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.
17 using one of the 34-meter diameter Deep Space Network stations at
Canberra, Australia. 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.
The main event this week was Thursday's Titan T94 flyby at 1400
kilometers altitude. Cassini's optical remote-sensing instruments and
direct-sensing instruments carried out science observations, while the
encounter provided a gravity-assist boost to reshape the spacecraft's
orbit according to plan. Orbital inclination was brought down by 1.5
degrees and the period was increased by eight days.
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/.
http://saturn.jpl.nasa.gov/mission/presentposition/.
Wednesday, Sept. 11 (DOY 254)
As Titan loomed closer, Cassini turned to train its optical
remote-sensing instruments on it. The Composite Infrared Spectrometer
(CIRS) led the encounter's observations by obtaining information on
the stratosphere's thermal structure.
Thursday, Sept. 12 (DOY 255)
As the spacecraft encountered Titan, the optical instruments
carried out their planned observations as described on the T94 Flyby
page:
http://saturn.jpl.nasa.gov/mission/flybys/titan20130912
Meanwhile, with closest approach occurring on Titan's dayside,
Cassini's direct-sensing instruments studied the diffusion of Saturn's
magnetic field at low Titan altitudes and low solar zenith angles. The
Magnetospheric Imaging Instrument (MIMI) measured energetic ion and
electron energy being input to the atmosphere. The Radio and Plasma
Wave Science subsystem (RPWS) measured thermal plasmas in the
ionosphere and surrounding environment, and searched for
lightning.
Twelve hours after closest approach, Cassini turned to point its
high-gain antenna toward Earth. An hour and a half later, the 70-meter
aperture Deep Space Network (DSN) station at Canberra, Australia
locked onto Cassini's signal and began to decipher T94 telemetry data
coming from the spacecraft's solid-state recorder. At the same time,
the DSN station transmitted a continuous uplink signal for navigation
and sent some routine realtime commands from the Cassini flight team.
This DSN period ended after seven and a half hours.
Friday, Sept. 13 (DOY 256)
The 70-meter DSN station at Madrid, Spain tracked Cassini for
three hours in downlink-only mode today, capturing more of the data
recorded onboard during the T94 science observations. Then the
spacecraft turned away from Earth to allow the Imaging Science
Subsystem (ISS) look back at Titan and monitor its clouds. This was
followed by another two-way session with the 70-meter DSN station in
Australia. After eight and one quarter hours the entire T94 telemetry
data playback was complete with no data lost. The science teams who
had designed the T94 observations now had all the results in hand.
There were a total of six DSN sessions this week for routine tracking
and communications.
The navigation team iterated Cassini's orbit model using
Doppler-shift and ranging data from the DSN passes following T94, and
determined the correction needed to adhere to the intended Saturn-tour
trajectory. The flight team created commands to achieve this
correction with Orbit Trim Maneuver (OTM)-359, and transmitted them to
the spacecraft during tonight's DSN pass. The commands are timed to
execute on Sunday night.
Saturday, Sept. 14 (DOY 257)
CIRS performed a far-infrared map of Saturn's southern
hemisphere to determine the atmospheric and ionospheric thermal
structure. ISS then performed an observation in the Satellite Orbit
Campaign, looking at small objects orbiting close to the planet.
Sunday, Sept. 15 (DOY 258)
ISS created a fifteen-hour, low-resolution movie of the narrow
F-Ring. The day concluded with execution of the T94 trajectory
cleanup maneuver OTM-359.
Monday, Sept. 16 (DOY 259)
With Titan at a distance of 1.4 million kilometers, ISS, CIRS and
the Visible and Infrared Mapping Spectrometer (VIMS) performed an
observation in the Titan monitoring campaign. ISS then looked back at
the irregular moon Tarvos, the small dark object described last week,
and studied it for 13.5 hours.
An image featured today shows one of the F ring's many
peculiarities:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4888
Tuesday, Sept. 17 (DOY 260)
The Ultraviolet Imaging Spectrograph (UVIS) began its yearly
campaign to study Saturn's magnetosphere by starting a 37-hour
mosaic scan, imaging oxygen in the vicinity of the Saturn disk.
Observing at longer wavelengths, you can view more deeply into
Saturn's atmosphere. A Cassini Science League feature released today
discusses the results of using Cassini's Radar instrument in its
passive microwave-radiometer mode, which is sensitive to radiation
coming from deep within Saturn at 2.2 centimeters wavelength:
http://saturn.jpl.nasa.gov/news/cassiniscienceleague/science20130917/
------------------------
To unsubscribe from Cassini Spacecraft Updates or to subscribe
with a different email address, visit:
<http://saturn.jpl.nasa.gov/news/mailinglistsignup/ >
------------------------
This email address is not monitored. For comments and questions,
please contact Cassini Outreach at:
<http://saturn.jpl.nasa.gov/feedback/>
------------------------
Visit the JPL Cassini home page for more information about the
Cassini Project: <http://saturn.jpl.nasa.gov/>
------------------------
