NMS) measuring the atmospheric and ionospheric thermal structure of Saturn, and the Magnetometer (MAG) and the RPWS performing magnetospheric measurements.
ISS undertook the first of three three-hour observations of Saturn's bright crescent limb today, with UVIS and VIMS riding along. The second one took place on the next day, and the third on Sunday. After today's, there was a 11.2-hour VIMS observation of the Saturn globe as it rotated through one Saturn day; CIRS participated. Cassini's view of the looming gas giant is simulated here.
Saturday, April 15 (DOY 105)
During today's communications session with the Deep Space Network, the spacecraft was slowly rolling about its longitudinal axis, so that UVIS could conduct an interplanetary hydrogen survey, while CIRS performed a calibration with cold deep space in its field of view. Next, CIRS spent 12 hours making a mid-infrared map of Saturn’s northern hemisphere, to determine upper troposphere and tropopause temperatures.
Sunday, April 16 (DOY 106)
During the CIRS activity, the spacecraft coasted through apoapsis. This marked the start of Cassini's Orbit #270, which will be the final one in its series of 20 F-ring grazing orbits.
None other than Cassini's view of Enceladus was the subject of NASA's Astronomy Picture of the Day today: https://apod.nasa.gov/apod/ap170416.html .
Monday, April 17 (DOY 107)
CIRS began the day with far-infrared mapping of Saturn’s northern hemisphere, again to measure upper troposphere and tropopause temperatures; VIMS rode along with this 22.3-hour observation, taking images about once every hour.
Late in the day, UVIS and VIMS began 12 hours of daytime observations of Saturn's northern auroral region, with CIRS riding along.
Saturn cloud patterns were the subject of today's featured image: /resources/17645 .
Tuesday, April 18 (DOY 108)
Cassini's final targeted Titan encounter, T-126, is coming up on April 22. This page offers details of the flyby: /news/13019/titan-flyby-t-126-final-close-encounter-gateway-to-the-grand-finale .
The DSN communicated with and tracked Cassini on six occasions this week, using stations in California and Australia. A total of 153 individual commands were uplinked, and about 1,718 megabytes of science and engineering telemetry data were downlinked and captured at rates as high as 124,426 bits per second.
Cassini is executing its set of F-ring-grazing orbits of Saturn, with a period of 7.2 days in a plane inclined 63.5 degrees from the planet's equatorial plane. The 20 orbits are nearly identical, with Cassini's nearest point at about 150,000 km, and farthest point at about 1.28 million km from Saturn. Speeds relative to Saturn at those points (periapsis and apoapsis), are close to 76,150 km per hour and 9,000 km/h respectively.
The most recent spacecraft tracking and telemetry data were obtained on April 19 using one of the 34-meter diameter DSN stations in 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/anomalies .
The countdown clock in Mission Control shows 150 days until the end of the Mission.
This page offers all the details of the Mission's ending: https://saturn.jpl.nasa.gov/mission/grand-finale/overview .