From: Jet Propulsion Laboratory
Posted: Saturday, August 9, 2014
Cassini is orbiting Saturn with a 31.9-day period in a plane inclined 48 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on August 5 using one of the 34 meter-diameter Deep Space Network (DSN)stations at Goldstone, California. The spacecraft continues to be in an excellent state of health with all of its subsystems operating normally except for the instrument issues described at http://saturn.jpl.nasa.gov/news/significantevents/anomalies. Information on the present position of the Cassini spacecraft may be found on "Eyes on the Solar System."
This week, sequence Implementation teams worked on developing the 10-week spacecraft command sequences S86 and S87, while the S85 sequence commanded the spacecraft; some early S88 implementation activities occurred. Work included determining Deep Space Network antenna allocations and choreographing Cassini's actions in sync with these ground-stations; these are negotiated among many other DSN users. Mission planners continued to work on the 2016-2017 Cassini Grand Finale mission segment, which is described here:
Wednesday, July 30 (DOY 211)
The Ultraviolet Imaging Spectrograph (UVIS) completed a 38-hour Saturn system scan, mapping the location of oxygen near the planet. The spacecraft then turned to face its high-gain antenna to Earth, and carried out two-way communications with Cassini's engineering and science teams for nine hours via the DSN's 70 meter-diameter dish antenna at Goldstone, California. This session was the last activity commanded by the S84 sequence, which had been directing the lion's share of Cassini's activities for the past 10 weeks.
Thursday, July 31 (DOY 212)
The S85 command sequence, the first part of which was loaded on board Cassini last week via the DSN, began executing on the spacecraft with a 17-day period of interdisciplinary science data collection. First off, the Imaging Science Subsystem (ISS), the Composite Infrared Spectrometer (CIRS), and the Visible and Infrared Mapping Spectrometer (VIMS) made a 90-minute observation in the Titan monitoring campaign at a distance of 3.7 million kilometers from Saturn's largest moon. Next, ISS turned to nearby Saturn and made a two-minute storm-watch observation. UVIS then began a 33-hour series of mosaic scans of Saturn’s magnetosphere, again identifying regions of oxygen near the planet as it had begun last week. ISS and VIMS took data in ride-along mode during this observation; storage space had been allocated on the spacecraft for their data as well.
Friday, August 1 (DOY 213)
Upon completion of UVIS's scan, ISS and VIMS spent two minutes looking at Saturn for another storm-watch observation.
Saturday, August 2 (DOY 214)
ISS, CIRS and VIMS made another 90-minute Titan monitoring observation; the hazy planet-like moon was a little farther away. ISS then made a two-minute storm watch of Saturn, after which UVIS started off another long-duration mosaic scan for oxygen near the planet, part of its yearly campaign; this one would last 34 hours; ISS and VIMS rode along again.
Sunday, August 3 (DOY 215)
While UVIS was making its observation, Cassini coasted through apoapsis, marking the start of its Saturn orbit #207. Sir Isaac Newton's laws had carried the spacecraft up to 2.9 million kilometers "above" the planet. It had slowed to 9,185 kilometers per hour relative to Saturn, about one third its speed at periapsis passage on July 18. Once UVIS's scan finished up, ISS and VIMS spent another two minutes on a Saturn storm-watch observation.
Monday, August 4 (DOY 216)
With Titan now 3.8 million kilometers away, ISS, CIRS and VIMS performed another 90-minute monitoring observation. Finally, after another quick ISS Saturn storm-watch, UVIS began leading ISS and VIMS again in a 34.5-hour mosaic scan similar to the previous one.
As northern spring progresses in Saturn's 29.45-year solar orbit, Cassini has a superb view of a hurricane centered right on the pole as seen in an image featured today:
Backlit by the Sun, a stunning view of icy plumes streaming from the south polar region on Enceladus, the 500-kilometer diameter moon of Saturn, were selected as NASA's Astronomy Picture of the Day:
Tuesday, August 5 (DOY 217)
As usual, the week's activities included observations made by the direct-sensing Magnetospheric and Plasma Science instruments. The last remote-sensing observation for the week was another two-minute telescopic Saturn storm watch by ISS and VIMS, once the 34.5-hour UVIS scan completed.
This week, the DSN communicated with and tracked Cassini on four routine occasions, all from Goldstone, California. A total of eight individual commands were uplinked, and about 890 megabytes of telemetry data were downlinked at rates as high as 142,201 bits per second. Also this week, coherent Doppler-shift data and ranging data were obtained for a total of about 24 hours, and nine hours of Radio Science data were collected for system calibration.
In addition to this routine support, a newly commissioned 34 meter-diameter station in Canberra, Australia executed a Project Interface Test, successfully demonstrating its ability to capture Cassini's incoming 8 GHz carrier signal, and to resolve and process the binary digits of Cassini's telemetry data at up to 27,650 bits per second. Next week, the new station will demonstrate its ability to send commands and generate two-way coherent tracking data for navigation. Delivery to operations of the new beam-waveguide-design station is on schedule for Oct. 1.
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