PART 1: Galileo fact of the day
PART 2: Following the events of arrival day
PART 3: ProbeSquash activity: Installment #9
PART 4: The future -- it still looks fantastic
PART 5: Fun and exciting: the work life of a Galileo secretary
PART 6: Aiming the spacecraft 1000 km above Io

To keep up with the events of Jupiter arrival (tomorrow!),
tune into NASA TV or the Galileo home page.  

Also consider dropping by the WebChat area of the Teacher's Lounge:
http://quest.arc.nasa.gov/galileo/webchat/chat.html
Folks will be gathering there December 7 between 3-6:00 PM Pacific.

NASA TV SCHEDULE (all times PM PST, UTC - 8 Hours)
    1:00    Arrival Day Press Briefing (live)
    1:45    Beginning of live mission commentary from JPL
   ~3:05    Probe Mission Status
    3:30    Program Break
    5:00    Live programming resumes
    5:15    Jupiter Orbit Insertion (JOI) Status
    6:10    Closeout Interviews/Discussion
    6:45    Galileo Post Probe entry and JOI press briefing
   ~7:15    End of live programming from JPL

   If you have a satellite dish, you can find NASA TV on Spacenet 2,
   transponder 5, channel 9, 69 degrees West.  Transponder frequency is
   3880 MHz, audio subcarrier is 6.8 MHz, polarization is horizontal.

CUSEEME & MBONE
   Video and audio broadcasts of the Galileo coverage on NASA TV will also be
   available on the Internet via CuSeeMe and the MBone.  For more additional
   information on CuSeeMe and MBone, refer to the following home pages:

MBone:
http://www.best.com/~prince/techinfo/mbone.html

GALILEO HOME PAGE

The Galileo home page will also be updated frequently with the current status of Galileo's arrival at Jupiter. Look in the "Countdown to Jupiter" section: http://www.jpl.nasa.gov/galileo/

Thanks to Ron Baalke (baalke@kelvin.jpl.nasa.gov) for providing this info

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 #9: Back on the Orbiter: Is Anybody Listening? 

Since the Probe's data is so unique and important, you might think
that Galileo's scientists and engineers would arrange to keep the
Orbiter "listening" for the Probe's signal until the Probe had gasped
its last.  

Nope. The Orbiter will receive Probe data until 78 minutes after the
Probe enters the Jovian atmosphere, giving a **maximum** relay
duration of 75 minutes.  This corresponds to reaching a depth of
about 164 kilometers below the cloud tops, and a pressure of 30
bars.  After that 75 minutes is up, the Orbiter will stop listening to
the Probe, even if the Probe is still working.  

Although the Probe's mission will have ended, the Orbiter will be
getting ready to spend the next two years in orbit around Jupiter.
Just over an hour after the end of Probe relay, the Galileo Orbiter will
fire its main engine so that the spacecraft enters orbit, and doesn't
just go flying by the giant planet!  As you can imagine, this is a
tremendously important event, and there's a lot of concern with
making sure that the spacecraft is ready for this maneuver. It takes
time to get ready for the Jupiter Orbit Insertion burn, or JOI: the
relay antenna used to listen to the Probe must be stowed away, and
the Orbiter must start spinning faster (10 revolutions per minute,
instead of the usual 3.5) to make the spacecraft more stable. So, since
it's predicted that the Probe's signal strength will quite probably be
too weak to be picked up by the Orbiter by the 75 minute mark, it
makes sense for the Orbiter to end Probe relay, and start
preparations for JOI.

This is the next to last installment of ProbeSquash.  At this point, you
know about the different challenges facing the Probe, ranging from a
delayed launch to high temperatures in Jupiter's atmosphere.  We've
given you a look at how experts have tested the Probe, and the test
results.  Just like many people working on Galileo, you've made your
predictions about how long the Probe will last.

And now, we wait.  The final installment of Probe Squash will come
after December 7,  when we'll all find out if the Probe had a
successful flight.  As a bonus, we'll also learn about the ultimate fate
of the Galileo Probe, lost forever in the swirling winds of our solar
system's largest planet.

November 17, 1995
Last night, was an especially dramatic night.  On its way to Jupiter, an
interplanetary spacecraft suffered a major system malfunction.  All
seemed lost as the onboard computer ran amuck and starting
shutting down vital equipment. In the end, human intervention shut
down the malfunctioning computer and the mission was saved.

Happily, this was not a night at Galileo Mission Ops.  Last night, a
Hollywood movie theater played _2001: A Space Odyssey_ to a
packed house. A friend and I found two of the last remaining seats
and sat back to watch the adventure unfold.  The experience of
viewing 2001 on a large screen, aided by full stereophonic sound,
took me back to the first time I saw it, almost 27 years ago.  Pan Am
flights to a rotating space station,  regular shuttles to the Moon, a
ship sent to explore Jupiter -- the future looked fantastic!

