Cassini Significant Events 12/21/04 - 12/27/04

December 28, 2004

(Source: Jet Propulsion Laboratory)

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Monday, December 27. The Cassini spacecraft is in an excellent state of health and is operating normally.

Diary of a Probe Release:

It's Tuesday, December 21.

Only 4 more shopping days till Christmas.

Yesterday the loading of the Probe Relay default pointing vectors to the spacecraft took longer than anticipated. The flight team was not able to complete this activity before the Probe Mission Timing Unit (MTU) loading window opened. It was decided to postpone the final two uplinks until today.

Huygens personnel reported that the MTU loading went well. They saw the timer counting down. As battery power on board the probe is limited, the timer is responsible for activating the Probe suite of instruments about four hours prior to entering the atmosphere of Titan.

Just found out that the Probe is carrying rock-n-roll on board! Lalala, Bald James Dean, Hot Time and No Love are all heading for Titan. The European Space Agency (ESA) wanted to have music on board to arouse the interest of the world's public, particularly the young, and to leave a trace of humanity in the unknown. The music will be available on the Music2Titan website starting today, 21 December. For more information link to and

Wednesday, December 22

The minor delays reported yesterday were just that - minor. We are back on schedule. All subsystems are normal.

There were three spacecraft activities today. The S07 online background sequence was re-activated, and we performed Inertial Reference Unit (IRU) Calibration #6 - the last calibration prior to Probe Release. The third activity was Orbital Trim Maneuver (OTM) #9, the Probe Targeting Clean-up maneuver. This maneuver is based on the long-planned Probe Release attitude with no update required, since the trajectory control has been right on target up to this point. That means there will be no changes to the current Probe Release sequence. The Integrated Test Laboratory is currently testing the Iapetus mini-sequence. They can now let it continue to clock out.

We have heard back from the maneuver team. OTM #9 was successfully completed on the spacecraft. This maneuver refines Cassini's trajectory in preparation for the Huygens probe mission.

The reaction control system (RCS) burn began at 6 p.m. Pacific Time. The "quick look" immediately after the maneuver showed the burn duration was 18.8 sec, giving a delta-V of approximately 20 mm/s. This was the shortest duration RCS maneuver performed to date.

Off-Earth engineering data from SSR partition B-6 was successfully played back once the spacecraft was back on Earth point. This contained high-rate propulsion data. ACS, Propulsion, and Thermal teams all reported nominal states.

Tomorrow will be a quiet day for the spacecraft.

Thursday December 23:

We received a Go at the Probe Release Approval Meeting for uplink of the Probe Release sequence. We will be uplinking the Release sequence and the two supporting files tonight.

ACS has analyzed the data from yesterday's IRU calibration #6. IRU A is nominal.

Mission support area staffing for probe release begins at 3 PM tomorrow.

Tomorrow evening is Probe Release!

Friday, December 24. Christmas Eve.

Made sure to get all my shopping done. Have plans for the 24th. Supporting Probe release!

Everything looks good and nominal.

JPL provided dinner for those of us who had to work. Slight congestion at the dessert table, but everything else nominal.

Navigation reported that their orbit solutions from yesterday have not changed.

All Orbiter instruments reported in. Everyone is in the correct configuration and is ready for release.

Set up a conference line so that Cassini flight team members that are not working the event but who came in anyway to show their support can listen in on events as they unfold. 

The Huygens Probe was successfully deployed from the Cassini Orbiter! Navigation and Spacecraft Operations Office teams confirmed the nominal separation of the Probe at 7:24 Pacific time. The Probe is now in free flight at a spin rate of 7.5 rpm as detected by the Magnetometer Subsystem. All systems performed as expected, there were no problems reported with the Cassini spacecraft, no red alarms, no fault protection responses. Congratulations everyone!

The Head of Science Programmes for the European Space Agency expressed his thanks to the team for a wonderful adventure in the exploration of Saturn. Huygens personnel are now awaiting with great expectation the Probe descent on January 14, 2005.

After release, the Uplink Operations (ULO) sequence lead called for the start of planned Probe optical navigation imaging. This is a 4.5 hour process. Currently we are on schedule.

The orbiter instrument restoration mini-sequence was uplinked around 10 pm local time. 

Saturday, December 25. Christmas Day:

All quiet in the trenches. 

Uplinked the first Probe Imaging Sequence. The first Optical Navigation Images (OPNAV) of the Probe are in. We nailed it! With the wide-angle camera image, we were able to see the Probe about 3 pixels wide. Confirmed that the Probe is well within the entry corridor with an entry flight path angle estimate of -65.1 degrees (target was -65.0!).

ACS has released a preliminary analysis. ACS will not need to send up an ACC Parameter patch tomorrow morning.

ULO will be sending up the Probe Support Avionics (PSA) checkout sequence today. This sequence will verify that the avionics are still functioning correctly.

This afternoon, we will also be uplinking the second Probe imaging sequence. This sequence uses the narrow angle camera (NAC). The Probe should be about 10 pixels across in this image.

PSA checkout executes on the spacecraft after the probe imaging sequence.

Telemetry has been received for the instrument restoration sequence. The Orbiter instruments are nominal.

Sunday, December 26:

The spacecraft is nominal.

Huygens Probe Release Zoom

Huygens Probe Release Zoom

Navigation stopped by and gave a status on Probe image #2. They got a good picture of the Probe with the NAC. The Probe is about 10 pixels across, round, and one can see what looks like sun glint off the backside of the Probe.

Probe personnel reported on the PSA checkout. ESA reviewed the dump packets. They look good. ESA is ready to go.

Tonight we will uplink the sequence for the third and last Probe imaging OPNAV. Generating the OPNAV sequence took a really long time last night. Those involved expect the process to go faster tonight.

Monday, December 27:

The third Probe OPNAV image is available. They got a nice 6-pixel image of the Probe. Two of the Probe OPNAV images are posted on the Cassini web site at

ACS will execute their 7th IRU calibration during the last Probe imaging OPNAV.

Orbital trim maneuver #10 (OTM-10) was successfully completed on the spacecraft today. This maneuver, also called the Orbit Deflection Maneuver (ODM), takes Cassini off of a Titan-impacting trajectory and on to a flyby trajectory with the required altitude to receive data from the Huygens probe as plunges into Titan. The main engine (ME) burn began at 5:44 p.m. Pacific time. The "quick look" immediately after the maneuver showed the burn duration was 153.4 sec long, giving a delta-V of 23.7 m/s.

ACS reported the burn termination was a "nominal complete" with an accelerometer cutoff. Propulsion and thermal teams also reported nominal conditions. There was no unexpected CDS or Fault Protection activity.

Tomorrow's schedule shows another quiet day for the spacecraft.

As of today (December 28), the Program is 17 days from Probe relay.

Image advisories, press releases and the latest Cassini information can be found at