Cassini Update - November 30, 2007
- From: baalke@xxxxxxxxxxxxx
- Date: Fri, 30 Nov 2007 09:43:18 -0800 (PST)
Cassini Significant Events
for 11/14/07 - 11/27/07
Due to the Thanksgiving holiday, this report covers two weeks instead
of
the usual one week.
The most recent spacecraft telemetry was acquired on Tuesday, Nov. 27,
from the Madrid 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" page at:
http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, Nov. 14 (DOY 318):
A member of the Cassini AACS team gave a presentation on "Status of
Cassini Reaction Wheels at Launch +10.074 Years" to various levels of
JPL management today.
A Delivery Coordination Meeting (DCM) was held addressing two software
deliveries. Both are for updated Spacecraft Operations (SCO) ground
software tools in order to make them compatible with the new CDS V10
flight software. The first is the Downlink Uplink Coherency Tool
(DUCT),
which inserts a 5-minute playback pause at the one-way-to-two-way
transition in every downlink. This tool was created to automatically
pause playback so that no science data is lost during the brief
telemetry outage that occurs during this transition. The second is the
Assisted Load Format (ALF) tool used with instrument expanded block
files.
Today ring science was the focus for Imaging Science, the
Magnetospheric
and Plasma Science (MAPS) instruments, and RADAR. Probing the rings at
wavelengths of 2 centimeters, the goal of the RADAR team is to
determine
the rings' global properties, as well as image the rings at
wavelengths
much longer than those used by the ORS suite of instruments.
Thursday, Nov. 15 (DOY 319):
Orbit Trim Maneuver (OTM) #133 was performed today. This is the
approach
maneuver setting up for the Titan 37 encounter on Nov. 18. The
reaction
control subsystem (RCS) burn began at 8:14 AM PST. Telemetry
immediately
after the maneuver showed the burn duration was 50.75 seconds, giving
a
delta-V of 0.067 m/s, as planned. All subsystems reported nominal
performance after the maneuver. For the first time, a reaction wheel
bias was performed in the background sequence before the OTM. This was
done at the request of the Navigation team to ensure that a bias
occurred over that pass regardless of the OTM status.
Friday, Nov. 16 (DOY 320):
The Satellite Orbiter Science Team (SOST) held its first meeting to
integrate the Enceladus flybys in the proposed Extended Mission (XM).
Meanwhile, XM integration activities continue for the rest of the
Target
Working Teams.
On DOY 320, Cassini made non-targeted flybys of Rhea and Pandora.
Closest approach for Rhea was 91,537 km from the moon. As the
spacecraft
approached the satellite, the Optical Remote Sensing (ORS) instruments
conducted a coordinated campaign to observe Rhea, with the Visual and
Infrared Mapping Spectrometer (VIMS), Ultraviolet Imaging Spectrograph
(UVIS), and Composite Infrared Spectrometer (CIRS) teams, in turn,
controlling the pointing of the spacecraft. Some of the goals of these
observations are to constrain the shape of this moon, which has
implications for its internal structure and evolutionary history, and
to
measure the ultraviolet albedo. Following the ORS observations, the
Cosmic Dust Analyzer (CDA) began a series of observations, sampling
the
particles in the vicinity of Rhea as the spacecraft crossed Rhea's
orbit. This was followed by a second coordinated Rhea observation
campaign by the ORS instruments.
Saturday, Nov. 17 (DOY 321)
Non-targeted flybys occurred today with Pan, Epimetheus, and Calypso.
The first real-time Radio and Plasma Wave Science (RPWS) Whistler
event
occurred today at ~32 hours prior to T37. "Whistlers" are waves that
result from lightning in the clouds of Saturn. Over the last few days,
trigger commands have been sent to the instrument in preparation for
the
event. For this activity, the spacecraft will transition into and out
of
RCS control during a 9-hour downlink pass.
Sunday, Nov. 18 (DOY 322)
Titan T37 closest approach occurred at 2007-323T00:56:25 Spacecraft
Event Time. The spacecraft flew past at 1,000 km altitude, and used
393.6 grams of hydrazine for science pointing and attitude control,
within 10% of predict. Owing to the relatively low altitude of the
flyby, it was expected that Cassini would pass through Titan's
ionosphere. Prior to the flyby, the orbit period was about 24 days, at
5
deg inclination. The encounter reduced the Saturn orbit period to 16
days and increased the inclination to 12.3 degrees, beginning a series
of Titan encounters that will increase the inclination to about 75 deg
before end of prime mission.
As Cassini made its closest approach to Titan, the Ion and Neutral
Mass
Spectrometer (INMS) sampled the upper reaches of Titan's atmosphere,
measuring composition and thermal structure. This was followed by VIMS
observations to perform high resolution mapping of Titan for geology
and
composition, as well as mapping the limb of Titan and Titan's cloud
distribution.
