Cassini is orbiting Saturn with a 31.9-day period in a plane
inclined 51.9 degrees from the planet's equatorial plane. The most
recent spacecraft tracking and telemetry data were obtained on Sept.
25 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 and speed of the Cassini
spacecraft may be found on the "Present Position" page
at:
http://saturn.jpl.nasa.gov/mission/presentposition/.
The on-board sequence S80 issued commands controlling Cassini
this week. Meanwhile, work proceeded at JPL on the ten-week command
sequences S81, S82, and S83, and on planning for the 2016 start of the
F-ring and Proximal Orbits phase.
Wednesday, Sept. 18 (DOY 261)
The Ultraviolet Imaging Spectrograph (UVIS) completed a 37-hour
long mosaic scan of Saturn's magnetosphere, part of a yearly campaign
to image oxygen in the vicinity of the Saturn disk. Similar
observations, of roughly similar lengths, were repeated on Thursday
going into Friday, and on Saturday into Sunday.
Thursday, Sept. 19 (DOY 262)
The Navigation team used the Imaging Science Subsystem (ISS) to
take an image of Saturn's moon Iapetus for Optical Navigation
purposes. Typically, such "opnav" images purposefully
overexpose the body so that the background stars can be seen; their
relative positions are then measured. Next, ISS performed an
observation in the satellite orbit campaign looking at small objects
near Saturn, and searching for new ones. Then, prior to UVIS's next
long-duration oxygen search, the Visible and Infrared Mapping
Spectrometer (VIMS) made a two-minute Saturn storm watch
observation.
Friday, Sept. 20 (DOY 263)
The Radio and Plasma Wave Science subsystem (RPWS) collected data
for its survey of emissions in the neighborhood of 80 kilohertz. RPWS
actually takes data frequently in the background as the spacecraft
moves through various parts of the Saturnian environment, while the
other instruments are prime.
Saturday, Sept. 21 (DOY 264)
UVIS began a 31-hour long mosaic scan of Saturn's magnetosphere,
the last of three observations this week as part of a yearly campaign
to image oxygen in the vicinity of the Saturn disk.
Our name for this day of the week comes from the Roman god Saturn
who was, among many other things, the god of time: literally Saturn's
day.
Sunday, Sept. 22 (DOY 265)
The Realtime Operations team sent part two of the S80 command
sequence to the spacecraft today using the 70-meter aperture DSN
station at Goldstone, California. After a round-trip light time of two
hours fifty-seven minutes, telemetry confirmed that all 4861
individually timed commands had been received intact and stored
onboard. They will control the spacecraft's activities through October
22, when S81 will take over.
Monday, Sept. 23 (DOY 266)
Calibrations are important components of Cassini's science
observations, though they are not frequently mentioned in these
reports. Today the Magnetometer (MAG) performed a calibration that
involved rotating the spacecraft about its X-axis, pitching the MAG
boom "head over heels." At other times, the spacecraft
performs MAG calibrations by rolling about its Z-axis while keeping
the high-gain antenna pointing toward Earth for communications.
Following the MAG calibration, the Cosmic Dust Analyzer (CDA) began a
29-hour observation of dust that orbits Saturn in the retrograde
direction.
Enceladus and its enigmatic constantly erupting jets are seen
under unusual lighting conditions in an image featured today:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4890
Tuesday, Sept. 24 (DOY 267)
The Radio Science team conducted a calibration of the Deep Space
Network (DSN) Monopulse system using Cassini's Ka-band (32 GHz)
downlink radio signal. Monopulse, when operating, constantly makes
fine adjustments in the DSN antenna's pointing while producing a
record of those adjustments. One of the 34-meter diameter DSN stations
at Goldstone, California participated in the calibration while
conducting two-way digital and radiometric tracking of the spacecraft
at the same time; this was one of five DSN-Cassini tracking periods
this week.
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