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U P D A T E # 1 3 PART 1: Looking
for certain teachers
I would like to identify any teachers in the San Francisco Bay Area who may be using Online from Jupiter in their classroom. Please send me brief note with your phone number to marc@quest.arc.nasa.gov if the above describes you. Thanks so much. Back now, to our regular programming. (see http://www.jpl.nasa.gov/galileo/fact for a complete list) It's much more difficult to go into orbit around a planet than to just fly by it because you have to slow the spacecraft down somehow for it to be captured by the planet's gravity. Five spacecraft have previously flown by Jupiter: Pioneer 10 and 11, Voyager 1 and 2, and Ulysses. Galileo will be the first to go into orbit around Jupiter, or for that matter, any outer planet. The Galileo spacecraft is currently enroute to Jupiter, with arrival scheduled for December 7, 1995. At that time, Galileo's atmospheric probe will plunge into Jupiter's atmosphere, relaying information on the structure and composition of the solar system's largest planet. The spacecraft's orbiter will make an Io gravity assist (1000 km closest approach) and then fire its main engine for 49 minutes to be captured into orbit around Jupiter. The orbiter will then spend two years orbiting the giant planet, studying Jupiter and its moons, and returning a steady stream of images and scientific data. A special Galileo Countdown to Jupiter Home Page has been created which is dedicated to Galileo's arrival at Jupiter. The home page is now available at the following URL: http://www.jpl.nasa.gov/galileo/countdown/ This home page has the following features: o Computer-generated Jupiter approach images are displayed at the top of the home page, including Galileo's view of Jupiter and an overhead view of the Jovian system. These images will be updated daily until arrival day, and on arrival day will be updated every five minutes. o The latest Galileo Jupiter orbit insertion status reports will be available on the home page, and will be updated every hour on arrival day. o Galileo's current position is updated every minute. This includes the distance of the orbiter from the probe, distance from Io, distance from Jupiter's atmosphere, Earth and Sun distance and more. o A detailed timeline of events and sequences that the spacecraft will perform for Jupiter orbit insertion. o Images of Jupiter of the Galileo probe entry site are available. These images were taken by various observatories including the Hubble Space Telescope. o A number of computer-generated Galileo probe animations are available. These animations show the probe's arrival at Jupiter, entry into the atmosphere, parachute deployment and descent. Thanks to Ron Baalke (baalke@kelvin.jpl.nasa.gov) for this great resource
To recap, we suggest that after each Probe Squash installment, you
and your students make a prediction about how long the Probe's
mission will last.
Installment #6: Helping the Probe to Keep Its Cool
Assuming that the Probe lasts long enough to send data back to the orbiter
during the entire 75 minutes allowed for data transmission, the surrounding
atmosphere will register 184 degrees Celsius (363 degrees Fahrenheit)--
quite a change from the roughly -162 degrees Celsius (-323 degrees
Fahrenheit) at the start of the Probe's mission!
How do we protect the Probe from these extreme temperature changes?
Before entry, thermal control is provided by hardware in the outer shell.
After entry, layered blankets made of a material called Kapton slow down
the rate of temperature changes in the Probe capsule, protecting the interior
structure because it doesn't conduct heat well (it would be a poor choice for
cookware).
As you can imagine, testing the Probe's ability to withstand high and low
temperatures is vital--but measuring the actual atmospheric temperature
where the Probe might fail isn't easy. It seems like it would be simple:
stick the Probe in the Descent-Pressure-Temperature testing chamber, and
heat up the chamber.
The problem is that while some parts of the Probe and its instruments are
designed to take high heat, other, more sensitive parts have to be protected
Jupiter environment, we still have to isolate the Probe from that very
environment! Essentially, the Probe is like a big thermos bottle. When the
Probe was heated up to test limits, it then took several *days* until the
Probe cooled down enough for the next test! Engineers even brought in fans to
blow air across the Probe's nose (which didn't end up helping much).
While this helps to keep the Probe working, it makes it very difficult to
figure out what the temperature will be *inside* the Probe for a given
temperature *outside* the Probe. Engineers can look at predictions of the
Probe's trajectory, and scientific models that predict what the gas
temperature will be at different distances below the entry point, but they
can't predict the temperature inside the Probe without a awful lot of effort.
