Cassini Update - August 20, 2010
baa...@earthlink.net
for 08/11/10 - 08/17/10
The most recent spacecraft telemetry was acquired on Aug. 17 from the
Deep Space Network tracking complex at Canberra, Australia. 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/mission/presentposition/ .
Wednesday, Aug. 11 (DOY 223)
Beginning today, the first of a series of Command & Data Subsystem
(CDS) flight software V10.0 patches was loaded to the solid state
recorder (SSR) via a real time command spacecraft operations procedure.
Thursday, Aug. 12 (DOY 224)
A kickoff meeting was held for the S66 Sequence Implementation Process.
Port 1 for the first set of input files from the teams occurs August 30.
Saturn's moon Titan ripples with mountains, and scientists have been
trying to figure out how they form. The best explanation, it turns
out, is that Titan is shrinking as it cools, wrinkling up the moon's
surface like a raisin. For more information on this subject, link to:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20100812/
Friday, Aug. 13 (DOY 225)
The Enceladus 11 (E11) encounter occurred at an altitude of 2,550
kilometers, a speed of 6.8 km/sec, and closest approach at
2010-225T22:29:42.33. The focus of the flyby was the study of thermal
emission from the south polar tiger stripes. Because of the
relatively high altitude, the spacecraft was able to track the moon
throughout the flyby. The Composite Infrared Spectrometer (CIRS) had
prime pointing control during closest-approach. The instrument mapped
the thermal radiation from the tiger stripes, continuing coverage
from previous flybys, and took advantage of the excellent viewing
geometry of this flyby. In particular, CIRS focused on warm
transverse fractures that connect the Alexandria and Cairo Sulci to
study whether substantial heat is escaping from the interior in the
regions between the tiger stripes. To close out this flyby, the
Visual and Infrared Mapping Spectrometer collected compositional
data, and then handed over to the Imaging Science Subsystem (ISS) for
further imaging of Enceladus's sister satellite Tethys. For more
information link to:
http://saturn.jpl.nasa.gov/mission/flybys/enceladus20100813/ .
Sunday, Aug. 15 (DOY 227)
A test was performed today to determine whether the low-gain antenna
could be used to acquire coherent Doppler data during Titan flybys
for gravity study purposes while the spacecraft is being turned and
the high-gain antenna is off Earth-point supporting acquisition of
data by other instruments. There were three objectives for the test.
First was to determine whether the spacecraft could maintain lock on
the uplink carrier signal at Saturn ranges with the LGA moving and at
significant off-Earth angles. This was the first time for Cassini to
attempt two-way coherent tracking at Saturn ranges using the LGA.
Next was to verify that the statistical noise on the Doppler data
using the LGA was sufficiently small to be scientifically useful, and
finally, to verify that the observed Doppler from the moving LGA
could be connected to the center-of-mass of Cassini with any
systematic errors small compared with the statistical noise. All data
were successfully acquired and analysis is still ongoing, but initial
results look favorable.
Monday, Aug. 16 (DOY 228)
Orbit Trim Maneuver 260, the clean up maneuver for the E11 flyby, was
cancelled. The cost of cancellation was only about 10 mm/sec.
Cancellation will require some pointing vectors to be updated, but
there are approximately two weeks to accomplish this activity.
Tuesday, Aug. 17 (DOY 229)
This week's science included a number of observations by the
instrument teams. CIRS observed Dione and then moved on to Enceladus,
where it examined the plume. CIRS also measured the oxygen compounds
in the stratosphere of Saturn for 13 hours. ISS took prime control of
the spacecraft and captured further images of Enceladus's plume, took
images of Dione, and also searched for a Dione plume. ISS performed
another observation in its Satellite Orbit Campaign. The
Magnetospheric and Plasma Science (MAPS) instruments collected data
at their nominal survey rates, and the Magnetometer performed a
seven-hour calibration while rolling about the X-axis of the
spacecraft. ISS and CIRS completed another observation in the Titan
monitoring campaign.
Visit the JPL Cassini home page for more information about the
Cassini Project:
http://saturn.jpl.nasa.gov/