Cassini Significant Events -- for 09/08/05 - 09/14/05

September 16, 2005

(Source: Cassini Project)


The most recent spacecraft telemetry was acquired Tuesday, September 14,
from the Madrid tracking stations. The Cassini spacecraft is in an excellent
state of health and is operating normally. Information on the present
position and speed of the Cassini spacecraft may be found on the "Present
Position" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, September 8 (DOY 251):

All teams and offices supported the Cassini Monthly Management Review.

Friday, September 9 (DOY 252):

A meeting was held today to determine if Orbit Trim Maneuver (OTM) #32 could
be cancelled. It turned out that this maneuver would provide a maximum
pointing improvement of only ~8 microradians, or, according to a member of
the Spacecraft Operations Office, "It's teeny." Science representatives at
the meeting agreed. Other factors discussed included some additional
delta-V farther along in the tour if the OTM was cancelled, around 200 to
250 mm/s, and the fact that navigation accuracy requirements are met without
doing the maneuver. With this information, the Project decided not to
perform the maneuver.

A Delivery Coordination Meeting for Ck-compare Version 2 was held today.
The biggest change in the software involves allowing comparisons of
C-Kernels produced by a number of different tools. Another new feature is
the capability to turn on or off the Autoscaling feature of Gallery Plot.

All proposed science and engineering changes were submitted today as part of
the Aftermarket process for S19. The process will kick-off next Wednesday
with a meeting to assess the list of changes.

Saturday, September 10 (DOY 253):

A Reaction Wheel Assembly bias command was uplinked to the spacecraft today.
This commanding was necessary as a result of the cancellation of OTM-32,
which otherwise would have included the biasing as part of the maneuver
sequence.

A three-day procedure to perform a fuel-side re-pressurization on board the
spacecraft began today. This is the first of two fuel-side
re-pressurizations planned for the tour. One was performed previously
during the Cruise phase between Trajectory Correction Maneuvers 9 and 10.
The timing of the re-pressurization optimizes the mixture ratio for maximum
mission delta-V.

A Cassini Image of Jupiter was Astronomy Picture of the Day (APOD) today.
This is an encore of an image that was first APOD in July of 2000. Our
outreach folks did some research and it turns out that Cassini images have
been selected for encores five times.

Monday, September 12 (DOY 255):

The S17 SOP Update preliminary port occurred today. The products were
merged and the reports published for review. Official port is scheduled for
Friday, September 16.

The S18 Aftermarket process concluded today with the Target Working Teams
and Orbiter Science Teams completing their re-work of the sequence. S18 is
now being prepared for SOP Update, which will kickoff Monday, September 26.

Tuesday, September 13 (DOY 256):

A significant amount of science data was lost during the recent Titan flyby
as a result of an operational problem at the DSN tracking station, and a
software error on the spacecraft. The software error was the larger
contributor of the two causes, and the data loss resulted from an improperly
set flag preventing the spacecraft from writing to or reading from the A
side of the solid state recorder, so the result was performing the encounter
with only half of the expected data storage volume. Commands will be sent on
September 15 to reset the flag to its proper value, and normal operation is
expected after this. The nature of the code error is now fully understood
and has been reproduced in the spacecraft test bed. A decision will be made
in the near future whether to correct the flight code or to implement
workarounds to prevent the conditions that led to execution of the faulty
code.

Wednesday, September 14 (DOY 257):

An Assessment meeting was held today to review all of the requested changes
to the S19 sequence. At this point it looks like all of the changes can be
accommodated. If there are no alterations to the recommendations of the
Target Working Teams and Orbiter Science Teams, there will be no need to
hold the decision meeting on September 27.

Cassini Outreach addressed 85 attendees at the NASA Education Professional
Development Conference last week. The presentation focused on how the Saturn
Observation Campaign members throughout the US could be tapped for Cassini
programming and Saturn observing events. Most attendees were Aerospace
Education Services Program specialists who deliver NASA's education products
and services to different regions of the country.