NASA Cassini Significant Events 07/06/11 – 07/12/11
The most recent spacecraft telemetry was acquired on July 12 from the Deep Space Network tracking complex at Canberra, Australia. 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, July 6 (DOY 187)
A news release called “Cassini Spacecraft Captures Images and Sounds of Big Saturn Storm” is available on the Cassini web site. Scientists analyzing data from the Cassini spacecraft now have the first-ever, up-close details of a Saturn storm that covers eight times the surface area of Earth. Cassini first detected the storm on December 5, 2010, which has been raging ever since. It lies approximately 35 degrees north latitude on Saturn. Pictures from Cassini’s imaging cameras show the storm wrapping around the entire planet, covering approximately 5.5 billion square km. For more information on this subject link to: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20110706/.
Thursday, June 7 (DOY 188)
In this week’s science observations, the Composite Infrared Spectrometer (CIRS) started off the week with a 23 hour observation to map Saturn in the mid-infrared to determine upper troposphere and tropopause temperatures. CIRS later observed Saturn for 12 hours in order to measure oxygen compounds in the stratosphere. Next, the Ultraviolet Imaging Spectrograph (UVIS) performed an 11 hour observation of Saturn’s auroral region to study temporal variability in auroral emissions, and RADAR observed Titan for 2.5 hours to obtain distant radiometer science and calibration data. On approach to periapsis, the Visual and Infrared Mapping Spectrometer (VIMS) performed a 12 hour equatorial map of Saturn to complete a census of the size and shapes of the plume-like features it had spotted previously underneath the unusually thick layer of upper-level hazes in the equatorial region. These features are thought to be sources of the hazes, delivering gases and aerosols from the deep troposphere to the upper atmosphere. The Cosmic Dust Analyzer (CDA) made measurements to understand the shadow resonances of charged particles, their charging time, and how they influence the asymmetry of the E ring.
VIMS made further measurements to map the equatorial region of Saturn and then made observations of two stellar occultations by Saturn’s atmosphere, as the star Alpha Ori (commonly known as Betelgeuse) and then the star Alpha Mi were occulted, to gather data to determine the Hydrogen/Helium (H/HE) ratio in the atmosphere; CIRS also participated in these observations. The occultations were followed by more Saturn equatorial observations by VIMS. As part of the Titan Meteorological Campaign, the Imaging Science Subsystem (ISS) then observed Titan (along with VIMS and CIRS) to look for planet-wide cloud events observed by Earth based telescopes in the past. CIRS then targeted the Saturn limb to measure oxygen compounds in the stratosphere. Lastly, VIMS mapped Saturn’s northern hemisphere continuously over 23 hours to observe time variability of winds and to study temporal variations of features comprising the “string of pearls” (clearings in the clouds), the Saturn “ribbon” feature, and the “smoke rings”. Observations over two rotations provide valuable information on the oscillatory nature of the pearls.
The Attitude and Articulation Control Subsystem (AACS) flight software Reaction Control System (RCS) high-rate to low-rate timer value was patched from 10 minutes to 40 minutes today. This will save hydrazine and minimize the delta-V generated by RWA biases by approximately 3-5 percent.
Friday, July 8 (DOY 189)
A pair of panoramas of Saturn’s storm was Astronomy Picture of the Day today. It is available at: http://apod.nasa.gov/apod/ap110708.html.
The Navigation Team continued preparations for an updated ephemeris delivery on July 22 in support of a Radio Science occultation observation.
Saturday, July 9 (DOY 190)
A non-targeted flyby of Titan occurred today.
Sunday, July 10 (DOY 191)
Non-targeted flybys of Helene, Janus, Pan and Prometheus occurred today.
Monday, July 11 (DOY 192)
The Science Forum for S71 was held today. Topics included an overview of science planned for this sequence followed by highlights, unique activities, and highest priority observations as described by the Target Working Team (TWT) and Orbiter Science Team (OST) leads, with comments from the Investigation Scientists and other instrument team representatives.
Tuesday, July 12 (DOY 193)
Last month, the decision to turn off the Cassini Plasma Spectrometer (CAPS) was made as a precautionary measure in light of recent shifting spacecraft bus voltages attributed to the instrument. Today a CAPS anomaly discussion was held where it was decided that the current T-79 integrated timeline will be kept as is, with CAPS having prime pointing control. There will be no changes to the timeline in the event of a CAPS-off scenario, and sequencing will proceed for S71 with the assumption that CAPS will be prime, regardless of its off or on state. Analysis of the CAPS anomaly continues, and power-on tests are being planned for diagnostic purposes.
Port 1 products were due today as part of the S71 Sequence Implementation Process (SIP). The products will be merged and sent out to the flight team for review.
