"LIVE FROM THE STRATOSPHERE"          P R O J E CT  U P D A T E # 24

PART 1: A new opportunity to follow NASA: "Online from Jupiter"
PART 2: Juan's mission log from a flight

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A new opportunity for you and your students to follow the exciting
NASA Galileo project is now available.  

Members of NASA's Galileo project are providing a
behind-the-scenes look at what it's like to be part of the
flight team on a pioneering interplanetary expedition through
the "Online from Jupiter" project.

Galileo scientists and mission engineers are opening
their notebooks to classrooms, museums and the public via the
Internet to share their observations and experiences working on
the NASA spacecraft mission to Jupiter.

>From now through January 1996, members of the
flight team will write brief field journal entries describing
the scientific puzzles, engineering challenges and excitement
of discovery as the Galileo orbiter and atmospheric entry probe
begin their scientific investigation of Jupiter. The
atmospheric probe is set to descend into Jupiter's atmosphere
on Dec. 7, the same day the Galileo orbiter begins circling the
giant planet for a two-year mission.

"For the first time, we're providing a window on the
inner workings and interactions of a scientific deep space
mission," said Dr. Jo Pitesky, member of the Galileo Mission
Planning Office.  "In sharing the journal entries, we hope to
give readers, particularly students, an idea of the tremendous
efforts that go into controlling and collecting data from a
robot spacecraft a half-billion miles away."

After reading background material and the journals,
kindergarten through 12th grade students and their teachers can
ask project members questions -- via E-mail -- starting in late
November and running through January 1996.  They will receive
personal responses, corresponding with experts on subjects
ranging from atmospheric science to spacecraft systems. An
archive of all questions and answers will be available online.
In addition, students will be able to take part in online
experiments that will use actual probe data. 

Some limited curriculum resources will be available to help
you integrate the Galileo project into your teaching. Unlike 
"Live From the Stratosphere", no live television will be offered.
As well, an integrated Teacher's Guide will not be available.

But the Galileo mission promises to capture significant media
attention in early December and "Online from Jupiter" may
provide a special way to intrigue students with the wonder of
science.

To participate, you must sign up for the Online from Jupiter maillist.
To do this, send an email message to .
In the message body, write these words: subscribe updates-jup




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[Editor's note:  a recent dry spell in fresh journals has led me to 
bring back this classic journal from last year]

                           Kuiper Airborne Observatory
                   Juan Rivera - Airborne Telescope Operator
                             Saturday, May 14, 1994

10:24 PM Local Time (0824 UT)

Passing through 14,000 feet headed for 38,000.  Actually we are headed
for what is known as Flight Level 380, or FL 380 for short.  Aircraft
that fly low and slow set their altimeters to the local barometric
pressure and then fly by what the altimeter says.  But when you're
really high, or moving very fast as big transport aircraft do, you
would be constantly changing the barometric pressure setting each time
you flew over another airport.  You would also constantly have to climb
or descend after each change.  So the big fast planes set their
altimeters to 29.92 inches of mercury and leave them there above a
certain altitude.  Then we say we are flying a particular flight
level.

0840 UT

Passing through 33,000 feet (We use feet in the back).  I have all my
equipment preset and ready to go, and the liquid nitrogen is turned
off.  The telescope optics are sitting at -13c at the moment, so we
achieved a good pre-cool this evening.

I'm expecting a bit of work getting the telescope operating properly
since this is the first flight of a new flight series with a new
detector.  This one is really large.  It's hard to describe it...  In
the center is their dewar which is a triple one.  It's like three
thermos bottles in side of each other. In the outside is liquid
nitrogen, then the next is cooled with liquid helium-4, then the inner
is cooled with liquid helium-3.  The inside is sitting at about .26
degrees above absolute zero.  That's right, point two six!  The dewar
is about the size of a small water heater.  Around the outside of the
dewar is the amplifier chassis and various cables and tubing.  It's an
impressive collection of stuff.

Note:  There is no natural source for helium-3.  It all comes from the
radioactive decay of tritium which is used in atomic bomb triggers.
1 liter costs about $30,000.

0934 UT

There are the usual start-up problems that can occur with a new
experiment.  The PI's are having various problems with their amps and I
don't know what else.  The computer operators are off on another
channel working on something, and I'm standing by to swap a circuit
board on the compensation chassis.  I'll try to explain what I'm up
to...  The telescope is "locked" on to a guide star which is selected
because it's close to the object we want to observe.  It's the tracker
operator's job to find that one star out of the bazillions of stars out
there.  Once that happens, then the tracker camera video is fed to the
tracker chassis which is a lot like the gun sights you probably saw on
tanks and helicopters during Desert Storm.  We place a little box over
the track star and tell the equipment to lock on to it.  From then on,
it generates an error signal that is proportional to how far away the
star is from the center of the box.  So far, so good? OK.  Now, that
error signal (actually two signals - azimuth, and elevation)) is fed
off to the compensation chassis which in turn takes those signals and
sends them off to a powerful amplifier which runs torquer motors that
move the telescope in a direction that will make those error signals
get smaller.  That's called a servo system.  They're very common in
electronics.

