NASA Cassini Significant Events 07/04/2012 – 07/10/2012
The most recent spacecraft tracking and telemetry data were collected on July 10 by the Deep Space Network’s 70 meter Station 43 at Canberra, Australia. Aside from the Cosmic Dust Analyzer (CAPS), which is off, and the Ultrastable Oscillator (see the Jan. 5, 2012 Significant Events), the Cassini spacecraft is in an excellent state of health with all its subsystems functioning normally. Information on the present position of the Cassini spacecraft may be found on the “Present Position” page at: http://saturn.jpl.nasa.gov/mission/presentposition/.
This week the Cassini flight team and the Deep Space Network (DSN) coordinated closely to conduct a definitive engineering test on the spacecraft which confirmed that the Ultra Stable Oscillator (USO) is inoperative, rather than other in-line telecommunications subsystem components. This will have no effect on engineering operations, but will impose some degradation on the accuracy of Radio Science occultation experiments.
With Cassini’s orbits now inclined about 21 degrees with respect to Saturn’s equatorial plane, not only are ring observations possible, but the polar regions of Saturn and its satellites are again in view. This geometry led to the news releases linked below.
Wednesday, July 4 (DOY 186)
Yesterday, a Cassini ground-system database issue halted Imaging Science Subsystem (ISS) and Visible and Infrared Mapping Spectrometer (VIMS) product generation from the downlinked data. Flight team members restored the processes before the holiday and no data were lost.
Cassini’s S-band transmitter came on today, the result of a timed command sent last week. Realtime commands were then uplinked to power on Deep Space Transponder (DST)-B for the first time in flight. Manipulating the DSN uplink frequency from the ground provided a chance for DST-B to operate from a USO reference, had it been operable, without having to turn off DST-A. DST-B appeared healthy, but there was no evidence of a USO-based signal. The spacecraft was then re-configured for normal operations.
ISS, VIMS and the Composite Infrared Spectrometer (CIRS) monitored Titan from a distance of 3.2 million kilometers, then the Ultraviolet Imaging Spectrograph (UVIS) and VIMS began a 35 hour observation of Saturn’s south polar auroral oval while the planet rotated three and a half times.
Thursday, July 5 (DOY 187)
Round-trip light-time with Cassini, as close to “realtime” as we can get, is 2 hours 38 minutes and increasing as Earth moves farther from Saturn.
Since Approach Science began in January, 2004, there have been 272,652 ISS images and 142,355 VIMS cubes acquired, downlinked, and processed.
Friday, July 6 (DOY 188)
ISS, CIRS and VIMS monitored Titan from 2.9 million kilometers, then UVIS and VIMS began another long duration Saturn aurora observation.
Saturday, July 7 (DOY 189)
The Attitude and Articulation Control Subsystem team performed a Reaction Wheel Assembly (RWA) bias maneuver while being tracked by the DSN. Thrusters stabilized the spacecraft attitude so the RWA speeds could be adjusted. An RWA bias maneuver was also performed during the busy 4th of July holiday while off Earth-point and not being tracked.
Sunday, July 8 (DOY 190)
UVIS and VIMS began another long aurora observation.
Monday, July 9 (DOY 191)
The feature “Saturn’s Rings are Back” was made available here: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20120709/
A member of the Cassini Navigation team published a blog entry called, “A Different Slant: Cassini Has a Special View of Saturn These Days – How Did It Get There?” It can be seen here: http://blogs.jpl.nasa.gov/2012/07/a-different-slant/
Tuesday, July 10 (DOY 192)
Apoapsis in an orbit around Saturn can also be called “apokrone”. Cassini passed through this point today at more than twice the “height” of Titan’s orbit, going 5,695 kilometers per hour relative to the planet. This marked the start of orbit #169, which has a period of 24 days and an inclination of 21.2 degrees.
ISS, CIRS and VIMS monitored Titan from 1.8 million kilometers. The Magnetometer then executed a sensor offset calibration by rotating the spacecraft about its X axis.
Heavy rain over the DSN station at Canberra, Australia, drowned out Cassini’s incoming signal for more than six hours, causing loss of science telemetry for large portions of the last two aurora observations. Compelling images of a high-altitude vortex on Titan were released today and discussed in a feature titled, “The Titanian Seasons Turn, Turn, Turn”: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20120710/
