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NASA Cassini Significant Events 07/11/2012 - 07/17/2012

Status Report From: Jet Propulsion Laboratory
Posted: Tuesday, July 24, 2012

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The most recent spacecraft tracking and telemetry data were collected on July 18 by the Deep Space Network's 34 meter Station 45 at Canberra, Australia. 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: http://saturn.jpl.nasa.gov/mission/presentposition/.

Having passed through apoapsis the previous day, Cassini spent this week more than 2 million kilometers from Saturn making in-situ measurements in the outer magnetosphere and magnetosheath, remotely observing Saturn's aurora and monitoring Titan. On the ground, preparations were conducted for a busy period around periapsis next week, when the rings will again be observed by remote sensing, and actively probed in another Radio Science occultation experiment.

Wednesday, July 11 (DOY 193)

The Imaging Science Subsystem (ISS) observed the small dark moon Ymir in its retrograde orbit 23 million kilometers from Saturn.

Sequence planners for S75, which goes active in September, are evaluating whether there will be a need to do a Live Inertial Vector Propagator Update to ensure adequate instrument pointing accuracy for observations of the outer irregular satellite Bestla, based on newly delivered ephemeris data.

Thursday, July 12 (DOY 194)

Deep Space Network (DSN) tracking allocations to Cassini were changed late in the S74 sequence process after the sequence had been built, so commands were uplinked today to change downlink telemetry rates to accommodate a short DSN tracking pass on Monday.

The Attitude and Articulation Control Subsystem team performed a Reaction Wheel Assembly (RWA) bias maneuver. While off Earth-point and not being tracked, thrusters stabilized the spacecraft so the RWA speeds could be adjusted.

The 70 meter DSN station in Canberra, Australia, participated in an Operations Readiness Test (ORT) for next week's Radio Science rings and atmosphere occultation experiment.

Friday, July 13 (DOY 195)

The Navigation team took images of Saturn's moon Iapetus against a background star field to be used in support of optical navigation.

Today, and again on July 15 and 17, the Ultraviolet Imaging Spectrograph (UVIS) observed Saturn's aurora by performing a mixture of slews and fixed pointings at the southern auroral oval. The visible and infrared mapping spectrometer (VIMS), the Composite Infrared Spectrometer (CIRS), and ISS took advantage of the pointing to also make auroral observations.

Saturday, July 14 (DOY 196)

A 34 meter DSN station in Canberra, Australia, participated in an ORT for next week's Radio Science experiment.

Sunday, July 15 (DOY 197)

Saturn and Titan are still prominent for viewing in small telescopes; look toward the southwest as soon as it's dark. You might notice Mars is in the same part of the sky. This affects Cassini in that many of the same DSN antennas that might otherwise be tracking Cassini are needed for communications with the Mars Science Laboratory, which is due to land on Mars on Aug. 5 Pacific time.

Monday, July 16 (DOY 198)

ISS led the pointing, with CIRS and VIMS also taking measurements, to monitor Titan as part of the Titan Meteorological Campaign.

The navigation team released a trajectory update in support of the Live Moveable Block that will execute during next week's Radio Science experiment.

Tuesday, July 17 (DOY 199)

A Mission Planning forum was held today to review propellant use in the S73 sequence and the status of the propellant budgets. This status is provided on a regular basis so the Project can maintain cognizance of propellant usage and end-of-mission margins. Work began today on realtime commands that make up what is known as a Live Moveable Block that will ensure the best possible timing of spacecraft activities during the RS occultation experiment next week.

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