PART 1: Galileo fact of the day
PART 2: Information about pictures
PART 3: Many things to do after JOI burn
PART 4: An engineer meets the press

Galileo's cameras will capture pictures that can detect objects as
small as 12 meters (39 feet). That's an improvement on Galileo
Galilei's original telescopic observations by factors up to
100,000 to 1,000,000.

Steve Collins and Greg LaBorde recently shared this in response
to a continuing question barrage of the type
"when are we going to get pictures":

There are no new photos to get. The last image was taken on Oct 11, 
the day the tape recorder suffered its anomaly. Images are very 
tape-recorder-intensive, since they cannot be downlinked directly. 
To preserve the tape recorder, it was moved only a few times to 
"exercise" it, remaining essentially where it was after the anomaly 
to capture the all-important arrival day science data (now much 
scaled down from the originally planned imaging and high-rate 
spectroscopy data that would have burned up a lot of tape), 
especially the Probe Relay data. 

Now that the science/Probe data record is finished, the tape 
recorder will just sit until we have implemented certain software 
protections to allow us to move it in the reverse direction safely 
(that is the problem direction associated with the sticky tape head). 
In the meantime we have solar conjunction, and the readout of the 
Probe data stored in the memory of the central computer. This is 
important, because tape playback uses the memory where the Probe 
"symbols" are stored (tape playback involves dumping the tape into 
memory and then reading that memory out over many hours) so we 
have to be done with the readouts to everyone's satisfaction before 
we start dumping the tape. Symbol readouts are expected to be over 
by mid-January. 

The tape recorder protection algorithms should be aboard after that, 
and tape playback will commence around Jan 29. It should take about 
a month. Only after we are completely satisfied that there is no 
more left to get will the tape recorder then be free to go through 
"conditioning" to "work it in" to increase its reliability for Orbital 
operations. That brings us to March, and the Perijove Raise maneuver 
to raise the low point of Galileo's orbit out of the heavy radiation 
belts it traversed on arrival. It would probably not survive a second 
dip into the Io torus. 

Finally in April we could actually think about doing some science 
again, including possibly images. However, towards the middle of 
April we will be loading the new flight software which will control 
orbital operations, so there is not much of a window. Finally the 
flight software should be loaded by mid-May, in time for two Orbital 
Trim Maneuvers to fine-tune the Ganymede encounter and flyby. Then 
we can start data-collection in earnest, pictures and all. I would not 
expect, therefore, any pictures to be taken before mid-May, to be 
downlinked at the end of May and into the Summer.

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

For those who cannot wait for pictures, Ron Baalke writes:

Jupiter images taken by NASA's Infrared Telescope Facility (IRTF) as
the Galileo probe entered Jupiter's atmosphere are now available on
the Galileo home page: http://www.jpl.nasa.gov/galileo/
The caption file to the IRTF images is appended below.

MIRAC2 Images of Jupiter at the Time of Galileo Probe Entry

These images of the heat radiation from Jupiter were obtained at 
the NASA Infrared Telescope Facility (IRTF) during the period Dec. 7 
UT 22:06 to 23:18 covering the Galileo probe entry time of 22:57. 
The 4.8 micron image shows the cloud structure with holes in the 
clouds appearing bright because of increasing temperature with 
depth in the Jupiter atmosphere. The image at 10.74 microns is 
sensitive to ammonia gas abundance and those at 17.4 microns and 
20.6 microns to tropospheric temperature. The images all show 
Jupiter's bands. All but the 20.6 micron image show the longitudinal 
wave structure. On the 4.8 micron image the probe site is at the 
lower edge of the upper (North) equatorial band 2/3 of the way from 
the center to the right (West) limb.

These observations were part of a special daytime observing 
program carried out Dec 1-10 with the IRTF's NSFCAM at 5 microns 
and the guest instrument MIRAC2 at 4.8, 7.95, 8.57, 10.74, 13.3, 
17.0, 17.4, and 20.6 microns. The telescope primary mirror was 
covered with a sheet of white polypropylene to protect it from 
direct radiation from the sun, which was 8 degrees from Jupiter 
during this period. This resulted in a reduction of signal-to-noise of 
a factor of 20 at 4.8 microns and 4 at 20 microns.

