PART 1: Galileo fact of the day
PART 2: Evaluation status
PART 3: The Final Push: On to Jupiter!
PART 4: Galileo Probe press release

On its journey from Earth to Jupiter, Galileo traveled 2.4 billion
miles. Along the way, about 67 gallons of fuel from the propulsion
sys0tem were used to control Galileo's flight path and to keep its
antenna pointed at Earth. That's equivalent to getting 36 million
miles per gallon! With that kind of mileage, one would use up only
4 tablespoons of gasoline to drive to the Moon and back! 

The readers of Online from Jupiter are really coming through on the
evaluation survey. We've received over 320 responses so far; most of
these are filled with good ideas on how we can improve . THANK YOU SO
MUCH! For those who haven't yet responded, please consider doing so.

Until today, there was a problem with our Web form. I made a silly
mistake that resulted in people getting "Domain Name Service"
errors. My apologies to anybody that filled out a form and then had it
rejected. Please try again; it will work this time. Thanks for
your patience on this front.

November 30, 1995
Less than one week from Arrival Day, and there is a massive effort 
to use as many telescopes around the world to obtain as many 
observations of Jupiter as possible, the better to see what the Probe 
is heading into. I've made preparations in the preceding days for 
people observing at the Swedish Solar Telescope at La Palma in the 
Calary Islands, and Mt. Wilson here in California. Others observers 
are or will be at Pic-du-Midi, a French telescope in the Pynenees 
which is obtaining some really great images; Yerkes Observatory 
near Chicago; a gifted amateur astronomer in south Florida; the 
McMath Solar Telescope at Kitt Peak - just outside Tucson; and my 
primary work at the NASA Infrared Telescope Facility. Part of our 
group will also try to observe from an old solar telescope at Mt. 
Wilson, the Snow Horizontal Solar Telescope.
 
All of the observing makes home life rather hectic. Two nights ago, 
my wife came in at 8:30, arriving from an observing run at Kitt Peak. 
I left for Mauna Kea, Hawaii, the following morning. On the plane 
from Los Angeles to Honolulu I made the best preparation that I 
could for my observations. But what occupied most of my time was 
writing out Christmas cards (early!). 

I arrived to fairly cloudy skies. The weather map shows a relatively 
clear area to the west of the Hawaiian Islands - let's just hope 
that's where the weather is coming from. I also find that I totally 
forgot to pack both of my long- sleeve shirts. Two quick email notes 
to my wife and to a close colleague who will join me up on the 
mountain in a few days, asking for at least one shirt. One thing that 
I'd REALLY also like is a tube of Chapstick. I'm really needing it up 
here. I also forgot jogging shorts, but I'll have to live without them. 
Up here, there are no convenience stores.

I *hate* first nights on the mountain at 14,000 feet elevation, with 
only 60% of sea-level oxygen: you get headaches and sinus aches 
where the air trapped inside is bursting to get out. Plus, part of our 
imaging system (MIRAC -- Middle Infrared Array Camera, sensitive 
to Jupiter's heat (thermal) output) warmed up; it's supposed to be 
kept VERY cold - just a few degrees above absolute zero. To get it 
cold again, we have to pump the air out of a space between the very 
cold detector and the outside. We'll end up losing 1-2 hours of 
observing time before the detector is cold enough to use again.


1995 December 1
We awake to find that most of the sky is starting to look a 
wonderful color of blue - mostly clearing clouds! But it's still very 
humid. The telescope operator won't open the telescope dome if it's 
over 95% relative humidity in order to avoid dew or frost forming on 
the telescope mirror - it can take the aluminization coating off of 
the mirror and leave you with a several-ton useless piece of glass. 
The humidity is hovering around 93% now.

Shooting images through local cumulus clouds, I tried to work with 
the sensitive near-infrared camera. When we got near Jupiter, we 
weren't able to see anything. We tried playing with the electronics 
that control the image coming from the camera, trying to reduce the 
ferocious background "noise" caused by the thin layer of 
polypropylene (what potato chip bag liners are made of) which has 
been placed over the primary mirror to protect it from damage by 
sunlight.

MIRAC finally cooled down and we put it in place on the telescope. 
Some patches of blue sky are showing up! The Probe Entry site will 
rise about 3 hours from now, and I'm still very nervous about just 
how successful this is going to be! Or is it just that it's really cold 
up here?

Not much luck. We took some observations of the inside of the 
telescope dome (for later use in telling us about the sensitivity of 
different parts of the camera's detector), but clouds got in the way 
of Jupiter. :( On the other hand, if the weather holds up tomorrow, 
we should be able to observe many hours on the Probe Entry site 
rising before the great cumulus monster climbs up the mountain 
again... I hope! It depends on the direction of the wind and that's 
quite variable.

