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Cassini Significant Events
for 01/13/05 - 01/19/05

A Journey to Titan: The Diary Continues (Part IV - Final)

Thursday, January 13:

It's the calm before the much hoped for storm. There is no activity on the
spacecraft at this time. Subsystems are normal. All sequences are clocking
out for Probe Relay. Information on the present position and speed of the
Cassini spacecraft may be found on the "Present Position" web page located
at saturn.jpl.nasa.gov/operations/present-position.cfm .

The Outreach folks shared some pre-relay comments from members of the Saturn
Outreach Campaign. Are they excited! Many took the opportunity for a last
look at Titan before the first Earth-based spacecraft will touch down on its
surface. When they look at Titan next, they will be looking at the farthest
place in the solar system where a spacecraft has landed! There are
apparently 'Huygens Plunge Parties' planned all over the globe. Australia
has an X-Cyclone attending theirs, but they don't plan on letting it
interfere with their event.

Operations staffing in the Mission Support Area begins at 11:00 PM tonight
Pacific Time. The Probe Relay sequence will begin at 11:37 PM.

Friday, January 14:

WOW. What a day. I'll try to write it up for you giving an idea of how
events unfolded. Wish me luck! All times referenced are Pacific Time and
time of receipt of signal at Earth.

At about four hours before the probe reached 1270 km above the surface of
Titan, the sleep timer went off, awakening the probe's science instruments.

12:10 AM - Loss of Signal from Cassini as it turns off Earth point to Probe
relay attitude

2:12 AM - Probe begins transmission to Cassini

2:25 AM - The Robert C. Byrd Green Bank Telescope (GBT) of the National
Radio-astronomy Observatory in West Virginia, USA detected the probe's
'carrier' signal.

Presence of this signal indicated that the back cover of Huygens must have
been ejected, the main parachute deployed, and the probe had begun to
transmit. In other words, the probe is "alive".

The carrier signal is sent continuously throughout the descent but by itself
does not contain any scientific data. It is similar to the tone signal heard
in a telephone handset once the latter is picked up. Detection occurred
shortly after the probe began its parachute descent through Titan's
atmosphere.

The parachute deployment sequence was initiated when the Probe reached Mach
1.5, and a pyrotechnic charge was fired deploying a 2.6 meter pilot chute.
This chute then pulled off the back heat shield and deployed the 8.3 meter
main chute, which was followed shortly by the release of the front heat
shield.

After a 30 second delay to ensure the shield was sufficiently far away to
avoid instrument contamination, the science packages deployed and began to
make measurements of Titan's atmosphere.

After a further 15 minutes, the main parachute was jettisoned to avoid a
protracted descent and a smaller 3.03 m diameter parachute was deployed.

The descent lasted 2 hours and 27 minutes. Five batteries on-board the probe
were sized for a minimum mission duration of 153 minutes, corresponding to a
maximum descent time of 2.5 hours plus at least 3 additional minutes on
Titan's surface.

7:04 AM - Cassini is now on Earth point

7:06 AM - End of the Probe Relay Sequence

7:07 AM - Begin 1st Playback Sequence

7:14 AM - Begin Solid State Recorder (SSR) partition B4 playback. Data
from Huygens was relayed to the Cassini Orbiter passing overhead and stored
on the SSRs. Closest approach distance of Cassini to Titan was 60,000 km.

10:00 AM - First B4 playback complete

The probe signal was lost to Cassini before the batteries expired, and
before the orbiter went over the horizon - loss of signal was due to the
orbiter moving outside the beamwidth of the Huygens transmitting antennas.

Radio Science/ Very Long Baseline Interferometry (VLBI) stations continued
to receive data after loss of signal. After GBT set, Parkes, a 64-m radio
telescope in Australia, received and recorded via a Radio Science Receiver
borrowed from the Canberra DSN complex. Parkes recorded the signal for over
three hours after probe landing and set at 8:00 AM while the Probe was still
transmitting and the signal was still present.