The observing was done by Jim Friedson, Jay Goguen, Glenn Orton, 
Sarah Stewart, and Padma Yanamandra-Fisher (JPL), John Spencer 
(Lowell Observatory), Bill Hoffmann (Steward Observatory), and Bill 
Golisch (telescope operator, IRTF), with support from Joseph Hora at 
the Institute for Astronomy and Joe Spitale and Jose Ortiz at JPL.

MIRAC2 was built by the Steward Observatory, University of 
Arizona, and Smithsonian Astrophysical Observatory, with support 
from NASA, NSF, Steward Observatory, and Smithsonian 
Astrophysical Observatory. It is operated by Bill Hoffmann, Giovanni 
Fazio, Joseph Hora, and Lynne Deutsch (FCAD University of 
Massachusetts).

December 11, 1995
"What Project do you work on?"
I've heard this question around JPL a lot in the past 17 years.
The people who said "Voyager" received looks of respect.
Those who said "Galileo" got looks of pity.

Until December 7. We passed two big tests, and now we're JPL's 
flagship Project. I always knew we had a good team. Now everyone 
knows. The most dramatic moment was getting the first data 
showing a communications relay link to the Probe. Everyone was 
nervous and looked anxious. Then the data finally arrived. The 
spontaneous smiles were something to behold. The Jupiter Orbit 
Insertion (JOI) burn was different. There was little doubt in my mind 
that the burn would start. There was little doubt that it would end if 
it made it to the finish. But what would it do in the meantime? The 
first few minutes told the tale: this burn would be a success. It was 
very satisfying (it would have been so frustrating if JOI hadn't 
worked and the Orbiter had flown past Jupiter...).

There was a triumphant press conference at 6:45 PM, right after the 
successful JOI burn. After about an hour, the conference ended, with 
the participants explaining that they had to get back to work!

Work? How do you work effectively after your day starts with what 
looks like a successful Probe Relay and JOI?

Do you wonder what we did?

First we had to get some tracking data (specifically, two-way 
Doppler data) to find out what kind of orbit we were in. If our orbit 
was too long or too short, we might change it with our first Orbit 
Trim Maneuver (OTM-1). Several of us were asked to say "Go" or "No 
Go" on getting 2-way data. After a short discussion, everyone said 
"Go", and we prepared to get data that would pin down our orbit.

I was waiting to see what would go wrong on December 7. So far, 
everything had been perfect. But, sure enough, there was an 
error...just about the most minor error I could think of (but one I 
could have prevented). We were considering sending a command at 
the wrong time. Sending it at the right time would now be a 
nuisance.

Now, what was this command?

The command was to change the "limit on helium loss fault 
protection." This limit was a "trip point," meaning that when you 
reach that point, you essentially trip an alarm, and something 
happens to respond to the alarm (this is what is meant by fault 
protection). In this case, once the helium pressure dropped below the 
trip point, it meant that helium was leaking out of the helium tanks 
and into space, presumably through what's known as the "pilot valve 
vent." Something would have to be done to prevent more helium from 
leaking out, or there would not be enough left to push fuel and 
oxidizer into the engine for our next big maneuver and our entire 
Tour would be jeopardized.

I had designed a computer program--a piece of fault protection--
that responded to "tripping the alarm" by automatically sealing up 
the pilot valve vent. We needed this program on board because there 
might not be enough time to give the commands from the ground 
after we found out about a leak--all of the helium could leak out 
during that time. We couldn't simply seal off the vent as protection 
against a leak, because then we couldn't use the pilot valve at all. 
We wouldn't want to use the engine in a "no pilot valve" setup if we 
didn't have to, and we would now lose everything if our latch valves 
ever leaked. So we were stuck with having the spacecraft fix itself 
automatically in the event of a helium leak.

Now that we had this fault protection on board, we had to be careful 
to make sure that the trip point was set correctly. A lot of helium 
was used at JOI, and the helium pressure in the tanks was now 
lower, so the trip point that would warn us about low helium 
pressure had to be reduced at the end of the burn. It was. But (this is 
a tricky point) after the end of the burn the limit would have to be 
increased a little. This was because the helium would warm up after 
the burn, increasing the helium tank pressure. The limit had to be 
raised or there would not be enough protection to save the Tour if 
the trip point were reached.