Of course, we're not the only observers hard at work. Two (very 
serious) amateur astronomers working in south Florida, have started 
their own attempt to image Jupiter before the Probe entry, in what 
they call their "Jupiter Imaging Marathon".

To my family I write: Linda, Gregg and Sarah, 
Things are going OK here. They are far from perfect, but they are 
working out OK. I hope that the weather is getting better, so that we 
have less clouds (they were all above the telescope all yesterday 
afternoon). On the first day up here, it's always hard to start 
because your body is not used to the high altitudes and the low 
amount of air, but I'm feeling better.

I'm very nervous about succeeding in getting observations of Jupiter 
for helping to determine where the Galileo Probe went into the 
atmosphere. I've been waiting for this time for 17 years, since I 
first started working on Galileo.

I hope CC [our cat] got her stitches out without a problem. I'm sure 
you'll do well on Sunday (don't forget Sunday school in the morning). 
Pray for me here - I do miss you all. ...and I'm going to miss sleep 
soon if I don't go to bed.
xoxoxoxooxx
Dad


December 2
I'm still nervous about whether we're going to have data that's going 
to be good enough to help the mission at all. Things seem to be OK, 
but the wavelengths that we're observing at--5 microns (sensitive 
to detecting clouds and a very important diagnostic of what sort of 
cloud and temperature system the Probe actually goes into), 7 
microns (useful for picking up temperatures in Jupiter's 
stratosphere) and 8.57 microns (helps to establish the thickness of 
ammonia clouds high in Jupiter's atmosphere) are all very hard to 
pick up through the polypropylene covering the mirror.

Everyone is having a hard time observing. Humidity is rising, with 
the threat of having to close the dome. Only 15% of the light gets 
through to the camera because of the polypropylene, so we have to 
"add" a lot of images together in order to get anything worth looking 
at. We are getting consistent clobbering by clouds by 1 PM. And it 
looked SOOOO very dry in the morning!

I'd consider the data we got today OK only in a pinch. Mostly we were 
testing and creating automatic programs for the instrument.

Tomorrow, we'll start our day even earlier, so that we can get more 
observing done. It takes a little longer to set up than usual, because 
we can't fill the cooling containers (with liquid nitrogen and liquid 
helium) until we've put on the plypropylene screen (which is taking 
less time than I had feared). Even so, one hour of setup time goes by 
until we get any real observing begun.

My other fear is that we and our long days are pushing Bill, the 
telescope operator. We seem to have good "bi-modal" observing: 
we're getting good data in the early morning and the late afternoon! 
Can we tell him to take a long siesta in the mid-day?

Today's email home to the family:
The clouds unexpectedly cleared up and we got Jupiter at almost all 
wavelengths. Bill (William Golisch, the telescope operator who 
volunteered to run the telescope for the entire 10-day stretch) 
kindly agreed to work overtime.....
  YAY YAY YAY YAY YAY :) :) :) :) :) :) :) :) 
Hope your Inter-Country Adoption Network (ICAN) holiday party was 
GREAT!!!


Sunday, Dec. 3
When I'm observing, I keep in touch with my family and my 
colleagues via email. I'll often write the same things to them, but in 
different ways. For instance, today, writing to my family about the 
great weather and observing the Probe Entry site for 90 minutes:
We are having the best weather during daytime observing I have ever 
seen. We got some of the Probe Entry site about 1-1/2 hours before 
it set on Jupiter until past setting. It's taking about 2 hours for us 
to run through the entire sequence of wavelengths for the planet, 
plus another hour for [Jupiter's satellite] Io observing and getting 
calibration. Everything should be set up really well now for the next 
few days on automatic programs (well, sort of automatic programs), 
if the weather cooperates with us. Anyway, today is just splendid 
and I couldn't ask for more. I just hope that the weather doesn't go 
and clobber us any this afternoon.
Glenn/Dad XOXOXOXOOXOXOXOX 

To my colleagues at JPL, I wrote:
Wonderful data.
Totally photometric all day, but we may have run out of time to get 
adequate extinctions (tests to see how the atmosphere reduces the 
light level as you go from up in the sky to closer toward the 
horizon).

Got a series of observations with PES [Probe entry site] rotating off 
very early in the day, starting with 4.8 and 8.57 microns [two 
wavelengths sensitive to clouds]. By the time we got to 7 microns, it 
was off. We tested and found that we could get a little better signal 
at 7.95 microns than our old standard at 7.85 microns, moving out of 
a real extinction feature in the polypropylene. At 8.00 microns we 
were getting better signal still, but not nearly so distinct limb 
brightening. At this point, I'd say to coadd everything that got 
created there: even with "improved" signal we were unable to see 
where waves exist. 


