Status Report

NASA Cassini Significant Events for 05/05/05 – 05/11/05

By SpaceRef Editor
May 13, 2005
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NASA Cassini Significant Events for 05/05/05 – 05/11/05

The most recent spacecraft telemetry was acquired Wednesday from the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the “Present Position” web page located at rations/present-position.cfm .

Update on RSS Occultation Experiment

Last week the Cassini Radio Science Subsystem (RSS) along with the Radio Science Systems Group (RSSG) conducted their first ring and atmospheric occultation experiment, and broke a number of records in the process.

Three frequency bands were transmitted by the spacecraft and received at the stations of the Deep Space Network; S-, X-, and Ka-band at two polarizations in one-way mode referenced to the ultra stable oscillator.  Five stations supported occultation entry simultaneously.

A total of 14 open-loop receivers was operated remotely by the RSSG simultaneously, six Radio Science Receivers (RSR) at Goldstone, four at Canberra, and four Very Long Baseline Interferometry Receivers, two at each complex.

Each RSR was recording data at multiple bandwidths leading to a total of almost 200 GBytes of data.  This experiment also marked the first time ever of recording Ka-band science data over DSS-34.  A special spacecraft limb-tracking maneuver was utilized. This experiment was aimed at studying the ring structure, particle size distribution, and dynamics, as well as the ionospheric composition and atmospheric temperature-pressure profiles.

Among the other “firsts” achieved with this experiment are:

1- First diametric ingress-egress radio occultation of Saturn’s rings

2- First near-equatorial ingress-egress radio occultation of Saturn’s atmosphere and ionosphere

3- First planetary radio occultation conducted using three frequencies (X-, S-, and Ka-bands), transmitted simultaneously from a spacecraft.

4- First rings or atmospheric occultation conducted using Ka-band.

5- First detected forward scattered signal from Saturn’s rings observed at S- and Ka-band (X-band scattering was detected by Voyager).

6- First detectable man-made radio signals (X/S/Ka) observed during radio occultation by Saturn’s dense Ring B  (Voyager X/S signals were blocked by the optically thick Ring B).

Activities this week:

This week the Optical Remote Science instruments continued observations of Saturn. The Visual and Infrared Mapping Spectrometer (VIMS) imaged the entire rings system while Cassini was still near apoapse, the Ultraviolet Imaging Spectrograph (UVIS) performed mosaics of Saturn’s inner magnetosphere, and the fields and particles instruments performed a magnetospheric boundary campaign also near apoapse.

Thursday, May 5 (DOY 125):

Uplink Operations sent commands to the spacecraft today to execute a memory readout (MRO) for the Ion and Neutral Mass Spectrometer, clear the CDS error logs and execute MROs for CDS and ACS, verify and MRO all partitions, MRO the actions log, non interfering, and interfering error logs.  What can we say, it was an MRO kind of day. (:>)

Science Planning gave a Cassini presentation at a dinner for the CalTech Y support group. The event brought 110 people to JPL.

Cassini Outreach introduced Cassini education resources and the kids section of the website to 75 educators who host after school programs throughout the Los Angeles area. The educators spent the day at JPL learning about the different opportunities available to them.

Friday, May 6  (DOY 126):

The Cassini Imaging Science Team (ISS) has reported the discovery of a new satellite of Saturn, designated S/2005 S 1, orbiting within the Keeler gap in Saturn’s outer A ring.  The object had been previously inferred from the presence of features observed on the outer edge of the Keeler gap and was discovered in six images taken over 16 min on May 1 from a time-lapse sequence of narrow- angle-camera exposures that were targeted to the illuminated side of the outer edge of the A ring.

S/2005 S 1 was subsequently found in 32 (7 km/pixel) low-phase images taken of the F ring on Apr. 13  (spanning 18 min) and again in two high-resolution (3.54 km/pixel) low-phase images taken on May 2, when its 7-km disk was resolved.  The satellite orbits Saturn every 0.594 days at a distance of 136500 km.  The estimated geometric albedo is 0.5.  The data at this time are too coarse to yield any statistically significant orbital eccentricity or inclination.

The Spacecraft Operations Office (SCO) radiated an ACS Reaction Wheel Assembly bias to the spacecraft today.  The file will execute on DOY 133, Friday of next week.

System Engineering, the Mission Support and Services Office, and other interested stakeholders attended the Deep Space Mission Systems TPS V14.1 Jumpstart Server delivery review.  This is the fundamental software product that is used to upgrade all Cassini workstations prior to the installation of telemetry, command, Spacecraft Operations, and Mission Sequence Subsystem software.  The review identified no major problems.

ISS used the Automated Sequence Processor (ASP) process to load one of the two flight software patches.  This patch was not loaded at the last power cycle because it was still in development.

All teams and offices participated in this month’s NASA/Cassini Quarterly Review.

Monday, May 9 (DOY 129):

The S11 background sequence was approved today at a final sequence approval meeting.  Uplink of instrument expanded block (IEB) files began later in the day with the sequence itself scheduled to go up to the spacecraft on Wednesday.  Execution will begin on Friday the 13th.

SCO hosted an uplink readiness review for ACS flight software version A8.7.2.  This is a patch delivery that updates parameters.  The Software Review/Certification Requirements meeting will be held Wednesday and the software will be uplinked on May 26.

Wednesday, May 11 (DOY 131):

Science Planning hosted a Tour Science Talk today.  ISS presented some of their results on Enceladus.

ACS V8.7.2 passed its Software Review/Certification Requirements meeting and is now ready for uplink to the spacecraft.

The S13 Project Briefing / Waiver Approval Meeting was held today.  S13 is significant in that it is the first time the Program has had to consider splitting the background sequence into two parts. The reason for considering the split is that at this time in development it is just too large to fit into the region of memory assigned to the background sequence. Development is continuing and multiple avenues are being pursued both to reduce the size of the sequence and to develop the process necessary to successfully uplink a two-part sequence.  A final decision, to split or not, will be made in early June.

In a memo released today it was announced that a number of Cassini Flight team members are to be recognized with NASA Board Action Space Act Awards. Although the announcement was released this week, the actual ceremony will be held on June 21.  Recipients include developers for LMBRRK and Predicts software, Cassini Downlink and Reconciliation Architecture – Cassini Downlink and Reconciliation Subsystem (CDRS), Cassini Main Engine Cover Assembly, and Automation of Ground Processing to Track Spacecraft Memory.

Wrap up:

Check out the Cassini web site at for the latest press releases and images.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C.  JPL designed, developed and assembled the Cassini orbiter.

SpaceRef staff editor.