We were planning to raise the limit. I didn't care about whether we 
changed the limit on December 7 or December 8, as long as we did it 
*sometime* in the next few days. After December 10, the craft 
would be behind the sun (or close to it) for about three weeks. We 
wouldn't be able to communicate with the craft during most of those 
three weeks, so I wanted to be sure that we were protected against 
a slow helium leak during that time.

There was one catch. If we sent up the command too soon....

(...you might be thinking that if we sent up the command too soon, we 
would then have a high trip point when we were supposed to still 
have a low one...but that wasn't the problem....)

...the spacecraft would still be in "critical mode" and for very 
complex reasons, we did not want to make this particular change 
during critical mode. It wasn't especially dangerous, but it was just 
a tiny bit riskier than sending the command at the right time. Just 
enough so I would have to say "No Go" to the sending of the command 
at the wrong time. Just enough so that I was surprised that we were 
considering making this mistake. We could have changed the 
command to make it safer to send at this earlier time, but it was 
too late to do that safely any more. I felt annoyed. I should have 
noticed this change before. We had indeed made a very small 
mistake. *I* had made a mistake. Luckily, it was not very important. 
We had two reasonable choices. We could send the command early or 
postpone it.

Well, we decided to postpone the helium loss trip point update to the 
following day. That was quite reasonable. Normally, a decision on 
such a matter would be made pretty quickly. But everyone was tired 
after such an eventful day, so it took us all much longer than usual.

Next was a big issue, the "spin-down." The spacecraft's spin rate, 
usually around one revolution every 20 seconds, had been "spun up" to 
about one revolution every 6 seconds for the JOI burn. Originally, we 
had planned to spin down automatically, right after the JOI burn. But 
then we realized that the spin-down might be unsafe or even 
undesirable in some fault scenarios. So we decided to spin down only 
if all systems were "Go."

It was about 9:30 PM, and already the word "go" no longer had a 
unique meaning. Most of us simply wanted to "go" home and get some 
rest!

We decided it was safe to spin down.

For some of us, there was still no rest. As I said, it wasn't all that 
late, but it had been a very long day. Now we had to decide whether 
or not to perform the first Orbit Trim Maneuver (or OTM for short).

Maybe by midnight, we would have proof that we no longer needed to 
do it. Shortly before midnight, we looked at the evidence. Our orbit 
about Jupiter was almost exactly a week shorter than intended, just 
perfect for a June 27 encounter with Ganymede. That would mean no 
trim maneuver Saturday!

But what if we were wrong?

We decided to wait until morning for the final decision. The 
Navigation Team would stay up all night to get more data. The 
survivors would show up at 9 AM to report on it. The rest of us 
would be awake enough to make an intelligent decision. Best of all, 
if we had to implement some maneuver, our team would have had 
enough sleep to do it right.

As I drove home, I felt happy not only about the Probe and JOI, but 
about OTM-1. Of course, OTM-1 would be cancelled. We already knew 
early on Thursday that after a perfect JOI, OTM-1 would not be 
needed. And JOI had been just about perfect! The one-way Doppler 
data confirmed it. The more accurate 2-way Doppler data did too. Not 
only would Saturday's maneuver be cancelled, but the next one, 
scheduled for January 2, would be unnecessary as well.

Sure enough, there were no navigational surprises the following 
morning. The NAV team, speaking with inspiring clarity after their 
long night, explained why they recommended no OTM-1.

Yesterday was a big day for Galileans.

We are on our way to Ganymede.

7 December 1995 (Part 1)
A billion kilometers from Earth, the Galileo Orbiter and Probe began 
executing their programmed instructions to collect important 
scientific information from Jupiter. On a quiet street in Pasadena, 
California, I stumbled about my home, alternately dressing and 
looking for a mislaid lapel pin. Galileo was preparing to encounter 
intense radiation and heat. I would meet the Press.

For the previous six years, most of Galileo's big events, including 
flybys of two asteroids and the Earth, put me in Galileo's Mission 
Support Area (MSA). That's where we "watch" the spacecraft. From 
the computer displays, cryptic numbers and symbols tell minute 
details of how the spacecraft is working. Sometimes, hidden in all 
that information, we can hear the spacecraft calling, "Pasadena, we 
have a problem." Everyone on this assignment spends long uneventful 
hours hoping there would be no such message on their watch.