Here's what the engineers do know: The probe has a unit temperature
qualification value of 60 degrees Celsius (140 degrees Fahrenheit). While
building and testing the Probe, a test was run in 1983, where the Probe was
put into a large test chamber and the engineers tried to simulate Jupiter's
atmosphere while the Probe sampled the atmosphere in the chamber. Just
like in the mission, the Probe started quite cool and then was suddenly given
a very cold dose of helium which then started to warm up. Slowly at first, but
faster and faster as the test went on. Although the test didn't go the whole
75 minutes, the engineers could still use it to guess what will happen.
Can you? Here are some of the important results of the test showing how the
different parts of the Probe warmed up:
Time from entry 0 min 10 min 20 min 30 min 40 min 47 min
External Atmosphere -76 C -50 C -9 C 51 C 92 C 119 C
Transmitter -9 C 0 C 7 C 15 C 27 C 40 C
Exciter A -13 C -18 C -18 C -10 C 6 C 24 C
Exciter B -10 C -14 C -11 C -7 C 9 C 27 C
Data and Cmd Processor -2 C -4 C -5 C -1 C 5 C 11 C
Subsystem Power Supply -3 C -6 C -7 C -5 C 2 C 9 C
Instrument Power Supply -3 C -8 C -1 C -2 C 14 C 32 C
Science Instruments
ASI -2 C -8 C -10 C -4 C 11 C 29 C
NEP -10 C -8 C -9 C -5 C 7 C 21 C
HAD -10 C -13 C -13 C -4 C 11 C 28 C
NFR -7 C -11 C -12 C -5 C 12 C 31 C
NMS 0 C -1 C -4 C 0 C 16 C 31 C
LRD -3 C -6 C -8 C -5 C 9 C 25 C
Can you guess why some parts of the Probe warm up faster or more slowly
than other parts?
Obviously none of the parts of the Probe failed in the 1983 test because the
test was stopped before anything got too hot. But what will happen when
things keep getting hotter? To help you with this, here is how we expect
the atmosphere of Jupiter to warm up during the Probe's mission:
Entry (0 minutes) -8 C
10 minutes -94 C
20 minutes -23 C
30 minutes 28 C
40 minutes 71 C
50 minutes 107 C
60 minutes 140 C
70 minutes 170 C
75 minutes 184 C
Marcia Segura Friday, November 10, 1995 Well, the Near Infrared Mapping Spectrometer was turned on Monday, November 6 as we get ready for Jupiter approach and the beginning of Galileo's main mission. The radio signals from the spacecraft, or "telemetry," indicate that NIMS is operating normally. At some point in the near future, the instrument will get new software to enable NIMS to work with the new spacecraft software. The instrument will remain on for the next 2 years, making observations of Jupiter, the rings, and the large satellites. At this time, had things gone per the plan, we would be anxiously anticipating the return of data from Jupiter's moon Io - the best to date. But alas, it's not to be. As you've undoubtedly heard, Galileo's tape recorder has had some problems. The tape isn't broken; engineers are still analyzing exactly what's wrong. The project, in an effort to protect the tape recorder from damage, has decided not to collect remote sensing (imaging) data until after the probe data has been played back and the engineers have finished their work. Whatever the engineers find, I am sure that it will have an effect on the science observations planned throughout the mission. It really hasn't been a very easy time for the science teams on Galileo. Losing the Io encounter and the Jupiter Probe Entry Site observations has been disappointing and frustrating for all involved. I'll attempt to describe the feelings in this way. Let's just say... You're going out on the town. You have tickets to your favorite play (they cost you an arm and leg) and you're going out for dinner at Spago's (Wolfgang Puck's ritzy restaurant here in Los Angeles). You splurge on a new dress for the occasion (the VISA bill comes next month). On the day of the big event, here's what happens.... no hot water when you shower, a run in your pantyhose, the waiter at Spago's tips your FULL wine glass into your lap, the valet attendant misplaces your car keys, you miss the opening act and the usher won't let you in until intermission!! As you can tell, the past three weeks haven't been fun... but enough about that! This week marks the start of science planning for the ninth orbit, or "C9" as it's called. "C" stands for Callisto (another of Jupiter's satellites, and the one that Galileo passes the closest to) and 9 stands for ninth orbit. I'll be spending a lot of my time working as the lead NIMS coordinator for this orbit. (Each NIMS coordinator has assigned orbits and assigned targets; mine is Callisto) I'm responsible for making sure that all the NIMS observations planned for the C9 orbit are properly put into a sequence (computer program) which will tell the instrument and the spacecraft what to do. C9 will have 70 or so NIMS observations (Jupiter, Io, Europa, Ganymede, and Callisto are all included in that total). I'll be attending MANY meetings and negotiating with other science teams for observing time and other resources, since all the instruments want