The beauty of the film to me is that it doesn't look dated.  Its view of
the future was a reasonable extrapolation of what the 1990s _could_
have been. Our 1990s may not look quite like the film version, but
the vision is there to challenge us.

As I write this, an American Space Shuttle orbits the Earth, docked to
a Russian space station.  An interplanetary spacecraft, Galileo, is
almost in orbit around Jupiter after a six year voyage.  I am now
working on a project to send a spacecraft off to a comet using an ion
thruster, a step towards making space travel as fast and routine as in
the movie.

The future -- it still looks fantastic!

--------------------------------------------------------------------------------

Until recently, Bob Gounley was a Deputy Chief of the Galileo Orbiter
Engineering Team.  He now works on the NSTAR project doing system integration 
(a fancy way of saying that he makes sure all the parts will work together).
He now observes the Galileo project from a distance and expects their
discoveries will be "something wonderful".

November 28, 1995
As a secretary I always get asked, "What are you really going to do when you
grow up?" No one seriously looks at the secretarial profession as rewarding 
or interesting for someone with ambition. People always assume that it is 
stop gap job that you are doing until you get a "real" one. Or they assume 
the worst possible - that you are dumb and couldn't get a better job. I'm 
here to tell you that you can be creative and educated, and still be a 
secretary with career goals and responsibility. The pay could be better - 
don't get me wrong - but the career secretary is an individual that can 
enjoy and grow in his or her job.

I originally went to college to learn nursing. I was an A student and had
several scholarships. I started in nursing because I was more interested in
science then medical practice. I think that I was a good nurse, but it was 
very nerve racking, and after a year I found it boring. I had the same 
chores to do just different faces to look at. I also had no further career 
goals other than working the day shift instead of the night shift. Talk about 
a short career! I still hadn't finished my B.S. degree in Nursing when I had 
to relocate to Los Angeles. At that time I had a choice. My college credits 
would not be as transferable as they promised, and it would take an additional 
three years to finish my degree, or I could start another degree and 
finish in two years. I was bored in nursing, and a shorter time in school 
looked wonderful! Well I made a radical change, and picked a major that 
had science and skills that could later be parlayed into a teaching 
credential if needed. I finished my B.A. in Geography in June of 1993. 
Now the quest for the job!

I'll tell you truthfully, it was looking grim when I got out of college. It
looked like I would have to go to school again for that teaching credential -
but then a friend asked for some help (Here's where that stop-gap theory
starts!). She was working in a program office at the Jet Propulsion Laboratory
(JPL). The office was in need of someone to fill in until they had a regular
person. It was originally a contractor position that would last two weeks, and
I would answer all of the phones. That was all. Well, it didn't work out that
way. Even though I was originally hired as a two week receptionist, I stayed
for a year and was the program manager's secretary until he left. When I
started I could barely keep all of the lights on the phone straight on 
the first day. By the time that I left, I was skilled at typing, phones, 
travel, and different hardware and software for both the Mac and the PC. 
I could run the office of 20+ people by myself. When the office reorganized 
I was out of a job and had to leave. Or so I thought. Before my last two 
weeks were up I had another job on lab working with another group. There 
was not one single day that I was out of a job because of my great skills. 
And the best part was it was always interesting and exciting! Everyday was 
different. Different tasks, people, and skills were constantly in flux. 
As soon as I learned something new there was something else that was there 
to catch my attention. Don't get me wrong. I do not bore easily! I am 
very traditional, and like things kept in their place, but I also thrive 
on change. I am always learning new things and using them to be a more 
professional secretary.

So how did I get to the Galileo Science Team? Well it was that need to learn
new things. It was also closer to science which is my first love. I am always
amazed by what life has to show us. And that need to explore led me to the
Galileo Project in July 1994. I was extremely thrilled to be chosen for a
project that was exploring the solar system. Everyone on my team is great.
You can meet some of them through their journals, or you can send them
questions. We would love to hear from you.

November 30, 1995
Okay - I know.  You clicked on my journal by mistake. But you haven't realized
yet how deceptive the title of a job can be. "Secretary" originally was the
scribe and keeper of the records. And those records kept secrets. So the
secretary was the confidant of those in power, and they wrote and kept the
secrets. Wow. Bet you didn't know that!  Unfortunately the word has gone from
being powerful and knowledgeable to one that answers the phone and shuffles
papers. Wrong! I do not answer the phones in my job unless it is my own. I
may shuffle paper, but only when I am agitated and I have to do something with
my hands. The connotation that secretaries are menial and submissive is a
stereotype that is perpetrated to keep you in the dark. Professional
secretaries are smart, creative, and usually the helper behind the powerful
manager in our executive world. If you have a good secretary, he/she is worth
his/her weight in gold. The whole group dynamics of an organization can be
affected by the secretary that pulls them together.

