NASA 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 http://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 http://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.