as much observing time as possible. We'll continue working on this until the end of January. Meanwhile, I'm still involved with testing the new NIMS software. Many hours this week was used helping to analyze the results of our latest test. Bob Mehlman (one of our programmers - his office is at UCLA) and I spent some time discussing the test results. We had some questions that we couldn't answer ourselves, so we arranged to meet with Tal Brady (the ultimate expert on Command and Data Subsystem (CDS) software). As it turns out, we uncovered a "bug" in the code. The software group will fix it and then we'll test it again. Such is life on Galileo .... Life outside of Galileo this week was filled with the normal everyday stuff. A football game for Matthew on Tuesday; they lost by a touchdown. The flu caught up with him on Wednesday (I had it last week). Parent-teacher conference on Thursday (it was planned and reports were good). Adrian called to give his new phone number (his room assignment at Emerson changed) and remind us to bring thermal underwear with us on our upcoming Boston visit. No, I didnŐt go sky-diving, bungee jumping, or drag racing. Maybe next week.... Have a safe and happy Thanksgiving. Weeks end. Marcia Segura "Online from Jupiter" Jim Erickson
Week of 10/29
Meetings. Sometimes I feel they are the bane of my existence. Sometimes I feel
they were really productive and necessary. Flying a spacecraft can't be done
without meetings, so you learn to live with them. But whatever you decide to do
for a living, you end up having meetings.
We use meetings to educate ourselves on something, to decide what to do, or to
educate others in the organization. Sometimes we have meetings to raise our
spirits before or during crucial events. We even have meetings to schedule
meetings! This is because some types of meetings require the same people, and
can't happen simultaneously.
As time to Jupiter orbit insertion grows short, meetings seem to increase. This
week is a dramatic example.
Tuesday:
7:45 - 8:00 Read and respond to e-mail messages. E-mail is electronic mail.
8:00 - 9:00 Meet with project staff and others to decide what changes to make
to the science data gathering that will occur shortly before and during the
probe relay and Jupiter orbit insertion. The meeting ends early because we have
to all go to another meeting:
9:00 - 10:00 All hands meeting. This was a gathering of all the people on the
project. It was to enable the project manager to inform everyone about the
overall decisions on the rapidly changing status of the tape recorder, and our
plans for using it during the probe relay/Jupiter orbit insertion period.
10:00 - 11:00 Continued the 8:00 decision meeting on what changes to make to
the science data gathering.
11:00-12:30 Command conference. At this meeting the decisions on what real-
time commands are to be sent to the spacecraft for activities that can't be
sent with the stored commands in a sequence load.
12:30 - 1:00 Quick lunch at the cafeteria (BLT on wheat with iced tea).
1:00 - 2:00 Meet with project staff and others to decide what changes to make
to the Critical Engineering Sequence. This is the sequence of commands that the
spacecraft will perform to relay the probe data, and to fire the main engine to
place us into orbit as the first artificial satellite of Jupiter. This sequence
of commands has been extensively verified and tested, and is designed to
continue operating even if really bad things were to happen to the spacecraft.
We take exceptional care, and hesitate to make even slight changes to this
particular sequence.
2:00 - 3:00 Meet with the sequence builders to approve the last sequence to
perform science on Jupiter approach, starting on 11/6/95. It is approved, and
represents the last sequence to be executed on the spacecraft before arrival at
Jupiter.
3:00 - 5:00 Teleconference with the Probe people at Ames Research Center,
discussing the implementation of backup storage of the probe data. All of the
probe data is supposed to be stored on the tape recorder, with some of the data
also stored in Galileo's computer memory as a backup. Due to the tape recorder
difficulties of the preceding weeks, we're increasing the amount of backup data.
All told, that was 8.5 hours of meetings in one day.
Wednesday was similar. We had an all day review of the project's plans for
arrival at Jupiter, and whether the flight team (the people who work on the
project to fly the spacecraft) are ready. We brought in experienced people from
outside of JPL to look at what we have done to get ready, and to suggest any
improvements. We want them to look for anything which we might be able to
improve, and comment on whether we're ready. We know we have work left to do,
and have plans to finish it all in time. The review team has to decide if
we'll be able to get it all done and be ready in time.
The review team agrees. We'll be ready!
