A new Teacher Registration page is now available on the Web. We
hope that a rich variety of tuned-in teachers (we  mean teacher in
the broad sense) will take a few moments to provide some details 
about themselves.  Any information input will be browsable by other 
folks. We hope that it may help like-minded folks find one another
by grade level, geography or special interests. If you consider 
yourself a teacher (involved parents count), please register....and 
then browse....and then connect.  

The Web specific is: 

http://quest.arc.nasa.gov/galileo/lounge/database.html
For you browse-around types, this is found in the Teacher's Lounge.

A discussion group for teachers is now forming. Its name is discuss-jup;
it will provide a forum for teachers to discuss a wide variety of issues, 
concerns, teaching strategies, useful resources, project collaboration 
opportunities, and suggestions about the Online from Jupiter project.

Anybody with something meaningful to share will be invited to send 
their thoughts to the rest of the group.

Over the next week, we hope people will sign up for the list but will 
refrain from posting so we can first grow to a critical mass. On 
November 21 you will be encouraged to let the words fly.

We are hoping to identify a few experienced moderators for this discussion
group. If you are familiar with the vagaries of online discourse, and are
interested in helping to lead this discussion group (as a volunteer), 
please send an email note to marc@quest.arc.nasa.gov

A special digest version of the list (called discuss-digest-jup) will 
allow you to receive all the day's messages in a single post. This 
will help keep mailbox traffic down but it will be somewhat harder 
to reply to an individual message.

The discussion can be followed through simple Email or through a 
Web interface. The choice is yours. To receive the information in your 
mailbox, send a mail message to listmanager@quest.arc.nasa.gov
In the message body, write one of the following lines:
  subscribe discuss-jup
  subscribe discuss-digest-jup

To see the action Web wise action, visit:

http://quest.arc.nasa.gov/galileo/discuss-jup-lwgate.html

1995 October 27
Interesting week, showing just how life can be a roller coaster.

Keep in mind that for 17 years, I've been preparing for the chance to 
compare direct atmospheric data from the Galileo Probe with 
various remote sensing results (that is, images) from the Orbiter.  
The point is to learn about the relationship is between what we 
determine from external sensing of radiation  and what's really 
there, as well as how the Probe entry site compares with other 
interesting regions.

Then the "tape anomaly" occurs. So maybe we don't have a tape and 
we don't get any Orbiter data.

Then the early tests show that we DO have a tape, we can read data.

The tests that took place later, backing up the tape 25 "windings" 
from the tape end to cover a spot where the tape might have been 
worn a little thinner, were also successful.  So, we'll live with a 
little less tape, and the show goes on.

Not.

The Project decided that since the Probe data are so valuable, and 
since they won't trust their primary medium for recording them--
you guessed it, the tape recorder-- that they'll back everything up in 
the spacecraft's computer memory. That's fine with me, since I'm 
quite concerned with the value of the Probe data.

Now for the Catch-22... In order to do that, they make room in the 
memory by erasing all the commands for the scan platform and the 
various remote sensing instruments.  So, NO Probe entry site 
observations - also no Io clasp observations (which REALLY has the 
"Io-philes" upset!).

Worse yet, they're not even sure how data from the SSI (the solid 
state imaging camera) is going to be played back. The tape recorder 
has to be running at relatively high speed to capture SSI data. 
However, the tape recorder tests were run at a low speed, no faster 
than what's required for the Probe "relay link" (when the Probe sends 
its data to the Orbiter; the Orbiter will later relay the data back to 
Earth). So, maybe there is an outside chance that the Ultraviolet 
Spectrometer (UVS) or the Photopolarimeter Radiometer (PPR), 
(two imaging instruments that don't need to have the tape recorder 
running at high speed) can get data, but there is no guarantee of 
anything else. These tests won't be made until after the safe arrival 
of the Probe.

So this week, I went to two "emergency" meetings to help determine 
how we'd use Galileo to conduct an atmospheric investigation 
without any tape recorder at all. Answer: it's still possible - about 
20-30% of our tape-relayed data would be returned to Earth. 
However, we'd have to change the way we plan observations.  Right 
now, if we want to observe a certain feature in Jupiter's 
atmosphere, we simply schedule a "window" of time to look at it.  
Under the new strategy, we'd first look at it when the "downlink" 
between Galileo and Earth was high (meaning that the spacecraft's 
transmission rate was as high as possible), then look at ground-
based observations of Jupiter and pick out whatever interesting 
objects were available at that time. Not a big worry - there is an 
endless list of interesting things on the planet, but our ties with 
ground-based observers had better be extremely good!

All during this time, I was working with a visiting scientist from 
Queen Mary / Westfield College, University of London, preparing him 
for helping to model the atmosphere of Saturn (and other outer 
planets) in anticipation for the operation of the Long-Wavelength 
Spectrometer on the European Space Agency's Infrared Space 
Observatory (ISO) mission, due to be launched on November 10. So, 
while emergency meetings came and went, I had to see what I could 
teach him about my radiative transfer programs and, in general, 
about Saturn.