Monday, December 4
Jim Friedson, a close colleague from JPL, arrived today. After taking 
a look at our observations, he recalled that we didn't have nearly the 
same difficulty in getting a decent signal level during last year's 
tests. Well, one of the nice things about having lots of computer disk 
space and never getting around to storing things on tape is that you 
can access those things from great distances over the Internet. I 
tapped into the data from our first tests of this technique a year ago 
to see if I could find out what had changed. Sure enough, the 
background level -- the amount of emission from the background -- 
was quite a bit lower last year, so it wasn't swamping the signal 
from Jupiter. That's why yesterday's Jupiter images at the shorter 
wavelengths (where "glowing" from the polypropylene contributes to 
the) look so awful.

Maybe there are some other reasons why the images aren't as good as 
last year's. The Sun's position, perhaps -- there's sunlight shining 
down onto the screen right over the hole in the telescope that leads 
to the instruments. That wasn't the case last year. Could that 
explain it? I lost sleep over the subject, trying to figure out what 
we were doing differently! 

We awaken to a perfectly cloudless sky! The Probe entry site will be 
right in the center of the planet by 11 AM, so I hope clouds don't 
climb up over the top of the mountain again today!

The good news continues. Bill Hoffmann, the person who built the 
camera, suggested that we re-align the instrument. This is usually a 
long and tedious exercise, but Bill recommended a shortcut. That 
improved the signal by a good 40%. Although all this kept John 
Spencer, the telescope operator here a good two hours over his usual 
time, he used a lots of tricks to find Jupiter and peak up on its 
sensitivity at last!

Also at Bill's recommendation, we check that there is no new 
adhesive tape on the part of the solar safety screen right in front of 
the hole leading to the instruments. Tape might be glowing more 
than the screen and adding to the background that we're trying to get 
rid of. We can't see any tape, however.

Today's data look good. We've been transferring the data to JPL over 
the Internet, and our colleagues at JPL have been working on them. 
Along with a quick technical outline of what we've done today, 
instructions on some computer processing on some of the images, I 
summarize today's work: " Today we skirted disaster, made some 
improvements and hit paydirt obliquely."

For those that missed it, here is the text of the press release from
one week ago

RELEASE: 96-10
GALILEO PROBE SUGGESTS PLANETARY SCIENCE REAPPRAISAL

Preliminary analysis of early data returned by NASA's 
historic Galileo probe mission into Jupiter's atmosphere has 
provided a series of startling discoveries for project scientists.

Information on the extent of water and clouds and on the 
chemical composition of the Jovian atmosphere is particularly 
revealing. Probe instruments found the entry region of Jupiter 
to be drier than anticipated, and they did not detect the 
three-tiered cloud structure that most researchers had 
postulated. The amount of helium measured was about one-half 
of what was expected.

These initial findings are encouraging scientists to 
rethink their theories of Jupiter's formation and the nature of 
planetary evolution processes, according to probe project 
scientist Dr. Richard Young of NASA's Ames Research Center, 
Mountain View, CA.

"The quality of the Galileo probe data exceeds all of our 
most optimistic predictions," said Dr. Wesley Huntress, NASA 
Associate Administrator for Space Science. "It will allow the 
scientific community to develop valuable new insights into the 
formation and evolution of our solar system, and the origins of 
life within it."

The probe made the most difficult planetary atmospheric 
entry ever attempted, according to probe manager Marcie Smith 
of NASA Ames. Entering Jupiter's atmosphere on Dec. 7, 1995, 
it survived entry speeds of over 106,000 mph, temperatures twice
those on the surface of the Sun and deceleration forces up to 230
times the strength of gravity on Earth. It relayed data obtained
during its 57-minute descent mission back to the Galileo orbiter
more than 130,000 miles overhead for storage and transmission to
Earth. The orbiter is now embarking on a two-year mission to study
Jupiter and its moons.

"The probe detected extremely strong winds and very intense 
turbulence during its descent through Jupiter's thick 
atmosphere. This provides evidence that the energy source 
driving much of Jupiter's distinctive circulation phenomena is 
probably heat escaping from the deep interior of the planet," 
Young said. "The probe also discovered an intense new 
radiation belt approximately 31,000 miles above Jupiter's cloud 
tops, and a veritable absence of lightning," he noted.

The composition of Jupiter's atmosphere offered some 
surprises, according to project scientists. It contains 
significantly lower than expected levels of helium, neon, and 
certain heavy elements, such as carbon, oxygen and sulfur.

