PART 1: Galileo fact of the day
PART 2: Prepare to provide feedback
PART 3: Computer-generated Galileo Jupiter approach images
PART 4: Anomaly on the spacecraft
PART 5: A hectic week at the AGU

Galileo passed about 100 km closer to Io than planned. This meant
that the gravity assist from Io slowed Galileo's speed more than was
planned, putting the spacecraft into a shorter orbit around Jupiter
than expected. Rather than use up over 10 kilograms of propellant to
"fix" this, Galileo's navigators realized that they could just let the
spacecraft continue on its way...where it would arrive at its first
encounter with the moon Ganymede a week early! Amazingly, going
slower means we're getting where we're going sooner! (The
Ganymede flyby was originally scheduled to occur on July 4, 1996.
Since it takes a little over one week for Ganymede to go around its
orbit, it would be in about the same location one week earlier on
June 27. Since Galileo's orbit was one week shorter than originally
planned, the first satellite encounter could simply be moved earlier
by one week) 

As the Online from Jupiter project begins to wind down, Jo and I
begin to think more about evaluating what happened here. Please
expect a structured evaluation form, hopefully next week. We hope
that you will feel an obligation to take a few minutes and provide us
with feedback.

Most of all, we would like to hear from folks who have ideas on how
we can improve in the future. Your thoughts in this area will lead to
better, more responsive efforts from NASA. So please put on your
thinking caps and visualize an even better project.  Then get ready to
share with us soon. Thanks.

New images are now available on the Galileo Web at http://www.jpl.nasa.gov/galileo/

These images were created by the Digital Image Animation Lab at 
JPL. The images cover a 10 hour period on December 7, 1995 during 
Galileo's Jupiter orbit insertion, and include the key events such as 
Io flyby, probe relay transmission and the 49 minute engine burn. 
These are presented as a sequence of 121 images spaced 5 minutes 
apart. There are two versions of each image available: a small 
version about 10K in size, and a larger version that ranges from 18K 
to 32K in size. All of the images are in the JPEG format.
Thanks to Ron Baalke (baalke@kelvin.jpl.nasa.gov) for this info.

December 12, 1995
So, what am I thinking about? Well, I'm thinking that it sure will be 
an easy day. Our January orbit trim maneuver has been cancelled. I 
guess I can start thinking about our March maneuver that will change 
our orbit dramatically. Right now, our orbit takes us within 215,000 
kilometers of Jupiter's cloudtops. We want to raise that minimum 
distance (the "perijove") to about 715,000 kilometers. Otherwise, 
we'll absorb a lot of radiation in each orbit, and after a couple of 
orbits our spacecraft will probably be incapacitated. As a matter of 
fact, our present orbit is no good for another reason. When we are 
far from Jupiter in the orbit, the gravitational pull of Jupiter is 
less, and the pull from the Sun becomes more noticeable. The result 
is that we would be only about 35,000 kilometers from the Jupiter 
cloud tops at perijove if we would stay in our present path. On the 
following orbit, we'd crash into Jupiter. So we'll do a "Perijove 
Raise" maneuver (or PJR for short) to fix all this.

December looks like it won't be such a busy month. Next week, I'll 
host a pot-luck party for the group I'm in. Then, maybe I'll have some 
time to spend with my family! We can try training our almost year 
old dog (a Basenji named Pepper). We'll go to a couple of UCLA 
basketball games, an LA Philharmonic concert, and maybe the Santa 
Anita race track...

But now I'm at work, and I abruptly awake from my daydreaming 
when I realize that there is an anomaly -- a problem -- on the 
spacecraft. It is nearly 8 AM. At 9:30 there will be a meeting to 
discuss it. We may need to send a command.

What does this mean? Is there a real problem? The Sun is just about 
in between us and the spacecraft, and with the solar radio 
interference, the telemetry from the craft may not be too good. 
Normally, we could "read out" parts of Galileo's computer memory to 
check this, but we can't do this while we are getting back our Probe 
data.

If there is a minor problem, we might not want to do anything. The 
Orbiter is close enough to being behind the Sun that sending a 
command might be risky. We'd rather not send a command until 
December 29. That's 17 days away!

Luckily, it seems to be a minor problem...our power margin (which 
tells us how much power is left between what the spacecraft is 
currently using, and the maximum it has to draw on) is a little lower 
than expected. That could be a symptom of something serious, but in 
this case, we think we know what the problem is. Our Relay Radio 
hardware, the equipment that the Orbiter used to communicated with 
the probe, is in the wrong "mode."

What are we doing using the Relay Radio anyway, you may ask? Didn't 
the Probe vaporize more than two days ago?