When it rains it pours...

The Probe Net Flux Radiometer, Dr. Larry Sromovsky, and his 
colleague, Dr. Andrew Collard, at the University of Wisconsin have 
been emailing me trying to get me (as a co-investigator on their 
experiment) to figure out, with them, why their programs and mine 
don't converge to similar answers. Finally, I think we did it, but 
they're now pushing that last 10-15%, narrowing down the answers 
to using a finer and finer vertical grid scale. This means more 
programming on my part, too.

I'm way way behind on getting similar, less well defined, work on 
creating model atmospheres for the Probe Nephelometer (cloud 
particle measurement) instrument, on which I'm also a co-
investigator.

Even though it'll be daytime here in the western United States during 
the Probe mission, we might still be able to use some telescopes 
here to observe Jupiter during that time. I managed to make some 
contact with the person working at NASA Headquarters on Planetary 
Astronomy who is contacting Kitt Peak National Observatory and 
Sacramento Peak Observatory on using their solar telescopes during 
the Probe entry time to "characterize" Jupiter. I've also started 
working with the Infrared Telescope Facility (IRTF) staff in a very 
preliminary way, to determine how we might leave much of the 
mirror uncovered and use the solar cover only over a part which will 
be covered by the sun. Our original plan was to cover the whole 
thing, back when the Near Infrared Mapping Spectrometer (NIMS, 
another imaging instrument) was going to get images and spectra 
from the Orbiter, and just concentrate on thermal images at 
wavelengths longer than 4 microns where the cover can transmit 
very well. Now, with no NIMS observations, we're going to try for a 
little bit more.

I also got off a general message to the group of "jovi-philes" who 
are on the receiving end of the International Jupiter Watch / 
Atmospheres Team email list, after my outgoing email problems 
finally cleared up.  (Nothing like using the mighty computing power 
of JPL's Cray Y/MP for email service!) This message told everyone of 
the problem and asked for help (the message can be obtained from an 
anonymous ftp site: 128.149.11.11 (lono.jpl.nasa.gov) in 
pub/ijw/ijwnotices as go951027.

Now I have to prepare for the observing run next week at the NASA IRTF.

November 2, 1995
Everyone is very relieved that the tape recorder is working again. 
However, there will be no pictures taken on the approach to Jupiter, 
so the Navigation Team will have to do without the three optical 
navigation pictures that were planned. What this means is that the 
our ability to control the Io flyby in the latitude (or North/South) 
direction will not be as good. This is not a problem, since there will 
be no pictures taken of Io during the approach to Jupiter. However, it 
is still very important to control the altitude of the Io flyby 
accurately, and this journal will explain why.

On October 25, the Navigation Team completed the final test and 
training exercise before the Jupiter encounter. This final test 
simulated the work the Navigation Team does for the "JOI Tweak". 
What is the "JOI Tweak"? Between now and the Io flyby (which 
occurs four hours before Galileo's closest approach to Jupiter),
the mission plan allows for three trajectory correction maneuvers 
(TCMs) to control the flyby conditions at Io. The Io flyby reduces the 
speed of Galileo (called a "gravity assist"); this reduces the velocity 
change (known as "delta V") required at the Jupiter Orbit Insertion 
(JOI) burn by about 175 meters per second (378 mph), which results 
in a large propellant savings.  Since the spacecraft has a limited 
amount of propellant, it's always good news to hear that we can save 
some more.

As the spacecraft gets closer to Io, the Nav team's aiming accuracy 
increases. With the final TCM (five days before the Io flyby), we are 
able to control the altitude of the Io flyby to within plus or minus 
115 kilometers of the desired value of 1000 kilometers. If Galileo 
passes closer to Io than 1000 kilometers, the spacecraft's speed is 
reduced more than was planned; in that case, we can reduce the JOI 
velocity change and save propellant. On the other hand, if Galileo 
passes further from Io than 1000 kilometers, its speed is reduced 
less than planned, and the size of the JOI delta V needs to be 
increased (using more propellant). 

So, the "JOI tweak" is simply a late adjustment of the JOI burn,
based on our improved knowledge of the altitude of the Io flyby. The
final TCM, which takes place 5 days before the Io flyby (or, in Nav
shorthand, Io - 5 days), is based on radio tracking data up to Io - 6
days. Three days later, with three additional days of tracking, the 
uncertainty in the altitude of the Io flyby drops to plus or minus 75
kilometers. Based on this improved estimate of the Io flyby altitude,
the Navigation Team computes a new JOI delta V.  Then, commands
are prepared and sent to Galileo to change (or "tweak") the JOI delta V
value in the computer on board the spacecraft.

On November 1, the Relay/JOI Readiness Review was held. Managers 
and analysts on the flight team presented to a review board the 
operations plans and spacecraft sequences for receiving and storing 
on the Orbiter the data sent from the atmospheric Probe and for 
performing the JOI burn. I was one of many people who gave a 
presentation. My presentation, which took most of about a week to 
prepare, discussed the navigation results for the Orbiter Deflection 
Maneuver (ODM) and TCM-26.

