News | February 11, 2016
Cassini Significant Events 02/03/16 - 02/09/16
Cassini is currently orbiting Saturn with a period of 16 days in a plane inclined 17.5 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Feb. 10 using one of the 34-meter diameter Deep Space Network stations 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 moving relatively slowly in the outer part of its 16-day orbit of Saturn, coasting through the space between the orbits of Saturn's moons Hyperion and Iapetus. Back on Earth, Cassini scientists met for a weeklong Project Science Group meeting #68 at JPL. Meanwhile, Sequence Implementation Process teams continued working on the 10-week command sequences S94, which will begin executing on April 18, and S95, which starts on June 26. Six sequences remain to be worked after that.
Wednesday, Feb. 3 (DOY 034)
While the spacecraft's momentum carried it "upward" in orbit away from the planet, the Composite Infrared Spectrometer (CIRS) and the Visible and Infrared Mapping Spectrometer (VIMS) stared back at the sunlit face of Saturn's rings to study its particles' composition for 15 hours. Even though the main rings span a diameter of hundreds of millions of meters, they might be only a few tens of meters thick at any given point. Cassini's remarkable viewing geometry of the crescent ringed Saturn illustrated here: https://space.jpl.nasa.gov/cgi-bin/wspace?tbody=699&vbody=-82&month=2&day=3&year=2016&hour=00&minute=00&fovmul=1&rfov=30&bfov=30&showsc=1&showac=1 .
Next, the on-board S92 command sequence had the spacecraft turn its high-gain antenna toward Earth. Cassini's continuous radio signal propagated for 87 minutes at the speed of light, then a Deep Space Network (DSN) station in Australia locked onto it began extracting the ones and zeroes of telemetry. After conversion of the binary data to engineering values, Cassini’s flight team engineers made a thorough check of the spacecraft's health, and then uplinked 142 freshly prepared commands to carry out an Orbit Trim Maneuver (OTM). The spacecraft turned to the commanded attitude and fired its liquid-bipropellent-fed main rocket engine for 3.3 seconds. This OTM-440 provided the 0.58 meter per second change in velocity required to clean up the error in Cassini's trajectory introduced during the Feb. 1 Titan encounter. Such trajectory errors are always expected, but can only be quantified after the encounter takes place.
Thursday, Feb. 4 (DOY 035)
Today marks 300 days until Cassini begins its F-ring orbits, in which periapses will come close to that narrow and ever-changing strand.
The Imaging Science Subsystem (ISS) controlled spacecraft pointing for 15 hours today to carry out an observation of Saturn's irregular moon Albiorix. Named for the king of the world in Gallic mythology, this moon has a diameter of about 26 kilometers and moves as far as 23.8 million km away from the planet, along an inclined, highly elliptical orbit.
Friday, Feb. 5 (DOY 036)
Today, the Cosmic Dust Analyzer (CDA) spent 13.5 hours searching for dust that might be orbiting Saturn in the retrograde direction.
Saturday, Feb. 6 (DOY 037)
ISS, CIRS and VIMS performed a 14.75-hour observation of the Encke gap in the outer part of Saturn's A ring. Particles within this 325-km wide gap take about 14 hours to complete a revolution about Saturn. This was the final science observation commanded by the S92 sequence.
Sunday, Feb. 7 (DOY 038)
The S93 command sequence, whose 11,911 individual commands were uplinked on Thursday, began its 72 days of orchestrating Cassini's activities today. Its first science observation was another CDA retrograde dust observation; this one lasted 11.5 hours.
During the CDA observation, Cassini coasted through apoapsis, marking the start of its Saturn orbit #232. Reaching an altitude of 2.2 million km from the ringed planet, the spacecraft had slowed to 6,456 km per hour relative to Saturn.
Monday, Feb. 8 (DOY 039)
About 190 scientists who are associated with Cassini, plus many of the engineers on the flight team, convened at JPL today to begin the weeklong Project Science Group meeting #68.
Meanwhile 1,556 million km away from here, CIRS and VIMS observed Saturn’s atmosphere for 15 hours, measuring temperatures in the upper troposphere and the tropopause. Finally, realtime commands arrived and executed OTM-441, turning the spacecraft and firing the main engine for 4.2 seconds. This OTM provided a change in velocity of 0.75 meters per second, taking advantage of the orbital-mechanics "leverage" near apoapsis to set up for the Feb. 16 Titan flyby dubbed T-117.
At just over a million meters in diameter, Saturn's icy moon Tethys is massive enough to be very nearly spherical. It is the subject of an image featured today, with Saturn in the background: /resources/16302 .
Tuesday, Feb. 9 (DOY 040)
Still taking scientific advantage of the environment out near apoapsis, this week's last science activity was a 14.75-hour CDA interstellar dust observation.
During the past week, the Deep Space Network communicated with and tracked Cassini on 10 occasions, using the 70-meter and the 34-meter DSN stations in Australia. A total of 12,212 individual commands were uplinked, and about 1,328 megabytes of telemetry data were downlinked and captured at rates as high as 124,426 bits per second.
This illustration shows Cassini's position on Feb. 9: http://go.nasa.gov/1OdNDqz . The format shows Cassini's path over most of its current orbit up to today; looking down from the north, all depicted objects (except the background stars of course) revolve counter-clockwise, including Saturn along its orange-colored orbit of the Sun.