Yes, and the Relay Radio receivers were heroes of the Probe Relay. And
now, how the mighty have fallen! We're using a Relay Radio receiver as
a lowly heater! It chews up 23.1 watts in "wideband" mode. 15.5 watts 
in standby. 1.8 watts get used for the oscillator (which provides a 
frequency for the receiver to lock on to). It is just the right thing to 
supply enough heat to protect the computer hardware against 
extreme cold...

But isn't there some problem with using equipment for other than its 
intended duty? I remember when I first considered using this Relay 
Radio Hardware (RRH for short) as a heater. I saw two problems. 
First, one has to turn on the oscillator and let it warm up for twenty 
minutes, otherwise you can't be sure how much power it will use. 
You might be off by a couple of watts (maybe as much as 5 watts). 
And you need to know *exactly* how much power is being used, 
because the spacecraft only produces about 500 watts of power 
total. We can't use more than that.

Second, if you only need 15.5 watts, you would like to go straight to 
Standby Mode when you turn on the RRH. That saves power, and 
protects against overheating the computer hardware. But you can't 
do that. It will come on only in Wideband mode, at 23.1 watts. You'd 
better be sure that you can survive being in Wideband mode for a 
while.

And now, I'm being told that Wideband mode is where we are. The 
power margin has gone down by an amount that corresponds to 
switching from Standby to Wideband mode. The temperatures in the 
propellant tanks are dropping appropriately (any extra power is 
basically shunted to the tanks, and the amount of extra power has 
gone down, so the tanks are cooling off). The Probe Engineering Team 
(you guessed it, PET for short) confirms that the RRH has switched 
modes (this report seems unnecessarily dramatic..."no, we are no 
longer in Standby, yes, we are in Wideband..." But this is fair, since 
they are reporting on two different pieces of data). Well, that isn't 
so bad. Just a few weeks ago, I helped determine our power margin 
strategy for this time period. I know that using an extra 7.6 watts is 
not ideal, but it is acceptable. We won't have to do anything about it. 
But I'm asking myself a few questions. What happened? WHY did the 
RRH change modes unexpectedly? Why wasn't our Team a little more 
suspicious of using the RRH as a heater?

In seconds I'm guessing about some of the answers. The answer to 
the final question is easiest. All of us subconsciously expected the 
RRH to work the right way. We expect equipment to stay in the state 
we put it in. After all, we wouldn't be able to fly spacecraft if 
equipment did anomalous things like this all the time.

It isn't that we wouldn't be prepared for an anomaly. Nor would we 
be shocked if a piece of equipment failed and turned itself off. But 
I'm not used to wondering about whether or not a 7.6 watt load will 
unexpectedly go ON, especially in the absence of a short circuit!

But now that it has happened, I'm not surprised at all. After all, the 
RRH was not supposed to be used as a heater. It was supposed to 
receive the Probe data! And that meant there was one awful thing it 
was never, ever supposed to do. It was *never* supposed to be in 
Standby during Probe Relay. That could have destroyed the entire 
Probe mission. No, the RRH was supposed to be in Wideband during 
the probe mission.

Hmm. Since it could be a disaster for the RRH to be in Standby, 
engineers designed the RRH so that any power glitch (and maybe any 
software glitch as well) would automatically put the RRH in 
Wideband mode. Wideband is where it wanted to be, and Wideband is 
where it would stay.

That meant that using the RRH in Wideband as a heater was probably 
reasonable. But putting it in Standby and expecting it to remain 
there might be asking for trouble.

In addition, we didn't have much real spacecraft experience with 
using the RRH in Standby mode before now. There was no reason to 
use the RRH before Probe Relay except for four or five sessions of 
checking it out. Any more and we would have been afraid of breaking 
it. So we had it on in 1989, eight days after we launched, in 1990, 
twice in 1992, and a couple more times this year. My guess was that 
the RRH had been in Standby only a couple of times since launch, and 
not for very long either time.

There is plenty of time before our meeting about the anomaly, so I go 
down from my eighth floor office to the fifth floor Mission Support 
Area to see how the spacecraft is doing. As I said, the data are going 
to be poor, because the Sun is "in the way." (Did you know that "data" 
is plural? When I was in high school, I did. But I always said "the 
data IS bad" when I really meant "the data ARE bad").

Sure enough, the first things I see on the Systems screen are a bunch 
of alarms. (In red, of course. That makes sense.) Now, are any of 
them real? The alarms say that we requested a standard response to 
a problem on the spacecraft -- "Safing." (As the name suggests, 
"Safing" puts the spacecraft in a "safe" state after it has developed 
some problem, which should keep anything else from going wrong.) 
But we can't just trust the alarms. Are we really in Safing? It would 
be no surprise to me if we *were* in Safing. It is easy to believe 
that the problem that caused our RRH to go to Wideband mode could 
trigger such a response.