ISS monitored the atmosphere for lightning and aurorae, and obtained
data for a series of regional and global scale mosaics. The area
imaged
in the regional mosaic, northwest of Ederi, is complementary to that
area imaged in T35 northeast of Ederi. UVIS obtained spectral images
of
Titan in the Extreme Ultraviolet and Far Ultraviolet to map the aurora
and day glow, to map hydrocarbon absorption, and to measure scattering
and absorption by aerosols in the stratosphere. CIRS obtained
measurements during this Titan flyby to carry out vertical temperature
sounding of Titan's tropopause and stratosphere, and to learn about
the
distribution of various components of Titan's atmosphere, such as
methane, water, carbon monoxide and aerosols.
The MAPS teams undertook an investigation of the large-scale and
distant
aspects of the interaction between Titan and the magnetosphere. The
Magnetometer Subsystem (MAG) compared data taken on this flyby with
that
taken during T36 to look for temporal variations in the magnetic field
in the wake/south polar region. RPWS took advantage of the
spacecraft's
close wake passage near the southern boundary of the geometric wake.
Tuesday, Nov. 20 (DOY 324)
A member of the Cassini Spacecraft Operations Office flew home for the
holiday this week. As part of his vacation, the plan was to give a JPL
overview presentation for all students K-12 in Greensburg, KS. The
problem was, Greensburg no longer existed. Six months ago, Greensburg
was a thriving county seat of 1600 people, block after block of nice
houses and businesses. On May 4, 2007, an F5 tornado leveled the town,
destroying over 95% of the town's buildings.
In showing the frontier spirit of the town, most folks have moved back
-
using FEMA trailers - and they decided NOT to disperse the school kids
far and wide, but rather to hold school in town, again, in FEMA
trailers. In honor of the completion of the first permanent school
building, the gym, the show went on! Over two hundred students were
given the presentation they were meant to have and were presented with
as many NASA goodies as could be sent to them in advance and packed on
the plane with the presenter.
Thursday, Nov. 22 (DOY 326):
JPL Holiday
OTM-134 was performed today. This is the cleanup maneuver from the T37
encounter on Nov. 19. The main engine burn began at 12:14 AM PST.
Telemetry immediately after the maneuver showed the burn duration was
7.2 seconds, giving a delta-V of 1.17 m/sec. All subsystems reported
nominal performance after the maneuver.
Friday, Nov. 23 (DOY 327):
JPL Holiday
The MAPS instruments continued their solar wind monitoring campaign,
with the Magnetospheric Imaging Instrument (MIMI) pointing the
spacecraft during science observation periods. MIMI briefly turned the
spacecraft towards Iapetus for ISS and UVIS observations on DOY 328.
Monday, Nov. 26 (DOY 330)
OTM-135 was performed today. This is the apoapsis maneuver setting up
for the Titan 38 encounter on Dec. 5. The main engine burn began at
11:59:56 PM PST. Telemetry immediately after the maneuver showed the
burn duration was 96.5 seconds, giving a delta-V of 15.75 m/s. All
subsystems reported nominal performance after the maneuver.
Navigation delivered the necessary orbit determination files today for
the DOY 336-337 Mimas/Epimetheus Live Update process. A kick-off
meeting
was held today and then participants went off to review the data. So
far, inputs from the teams have recommended going with the update. It
will be uplinked on Thursday or Friday of this week and begin
execution
Sunday, Dec. 2.
Science today included Cassini Plasma Spectrometer (CAPS) observations
of the dusk-side magnetospheric boundary at a variety of latitudes, a
UVIS study of the Saturn aurorae, ISS imaging of Telesto, Janus,
Pandora, Methone and Calypso to better determine their orbital
characteristics, and observations of the distant satellite Erriapo.
Tuesday, Nov. 27 (DOY 331)
At the Mission Planning Forum today the topics of discussion were 1)
New
telemetry modes for the proposed extended mission, and 2) Plans for
Main
Engine Cover operations after the project has exceeded the originally
predicted 37 cycles of use.
The final sequence development process for S38 kicked off today. The
process will complete mid February next year with execution beginning
on
Feb. 16. Issues discussed included the status of the currently posted
seven S38 waiver requests, the possible loss of the last DSN track in
the sequence, and the upcoming effort to re-evaluate the Enceladus
custom period with CIRS to possibly submit a sequence change request.
In
addition, S39 development continued with teams delivering products for
the preliminary port.
A Cassini-Huygens Analysis and Results of the Mission (CHARM)
teleconference was held today. The topic for this month was The Lakes
and Seas of Titan: Observations from Cassini RADAR.
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