Cassini Significant Events 02/28/07 - 03/06/07

March 8, 2007

(Source: Cassini Project)


The most recent spacecraft telemetry was acquired on Tuesday, March 6, 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 at http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Wednesday, Feb. 28 (DOY 059):


Part two of the S28 background sequence was uplinked to the spacecraft today. Due to its size, the sequence was split in order to avoid having to remove any science or engineering activities. Part two is registered on board, will begin execution on March 15, and will clock out for the remaining 14 days of the sequence.


As reported last week, an AACS Inertial Reference Unit (IRU) calibration completed yesterday. This calibration was performed with the IRU-A scale factor corrections that were uplinked recently with the A8.7.5 AACS flight software (FSW) update. After examining telemetry from the spacecraft, it has been determined that the new values reduce the residual per-axis gyro scale factor errors by at least a factor of eight. This improvement will be seen when a star id suspend period ends, and attitude propagated by the gyro and that determined from the SRU are compared. AACS expects these values to remain valid for about two years.


As part of the Cassini Extended Mission NASA Senior Review, held on February 15, four Cassini scientists gave presentations on the value of the science that will be obtained during the two-year period from 2008 to 2010. The presentations were extremely captivating. As a result, Science Planning requested that these four individuals give their presentations to the flight team. The first occurred today as part of the Program internal Tour Science Talks. The other three presentations will occur over the next several weeks.


Thursday, March 1 (DOY 060):


On March 14, a naming ceremony for the Huygens Probe landing site will be held at the European Space Agency (ESA) Headquarters. ESA, the international Committee for Space Research (COSPAR), and NASA have decided to honor Professor Hubert Curien's contribution to European space activities by naming the Huygens landing site on Titan after him. The part played by ESA in the Huygens landing, in cooperation with NASA and the Italian Space Agency (ASI), was made possible thanks to the commitment of Curien who, for several decades, worked to promote and strengthen the role of scientific research in his home country - France - and in Europe. Among his numerous responsibilities, Hubert Curien was French Minister of Research and Space under four Prime Ministers. For more information link to the ESA and Cassini websites.


Friday, March 2 (DOY 061):


Orbit Trim Maneuver (OTM) #96 was performed today. This is the apoapsis maneuver setting up for the Titan 26 encounter on March 10. The main engine burn began at 11:59 PM PST. Telemetry immediately after the maneuver showed the burn duration was 4.08 seconds, giving a delta-V of 0.67 m/s. All subsystems reported nominal performance after the maneuver.


Sunday, March 4 (DOY 063):


Flight Software (FSW) A8.7.5 normalization was successfully completed on board the spacecraft today. Although the software was uplinked in early February of this year, the Spacecraft Team decided to wait till after the IRU calibration on Wednesday, Feb. 28, before performing normalization. The process of normalization involves placing identical copies of the software on all four partitions on the SSR, then performing memory readouts to verify all copies are correct. AACS now has A8.7.5-32 on default partitions 0 through 3 on both SSR-A and SSR-B. The next update to AACS flight software is scheduled for early 2008.


Monday, March 5 (DOY 064):


The Aftermarket Process for the S33 sequence covering orbits 49 and 50 begins today. This 5-week process will address proposed changes that require re-integration of the science segments contained in the S33 sequence. All proposed changes are to be submitted by end-of-day today. If all of the requested changes do not fit, there will be an assessment meeting held on March 7, where the Project Scientist will review the requests. If necessary, on Tuesday, March 20, a final decision meeting will be held to decide what changes will be made to the S33 plan. The approved changes will then be integrated by the appropriate target working teams or orbiter science teams.


In support of S30, a test has been planned in the Integrated Test Laboratory for solar occultation ingress & egress and rings egress on DOY 130 for Radio Science, the Titan 30 flyby on DOY132 for RADAR and Spacecraft Operations (SCO), and Titan 31 ingress & egress on DOY148 for Radio Science. The tests are currently scheduled for March 23-29. The details are yet to be worked and will be addressed at the S30 Simulation Coordination Meeting. The length of the test is unusually long and as a result, the S30 development process will be compressed to accommodate it.


A delivery coordination meeting was held today for the SCO tool Maneuver Automation Software (MAS) version 6.1.1. MAS is an application used to generate maneuvers based on maneuver parameters, and generate reaction wheel bias (RWA) commands. With this software, the maneuver commands and RWA biasing may also be merged with a specified background sequence. Output products and comparison reports are created throughout these processes. The MAS software automates and verifies as much of the maneuver, RWA bias, and merge generation processes as possible.


Tuesday, March 6 (DOY 065):


The orbit determination solution using tracking data through 3 PM today converged sufficiently to allow the OTM-97 maneuver decision to be based on today's orbit solution. Using today's data, OTM-97 has a delta-V of 6 mm/s. The cost of cancellation on the downstream maneuvers is estimated to be about 0.4 m/s. Given the reasonable delta-V cost of canceling the maneuver, and the difficulties associated with implementing such a small maneuver, the Program manager has decided to cancel the maneuver. There will be a command approval meeting tomorrow for an RWA bias in lieu of OTM-97.


Last week images and movies were released of views of Saturn and the rings taken from a highly inclined orbit. Today one of those images was showcased as Astronomy Picture of the Day. The direct link to the image may be found at:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=2509


The high inclination views of Saturn mentioned for the last few weeks are the visible documentation of a pi transfer completed with the Titan 25 flyby. Cassini's orbital inclination between T24 and T25 was approximately 59 degrees. From T25 through T33, the inclination will be lowered back nearly into Saturn's equatorial plane. Prior to the pi-transfer, Titan flybys and apoapsis, the farthest distance of Cassini from Saturn in a given orbit, had occurred on the night side of Saturn in order to support magnetotail observations. Now they occur on the dayside of Saturn offering several low altitude Titan flybys and favorable ring observation geometry to the science community.