ODM, which was performed two weeks after the atmospheric Probe 
was released, was the first maneuver to target Galileo for its flyby 
of the moon Io and the first TCM to use the big 400 Newton engine 
(although it uses different letters, the Orbit Deflection Maneuver is 
a Trajectory Change Maneuver, too). Trajectory Change Maneuvers are 
never perfect, because 1) the navigators do not have perfect 
knowledge of where Galileo is and where it is headed at the time of 
the TCM and 2) the actual change in velocity performed by the rocket 
thrusters on Galileo never turns out to be exactly what was 
commanded. So we keep performing TCMs until the errors are so 
small that they no longer matter. TCM-26 was performed about one 
month after the ODM as part of this trajectory error correction 
process. The improvements are fairly significant: after ODM, the Io 
flyby altitude was about 1800 kilometers away from the desired 
value of 1000 kilometers. After TCM-26, the miss will be no more 
than a few hundred kilometers (and perhaps a lot less).

The next Trajectory Change Maneuver (TCM-27) is scheduled for 
November 17 (20 days before the Io flyby, or Io-20). The design of 
TCM-27 starts next week on November 8 (nine days before the 
maneuver is performed). My next journal entry will contain the 
results of the design of TCM-27. Stay tuned!

September 29, 1995
Today is a Friday and the week hasn't gone very well.  Our Team (the 
Radio Science Team) is planning to conduct two Operational 
Readiness Tests (ORTs; basically, a type of dress rehearsal) before 
our occultation experiment in December. Occultation experiments 
can be run when anything is between the Earth and the spacecraft: a 
planet, a satellite, the Sun, or the solar wind. The experiment (where 
we'll be looking at Jupiter's atmosphere) is on Dec 8. So we're 
planning the first ORT for either Oct 10 or 12. We would like the 
second one to be somewhere around Nov 8. It is the job of the Radio 
Science Support Team to put together the plan for these ORTs.

YIKES!  Well, it's less than two weeks before the first ORT and I have 
yet to finish the test plan.  Why? First of all, I have to write a 
"script" for the actual experiment that details every event pertinent 
to the experiment. This includes when files will be delivered, when 
certain software will be run (and by whom), what activities need to 
be performed at the ground station to get the equipment ready for 
the experiment, and so on.

Second, the normal work of getting future sequences ready 
continues. The spacecraft will orbit Jupiter 11 times during the 
lifetime of the prime mission. Each orbit has three parts to it.  The 
first--and most busy--part is called the "encounter" period (when 
the spacecraft is closest to  Jupiter and its satellites). Each orbital 
encounter period will come very close to one of Jupiter's largest 
moons (Ganymede, Callisto, and Europa), which is why we use the 
term "encounter." This week, the Project is working on 5 different 
sequences: the 7th, 8th, and 10th orbits (two encounters with the 
moon Ganymede, one with Callisto: G7A, G8, C10), and two sequences 
just before and after arriving at Jupiter. As the team chief for the 
Radio Science Support Team and as Science Coordinator for the Radio 
Science Team, it is part of my job to supervise the work that other 
members of the Support Team do on each of those sequences. Right 
now, I also have a stack of 13 other issues that I am working on or 
that I have assigned to people on the Support Team. So, you can see 
that there's a lot to do (and why I haven't been able to finish the ops 
script).

11/7/95
So, OK, I was whining quite a bit in my last entry...but hey, it 
relieves stress.

Well, A LOT has happened since my last entry.  We thought we had 
lost the tape recorder but then it turned out we hadn't.  At least 
Radio Science is unaffected by the use of the tape recorder -- our 
data is recorded at the ground station on the Earth, and not on the 
spacecraft.

Our first big experiment for the Tour is on the day after Jupiter 
Orbit Insertion (JOI, when the spacecraft actually gets into orbit 
around Jupiter). There is an occultation of the Earth by Jupiter on 
that day. As the spacecraft's radio signal disappears behind the 
planet, we record the signal at the ground station. Analyzing that 
data allows our investigators to come up with pressure and 
temperature profiles of the Jovian atmosphere while the spacecraft 
stays high above the atmosphere. Pretty cool, huh?

We had the second ORT on Thursday night/Friday morning last week.  
I came in at 11 pm and left the next day around 2 pm -- long day!!  
We have the third and final ORT on Thursday night/Friday morning 
this week. Again, I'm to come in at 11 pm but this time, I'll leave 
sometime Friday morning.

We seem to be having a problem with some of the equipment at the 
station. The tapes that contain the data seem to have a few data 
points that are duplicates. This is our highest priority right now - 
figuring out why this is happening. Some new equipment was 
installed in early July but not the equipment which produces these 
apparently faulty data. So, it's a mystery right now.

Another minor concern is the type of food to have available for the 
ORTs and for the days of JOI and our experiment. Radio Science here 
at JPL is known for its food ("It's the food, stupid"). So we're trying 
to figure out how many people to expect over the course of the two 
days and whether to have it catered or what.  We have our priorities 
you know....

That's all for now folks.