Cassini Significant Events 07/08/15 – 07/14/15

Cassini is currently orbiting Saturn with a period of 21.8 days in a plane inclined 0.5 degree from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on July 15 using one of the 34-meter diameter Deep Space Network stations in Spain. 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 .

Interplanetary history played out in real time this week when the New Horizons Spacecraft sped through the Pluto-Charon system, right on target, en route to even more encounters in the Kuiper Belt. New Horizons’ two recorders have stored a vast amount of unique scientific data, and will play it all back during the next 16 months using the Deep Space Network. Cassini, which has been orbiting Saturn during New Horizon's entire flight, joined other spacecraft and Earth-based observatories by snapping an image of Pluto during New Horizons' long-awaited encounter on Tuesday. This was in addition to the 879 "routine" targets that Cassini also imaged this week within the Saturnian system.

Wednesday, July 8 (DOY 189)

A five-day period of interdisciplinary science data collection began today when Cassini turned its telescopes toward Saturn's faint outer rings for five hours. The optical remote-sensing (ORS) instruments, which are the Imaging Science Subsystem (ISS), the Composite Infrared Spectrometer (CIRS), the Ultraviolet Imaging Spectrograph (UVIS), and the Visible and Infrared Mapping Spectrometer (VIMS), made their observations while the faint rings were sunlit from behind. When this was completed, ISS made a two-minute Saturn storm-watch observation, and then ISS and UVIS turned to Saturn's small moon Enceladus. It too was lit at high phase angles, and the observation measured the variability of its icy south-polar plume for 2.5 hours. Finally, the ORS instruments returned to the faint rings for another 7.5 hours of observation.

Appropriately, NASA's Astronomy Pictures of the Day this week were heavily dedicated to Pluto. Today's Picture of the Day however, was an unusual image from Cassini: http://apod.nasa.gov/apod/ap150708.html .

Thursday, July 9 (DOY 190)

After another quick Saturn storm watch by ISS, and a nine-hour communications and tracking session with the Deep Space Network (DSN), the Magnetospheric Imaging Instrument (MIMI) led the Magnetospheric and Plasma Science (MAPS) instruments in a 15-hour observation of Saturn's magnetotail.

A news feature was released today describing Cassini's small part in a very extensive Pluto observing campaign complementing the New Horizons mission's fast flyby of the Pluto-Charon system: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20150709 .

Friday, July 10 (DOY 191)

Commands were uplinked today that had Cassini turn and fire its small rocket thrusters for 98 seconds, performing Orbit Trim Maneuver (OTM) 416. This propulsive event gave the spacecraft a velocity change of 96 millimeter-per-second, sufficient to clean up its trajectory following last week's Titan (T-112) flyby.

With the OTM completed, ISS, CIRS and VIMS performed a 90-minute observation in the Titan monitoring campaign, from a distance of 1.7 million kilometers. ISS made another two-minute Saturn storm-watch observation; there would be one more of these on each of the next three days, with VIMS participating in Saturday's. Right after today's observation, UVIS spent 95 minutes creating radial profiles of Saturn’s atmosphere.

Saturday, July 11 (DOY 192)

ISS tracked and observed Saturn's dark-surfaced irregular moon Ymir. This object is about 18 kilometers in diameter and occupies a highly elliptical, retrograde orbit that stretches 23 million kilometers from Saturn; it was named after a figure in Norse mythology that was the ancestor of all the frost giants.

Sunday, July 12 (DOY 193)

CIRS observed Saturn’s atmosphere in the mid-infrared part of the spectrum for 12 hours to better determine temperatures in the upper troposphere and tropopause. VIMS rode along.

Monday, July 13 (DOY 194)

Cassini's Navigation team used ISS to take images of Saturn's moon Hyperion today against the background stars for optical navigation purposes. This was the final observation in the 10-week-long command sequence S89 on board the spacecraft. The S90 sequence, which was uplinked to Cassini on Saturday, began its 70 days of control by having UVIS start a 22-hour observation of Saturn’s auroral oval. The other ORS instruments rode along, taking data as well.

Which is a moon and which is a planet? It might not immediately be clear in the image featured today: /resources/16210 .

Tuesday, July 14 (DOY 195)

In response to commands that the flight team sent to Cassini near real time (rather than commands in the S90 sequence), ISS took control of spacecraft pointing and joined a worldwide Pluto observing effort by taking an image of that most famous Kuiper-Belt Object, just as New Horizons was nearing its closest approach.

CIRS observed Saturn's atmosphere for 14 hours to measure its chemical constituents.

During the past week, the DSN communicated with and tracked Cassini on nine routine occasions, using deep space stations in Spain, California and Australia. A total of 11,491 individual commands were uplinked, and about 1,134 megabytes of telemetry data were downlinked and captured at rates as high as 142,201 bits per second.

This illustration shows Cassini's position on July 14: https://space.jpl.nasa.gov/cgi-bin/wspace?tbody=-82&vbody=1001&month=7&day=14&year=2015&hour=23&minute=55&fovmul=1&rfov=45&bfov=30&brite=1&showsc=1&showac=1 .

Milestones spanning the whole orbital tour are listed here: http://saturn.jpl.nasa.gov/mission/saturntourdates .

Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at:
http://saturn.jpl.nasa.gov/mission/presentposition/ .