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.
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