From: Jet Propulsion Laboratory
Posted: Tuesday, October 20, 2009
The most recent spacecraft telemetry was acquired on Oct. 13 from the Deep Space Network tracking complex at Madrid, Spain. 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: http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, Oct. 7 (DOY 280):
The Science Operations Plan process for S59 kicked off today. The first delivery port for this sequence will not occur until Nov. 9, after the flight team has had a chance to review the results of the Enceladus 7 flyby, and determine if E9, occurring within S59, will use reaction wheels or thrusters. In order to prevent a delay in development, two versions of the flyby sequence have been developed, one on wheels, and one on thrusters. Only one of these will proceed past port 1.
Thursday, Oct. 8 (DOY 281):
An Instrument Operations Working Group meeting was held today to brief instrument personnel on various topics. This particular presentation was aimed at the Operations Team Leads and engineers responsible for telemetry processing. In addition, a demonstration was given on the new MPS editor, the SEQGEN GUI on Solaris 10.
Friday, Oct. 9 (DOY 282):
Orbit Trim Maneuver (OTM) #217 was performed today. This was the approach maneuver setting up for the Titan 62 encounter on Oct. 12. The Reaction Control Subsystem burn began at 5:30 AM PDT. Telemetry immediately after the maneuver showed the burn duration was 130.13 seconds, giving a delta-V of 0.15 m/s. All subsystems reported nominal performance after the maneuver.
The S54 DOY-286 Live Inertial Vector Propagator update for Rhea, Tethys, and Enceladus was uplinked on today at 17:27:51 UTC. Radiation was nominal, and it has been confirmed as registered onboard.
Saturday, Oct. 10 (DOY 283):
Today the Composite Infrared Spectrometer (CIRS) measured oxygen compounds, both H2O and CO2, in Saturn's stratosphere as a function of latitude. Afterwards the Cassini Plasma Spectrometer concluded its solar wind-aurora campaign with a final 3-hour observation. The day finished with data collection for the bi-annual Scientist for a Day outreach activity. The spacecraft obtained images of three possible targets, Saturn and the rings, Tethys with Saturn's rings, and Titan. The data will be returned to Earth on the next downlink. After reviewing essays submitted by participating students, winners will be selected and the results presented at a live teleconference on Oct. 20.
Monday, Oct. 12 (DOY 285)
Monday was a very busy day for those involved in sequence development. As part of the ongoing Science Operations Plan (SOP) processes, a port 3 delivery was due today for S57, and a port 2 delivery for S58. Last Friday Science Planners handed off all products for S56 to Uplink Operations for the final development process. Tomorrow a kick off meeting for that process will be held.
The main engine cover was closed/deployed today for dust hazard avoidance. It will be opened/stowed again on Oct. 14. This is the 51st in-flight cycle for the cover.
On Oct. 12, Cassini flew by Titan at an altitude of 1300 km and a speed of 6 kilometers per second. Closest approach for T62 occurred at 3:02 AM PDT, latitude 64 degrees S. This flyby marked Cassini's return to more nearly equatorial orbits, setting up the spacecraft for future close encounters with icy moons.
For T62, the Ultraviolet Imaging Spectrograph (UVIS) performed a self-calibrating solar occultation observation; the information came from a ratio of signal during occultation to signal of the unocculted sun or star just before and after occultation.
Solar occultations by Titan are the most valuable Titan observations for UVIS. They provide detailed vertical profiles of N, N2, and some hydrocarbons to more than 3000 km altitude. Solar occultation measurements give a measure of the density profile of the main constituents of the atmosphere, and the rate of change of the N2 density with altitude gives information on the temperature.
UVIS also conducted Extreme Ultraviolet and Far Ultraviolet observations during this flyby. These observations give information on airglow, hydrocarbon absorptions, haze and optical properties globally, but with lower vertical resolution.
The Visual and Infrared Mapping Spectrometer (VIMS) observed the formation, evolution, and decay of clouds, particularly mid-latitude and equatorial clouds. In ride-along mode, a solar occultation provided information on the vertical structure and composition of Titan's atmosphere and haze layer. VIMS also obtained a global map of the western region of Senkyo.
CIRS carried out far-infrared limb sounding at 70 and 75 degrees latitude South to collect information on the atmospheric temperature, aerosols, and composition. ISS acquired a full-disk mosaic of western Senkyo at low phase angles, and rode along with VIMS to monitor clouds.
T62 was a south polar, post-dusk flyby. Magnetometer (MAG) measurements provided a description of the draping and the pileup of the external magnetic field around Titan near the terminator. This will be a good complement to the data set acquired at T52-T61 and be used to characterize the background field for a similar local time with respect to Saturn and different SKR longitudes.
Radio and Plasma Wave Science (RPWS) measured thermal plasmas in Titan's ionosphere and surrounding environment; searched for lightning in Titan's atmosphere, and investigated the interaction of Titan with Saturn's magnetosphere.
Tuesday, Oct. 13 (DOY 286)
A non-targeted flyby of Rhea occurred today.
The topic at the Mission Planning Forum today was Y-thruster bias plans and strategies. In recent weeks the project has studied the options and met to review implementing reaction wheel biases using the Y-facing thrusters with S60 as the target start sequence. These new biases will be performed after the spacecraft turns to the delta-momentum vector. This saves hydrazine, and uses the Y-thrusters rather than the Z-thrusters, which will better balance the hydrazine throughput between the Y and Z thrusters, and therefore perhaps a longer life span for the B-branch thrusters. After studying various options, a final plan has been achieved, and was presented along with implementation specifics and details on what flexibilities exist for integration.
Visit the JPL Cassini home page for more information about the Cassini Project: http://saturn.jpl.nasa.gov/
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