Cassini Significant Events 11/23/11 - 11/29/11
Title: Cassini Significant Events 11/23/11 -
The most recent spacecraft telemetry was acquired on Nov. 29 from
the Deep Space Network tracking complex at Goldstone, California.
The Cassini spacecraft is in an excellent state of health and with the
exception of the CAPS instrument being powered off, 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/mission/presentposition/.
Wednesday, Nov. 23 (DOY 327)
Orbit Trim Maneuver (OTM) #300 was performed today. This was the
periapsis maneuver setting up for the Titan 79 encounter on Dec. 13.
The main engine burn began at 10:45 PM PST. Telemetry
immediately after the maneuver showed a burn duration of 17.175
seconds, giving a delta-V of 2.969 m/s. While the maneuver targets to
T79, the next encounter is actually a 100 km flyby of Dione (D3),
taking place one day before the T79 encounter. Additional effort is
required to make sure T79 should be targeted rather than D3, since not
both can be independently targeted, and to make sure the resulting
untargeted flyby is still safe. All subsystems reported nominal
performance after the maneuver.
Today the backup Sun Sensor Assembly (SSA B) was powered on in
preparation for tomorrow's dust crossing; it will be turned off via
real time command (RTC) on DOY 331.
A non-targeted flyby of Helene occurred today.
Thursday, Nov. 24 (DOY 328)
This week, while the spacecraft was near periapsis, science
observations began with the Imaging Science (ISS ) and other optical
remote sensing instruments monitoring clouds in Titan's atmosphere
from a range of 2.1 million kilometers. The Ultraviolet Imaging
Spectrograph (UVIS), ISS and the Visual and Infrared Mapping
Spectrometer (VIMS) observed Saturn's auroral oval for 10 hours.
Around periapsis, the Cosmic Dust Analyzer (CDA) made measurements of
the dust environment during the ring plane crossing. UVIS then
performed a 3 hour calibration using the star Spica. The
Composite Infrared Spectrometer (CIRS), ISS, and VIMS completed an 18
hour observation of the faint ring arcs at low elevation and low
phase, followed by a 14.5 hour light-curve observation of the outer
irregular moon Thrymr performed by ISS and VIMS. CIRS, ISS and
VIMS later performed a 15.5 hour Titan composition observation, and
CDA made a 13 hour interstellar dust observation.
Concluding the week, ISS observed a set of some of Saturn's small
inner moons, including Epimetheus and Methone.
Non-targeted flybys of Enceladus, Epimetheus, and Titan occurred
Friday, Nov. 25 (DOY 329)
The main engine cover was closed yesterday prior to the dust crossing
for dust hazard avoidance and was opened today. This was the
69th in-flight cycle of the cover.
Saturday, Nov. 26 (DOY 330)
OTM-300A and OTM-301, both statistical maneuvers targeting to T79, are
scheduled to execute on December 1 and 9 respectively. After the
post OTM-300 orbit determination solution is available, one of these
maneuvers will likely end up with a deterministic component.
Sunday, Nov. 27 (DOY 331)
A non-targeted encounter of Titan occurred today.
Monday, Nov. 28 (DOY 332)
The CDA - High Rate Detector (HRD) recovery command file was
uplinked today over Goldstone's DSS-14 station and is due to execute
on the spacecraft on 2011-334T15:30. This is in response to two
separate recent incidents. The HRD instrument stopped generating
data after 2011-310T23:26; this is currently under investigation.
The CDA instrument also underwent a known anomaly on DOY
2011-327T21:59 when a checksum showed an error. The spacecraft was in
the E-ring at the time and the CDA instrument has seen this occur
there before. A reset/reload activity is needed to get CDA back
into a normal operating state. Execution of the command going up
on DOY 334/335 includes reset/reload, HRD calibration, and other
tests. Once the results are on the ground, additional real time
commanding will ensure proper functioning of the instrument for the
upcoming Dione flyby on Dec. 12.
An insider's feature story called "Dr. Jean-Pierre Lebreton,
Huygens, and a Salute to the Mars Science Laboratory" is
available on the Cassini web site. It describes an interview
with Jean-Pierre Lebreton, the European Space Agency (ESA) Project
Scientist for the Huygens mission, just as he retired from a
decades-long career with ESA. Though he remains active in research,
Dr. Lebreton's departure from ESA is a noteworthy milestone, and this
article also honors his many contributions to space science in general
and Cassini-Huygens in particular. For images and more
information on this subject, link to:
Tuesday, Nov. 29 (DOY 333)
The most recent Cassini-Huygens Analysis and Results of the Mission
(CHARM) teleconference was held today. The topic:
"Powerhouses to PacPeople: An update on the recent discoveries by
Cassini/CIRS on the nature of the Saturnian satellite surfaces."
A PDF of the presentation package is available at:
An audio recording of the presentation was made and will be linked to
the same location within a few days.
In June, the decision to turn off the Cassini Plasma Spectrometer
(CAPS) was made as a precautionary measure in light of shifting
spacecraft bus voltages attributed to malfunctions in the instrument.
An analysis of this situation has been initiated at the NASA
Engineering and Safety Center (NESC), with a report expected in
January 2012. The final decision regarding whether or not to
turn the instrument back on will be made some time after the release
of this report.
Preliminary Sequence Integration and Validation (PSIV) Spacecraft
Activity Sequence File (SASF) products were due today as part of the
S72 Sequence Implementation Process (SIP).
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