Today was different. Other engineers were staffing the MSA, each 
one having spent months and years preparing for the big day. This 
was my opportunity to help out in a different capacity. I volunteered 
for "Guest Ops" -- escorting and speaking to the many visitors on Lab 
that day and, possibly, giving interviews to journalists visiting and 
phoning JPL.

Driving to work I listened to the radio give news reports from JPL. 
At the Lab's entrance, I saw a row of large TV broadcast vans, just 
like there were when Magellan and the Voyagers were the center of 
attention. The parking lot was full and, for the first time in 12 
years, I used an illegal space, hoping the security guards would be 
lenient.

Descending the area known as "Cardiac Hill", I made my way to Von 
Karman Auditorium where most of the day's visitors would be. 
Trudging the opposite way was Dan Carlock, a member of the Probe 
team. He greeted me with news that the Probe should have turned on 
and started preparations for Jovian entry. Of course, he couldn't say 
for sure since the Probe, preserving its precious batteries, wouldn't 
turn on its transmitter until reaching the atmosphere. All night long, 
Dan watched a computer display to observe the radio receivers on 
the Orbiter turn on and stabilize. Nothing much else was expected to 
happen that night and Dan made sure nothing much did. Bleary-eyed, 
he excused himself to crawl into a camper for a short nap.

Nearing Von Karman Auditorium, two men in suits passed me by. One 
of them was Dan Goldin, NASA's Administrator. He seemed cheerful 
and animated, chatting briefly with guards he seemed to know on a 
first name basis. At the auditorium, other men in suits promptly 
escorted him in. I showed my badge and walked in alone.

Inside, the rooms were filled with people and electronics. TV 
cameras were being hauled into formation in a line facing the stage 
while technicians checked the microphones for bad connections. 
Elsewhere, reporters alternated between their tape recorders and 
laptop computers. Walking through this maze, I had to be careful not 
stand in the way of cameramen televising reports "Live from JPL".

Past this hubbub, I greeted members of the Public Information 
Office, letting them know I was here and ready to be of any service. 
No, there wasn't anyone needing someone to interview at the 
moment. Perhaps later. I found a quiet area and waited.

My first request came an hour later. I would give a telephone 
interview sometime after noon for a radio station in Toledo, Ohio. 
That sounded like a good beginning. Work out any problems with 
nervousness speaking to a small geographic area, then things would 
be comfortable while talking to a larger audience. It didn't quite turn 
out that way. Before the Dayton interview, I was asked to give a live 
telephone interview for the BBC World Television ten minutes from 
now.

A director at the other end of the telephone line advised me on what 
to expect.

To be sure he could reach me when needed, I should stay on the line 
for about five minutes and he would tell me when my time was 
getting close. In the background, I could hear a news report about 
events in Indonesia. Then, the announcer began introducing a story 
with, "Scientists and NASA's Jet Propulsion Laboratory ...". ONE 
MINUTE. After a brief description of the Galileo mission, I was 
introduced and the interview began.

There followed several brief, innocuous questions. "What is the mood 
like?" ("Tense, but filled with anticipation", or something like that.) 
How soon could we expect to receive Probe data back? (I started to 
say next Monday, but began thinking it might really be Sunday. 
"Sunday or Monday, depending on your time zone", was my improvised 
reply.) Then came the tough one. "Aren't there concerns that the 
Probe may not survive its fiery entry?"

This is a difficult area to explain to someone who hasn't spent much 
of their life making something on the other side of the solar system 
perform complex gymnastics on command. From the beginning, 
everybody on the Galileo project has been dedicated to searching for 
the hidden flaw. Every assumption gets questioned. What can't be 
tested gets analyzed by experts. Yet, we know this is a risky 
business. Space exploration is inherently intolerant of human error. 
Of course something _could_ go wrong. It just isn't likely.

Taking the easy route, I said something to the effect that we were 
confident in the integrity of the Probe, thanks to extensive analyses 
and tests. Soon we would know for sure. The announcer thanked me 
and I was off the air.

Thus ended my first interview.