Kauser Dar is the System Fault Protection engineer, and I'm her 
backup. At the 9:30 anomaly meeting, she'll be asked if the 
spacecraft is really in Safing. That means both of us ought to have 
the answer. We are looking at the screens and checking what they 
mean in our System Fault Protection Design books. The data say yes, 
we have requested Safing. But it doesn't make sense. Safing would 
cancel our request for Probe data. And we're still getting back Probe 
data!

Kauser quickly reminds me that if we were in Safing, the Power 
margin should go up by a couple of watts, not down by about 8 watts. 
At first, I'm not convinced. There are a number of details I'm not 
sure of (such as the RRH state in Safing, and some other indicators 
of executing Safing that might be available). We ask the engineers 
who work on the spacecraft's main computers what they think is 
happening. Just then, almost as if the spacecraft is replying, a new 
Probe data readout begins. That simply can not happen if we are in 
Safing, so the discussion is ended.

At 9:30, there is an Anomaly Team meeting. Bob Barry, who did such 
a fine job in leading the design of the Jupiter Orbit Insertion 
sequence, is leading it. The evidence is presented for the RRH being 
in Wideband mode. It is pretty convincing. Now, what should we do 
about it?

Normally, we would quickly decide to do...nothing. But there is a 
problem. A few months ago, we realized that a valve to one of our 
tanks (one that holds oxidizer, which is needed to burn the 
spacecraft fuel) might be leaking oxidizer (not into space, but into a 
line which leads to the fuel tank). If we are not careful about what 
temperature we keep our tanks at, we might get more oxidizer 
leaking into the fuel tank (not enough to be a hazard, we think). Is it 
safe to let the tanks cool down? This is a question for the engine 
people. They agree that it is safe to cool down.

Now we've got a few minutes before the Project management asks us 
for our recommendation. There are four choices:

1) Do nothing (send no immediate commands to our spacecraft). We'll 
cool off the propellant a little more, but this might be completely 
safe and at worst provides a very small future additional risk.

2) Put the RRH back to Standby mode. This warms the propellant up 
right away. However, the propellant is already more than halfway to 
the final temperature it will reach if we simply leave things alone. 
If there is a risk, it will be in warming back up. Also, it is getting 
dangerous to send a command since the spacecraft is almost directly 
"behind" the Sun in the sky, and the Sun is interfering with radio 
communications.

Besides, if we put the RRH back to Standby, aren't we just asking for 
it to return to Wideband after the next glitch? We don't want to have 
this same problem pop back up!

3) Switch to other, smaller heaters, so that we stop cooling down, 
but so that we don't warm up either. This sounds tricky, doesn't it? 
But engineers like us ought to be able to figure out how to do it 
fairly quickly. The problem is that we have already cooled down a 
lot, so we save very little if anything with this plan. We also do not 
have a lot of time to figure out which heaters to use. It would be 
easy to make a mistake. We might pick a heater that works now. But 
there's just been a problem on the spacecraft, and it's not safe to 
assume that everything is working perfectly. What if there's a nasty 
surprise, and we wind up in an unsafe state? What if we 
miscalculate, and choose heaters that mess up our Safing strategy?

4) Quit sending back Probe data, so that we can watch the spacecraft 
more. But this doesn't help us much, and the Probe data is very high 
priority.

The Project meeting is fairly short. To nobody's surprise, we decide 
to send no immediate commands to the craft. After December 29, 
when the spacecraft comes out from behind the Sun, it may be 
completely safe to send some commands to go back to our previous 
power margin. If not (or if we aren't sure), we'll wait until it is 
safer, namely at Perijove raise in March.

But the Orbiter Engineering Team still has more work to do. We still 
have to figure out why we think the RRH changed state. And there is 
a smoking gun. There was a problem with how power was being 
distributed around the spacecraft at about the same time as we 
changed RRH states (we can't be sure whether it was at the same 
time, because the rate at which data is being sent from the spacecraft 
is slow right now, and we get a report on the RRH state only once 
every two hours). Tomorrow, we'll look at the spacecraft's circuit 
diagrams to see if this could actually affect the RRH. It's a start in 
figuring out what went wrong.

December 19, 1995
This past week was the winter meeting of the American Geophyiscal 
Union in San Francisco, and this AGU was one of my wildest ever. 
First off, I left my laptop computer in the limousine from the 
airport. (Did I mention before that I was the world's biggest 
moron?). I sweated for a few hours until I got it back! Thank God 
there are still a few honest people left!

I tried to stay in the hotel for the most part, so I used room service 
for several of my meals. That meant I spent $25 for a 13" pizza and a 
coke. I spent $18 for a cocktail glass full of muslix and a cup of 
coffee. (It's the first time I've ever had gourmet muslix). I spent $20 
for 2 pancakes, 2 slices of bacon and 2 eggs. Hmmm, that time I also 
had fresh squeezed grapefruit juice, so that must be where the 
money went.