Jim Erickson
David Atkinson With the government furlough, my trip to Ames this week was canceled and it was a chance to catch up on a few things. This semester I am teaching a junior level course in electromagnetic theory at the University of Idaho. I planned ahead, for once, and realizing that this was the semester that Galileo would finally reach Jupiter, I decided to teach the course on video. The University of Idaho has a very extensive engineering outreach program. It is not unusual for me to have students from around the world. This time one of my students is from Taiwan. One advantage to teaching a course on video is that I can pretape lectures. So, when I attended the Division of Planetary Science meeting in Hawaii in October, I pretaped 6 lectures. Electromagnetics can be a confusing subject for ...... well, everyone. But to make it even more fun, imagine giving lecture number 23 on Monday, lectures 27, 28, and 29 on Tuesday, lecture 24 Wednesday, lecture 25 on Thursday morning, followed by lectures 30 and 31 on Thursday afternoon, and lecture 26 on Friday It is difficult enough to give lectures in sequence. Trying to deliver coherent lectures out of order is somewhat mind numbing! Since I had planned to be at Ames this week, I once again pretaped the week's lectures. But with the government furlough and the trip canceled, I have now an open week with which to try and catch up. This semester I am the chairman of my department's promotion and tenure committee. We have four Assistant Professors going up for promotion to Associate Professor with tenure, one Associate Professor being considered for promotion to Full Professor, and four Assistant Professors undergoing a detailed third year review. This has kept me busy throughout the semester. I am also in charge of our department research colloquium, the Department of Electrical Engineering Honors, Awards and Scholarship committee, and the public relation committee. And, just so I don't find myself getting too bored, I am the Associate Director of the NASA Idaho Space Grant Consortium, and one of several Assistant Directors of the Idaho NASA EPSCoR (Experimental Program to Stimulate Competitive Research) Program. One of the advantages of working at a small school is you get to stay busy! But, of course, most of my time has been spent waiting for, planning for, and getting nervous for December 7. Throughout the semester (as well as last summer, and the previous year) I have been trying to understand the formatting and time tagging of Navigation team trajectory data files, and radioscience data files, something which is absolutely necessary in order for me to run my experiment. A graduate student and I have been frantically writing software to read, reduce, combine, and analyze the proper data for Doppler wind measurements (a topic for another journal). Now that my student has graduated, I am working alone to run simulation after simulation, understand the effect of errors on the wind measurements, and make final adjustments to the code. This work has, for the most part, been restricted to weekends and evenings since the week itself is filled with teaching and committee work. A real thrill for me is watching the local community, and, for that matter, the entire Pacific Northwest, get excited about the upcoming mission. In the past several weeks I have given talks to 75 enthusiastic fifth graders at Blue Ridge Elementary School in Walla Walla, to physics and astronomy students at Whitman College, and to the Spokane Astronomical Society. On Friday I spent a significant portion of my day on the phone with the science editors from the Seattle Times and the Portland Oregonian, and on Monday I will talk to fifth and sixth graders at St. Mary's school in Moscow. Next week I talk to two cub scout dens, give a graduate research colloquium and talk to the freshman astronomy class at the University of Idaho. And I don't mind a bit. I may not be the best speaker in the world, but I don't have to be. Galileo is such an exciting project and mission that it sells itself. And people I have talked to, especially the young people, cannot get enough. It is wonderful to be able to offer something that generates genuine interest and excitement among the kids. It is Saturday night, November 18. Less than three weeks until we get to Jupiter. I finalized my travel plans today - I will leave on Sunday, December 3 (my son's seventh birthday) for Ames. After one day at Ames I will fly to Pasadena on the 5th where I will stay at the Holiday Inn. On Wednesday, December 6 I get to talk with about 150 fifth and sixth graders at Ybarra school in Walnut (about 45 minutes from Pasadena), and then the big day on the seventh. My plan is to get to JPL about 6 AM and make a day out of it. The probe mission begins at just before 3:00 P.M. (local time in California). In the evening I expect a group of us will go to dinner, reminisce, relax, and just be excited. By Saturday I will head back to Ames to begin preparing for the preliminary data analysis, followed by a press conference on December 19 where we get to show off our early results. And, finally, on December 20 I head home. Merry Christmas! November 19 to December 7: Galileo is 18 days from Jupiter! If this is your first message from the updates-jup list, welcome! To catch up on back issues, please visit the following Internet URL: http://quest.arc.nasa.gov/galileo/journals/index.html |
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