So what does a technical/science secretary really do during the day? I work
with the science coordinators, and other staff members on the project. I
usually start my day at a run and keep going until it is time to go home!
Secretaries at JPL in general are non-exempt employees, so that means that
we are paid hourly. When we have worked our eight hours we go home.
Companies don't like to have you work extra minutes, even though your tasks
may not necessarily end on the dot when you shift ends. So that ultimately
means that you have unfinished business on your desk when you come in the
morning. So I usually start with that work, and then I check for new things
that need to be done urgently so that I can prioritize my work for the rest of
the day. While am doing this I am also checking my phone messages and my
electronic mail. I get in a mode called "multi-tasking". That means that I am
dividing my interest and doing several things at once. For a secretary this 
is a skill that is very important. Not everyone can do this, and some can 
only do two or three things at any one time. I have multi-tasking down to 
an art. I can't function at work unless I am doing several things at once!  
Which is a good thing because our team is very busy.

Right now the science coordinators are working on several of Galileo's future
science sequences, and part of my team is the Outreach group that is providing
this service to you. We are seven days away from arrival day, and the public
and press want to know what is going on!  On December 7th there are arrival
day activities that need to be coordinated, and things that need to be written,
copied, or put on-line. Volunteers from the flight team need to be organized,
displays need to be arranged and put up, office areas need to be cleaned up and
secured for our visiting guests. All of this is part of my job. I look forward
to telling you about it in my following journals, so pay attention!

December 1, 1995
Well, it is the Friday before arrival day. I have 20 people lined up as
volunteers to escort the visiting journalists, and also the interviews are
arranged. I thought that I would come in early today to get a jump start on my
day. Before I even turned on my computer, one of my team chiefs has a question
relating to timecards, and vacation time. As I look up the answer, I start
clearing my desk area. It is December 1st, and I decorate my station so that
everyone knows what season it is. We are so busy all of the time, that you 
never realize how fast those days zip by. We have started a countdown clock 
for Jupiter probe relay and Jupiter Orbit Insertion(JOI).  There are six days 
left (four if you count working days only) - until arrival day and there are 
tons of things to do!  I am presently working on a database project that will 
create a phone book of all of our project investigators (139 people). The 
phone book will have all of the information that we have gathered over the 
years in our contacts. Things like phone numbers, faxes, and email addresses. 
Everything has to be checked to see if it is current, and then it has to be 
put together in a report format that is pleasing to the eye before Thursday. 
The cover I designed myself, and it really catches your eye. Now I need to 
find time to run the program and proofread the product. After that is done, 
(probably Monday), I will have a master copy that I will reproduce for 
everyone that is coming.  Before I even got started however - another team 
chief has come with a request for additional displays for arrival day. Art 
work has to be organized and claimed. I also have to contact other project 
personnel to see if they have claimed that art before I did for some display 
that they might be doing. On Monday I will contact the public services office 
here at lab for the display panels that we call "stacks". They are called 
stacks because they all hook together one on top of the other in a flat board 
design that is then secured by wooden pedestal feet at the bottom. The end 
result is a black carpet-like board that the art work hangs on like a bulletin 
board.  Well I have to go to a meeting, and then rehearsal for the 
"Not Ready For Real-Time Players (I'll tell you about that later).  Then 
I will go home.  It will probably be 6:30 PM before I walk in my door at 
home, and I'm sure that my three cats will greet me hungrily.  It's going 
to be a loooooong day.

Our big day, Thursday December 7, is less than five days away.  Five
days was a special number for me. That's when we would do our last
course correction maneuver before reaching Jupiter, "Trajectory
Correction Maneuver 28A" (or TCM-28A for short).

We planned to do a correction maneuver 20 days out. But the one we
did back in August was so good that we didn't need to. At 10 days
out, we planned to do another correction. However, once again, we
were so close to being on target that there didn't seem much point to
it: we would probably wind up further from our target if we did the
maneuver! So we canceled that one as well.

Since we are not taking any close-up pictures of Io as we fly past,
the main issue is: what will our altitude be at Io? At 10 days out,
it looked as though we were right on target: 1000 kilometers above 
Io's surface.