In addition to the GBT, sixteen other radio telescopes in Australia, China,
Japan and the USA were involved in tracking the Huygens probe.

In the course of analyzing the data from the SSRs it was determined that
first signal detection occurred about 15 seconds earlier than the
prediction, so entry was perfectly nominal. Huygens collected 2:27:13 of
descent data, and 1:12:09 of surface data - far more surface data than was
expected.

The Radio Science carrier recording on the ground was intended to enhance
the Doppler Wind Experiment but became much more important in light of the
anomaly with the USO on Channel A.

There is much much more information available on events as they occurred and
on science analysis of the data thus far. Check the ESA web site for more
information.

We are not done yet. Gotta move on to tomorrow's events.

Saturday, January 15:

The post relay orbiter instrument power-on sequence was uplinked tonight at
015/07:00:00 UTC, or about 11:00 pm yesterday Pacific Time. By 3:00 AM
Pacific time Cassini's instrument teams had reported nominal power-on and
loading of Instrument Expanded Blocks. Then they went back to bed!

At 5:30 this morning a meeting was held to approve the release and use of
SSR Partition 4 for non-Probe activities. CDS analysis indicates that we
have successfully downlinked all SSR Partition 4 data for the Probe. The
approval was given and sequences MS1 and MS2 were uplinked to the spacecraft
within the hour.

MS1 and MS2 are science sequences that will take remote-sensing measurements
of Mimas, Enceladus and Rhea close to the time of Saturn periapsis following
Probe relay. These observations represent the best opportunities in the tour
to observe these moons under such observational situations. This will be the
first good look at Mimas from ) made Astronomy Picture of the Day on January 14, 15,
17, and 19.

The Huygens team passes their heartfelt thanks to the Cassini team for their
magnificent support resulting in this success.

The probe mission was a resounding scientific success. There was an
enormous, positive press response to the mission in Europe; some hailed it
as the greatest scientific success ESA has had.

Outreach shared some of the comments they received regarding Probe Relay
from people in the Saturn Observation Campaign. Here are comments from some
of the 374 members from 50 participating countries:

Italy: We will never thank you enough for the emotions you are giving us!
Cheers from Italy!

North Carolina: Woo Hoo!! Great day in the morning!
Kansas: Great updates. Had 30 people here for early breakfast and watched
the first press conferences. We made a banner that I will send - some great
comments.

Michigan: I've been watching on NASA TV. This is fantastic and really a
scientific wonder!!!! Let's carry on.

Illinois: NASA and ESA should be very proud. Both organizations have done a
wonderful service to the people of the world. I can recall as a boy the
excitement I felt as I watched man touch down on the Moon the first time and
Neil Armstrong's walk on the Moon. Watching the first pictures come back
from Titan brought back that same level of excitement for me.

Illinois: Now THIS is reality TV.

Arkansas: Please send my congratulations to the JPL and ESA teams. Proud to
be on the Saturn Observation Campaign.

Nevada: Success of such amazing magnitude makes the hairs on the back of the
neck quiver. Your team and the European agencies did it. One of the
greatest space explorations successes in history.

Ireland: I AM FIT TO BURST WITH EXCITEMENT.

India: Heartiest congratulations. We are all glued to the net / TV.

India: Congratulations to NASA, ESA & ASI for the historic creating of safe
landing of the Huygens probe. Just trying to grab images as soon as
possible.

Australia: We've been watching Saturn all evening and it looks so serene and
beautiful, it's just been magical knowing that a little probe from Earth has
now entered the atmosphere and is exploring one its moons.

Germany: We have all the reasons to celebrate this triumphant day for NASA,
ESA and all mankind!

Netherlands: It is nice to think of the movement of the Huygens now reaching
the body of Titan. Hoping that this day will bring another big success to
the Cassini-Huygens mission.

Check out the Cassini web site saturn.jpl.nasa.gov for the latest
press releases and images.

The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a
division of the California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Science Mission Directorate, Washington,
D.C. JPL designed, developed and assembled the Cassini orbiter