The issue of the colors of Jupiter's atmosphere has been 
much-debated, but no consensus has developed from probe data to 
date. The probe encountered no solid objects or surfaces 
during its entire 373-mile (600 km) journey. This was as 
expected for a gas-giant planet such as Jupiter.

What are the implications of these findings? Most 
scientists believe that Jupiter has a bulk composition similar 
to that of the gas and dust cloud of the primitive solar nebula 
from which the planets and our Sun were formed, with added 
heavy elements from comets and meteorites. The probe's 
measurements may necessitate a re-evaluation of existing views 
of how Jupiter evolved from the solar nebula. For example, the 
lower-than-expected helium and neon levels on Jupiter relative 
to the Sun influence scientific understanding of the process of 
fractionation, the "raining out" of helium and neon during 
planetary evolution.

During the probe's high-speed, atmospheric-entry phase, 
deceleration measurements high in the atmosphere showed 
atmospheric density to be much greater than expected. 
Corresponding temperatures were also much higher than 
predicted. The high temperatures appear to require an 
unidentified heating mechanism for this region of the atmosphere.

Following probe parachute deployment, six science 
instruments on the probe collected data throughout 97 miles 
(156 km) of the descent. During that time, the probe endured 
severe winds, periods of intense cold and heat and strong 
turbulence. The extreme temperatures and pressures of the 
Jovian environment eventually caused the probe communications 
subsystem to terminate data transmission operations.

Earth-based telescopic observations suggest that the probe 
entry site may well have been one of the least cloudy areas on 
Jupiter. At this location, the probe did not detect the three 
distinct layers of clouds (a topmost layer of ammonia crystals, 
a middle layer of ammonium hydrosulfide, and a final, thick 
layer of water and ice crystals) that researchers had anticipated.

Some indication of a high-level ammonia ice cloud was 
detected by the net flux radiometer. Evidence for a thin cloud 
which might be the postulated ammonium hydrosulfide cloud was 
provided by the nephelometer experiment. There was no data to 
suggest the presence of water clouds of any significance. The 
vertical temperature gradient obtained by the atmospheric 
structure instrument was characteristic of a dry atmosphere, 
free of condensation. Only the one, distinctive cloud 
structure was identified, and that was of modest proportion.

The latest analyses of data from the Voyager spacecraft 
that flew by Jupiter in 1979 have suggested a water abundance 
for the planet of twice the solar level (based on the Sun's 
oxygen content). Observations of the propagation of 
atmospheric waves across Jupiter's cloud tops from the Comet 
Shoemaker-Levy 9 impacts implied that Jupiter might have a 
water content of ten times the solar level. Actual probe 
measurements, while subject to scientific debate, suggest a 
level near that of the Sun. Scientists are left to wonder, 
"where is the oxygen?," "where is the water?," and to 
reconsider their interpretation of the S-L 9 impacts.

Scientists had expected to find severe winds on Jupiter 
ranging up to 220 mph. However, the probe appears to have 
detected winds far greater, perhaps up to 330 mph. The winds 
remained fairly constant as the probe descended deep into the 
Jovian atmosphere. This suggests that Jupiter's winds are not 
caused by differential sunlight at the equator versus the poles 
or by heat released by water condensation as on Earth, 
according to project scientists.

"The origin of Jupiter's winds appears to be the internal 
heat source which radiates energy up into the atmosphere from 
the planet's deep interior," Young said. "This impacts Jupiter's
climate and circulation patterns, and suggests a jet stream-like
mechanism rather than swirling hurricane or tornado-like storms."

The probe found that lightning occurs on Jupiter only about 
one-tenth as often as on Earth. This is puzzling, but 
consistent with the absence of water clouds. A virtual absence 
of lightning reduces the probability of finding complex organic 
molecules in Jupiter's atmosphere, particularly given its 
hostile, predominantly hydrogen composition.

Scientists caution that results obtained to date, while 
dramatic and exciting, are only preliminary and subject to much 
further analysis and refinement. Data transmission problems 
associated with solar conjunction between the Earth and 
Jupiter, the need to refine estimates based on probe and 
orbiter trajectories, the presence of higher than anticipated 
instrument temperatures, and the need for improved calibration 
all require a cautious approach to these early findings.

Additional information will be forthcoming over the next 
few months as scientists continue to evaluate the wealth of 
data obtained by the probe and to cross-compare results of 
individual scientific instruments.

The Galileo probe project is managed by NASA's Ames 
Research Center, Mountain View, CA. Hughes Aircraft Co., El 
Segundo, CA, designed and built the probe; General Electric, 
Philadelphia, PA, built the probe's heat shield. NASA's Jet 
Propulsion Laboratory, Pasadena, CA, built the Galileo orbiter 
spacecraft and manages the overall mission.