Cassini Significant Events 01/23/08 - 01/29/08

February 1, 2008

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired on Monday, Jan. 28, from the Madrid tracking complex. 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, Jan. 23 (DOY 023):

The official port for the Science Operations Plan Update (SOPU) process for S40 occurred today. The delivered products were merged, and reports sent to the science teams and AACS for end-to-end pointing analysis.

The Command Loss Timer (CLT) is part of fault protection onboard every spacecraft. Basically, if a spacecraft has not heard from the flight team by a specified time since it received its last command, the spacecraft calls safing, and "phones home." Based on analysis performed before Saturn Orbit Insertion, the Cassini CLT countdown duration, with a few exceptions, has been set for 85 hours. For some of the recent sequences in development, pre uplink analysis has shown points where the CLT countdown would exceed the limit and go negative. Under the current operational strategy for such occurrences, commands would have to be included in the background sequence to increase the CLT to some greater value before the event, and then return it to 85 hours after the event. Rather than doing all this commanding, it was determined that if the nominal timer default was increased by just five hours, there would be a minimum margin of two hours in many of the cases. With all this in mind, on Jan. 23, the nominal time duration for the CLT was changed from 85 to 90 hours.

On Wednesday and Thursday the Cassini Plasma Spectrometer (CAPS) and the Magnetospheric Imaging Instrument (MIMI) supported an on-going campaign to observe Saturn's magnetospheric boundaries on Saturn's dusk side at a variety of latitudes. In addition, the Visible and Infrared Mapping Spectrometer (VIMS) observed Saturn's F-ring for nearly 14 hours to obtain a movie of the ring's rotation. VIMS stared at one ansa of the F-ring and observed continuously for one orbital period to build up a 360-degree azimuthal map of the ring from a distance of 25-30 Rs.

Thursday, Jan. 24 (DOY 024):

The last Aftermarket Process for the prime mission concluded today with the delivery of Target Working Team (TWT)/ Orbiter Science Team (OST) products for S41. SOPU for S41 will kick off in about two weeks on Monday, Feb. 4.

Uplink Operations sent commands to the spacecraft today for a Radio Science Live Movable Block, a Cosmic Dust Analyzer (CDA) flight software demo set to execute on Jan. 27-28, and an increase in telemetry rates for DOY 30 over DSS-24.

The Imaging Science Subsystem's Wide Angle Camera (ISS WAC) began observations this week by searching for small satellites in the Mimas-Enceladus region. To do this, ISS stared off the ring ansa and took pairs of WAC images ~ every 5 minutes for 13.5 hours. After this, VIMS took data for a latitude-phase mosaic on each ansa on the unlit face by pointing the spacecraft at six locations for one hour each.

Other activities this week include a number of occultations. The Ultra Violet Imaging Spectrograph (UVIS) observed a series of eight stellar occultation events of Saturn's A and F rings. UVIS pointed at star SAO 205839 as it crossed the Cassini Division and then the F ring, and observed star Iot Cen and Kap Cen as they crossed the F ring.

Friday, Jan. 25 (DOY 025):

The TWT/OST integrated products for S42, covering orbits 74 through 80, were delivered today. The integrated products are in their final form. No re-integration is planned, as there will be no Aftermarket process to address re-integration issues. The next step in sequence development, SOP implementation, will kick off on Feb. 11. Between now and then, the instrument teams will be working on designs for the sequence, and requests will be passed to the DSN regarding when Cassini needs tracking passes to support uplink and downlink during execution of S42 in July of this year. S42 is the first of the sequences for the proposed extended mission. Over the next two years the TWT/OST teams will be delivering integrated sequence products for the extended mission about every five weeks.

Sunday, Jan. 27 (DOY 027):

Non-targeted flybys of Titan, Atlas, Epimetheus, Prometheus, and Pandora occurred today.

A Radio Science (RSS) orbit 57 rings chord occultation was completed successfully on Sunday, Jan. 27. For this experiment, Canberra Deep Space Station (DSS)-43 assisted with S- and X-band support, and DSS-34 provided X- and Ka-band support. With the ring opening angle at 7.4 degrees, the occultation probed all major ring features -- A, Cassini Division, B, and C -- on the way in and out. The data from this observation will provide valuable profiling of the dependence of detectable ring structure on observation longitude. This is important for characterization of the rings' microstructure, or, the spatial distribution of aggregates of ring particles. Like its sister occultation on Orbit 56, the Orbit 57 occultation geometry was optimized to allow capturing favorable Doppler contours alignment over Ring A near the end of the observation period, and facilitate determination of physical ring properties from the near-forward scattered signal observations. The experiment completed normally, and high quality data were acquired.

Monday, Jan. 28 (DOY 028):

Monday kicked off a weeklong set of science meetings at JPL as part of Project Science Group (PSG) meeting #44. Enceladus Plume, Titan Science, Titan Operations, Saturn, Rings, Magnetospheric and Plasma Science (MAPS), and Icy Satellite working group meetings will be held this week along with two Plenary Sessions where general status for Spacecraft, Operations, and Instruments will be presented along with science results.

Tuesday, Jan. 29 (DOY 029):

An AACS prime reaction wheel (RWA) friction test on wheels 1, 2, and 4 was performed today. This test is performed every three months and allows the Spacecraft team (SCO) to collect statistics on wheel performance and health. For the test, the RWAs are spun up to 900 rpm in both directions and timed as they are allowed to spin down to 0 rpm. SCO is in the process of analyzing the results.

Today an official dedication was held in Von Karman Auditorium at JPL for a set of wall murals created by students from the Academia de Arte Yepes in Los Angeles, California. Using data obtained by Cassini since 2004, the students have created wonderful works of art representing many Cassini discoveries. The murals extend through the hallways from floor to ceiling of the Cassini Instrument Operations area at JPL and provide beautiful portraits of the Saturnian system. This week was selected for the dedication as it coincides with the 44th meeting of the PSG. Many members of the instrument teams have traveled to JPL for the meeting and a dedication this week allowed the scientists to view the murals first hand.

A Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference was held today. A member of the Magnetospheric Imaging Instrument (MIMI) team gave a presentation on Energetic Particles in Saturn's Rotating Magnetosphere.