There is a problem.  The system is a compromise, like most things are.
If the servo system has too much amplification, called "gain", then the
system will oscillate and the telescope will jitter back and forth.  If
the gain is too low, then the pointing will be sloppy because there is
not enough control authority to correct for all the wiggles and bumps
imparted to the telescope by the airplane.  OK, so here is the
problem:  When the gain is turned up so the pointing is good, there is
a lot more current being sent to the torquer motors.  The PI's are very
sensitive to electrical interference and they see this torquer current
as electrical interference.  So here we are between a rock and a hard
place - Increase the gain of the compensation chassis to improve the
pointing and the noise goes up.  Get the noise down where they like it
and the pointing is unacceptable.  The PI's and the tracker operator
are having so many problems that I can't even work on this problem
yet.

NOTE: Remember I said that the inside of the dewar was at .26 degrees
above absolute zero?  Well, the reason is to keep thermal noise as low
as possible.  When electrons move around in anything above absolute
zero, they look like noise to electronic circuits.  When you hit
absolute zero, all molecular motion stops.  Presto!  No noise.
So when you're working with extremely small signals in this sort of
situation, it doesn't take a lot to interfere with the signal.

Anyway, the circuit board that was causing the noise problem was in the 
azimuth axis.  It was replaced by the day shift with one that has less 
gain.  They thought they had it all fixed because the noise went away.  
But unfortunately the telescope is a completely different animal in
flight.  We don't have any way to simulate in-flight conditions while
on the ground.  So what I just ended up doing was to replace the card
they installed with the one that was in there before they started.
Then I had the PI's watch their electrical noise and also
the pointing.  I simply tuned the system for a compromise between the
two.  Now they're satisfied with both.  The azimuth jitter was 17 arc
seconds peak-to-peak.  Now it's down to about 7.  That's nothing to
write home about, but as I said, in the real world many things are
compromises.  (When everything is running well the jitter is less than
2.5 arc seconds).

1040 UT (Sunday Morning now)

The only good thing about this shift is that I have a few hours off
during the day.  I managed to get sun burned today and now I'm paying
for it.  But at least I saw a really big sea turtle.  This one was at
least three and a half feet long from nose to tail.  We were snorkeling
near a research pier.  I noticed what looked like a small submarine in
a shed on the pier and I went to investigate.  I met a very nice fellow
who showed me all around.  There were two deep submersibles in there.
They were very interesting.  The big one could go down to 6000 meters.
Each increase in depth of 30 feet is one more atmosphere of pressure.
If you start at sea level with 14.7 pounds per square inch, what is the
pressure at 6000 meters?  You'll have to convert feet to meters...
Well, you figure it out.  Good practice!  The part where the people
stay is a sphere.  Do you know why?  How much pressure would there be
on a one square foot piece of the hull?

1101 UT

Now we're climbing to FL 410.  Let's see how long it takes...

Oh well, I got so busy I don't know how long it took but we're at FL
410 now.  The PI's have got me turning various pieces of equipment on
and off every few minutes because their equipment is noise sensitive.
This is going to be a very long night.  And exactly half way through my
one hour nap, someone called me on the phone.  Argh!!!

1209 UT

Jeez.  Still almost 4 hours to go.  It'll be light when we land.  I
hate that.  We'll probably get caught in traffic going back to the
hotel.

1247 UT

What a night!  We just experienced a loud hiss coming from somewhere
near the telescope.  Was it a door about to blow out and take a few
people with it?  Was it a stuck valve somewhere?  Was the compressor
system about to blow the back of the plane off?  I shut everything down
immediately while I tried to sort it out.  There are some things
back here that can kill you quick.  I checked everything I could then I
powered up the compressor system and went back aft to watch it come up
to pressure.  It is a potentially lethal piece of hardware.  There are
high pressure cylinders back there with 3000 Pounds of pressure in
them.  Once before I was hired, one blew and tore up a lot of stuff.  If
it hit the control lines that pass overhead, it would disable the
flight controls.  From 8 miles up we would take a long time to hit the
water.

I couldn't find anything wrong.  Another intermittent problem.  We
pulled up the last 30 minutes of data on the compressors and it all
looked normal.  I have no idea what that was.

1308 UT (3:08 AM local time)

I'm Beat.  I have a whole pile of books and magazines I brought along
but I'm too tired to look at them. It's funny, if anyone could see us
now they would think this is the neatest job on earth.  The lights are
down low and there are hundreds of instrument panel lights and TV
screens filled with data glowing away.  Most of the permanent flyers
are wearing NASA blue flight suits with patches all over them.  We all
have our headsets on with the noise-canceling microphones...  I'd
rather be in bed sleeping!

1450 UT

The pneumatic system just went nuts again.  I managed to get some good
notes to aid in trouble-shooting at least.  There isn't much I can
do up here.  If I were trying to work on this during the day, I'd pull
out all the schematics of the system and see if I could figure out
what that undocumented light does.  I'm going to take another look
at the compressor panel.  Everything look perfectly normal again.
At 5:00 AM it's hard to do much heavy thinking.

1520 UT (5:20 AM local time)

Well I have to wrap this up and get ready to start the descent.
I'll be very glad to get out of here!