Cassini Significant Events 08/19/09 – 08/25/09

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: http://saturn.jpl.nasa.gov/operations/present-position.cfm .

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: http://saturn.jpl.nasa.gov/video/products/MultimediaProductsCharm/

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:
http://antwrp.gsfc.nasa.gov/apod/ap090825.html