|
|
|
|
|
Posted by baalke on September 7, 2007, 5:06 pm
Please log in for more thread options
Cassini Significant Events
for 08/29/07 - 09/04/07
The most recent spacecraft telemetry was acquired on Tuesday,
September 4,
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, August 29 (DOY 241):
Cassini passed Tethys today for a non-targeted flyby at a distance of
55,499 km. The Optical Remote Sensing (ORS) instruments performed
imaging
and mapping activities, and obtained measurements of the ultraviolet
albedo
across both longitude and phase space. Additional science activities
included an F-Ring rotation movie and raster scans of the north and
south
regions of Saturn by the Composite Infrared Spectrometer (CIRS), and
scatterometry and radiometry observations of Phoebe performed by
RADAR.
Thursday, August 30 (DOY 242.):
The day after Tethys, Cassini encountered Rhea during the outbound leg
of
orbit 49. Closest approach was 5,737 km at a phase angle of 46 deg.
The Rhea
science observations included Imaging Science Subsystem (ISS) mosaics,
an
Ultraviolet Imaging Spectrograph (UVIS) map of the surface albedo of
Rhea in
UV and limb drifts to determine atmospheric scattering, and CIRS high
spatial resolution mapping. In addition to the ORS observations, the
suite
of Magnetospheric and Plasma Science (MAPS) instruments, which
includes the
Cassini Plasma Spectrometer (CAPS), Cosmic Dust Analyzer (CDA), Ion
and
Neutral Mass Spectrometer (INMS), Magnetometer Subsystem (MAG),
Magnetospheric Imaging Instrument (MIMI), and Radio and Plasma Wave
Science
(RPWS), simultaneously performed low-rate magnetospheric surveys. The
live
update commands uplinked to the spacecraft on Aug. 28 were extremely
successful. Very detailed images of a crater of interest have been
returned
and the scientists are quite excited.
Using the latest orbit determination (OD) solution, the maneuver team
has
been able to show that there is virtually no difference between the
trajectory to Iapetus with or without OTM-126. Further, the current
prediction is that OTM-126 would be very small and might have to be
cancelled as a result of being below the minimum delta V. There was
no
mission delta V penalty associated with deleting OTM 126. The current
OD
solution has a relatively large uncertainty. The consensus of flight
team
members was that even if there were sizeable changes in the OD
solutions,
the conclusions relative to the deletion of OTM-126 would not change.
Therefore OTM 126 is now deleted.
Near midnight, Cassini began observations for the Titan T35 targeted
encounter. Closest approach was at an altitude of 3,326 km, a speed
of 6.1
km/sec, outbound from Saturn at a phase angle of 87 degrees. The main
engine
cover was reopened just prior to the encounter. This flyby placed
Cassini
on a course to conduct the closest flyby of Iapetus that will be
performed
during the entire mission. On Sept. 10, Cassini will come within 1,650
kilometers from the surface of Iapetus. For more information on the
Iapetus
flyby link to:
http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=771
You may see differences in the date reported for when the T35 flyby
occurred. Was it the 30th or the 31st? The answer lies in Spacecraft
Event
Time (SCET), which is always stated in GMT at the spacecraft. Closest
approach for Titan was at 2007-243T05:32:34 SCET. DOY 243 = August
31.
But, when you convert SCET to Pacific Daylight Time, the time moves
earlier
and lands on the 30th. FYI.
Friday, August 31 (DOY 243):
Science for the Titan flyby included CIRS measurements of CH4 levels
in the
troposphere along with vertical profiles of temperatures in the
stratosphere
and on the surface, a UVIS observation of the Titan occultation of
Sigma
Sgr., a VIMS observation of the stellar occultation of alpha Sco and
AlpCMa., Titan very high resolution imaging, and ISS observations
including
a regional map of Titan.
Sunday, September 2 (DOY 245):
Science observations over the weekend included CIRS Saturn IR mapping,
ISS
Titan imaging, a UVIS mosaic of the Saturn inner magnetosphere, and a
MAG
calibration.
Orbit Trim Maneuver (OTM) #125 was performed today. This is the
cleanup
maneuver from the Titan 35 encounter on Aug. 31. The main engine burn
began
at 6:00 AM PDT. Telemetry immediately after the maneuver showed the
burn
duration was 2.98 seconds, giving a delta-V of 0.477 m/s. All
subsystems
reported nominal performance after the maneuver.
Tuesday, September 4 (DOY 247)
A real-time command to perform a reaction wheel bias was sent up to
the
spacecraft today. The bias replaces the one that would have executed
if
OTM-126 had not been deleted.
The preliminary port for the S36 Science Operations Plan process
occurred
today. All teams have submitted the necessary files. The final port
for
this process occurs Sept. 12.
Final end-to-end testing for the Command Data Subsystem (CDS) Flight
Software version 10 began today and will run through September 11,
2007.
CDS V10 uplink to the spacecraft is set for the end of September as
part of
the activities in S34.
Based on Spacecraft Office and Sequence Team recommendations, a real-
time
command is to be sent to the spacecraft as a result of changes to the
Cassini DSN allocation file for the S33 background sequence now
currently in
execution. The command will pause playback for appropriate durations
during
shortened passes, and change the priority playback table. Three
passes
needed to be shorted to accommodate the needs of other missions:
DOY 256 - shortened by 20 min. at the front end
DOY 260 - shortened by 20 min. at the front end
DOY 263 - shortened by 35 min. at the front end
A feature on how the studies of atmospheric turbulence on Earth and on
Titan
are each assisting the other is now available at:
http://saturn.jpl.nasa.gov/news/features/feature20070828.cfm
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.
|
| Similar Threads | Posted | | Cassini Update - September 14, 2007 | September 14, 2007, 8:20 pm |
| Cassini Update - September 21, 2007 | September 21, 2007, 6:32 pm |
| Cassini Update - September 28, 2007 | September 28, 2007, 5:20 pm |
| Dawn Update - September 7, 2007 | September 7, 2007, 12:59 pm |
| Dawn Update - September 14, 2007 | September 14, 2007, 12:15 pm |
| Phoenix/Dawn Update - September 27, 2007 | July 27, 2007, 4:42 pm |
| Mars Exploration Rover Update - September 10, 2007 | September 11, 2007, 11:31 am |
| Mars Exploration Rover Update - September 18, 2007 | September 18, 2007, 3:21 pm |
| Mars Exploration Rover Update - September 20, 2007 | September 20, 2007, 8:13 pm |
| Mars Exploration Rover Update - September 25, 2007 | September 27, 2007, 11:53 am |
|
|
|
|
XML Sitemap