Cassini Significant Events 06/06/07 - 06/12/07

June 15, 2007

(Source: Cassini Project)


The most recent spacecraft telemetry was acquired on Tuesday, June 12, from the Goldstone 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" web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm.

Wednesday, June 6 (DOY 157):


Last week the process to develop, approve and uplink an S31 Radio Science (RSS) Live Movable Block (LMB) began. A kick-off meeting was held, and the block was generated using the latest available orbit determination (OD) solution from the #114 maneuver. Science Planning checked the OD solution and recommended an update to three targets in the same time frame as well. Both the RSS DOY 162 LMB sequence and the Atlas/Rhea Live Inertial Vector Propagator Update sequence will be uplinked along with the S31 background sequence on DOY 159 over the DSS-14 track.


Thursday, June 7 (DOY 158):


There have been three minor impacts to DSN allocations for S32 identified as a result of the adjusted Dawn launch date to July 7, and 25 minutes of downlink time on DOY 209 must be cut. A sequence change request was submitted to make this change. The request has been approved and the teams are working around the shortened time. In addition, DOY 214 is impacted by 15 minutes and DOY 219 impacted by 1 hour and 10 minutes.


Friday, June 8 (DOY 159):


In the final days of S30, the Ultraviolet Imaging Spectrograph (UVIS) performed observations of Enceladus, RADAR executed an engineering test, the Visual and Infrared Mapping Spectrometer (VIMS) and Imaging Science Subsystem (ISS) performed global mapping of Saturn, and all the Optical Remote Sensing (ORS) instrument teams hunted for lightning on Saturn. Additionally, the Magnetometer Subsystem performed the last calibration roll for this sequence.


Sunday, June 10 (DOY 161):


Orbit Trim Maneuver (OTM) #115 was performed today. This is the approach maneuver setting up for the Titan 32 encounter on June 13. The reaction control subsystem burn began at 6:30pm PDT. Telemetry immediately after the maneuver showed the burn duration was 25.5 seconds, giving a delta-V of 0.036 m/s. This maneuver was targeted to lower the upcoming T32 flyby altitude by 10 km, from 975 to 965 km. Navigation analysis showed that lowering the T32 closest approach would save about 2.5 m/sec in downstream maneuver sizes, and would bring the trajectory back closer to the reference trajectory. All subsystems reported nominal performance after the maneuver.


A new background sequence, S31, began execution on board the spacecraft today. The sequence will run for 33 days, concluding on July 14. During that time there will be two targeted encounters of Titan, twelve non-targeted flybys of Mimas, Atlas, Prometheus, Epimetheus, Methone, Tethys, Enceladus, and Rhea, and five maneuvers, numbers 116 through 120, are scheduled for execution.


At the beginning of S31, ORS instruments will be targeting Rhea with the Composite Infrared Spectrometer (CIRS) scanning the Rhea crescent and ISS and VIMS searching for dust clouds or dust rings. RSS will observe a rings occultation ingress at Ka, X and S band frequencies beginning at the F ring and ending at the D ring. Atmospheric ingress occultation observations will follow. VIMS will perform a high phase mosaic of the D ring before solar egress at 3 Rs.


Monday, June 11 (DOY 162):


Beginning on June 11, CDS Solid State Recorder (SSR) B was designated the prime recording device, with SSR-A moved to backup. This will eliminate over 70% of any bad bits to ground by avoiding recording on SSR-A sub-module 39 most of the time. As was reported in the Significant Events Report for May 29, 2007, SCO will uplink version 10 of CDS flight software this September. This will allow SSR-A sub-module 39 to be "turned off" as well as any other sub-modules that may fail in the Dynamic Random Access Memory (DRAM) at some future time. Sub-module isolation capability may become more important as the spacecraft ages. FYI, each sub module makes up less than one percent of the memory capacity of each of the two SSRs.


Today ISS performed global color mapping of Mimas during a non-targeted flyby.


Around that same time, Spacecraft Operations (SCO) closed - or deployed - the main engine (ME) cover as a precaution against dust impacts during the ring plane crossing. In addition, the High Gain Antenna was pointed to the ring particle ram direction, and the backup Sun Sensor Assembly (SSA) was powered on. The cover will remain closed for about 24 hours and will be reopened - or stowed - before the Titan 32 flyby. This will be the 32nd ME cover cycle since launch. The cover was last used on October 12, 2006, when it was stowed prior to OTM-77. The backup SSA will be turned off via real-time commands on June 12.


Additional science observations at the start of S31 include the Ion and Neutral Mass Spectrometer (INMS) obtaining an inner magnetospheric scan, and ISS taking images for a continuing orbit determination study of new ring gap satellites, performing a high resolution radial scan of one ansa of the main rings, and undertaking zero phase photometry of the A and B rings.


Tuesday, June 12 (DOY 163):


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

Heads Up:

The Titan 32 flyby occurred on Wednesday, June 13. Details of the flyby will be reported next week.