I meant to work on my paper, but things kept coming up. First, my 
collaborator and I still had work to do on the poster we were 
presenting at the meeting. A poster is another way of showing 
people your research results: instead of giving a talk, you write up a 
summary and put it up as a poster for people to read. He was from 
Brigham Young University and I was from JPL, so we had not had a 
chance to see how our mutual contributions to the poster looked 
together. We laid everything out on a big table and noticed that there 
had to be a few changes. Since I was the one with the computer, I 
had to go back to my hotel and type all the changes we came up with, 
about a dozen pages in all. How do you print out something from your 
computer when you don't have a printer? Easy. I FAXed all the pages 
from my computer, to the phone in my room, to myself at the hotel.

Then I went downstairs to find the FAX machine I just FAXed to. I 
wandered around for some time, trying to find my FAXes, until 
finally the concierge said, peering at me over the top of her glasses, 
"Oh no, we bring those to your room when they are done."

So I went back to my room and twiddled my thumbs for awhile and 
sure enough eventually 12 envelopes were pushed under my door. My 
heart sank as I looked at those envelopes because I was not only 
thinking that some tree somewhere had given its all for 11 wasted 
envelopes, but also how tacky my poster was going to look because 
they had FOLDED my pages! Later my collaborator asked if the hotel 
had a paper iron to get the creases out. (no -- they had gourmet 
muslix but no paper iron!)

This poster contained some predictions for the magnetic 
environment of Jupiter that Galileo might encounter, and a lot of 
scientists came up and wanted to know all about Galileo. That was 
kind of cool. It was exciting to know other scientists in the 
community were paying attention and were interested in Galileo. 
Some scientists even collected "souvenirs" of Galileo from my 
poster!

When I took the poster down, I noticed two of my friends were 
confiscating some of the material, including a plot I had made of 
Galileo's orbits around Jupiter. I said, "Hey, that's mine," and one guy 
said, "not any more, I'm taking this home with me!"

(As an aside, another cool thing that happened this week was that I 
was finally asked to make an animated movie that would show how 
Jupiter's magnetosphere works! I have been trying to generate some 
momentum to get one made, because I believe it is important for 
scientists to show people what the cool stuff is that their tax 
dollars are paying for. But there was resistance, and part of the 
drawback is that we are not really staffed to do this. A lot of the 
work is going to have to come out of people's private time. Namely, 
my private time. For me, though, it was kind of cool to be recognized 
and asked to do it. To get it right will be a big job.)

The other thing that came up was that I have another project to work 
on that is an Internet public use/learning tool with which to present 
NASA science, called Windows to the Universe, or Windows, for 
short. We'll be showing this in a limited way to the public on Feb 1, 
1996, which means we don't have a lot of time left to get things 
ready. The person in charge of Windows -- who is also my good 
friend Roberta -- wanted me to prepare a section to be critiqued on 
Saturday by some teachers to see if we were writing the material 
well enough for kids to actually use. That meant I needed to work 
hard the entire week on *that* project as well.

Two other scientists who are on the staff of Windows, Jon and 
Janet, were also at the AGU meeting. Evidently Roberta found out and 
made (Janet) leave the meeting and go home so she could work on her 
Windows material! We were all laughing about what a slave driver 
Roberta had become, and I was trying to explain all this to a friend 
of mine at dinner when a professor who knows about the Windows 
project came over and said "I see you are not working on your 
Windows project... I think I 'm going to call Roberta and tell her that 
I saw you relaxing at dinner!" I got down on my knees in the 
restaurant and said "Please don't tell her I wasn't working, Please 
don't tell her I wasn't working!!"

The very last detail of the week is the Galileo Project Science Group 
meeting, which will take place Monday. The Project Science Group 
meeting was specifically set up for the end of the AGU meeting so 
that all of the Galileo scientists who were in the area for the AGU 
could hear about the probe results before they are released to the 
public. Among the important questions that the probe data should 
help answer: how close is Jupiter to the original material out of 
which all the planets formed? Did we really sample a remnant of the 
primordial solar nebula?

It is really a privilege, and very much a learning occasion to be able 
to attend these sessions. I have been present before, when the 
scientists, who are among a select group of the top scientists in the 
world, were discussing what was the really important science for 
Galileo to perform during one of its Earth/Moon flybys. I'll never 
forget that meeting as long as I live. I felt *very* lucky to be in the 
room. The presentation of these probe results will be a historic 
occasion and I *very* much want to attend, but I need to concentrate 
on finishing my paper, which was my original goal.

So I've decided to skip the Project Science Group meeting. I feel 
really bad about missing this historic occasion, not to mention that I 
would like to write about the results for the Windows project. 
Nevertheless, I really need to concentrate so I'm going to hide away 
in a special place and just work. I will get a full report on all the 
results later, and there will be many other historic occasions yet to 
come on the Galileo project.