NASA Cassini Significant Events 08/19/09 - 08/25/09

Status Report From: Jet Propulsion Laboratory
Posted: Friday, August 28, 2009

image The most recent spacecraft telemetry was acquired on Aug. 24 from the Deep Space Network tracking complex at Goldstone, California. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at: .

Wednesday, Aug. 19 (DOY 231):

As was mentioned in the report last week, due to the change of aim point for Orbit Trim Maneuver (OTM) 213, an unplanned update was deemed necessary for RADAR for just prior to the Titan 61 flyby on Aug. 25. The process for this update overlaps a similar process for an already scheduled update to Saturn, Titan, and Telesto vectors planned to execute two days later on the 27th. Should make an interesting week for the team.

An encounter strategy meeting was held today to cover the period between Aug. 25 and Oct. 12, Titan flybys T61 and T62, and maneuvers 215-217.

Thursday, Aug. 20 (DOY 232):

The predicted Titan 61 flyby point in the absence of OTM 214 is about 2 km lower than the planned flyby altitude, and the predicted downstream cost of cancellation is about 0.1 m/s. Since science did not identify any issues with the lower altitude, a decision was made to cancel OTM-214 due to execute Aug. 21.

Friday, Aug. 21 (DOY 233):

Autonomous Thermal Controls (ATC) 4 and 5 - responsible for controlling the Probe Receiver Front End (RFE) replacement heaters - were disabled today via real time commanding. These particular heaters are not needed to maintain requirement compliant RFE temperatures all the way to the end of the proposed Extended Extended mission in 2017. This "disable" commanding is being done to establish an interim condition until the CDS flight software version 10 effort is complete.

The first delivery port occurred today as part of the Science Operations Plan process for S57.

Sequence leads uplinked the S53 background sequence today along with the Titan Live Inertial Vector Propagator update, and a command to change the command loss timer value to 5 days.

At a Go/No Go meeting today for the Saturn, Janus, Telesto DOY-239 Live Update, it was determined that the update was a go. Based on graphics distributed for team review, Imaging Science (ISS) requested a go for the Telesto update. Janus is in the narrow angle camera field of view with or without the update, but the Composite Infrared Spectrometer (CIRS) is riding along for this observation and may need a Janus update. Uplink for the update files is scheduled for Monday.

Monday, Aug. 24 (DOY 236):

The second delivery port occurred today as part of the Science Operations Plan process for S56. The files will be merged Tuesday and the results analyzed by the development team.

To celebrate the International Year of Astronomy, the Cassini Scientist for a Day program is open to all nations and educational organizations. Cassini Scientist for a Day will also be a Special Project within the International Year of Astronomy 2009. The International Coordinator of IYA2009 will invite space enthusiasts in 142 countries to participate. Currently 27 countries have expressed interest.

Tuesday, Aug. 25 (DOY 237):

On Tuesday, Aug. 25, Cassini encountered Titan at an altitude of 970 km and a speed of 6 km/sec. Closest approach occurred at 7:17 AM PDT at latitude 19 degrees S. Science highlights for T61 included RADAR scatterometry, altimetry, and Synthetic Aperture Radar (SAR). The SAR observation was near equatorial, covering the features Dilmun, Adiri and Belet. The SAR track paralleled and overlapped the T8 flyby dataset, which should provide a good stereo opportunity over the Belet sand dunes as well as expanded coverage of Shangri-La and Belet. The Ion and Neutral Mass Spectrometer (INMS) rode along with RADAR, observing the night side wake at low and near equatorial southern latitudes. This was the only southern equatorial wake observation in the mission.

The outbound leg of T61 was a very good opportunity for optical instruments because the phase angle was about 10 degrees. Just after the RADAR observations at closest approach, VIMS observed the southern hemisphere at longitudes similar to those observed at T57, T58, T59 and T60. However, this flyby is the best of the group. The resolution can be as good as 5 km/pixel at the beginning of the observation. From T57 to T61, VIMS observed the same area with different phase angles, which should provide a phase curve.

The S52 sequence concluded and S53 began execution today at 2009-236T18:30:00 Pacific Daylight Time. The sequence will run for 41 days and conclude on Oct. 4. During that time there will be one targeted encounter of Titan and five non-targeted flybys - one each of Pallene, Telesto, Prometheus, Dione, and Titan. Two OTMs are scheduled, numbered 215 and 216. Solar Conjunction will begin around Sept. 11, and there will be a command moratorium - a period of no commands sent to the spacecraft - for five days beginning Sept. 15.

The Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference for August was held today. The topic: Sodium salts in cryo-volcanic ice particles: Evidence for liquid water on Enceladus. The presentation package can be downloaded from:

An image of Saturn's rings taken a few hours before the equinox crossing on Aug. 10 was Astronomy Picture of the Day today. This image captures what the rings look like when pointed edge-on to the sun. It may be seen at:

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