If we do TCM-28A, the Navigation Team will design the maneuver on
Friday morning, December 1.  By 11 AM they will give the Orbiter
Engineering Team (that's us!) the change in velocity (or delta-v) that's
needed. We'll start working on how we need to fire the spacecraft's
thrusters in order to get that delta-v. At noon there will be a
maneuver design meeting where we'll get approval to continue
working on the maneuver. By this time, we'll be just about through with 
our implementation. By the end of the meeting, the Attitude and
Articulation Control Team and Retro Propulsion Module Team (the
people in charge of the thrusters) will have finished their work and
we'll be ready to generate a sequence of events. We'll all look at it to
see if it's right and by 4 PM the Sequence Team will have our
product. They will have until 9 PM to produce a final sequence for
everyone to review. At 1 AM Saturday (yes, that's right, 1 AM--in
the morning), we'll have a final approval meeting, and by 2:30 AM
the sequence may be on its way to our spacecraft. The maneuver will
start at about 3:30 PM on Saturday. We call this schedule our "24-
hour template" ... it is the equivalent of a football team's 2-minute
offense. By the way, when I add it up, it comes to a little less than 24
hours for us, just like a football team sometimes has a little less than
2 minutes. Unlike a football team, we have no opponent who is
actively trying to stop us. Our team is ready, and we're becoming
increasingly confident.

Of course, there is no point in doing an unnecessary maneuver. Why
should we tire ourselves by working all night when our biggest week is
coming right up? It is becoming clear as the Friday noon meeting
approaches that this will be the time for a decision to be made. Will
we do the maneuver or not?

The argument for doing the maneuver is straightforward. New data are
showing that we are coming into Io a little low. Instead of 1000 km,
we'll probably be somewhere between 900 km and 975 km. If we do a
maneuver to raise our aimpoint up by about 60 km, we will be closer to
our target. The time to do this maneuver is now!

However, there is a counter argument. Even if we do nothing until
January about the error, the total cost in propellant will be less
than 8 kilograms. We can afford that. If the big Jupiter Orbit
Insertion burn works perfectly, this will be a small insurance premium
for us. It isn't true that we have fuel to waste: it is just that we
budgeted for losing about this much propellant due to an imperfect big
burn. If we are wrong by a little bit about the 937 km altitude at
Jupiter, or if the accelerometers (which measure how the burn is
progressing) are just a little bit off and our big burn is off by, say,
half of one percent, our insurance will pay off. If the errors add up to
between a third and two-thirds of a percent, the propellant penalty
will be about 3 kilograms of propellant.

Doesn't this sound strange?  It is easy to see that if we aim low and
our aim is off and we wind up higher than we expected, aiming low was
a good idea.  But what is so good about aiming low and then winding up
lower than we aim? Why does that save us anything?

The answer is complicated but interesting.  We are trying to get into
the proper orbit for our tour. Our first destination is Ganymede.
Ganymede takes about a week to orbit around Jupiter. If we are exactly
on target, we'll get to Ganymede in July of 1996. But if we are too
low at Io, we'll slow down more than expected, go into a tighter and faster
orbit around Jupiter, and get to Ganymede's orbit early. If our Io altitude
and big burn are perfect we'll be about half a week early. That's no
good because Ganymede won't be there: it will be on the other side of
Jupiter. If we are higher than expected at Io, we'll be closer to
getting to Ganymede at the right time. But here is the trick: if we
are lower than expected at Io, we'll be closer to getting to
Ganymede's orbit a full week early, and if we do that, Ganymede will
be there for us!  All we will need to do is be sure to choose a
different latitude and higher altitude for our encounter with
Ganymede, to get us back on track for the rest of our scheduled Tour
of the Galilean moons.

Now it is clear that aiming a little low at Io is a form of insurance.
But which is less dangerous anyway, being too low at Io or being too
high? We conclude that being too low is less dangerous. That just
puts us in too tight an orbit, and we can make up for that by getting
to Ganymede two, three, four, or even more weeks early. However, if
we are too high at Io, we won't slow down enough, and it won't be easy
to recover from that. We may be able to get to Ganymede a week late.
After that, we'd need to spend extra fuel to get back to our Tour.
The problem is that if we used a strategy to get to Ganymede two weeks
late, we would have to reduce our altitude so much that we'd hit
Ganymede. Even at one week late, we might get too close if we
miscalculated a little.

Today is Sunday.  Since we were already aiming a little low at Io, we
did not do the maneuver yesterday. Many of the people on the Orbiter
Engineering Team have a feeling that we'll be be right on our aimpoint
at Io and get the delta-v right on our big burn as well.  We'll be
pretty happy if this happens, especially if Probe Relay works well.

In a few days, we'll find out.