Cassini is orbiting Saturn with a 12-day period in a plane inclined 59.4 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained early on June 27 using the 70-meter diameter Deep Space Network station at Goldstone, California. Except for some science instrument issues described in previous reports (for more information search the Cassini website for CAPS and USO), the spacecraft continues to be in an excellent state of health with all of its subsystems operating 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/.
Since Cassini began studying Saturn, the Imaging Science Subsystem (ISS) has taken more than 300,000 images and transmitted them to Earth, where they have been processed and made public. Mark your calendar for Friday July 19, when the spacecraft will carry out a unique observation from behind the distant, ringed planet. When you see the tiny blue dot of Earth in the resulting image, will you be able to say you were "in the picture" when Cassini's telescopes were catching the light as it finished the long journey from our planet? You can check for yourself: this week the Cassini Outreach team updated the Saturn viewing charts and added a time-zone table: http://saturn.jpl.nasa/news/waveatsaturn/viewing/.
Wednesday, June 19 (DOY 170)
Cassini reached apoapsis, having coasted 1.4 million kilometers from the planet and slowing to 14,667 kilometers per hour relative to Saturn. This marked the beginning of Cassini's orbit #193.
The Composite Infrared Spectrometer (CIRS) mapped temperatures of the rings as their particles revolved into Saturn's shadow, to assist in determining their thermal inertia. The Visible and Infrared Mapping Spectrometer (VIMS) squeezed in a two-minute Saturn storm-watch observation, then the Navigation team used ISS to take five images of Saturn's moon Mimas for optical navigation purposes. ISS, CIRS and VIMS made another observation in the Titan monitoring campaign, this one from 2.4 million kilometers away; another was performed on Saturday from about the same distance. The purpose of these is to catch changes in Titan’s dynamic weather. Next, ISS performed a satellite orbit campaign observation, looking at small objects near Saturn that are known, and possibly discovering more of them; another of these observations was repeated on Friday. The Ultraviolet Imaging Spectrograph (UVIS) then imaged Saturn's thermosphere, which is a region that reaches a temperature of 420 kelvins around the 100 nanobar level, roughly 800 kilometers above the planet's visible edge. The day concluded with ISS starting a long, low-resolution movie of the F ring.
Thursday, June 20 (DOY 171)
The F-ring movie wrapped up today, having lasted a total of sixteen hours. This was long enough to watch a little more than one complete revolution of F-ring particles about Saturn.
Friday, June 21 (DOY 172)
VIMS observed an occultation of the deep-red star Mu Cephei (Herschel's Garnet Star) as it went behind the rings thanks to Cassini's motion in orbit. Radio Science and the magnetometer each performed a calibration, then VIMS made a quick Saturn storm-watch observation.
Winners of the Intel International Science and Engineering Fair enjoyed a tour of Cassini Operations today as part of their visit to Caltech and JPL in Pasadena.
Saturday, June 22 (DOY 173)
ISS tracked the orbits of known propellers (http://go.usa.gov/YyGR) in Saturn’s rings. Following this, VIMS and UVIS took turns pointing at Saturn’s southern polar regions to study the planet’s aurora.
Sunday, June 23 (DOY 174)
Today, during one of six Deep Space Network (DSN) communications sessions this week, the Radio Science team conducted a Saturn gravity science enhancement observation, using the Doppler shift to refine knowledge of both Saturn’s gravitational field and Cassini’s location in orbit around Saturn. CIRS then turned back towards Saturn so it and VIMS could acquire infrared spectra of the atmosphere to help determine its composition. Next, ISS observed Mimas to search for any plumes of material that might possibly be emanating from that satellite. The day’s science activities ended with ISS leading an observation of Saturn’s limb at high phase angles.
Monday, June 24 (DOY 175)
Earth passed behind Saturn’s rings from Cassini’s vantage point, while the Radio Science team used all three of the spacecraft's radio transmitters to carry out a chord ring occultation, which cut across all but the D ring and the very innermost C ring. After the occultation, ISS trained its telescopes on Saturn's small icy moon Enceladus, and all the optical remote-sensing instruments observed its intriguing jets and plumes while they were back-lit by the Sun. High-phase observations such as this allow scientists to study small particles in the plume. The days’ science activities finished up with a two-way DSN communications period that also served as the second half of the Saturn gravity science enhancement observation begun the day before. As Cassini passed northward through the ring plane, the Cosmic Dust Analyzer (CDA) and the Radio and Plasma Wave Science Subsystem (RPWS) measured the enhanced particle flux that typically accompanies passage through Saturn’s equatorial region.
Tuesday June 25 (DOY 176)
Having crossed Saturn’s equator, VIMS turned towards Saturn’s northern hemisphere, and mapped the northern mid latitudes in concert with CIRS. Next, UVIS complemented its studies of Saturn’s southern aurorae with observations of the northern auroral regions. VIMS watched an occultation of the red star R Carinae as it went behind Saturn’s atmosphere, and rounded out the day’s science by observing Saturn’s northern aurorae.
Cassini passed through periapsis of orbit #193, going 33,217 kilometers per hour relative to Saturn, at about 558,000 kilometers above the atmosphere.