News | January 27, 2016
Cassini Significant Events 1/20/16 - 1/26/16
Cassini is currently orbiting Saturn with a period of 15.9 days in a plane inclined 4.1 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on January 27 using the 70-meter diameter Deep Space Network station in Australia. 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
Cassini spent this week out near apoapsis in its orbit of Saturn, moving relatively slowly at a distance of about 2.2 million kilometers from the planet, nearly twice the distance of Titan's orbit. This altitude makes it possible to obtain some valuable observations of Saturn's magnetosphere, as well as carry out in situ sampling dust grains of various kinds. Many of the usual remote-sensing, telescopic observations of Saturn and its satellites continued as well; this week the number of images Cassini has taken in the realm of Saturn passed the 360,000 mark.
One particularly notable event during the week was Orbit Trim Maneuver (OTM) 438. OTM-438, a large apoapsis maneuver, was performed on Jan. 23. This 39-second main-engine burn provided a velocity change of 6.8 m/s to set up for the Feb. 1 Titan encounter T-116. This is the second largest of Cassini’s remaining planned OTMs and marked the initiation of a series of ten Titan flybys that will eventually increase Cassini’s orbital inclination to Saturn’s ring plane to 63.7 degrees. The final flyby in the sequence, T-125, will mark the beginning of the F-ring orbits. The T116 flyby alone will increase Cassini’s inclination by over 13 degrees.
Wednesday, Jan. 20 (DOY 020)
Cassini's Cosmic Dust Analyzer (CDA) began a 13-hour observation of dust that orbits Saturn in the retrograde direction. CDA can measure the mass, chemical species, velocity, and many other qualities of each grain of dust that enters the detector. The observation was repeated on Monday for 13.5 hours.
Thursday, Jan. 21 (DOY 021)
The Imaging Science Subsystem (ISS) tracked Saturn’s irregular moon Ijiraq for 13.5 hours today. Ijiraq, named after a creature in Inuit mythology, is about ten km in diameter, and occupies an inclined orbit that reaches as far as 14.6 million km from Saturn.
Friday, Jan. 22 (DOY 022)
Cassini’s Magnetospheric Imaging Instrument (MIMI) observed Saturn’s magnetic envelope while the Composite Infrared Spectrometer (CIRS) simultaneously studied the composition of Saturn’s atmosphere for just over 13 hours.
During the CIRS and MIMI observations, Cassini coasted through apoapsis, marking the start of its orbit #231. It had slowed to a speed of 6,164 km per hour relative to the ringed planet.
Saturday, Jan. 23 (DOY 023)
CIRS observed Saturn’s atmosphere at mid-infrared wavelengths for 12 hours, measuring temperatures in the upper troposphere and the tropopause. ISS and the Visible and Infrared Mapping Spectrometer (VIMS) made their own observations while riding along with the spacecraft's pointing. When this was done, ISS and VIMS looked over to Saturn to make a two-minute storm-watch observation. Finally, ISS spent an hour looking for small objects near the planet as part of the satellite orbit campaign.
Realtime commands that were sent up to Cassini on Friday executed today. The commands were designed based upon the most recent radiometric tracking data from the Deep Space Network (DSN), and the Navigation team's precise orbit solutions. In response, the spacecraft turned to the proper attitude and fired its 440-newton, bipropellent-fed, main engine for 39 seconds, accomplishing Orbit Trim Maneuver (OTM)-438. The white-hot engine provided a change in velocity of 6.8 meters per second for the spacecraft, setting up for the T-116 flyby of Saturn’s largest moon Titan on February 1.
Sunday, Jan. 24 (DOY 024)
Today marks 600 days until Cassini's fiery end of mission on Sept. 15, 2017.
A routine nine-hour DSN tracking pass was the most significant event for today. After spending one hour preparing the ground station and its equipment, the 70-meter diameter "Station 43" at the Canberra complex turned its six-million pound metal dish toward Saturn as it was rising in the eastern sky. Cassini's radio signal arrived right on time, at a power level in the DSN receiver of just under two attowatts; in watts, that's eighteen places to the right of the decimal point. And just as routinely, the DSN equipment teased the 1's and 0's out of Cassini's telemetered data. At the same time, Station 43 measured Cassini's line-of-sight distance to a precision of about one meter, and its speed, again line-of-sight, to within a fraction of a millimeter per second.
Monday, Jan. 25 (DOY 025)
A news feature released today elaborates on OTM-438, and the ever-increasing inclination of Cassini's orbit that Titan flybys are now providing: Cassini Heads for 'Higher Ground' at Saturn .
An half-lit view of Enceladus is featured today: /resources/16295 .
Tuesday, Jan, 26 (DOY 026)
CDA made a 6.5-hour observation as part of an exogenous dust campaign today, sampling material from outside our solar system. Next, ISS, CIRS, and VIMS performed a 90-minute Titan monitoring observation, from a distance of three million km to the planet-like moon. ISS then performed another one-hour satellite orbit observation. After one more two-minute ISS storm-watch observation on Saturn, CIRS looked into Saturn’s atmosphere for 11.6 hours at far-infrared wavelengths, again measuring upper-troposphere and tropopause temperatures.
During the past week, the Deep Space Network communicated with and tracked Cassini on eight occasions, using DSN stations in California and Australia. A total of 159 individual commands were uplinked, and about 1,495 megabytes of telemetry data were downlinked and captured at rates as high as 124,426 bits per second.