additional test is of any concern.