NASA Cassini Significant Events for 12/02/04 – 12/08/04
The most recent spacecraft telemetry was acquired from the Madrid tracking
station on Wednesday, December 8. 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
http://saturn.jpl.nasa.gov/operations/present-position.cfm .
Science observations this week focused on the Composite Infrared
Spectrometer (CIRS) integration of the main rings with the mid-infrared
focal planes. This will give the first detailed temperature measurements
across the rings. Additionally, CIRS examined the oxygen compounds H2O and
CO2 in Saturn’s stratosphere as a function of latitude.
The Imaging Science Subsystem (ISS) continued to image small satellites for
orbit determination, the Ultraviolet Imaging Spectrograph continued to
capture mosaics of Saturn’s magnetosphere, and ISS captured a 3×3 movie of
the Saturnian southern hemisphere in several filters with the Narrow-Angle
Camera to measure wind speeds and map the occurrence of “moist” convection.
On-board activities this week included real time commands for the Cassini
Plasma Spectrometer (CAPS) to restart the master Instrument Expanded Block
(IEB), update the IMS sweep table and IEB for the Titan-B encounter, and
restart actuation after Probe activities in S06. All activities executed as
expected. Additional real time commanding included a test of the
Magnetometer Subsystem scalar magnetometer, a Cosmic Dust Analyzer (CDA) RPX
calibration, and closing of the main engine cover. The cover will remain
closed until after the Dione flyby on December 14.
The main event this week was the second probe battery depassivation . An
initial assessment indicates that the data looks exactly the same as for the
first depassivation in September of this year. The depassivation sequence
lasted for 35 minutes after which there was a 5-minute pause before the
Probe Safing sequence started. This lasted for 8 minutes and was run to
ensure that no battery remained connected to the Probe power bus. Each
battery exhibited essentially the same behavior during each of the 5 minute
depassivation periods, with voltages starting at ~65V and slowly increasing
to ~70V. Measurements on the bus side showed battery currents ~1.9A with a
similar value being measured from the Cassini line, which indicated an equal
sharing of the busload between battery and Cassini. Bus voltage was
rock-solid at 28V. All Probe systems are exhibiting normal behavior.
The Cassini-Huygens program held two reviews on December 2 to support the
mission commitment for the Huygens mission. The first was the Huygens Probe
checkout F16 review. All probe instruments and the probe engineering systems
reported and are nominal and ready to support the probe mission. The second
review was an internal readiness review to assess the program’s total
readiness to support mission. All necessary teams, flight products, and
subsystems were reported ready to support the mission.
The Mission Risk Review concluded its activities on December 6 with an
updated assessment of the entry and descent studies. Refined analyses with
the latest Titan atmosphere models have shown further margin in the heat
shield performance. Residual action items from the November 29 review were
closed. The final report will be presented on December 16.
On Tuesday the Navigation Team led a meeting to discuss the impacts of
canceling Orbital Trim Maneuver 7 (OTM). The meeting was attended by
representatives from Program Management, Spacecraft Operations, Science
Planning, and Uplink Operations. It was determined that there was no
compelling reason to perform the maneuver–delivery differences at Titan
with and without the maneuver were negligible, delta-V cost was a “wash”,
there was negligible change to instrument pointing, and there was nothing
new that OTM-7 would provide from a spacecraft perspective to make OTM-9 any
more accurate. The decision was made to cancel this maneuver.
The Titan Orbiter Science Team and Huygens Science Working Team hosted a
Titan-B Preview Meeting with a special Dione preview following. This was an
open meeting for anyone on the project who was interested in a preview of Tb
science, objectives and activities.
The Science and Sequence Update Process (SSUP) for tour sequence S07
concluded this week. A Final Sequence Integration and Validation (FSIV)
Sequence Change Request (SCR) approval meeting was held with 8 SCRs
dispositioned. Later in the week the fully integrated sequence products
were released, and the final sequence approval meeting was held. Uplink of
IEBs and the background sequence begins on December 11. S07 begins
execution on December 16.
Also in SSUP, a PSIV SCR approval meeting was held for S08, and as well as a
Preliminary SCR meeting where 14 SCRs were approved.
The Science Operations Plan (SOP) Update process for S09 concluded this
week. A Project Briefing and Waiver Disposition meeting was held and a
handoff package transferred to the Sequence Team leads. S09 has begun the
Sub-Sequence Generation (SSG) phase of SSUP with a kickoff meeting held on
Tuesday. The stripped subsequences were released for teams to populate, and
the SSG Science Allocation Panel meeting was cancelled, as there were no DSN
changes.
Official port#1 of the SOP Update process for S10 occurred last Friday. The
products were merged and sent to ACS for the end-to-end pointing validation.
S11 has concluded the Aftermarket process and begins SOPU next week.
Official port #1 for SOP Implementation of S39/S40 occurred this week along
with Preliminary Port #1 for S41. The team files for S39/S40 were merged
and delivered to ACS for end-to-end-pointing validation. The products for
S41 were merged, the preliminary port analysis performed, and reports
provided to the teams.
Mission Planning has released the Titan-B and Huygens/Titan-C Mission
Descriptions. The Titan-B document provides a brief, concise description of
encounter events, including an estimated playback schedule for all
instruments. Also included is a one-page “quick look” reference sheet.
Updates to the Huygens/Titan-C document include the addition of the Probe
Release timeline and an updated sequence layout chart.
A beautiful picture of Mimas against Saturn’s rings and shadows was
Astronomy Picture of the Day on December 2.
Cassini has an impressive collection of 131 papers being presented at the
Fall AGU meeting next week in San Francisco, California.
“Cassini Captures Saturn Moon Red-Handed.” The Cassini spacecraft has
witnessed Saturn’s moon Prometheus snatching particles from one of Saturn’s
rings. This and the most recent image advisory may be found on the Cassini
website at http://Saturn.jpl.nasa.gov.
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.