Cassini Significant Events 05/20/09 - 05/26/09
The most recent spacecraft telemetry was acquired on May 26 from the Deep
Space Network tracking complex at Goldstone, California. 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/mission/presentposition/.
Wednesday, May 20 (DOY 140)
Today the Composite Infrared Spectrometer (CIRS) observed the rings at 20
degrees phase angle. This was part of an ongoing set of measurements to
study the vertical thermal distribution within the rings by looking at
the lit and unlit sides at similar geometries.
The Magnetometer (MAG) then performed an instrument calibration with the
spacecraft rolling for seven hours. The Ultraviolet Imaging Spectrograph
(UVIS) concluded observations for the day with an 8-hour Saturn system
scan to measure atomic oxygen and hydrogen.
Thursday, May 21 (DOY 141)
Today Cassini encountered Titan at an altitude of 965 kilometers, and
traveling at a speed of 6.0 km/sec. Closest approach occurred at 03:42 PM
PDT, latitude 22 degrees S. RADAR was the prime instrument and directed
spacecraft pointing during much of this flyby. The instrument
performed observations involving scatterometry, altimetry, and synthetic
aperture RADAR (SAR). The SAR observation occurred over the southern
hemisphere with the instrument sweeping across the NW Shangri-La dune
fields and into high southern latitudes.
The Ion and Neutral Mass Spectrometer (INMS) rode along with RADAR and
obtained night side coverage at low southern latitudes. This flyby
provided a unique opportunity for INMS, allowing coverage for the outer
flank of the magnetospheric interaction region.
On the inbound leg, the phase angle was much larger than 90
degrees. This provided an opportunity for the Visual and Infrared
Mapping Spectrometer (VIMS) to ride along and obtain information on
Titan¹s atmosphere composition. After closest approach, VIMS rode
along with CIRS. While CIRS obtained data for composition
integrations and stratospheric temperature maps, VIMS observed the south
polar region and obtained cloud-monitoring data.
The Ultraviolet Imaging Spectrograph (UVIS) obtained an image cube of
Titan's atmosphere at Extreme Ultraviolet and Far Ultraviolet
wavelengths. These cubes provide spectral and spatial information on
nitrogen emissions, H emission and absorption, absorption by simple
hydrocarbons, and the scattering properties of haze aerosols. This is one
of many such cubes gathered over the course of the mission to provide
latitude and seasonal coverage of Titan's middle atmosphere and
stratosphere.
The Magnetospheric Imaging Instrument (MIMI) measured energetic ion and
electron energy input to Titan's atmosphere, and 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.
Friday, May 22 (DOY 142):
A preview meeting for Titan flybys T55- T61 was held today. Between
May 21 and Aug. 25, there will be seven targeted flybys of Titan. This
meeting allowed personnel from all instrument teams to share what
observations are planned and the significance of the data to be
acquired.
T55 through T61 are all inbound to Saturn flybys. All are lit outbound
after the flyby and occur at roughly 2200 hours local solar time.
The T52-T62 sequence of flybys sets up the correct inclination profile
for rings viewing during the equinox period.
Saturday, May 23 (DOY 143):
At the Preliminary Navigation Review for Orbit Trim Maneuver (OTM) #197,
the NAV team demonstrated that the downstream cost of canceling the
maneuver was about 155 mm/s. Accepting this small cost would reduce
the Memorial Day holiday weekend workload for the flight team and save a
maneuver cycle on the reaction control subsystem thrusters. As a
result, OTM-197, the T55 cleanup maneuver, was canceled.
Science activities today included ring observations involving temperature
differences between the lit and unlit sides, and moon shadows on the
rings. The Cassini Plasma Spectrometer performed Magnetospheric and
Plasma Science (MAPS) surveys, and the Cosmic Dust Analyzer observed as
Cassini ascended through the plane of Saturn¹s rings.
Monday, May 25 (DOY 145):
Today images were taken of Dione, Prometheus and the rings, and
Epimetheus and Janus in support of the 7th edition of the Cassini
Scientist for a Day outreach activity. Students from around the
country have submitted essays as to why one of these three targets would
yield the best science results. Stay tuned for news on the winner next
week. For more information on this event link to:
http://saturn.jpl.nasa.gov/education/scientistforaday7thedition/intro/
Tuesday, May 26 (DOY 146)
Spacecraft Operations sent the first commands to the spacecraft today in
preparation for the ACS A8.7.7 flight software (FSW) update. The update
will be in place from June 2009 to July 2010, and will update the default
safing attitude and the default thruster magnitudes. Uplink will
continue for the next two days with FSW checkout planned for next
week.
The Cassini-Huygens Analysis and Results of the Mission (CHARM)
teleconference for May addressed "The effects of the solar wind on
Saturn's space environment." A PDF of the presentation can be found
at:
http://saturn.jpl.nasa.gov/video/products/MultimediaProductsCharm/
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