Cassini Update - June 15, 2007
- From: baalke@xxxxxxxxxxxxx
- Date: Fri, 15 Jun 2007 11:10:24 -0700
Cassini Significant Events
for 06/06/07 - 06/12/07
The most recent spacecraft telemetry was acquired on Tuesday, June 12,
from
the Goldstone 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" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, June 6 (DOY 157):
Last week the process to develop, approve and uplink an S31 Radio
Science
(RSS) Live Movable Block (LMB) began. A kick-off meeting was held,
and the
block was generated using the latest available orbit determination
(OD)
solution from the #114 maneuver. Science Planning checked the OD
solution
and recommended an update to three targets in the same time frame as
well.
Both the RSS DOY 162 LMB sequence and the Atlas/Rhea Live Inertial
Vector
Propagator Update sequence will be uplinked along with the S31
background
sequence on DOY 159 over the DSS-14 track.
Thursday, June 7 (DOY 158):
There have been three minor impacts to DSN allocations for S32
identified as
a result of the adjusted Dawn launch date to July 7, and 25 minutes of
downlink time on DOY 209 must be cut. A sequence change request was
submitted to make this change. The request has been approved and the
teams
are working around the shortened time. In addition, DOY 214 is
impacted by
15 minutes and DOY 219 impacted by 1 hour and 10 minutes.
Friday, June 8 (DOY 159):
In the final days of S30, the Ultraviolet Imaging Spectrograph (UVIS)
performed observations of Enceladus, RADAR executed an engineering
test, the
Visual and Infrared Mapping Spectrometer (VIMS) and Imaging Science
Subsystem (ISS) performed global mapping of Saturn, and all the
Optical
Remote Sensing (ORS) instrument teams hunted for lightning on Saturn.
Additionally, the Magnetometer Subsystem performed the last
calibration roll
for this sequence.
Sunday, June 10 (DOY 161):
Orbit Trim Maneuver (OTM) #115 was performed today. This is the
approach
maneuver setting up for the Titan 32 encounter on June 13. The
reaction
control subsystem burn began at 6:30pm PDT. Telemetry immediately
after the
maneuver showed the burn duration was 25.5 seconds, giving a delta-V
of
0.036 m/s. This maneuver was targeted to lower the upcoming T32 flyby
altitude by 10 km, from 975 to 965 km. Navigation analysis showed that
lowering the T32 closest approach would save about 2.5 m/sec in
downstream
maneuver sizes, and would bring the trajectory back closer to the
reference
trajectory. All subsystems reported nominal performance after the
maneuver.
A new background sequence, S31, began execution on board the
spacecraft
today. The sequence will run for 33 days, concluding on July 14.
During
that time there will be two targeted encounters of Titan, twelve
non-targeted flybys of Mimas, Atlas, Prometheus, Epimetheus, Methone,
Tethys, Enceladus, and Rhea, and five maneuvers, numbers 116 through
120,
are scheduled for execution.
At the beginning of S31, ORS instruments will be targeting Rhea with
the
Composite Infrared Spectrometer (CIRS) scanning the Rhea crescent and
ISS
and VIMS searching for dust clouds or dust rings. RSS will observe a
rings
occultation ingress at Ka, X and S band frequencies beginning at the F
ring
and ending at the D ring. Atmospheric ingress occultation
observations will
follow. VIMS will perform a high phase mosaic of the D ring before
solar
egress at 3 Rs.
Monday, June 11 (DOY 162):
Beginning on June 11, CDS Solid State Recorder (SSR) B was designated
the
prime recording device, with SSR-A moved to backup. This will
eliminate
over 70% of any bad bits to ground by avoiding recording on SSR-A sub-
module
39 most of the time. As was reported in the Significant Events Report
for
May 29, 2007, SCO will uplink version 10 of CDS flight software this
September. This will allow SSR-A sub-module 39 to be "turned off" as
well as
any other sub-modules that may fail in the Dynamic Random Access
Memory
(DRAM) at some future time. Sub-module isolation capability may
become more
important as the spacecraft ages. FYI, each sub module makes up less
than
one percent of the memory capacity of each of the two SSRs.
Today ISS performed global color mapping of Mimas during a non-
targeted
flyby.
Around that same time, Spacecraft Operations (SCO) closed - or
deployed -
the main engine (ME) cover as a precaution against dust impacts during
the
ring plane crossing. In addition, the High Gain Antenna was pointed
to the
ring particle ram direction, and the backup Sun Sensor Assembly (SSA)
was
powered on. The cover will remain closed for about 24 hours and will
be
reopened - or stowed - before the Titan 32 flyby. This will be the
32nd ME
cover cycle since launch. The cover was last used on October 12,
2006, when
it was stowed prior to OTM-77. The backup SSA will be turned off via
real-time commands on June 12.
Additional science observations at the start of S31 include the Ion
and
Neutral Mass Spectrometer (INMS) obtaining an inner magnetospheric
scan, and
ISS taking images for a continuing orbit determination study of new
ring gap
satellites, performing a high resolution radial scan of one ansa of
the main
rings, and undertaking zero phase photometry of the A and B rings.
Tuesday, June 12 (DOY 163):
Non-targeted flybys of Atlas, Prometheus, Epimetheus, and Methone
occurred
today.
Heads Up:
The Titan 32 flyby will occur on Wednesday, June 13. Details of the
flyby
will be reported next week.
Wrap up:
Check out the Cassini web site at http://saturn.jpl.nasa.gov for the
latest
press releases and images.
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.
.
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