The most recent spacecraft telemetry was acquired on Dec. 1 from the
Deep Space Network tracking complex at Goldstone, California. The
Cassini spacecraft is in an excellent state of health and all
subsystems are 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/operations/present-position.cfm.
Tuesday, Nov. 24 (DOY 328)
A close-up image of ice jets erupting from the tiger stripes on
Enceladus was Astronomy Picture of the Day today. Check it out at:
http://antwrp.gsfc.nasa.gov/apod/ap091124.html
The topic at the Cassini-Huygens Analysis and Results of the Mission
(CHARM) teleconference for November was "Science Highlights from
Cassini's Ion and Neutral Mass Spectrometer." An audio recording and
PDF of the presentation are available at:
http://saturn.jpl.nasa.gov/video/products/MultimediaProductsCharm/
Wednesday, Nov. 25 (DOY 329)
An AACS Periodic Engineering Maintenance (PEM) occurred today.
Performed every 90 days, this activity exercises the Engine Gimbal
Actuators and the backup Reaction Wheel Assembly (RWA). In the RWA
exercise, the wheel is commanded to +100 rpm, -100 rpm, 0 rpm, then
turned off.
The moon Prometheus is seen whipping gossamer ice particles out of
Saturn's F-ring in an image taken by the Cassini spacecraft on Aug.
21, 2009. The moon and the ring have eccentric, offset orbits, so
Prometheus dips in and out of the F ring as it travels around Saturn.
Its gravitational force drags the dust-sized particles at the edge of
the F ring along for the ride. To view this image and the full
description link to:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20091125/
Monday, Nov. 30 (DOY 334):
In a news release published today on the Cassini Website, scientists
suggest that the eccentricity of Saturn's orbit around the sun may be
responsible for the uneven distribution of lakes over the northern
and southern polar regions of the planet's largest moon, Titan. A
paper describing the theory appeared in the Nov. 29 advance online
edition of Nature Geoscience. Like Earth and the other planets,
Saturn's orbit is not perfectly circular, but is instead somewhat
elliptical. Because of this, during its southern summer, Titan is
about 12 percent closer to the sun than during the northern summer.
It is proposed that, in this orbital configuration, the difference
between evaporation and precipitation is not equal in opposite
seasons, which means there is a net transport of methane from south
to north. This imbalance would lead to an accumulation of methane --
and hence the formation of many more lakes -- in the northern
hemisphere. For the full text of the release link to:
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20091130/
Tuesday, Dec. 1 (DOY 335)
Science Operations Plan development for S58 was completed today with
the hand off of all files and status to Uplink Operations and the
kick off of the Science and Sequence Update Process, the final
process in sequence development.
An encounter strategy meeting was held today to cover the period
between Dec. 12 and Dec. 22, Titan flybys T63 and T64, and maneuvers
227-229.
A Y-thruster calibration took place on board the spacecraft today.
AACS reported very good results, with Y-thrusters averaging 14.2
seconds of on time and Z-thrusters averaging 0.7 seconds on-time.
This calibration was performed primarily for Navigation to measure
any thruster imbalances.
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