Status Report

NASA Cassini Significant Events for 07/18/2012 – 07/24/2012

By SpaceRef Editor
July 28, 2012
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NASA Cassini Significant Events for 07/18/2012 – 07/24/2012

The most recent spacecraft tracking and telemetry data were collected on July 25 by the Deep Space Network’s 70 meter Station 14 at Goldstone, California. Aside from the Cassini Plasma Spectrometer, which is off, and the Ultrastable Oscillator (see the Jan. 5, 2012 Significant Events), the Cassini spacecraft is in an excellent state of health with all its subsystems functioning normally. Information on the present position of the Cassini spacecraft may be found on the “Present Position” page at: .

A 21-day period wrapped up on Saturday that was focused on Magnetospheric and Plasma Science observations of Saturn’s magnetosphere and magnetosheath. Another Radio Science rings and atmosphere occultation experiment took place on Sunday. Finally, the Titan T85 encounter occurred on Tuesday as described here:

Wednesday, July 18 (DOY 200)

The Imaging Science Subsystem (ISS) led spacecraft pointing as part of the Titan Meteorological Campaign while the Composite Infrared Spectrometer (CIRS) and the Visible and Infrared Mapping Spectrometer (VIMS) also took measurements.

The feature “Cassini Spots Daytime Lightning on Saturn” was released today. It may be viewed here:

Thursday, July 19 (DOY 201)

A 34 meter Deep Space Network (DSN) station in Canberra, Australia, participated in an Operations Readiness Test for Sunday’s Radio Science rings and atmosphere occultation experiment. During this pass, the flight team uplinked “Live Moveable Block” commands to refine the timing of spacecraft activities during Sunday’s experiment.

Friday, July 20 (DOY 202)

A meeting with the NASA Engineering and Safety Center, the Cassini spacecraft team, and staff from the Southwest Research Institute was held to begin an investigation into the Cassini Plasma Spectrometer instrument anomaly that caused a solid state power switch to shut it off on June 3 of this year.

Saturday, July 21 (DOY 203)

Orbit Trim Maneuver (OTM) 328, the Titan 85 approach maneuver, was performed today using the Reaction Control Subsystem thrusters. The 161 second burn provided a delta-V of about 172 millimeters per second.

Sunday, July 22 (DOY 204)

The Radio Science Subsystem team performed an ingress occultation experiment, probing Saturn’s rings and then atmosphere, using Cassini’s 3-frequency radio beam. The DSN again provided the reference frequency via uplink because Cassini’s Ultrastable Oscillator is inoperable. This time the spacecraft performed a limb-tracking maneuver, rotating as it went behind Saturn to keep its antenna pointing in such a way that it would still be received on Earth when atmospheric refraction began to bend the signal. The spacecraft’s downlink was received and recorded at 70 meter and 34 meter stations at Canberra, Australia.

With the Sun eclipsed behind Saturn, Cassini was free to safely point its instruments toward the backlit rings. VIMS observed the unlit side at up to 175 degrees phase angle, looking for clouds from impacts of interplanetary debris on the A ring. Unusually high resolution should reveal most of the narrow gaps in the Cassini Division and narrow ringlets in the tenuous D ring. Riding on the VIMS observation, ISS took advantage of the opportunity to image the rings at high resolution and very high phase.

As Cassini crossed through the ring plane, the Cosmic Dust Analyzer measured particle count rates. CIRS then made a unique, high priority observation of the rings at high phase angles. VIMS observed the bright star Sirius rising through Saturn’s atmosphere. Finally, UVIS observed another star behind the rings, providing a virtually microscopic view of ring densities including locations where the A ring opens into the Cassini Division.

Monday, July 23 (DOY 205)

UVIS observed the bright star Spica passing near Saturn’s moon Dione due to Cassini’s motion to search for evidence of Dione’s exosphere in absorption spectra.

ISS searched for moonlets in gaps in the Cassini Division. CIRS carried out an infrared temperature mapping of Titan’s atmosphere, and then the spacecraft performed a reaction-wheel bias maneuver.

An image called “Wave Maker” was featured today, showing Saturn’s moon Daphnis causing out-of-plane structures in the A ring. It can be viewed here:

Tuesday, July 24 (DOY 206)

As planned years ago by Cassini’s tour designers, today’s close northerly flyby of Titan (see the T-85 page linked above) took advantage of that body’s gravitation and orbital momentum to increase the spacecraft’s orbital inclination from 21.2 to 32.2 degrees with respect to Saturn’s equatorial plane.

For closest approach, attitude control was commanded to switch from reaction wheels to thrusters to provide increased control authority over atmosphere-generated torques. The spacecraft rotated about its three axes to point optical remote-sensing and in-situ instruments. Telemetry data from all the instruments were stored aboard the Solid State Recorder. Playback will be complete Friday morning after three tracking periods with DSN’s 70 meter stations at Goldstone and Canberra. Cassini transmits its telemetry to Earth at rates up to about 165,000 bits per second.

Visit the JPL Cassini home page for more information about the Cassini Project:

SpaceRef staff editor.