From: baalke{at}familynet-international.net

Cassini Significant Events
for 05/21/08 - 05/27/08

The most recent spacecraft telemetry was acquired on Monday, May 26, from
the Goldstone, California tracking complex. 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.

Wednesday, May 21 (DOY 142)

Orbit Trim Maneuver (OTM) #156 was performed today. This is the apoapsis
maneuver setting up for the Titan 44 encounter on May 28. The reaction
control subsystem (RCS) burn began at 8:29 PM PST. Telemetry immediately
after the maneuver showed the burn duration was 155.13 seconds, giving a
delta-V of 0.2 m/sec. All subsystems reported nominal performance after the
maneuver.

The final approval meeting was held today for the S41 background sequence.
This will be the final sequence of the prime mission. Sequence leads will
begin uplinking the Instrument Expanded Block (IEB) files on Thursday, and
the background sequence will go up on Monday, May 26.

Based on analysis performed by Science Planning, there is currently only a
small deviation between the OTM-156 orbit determination solution and the
reference trajectory for the Janus observation scheduled for later this
week. The current pointing difference stands at 0.37 mrad. Because of this
it has been decided to cancel the Saturn/Janus live update scheduled for
May 25, 26.

Extended Mission sequence development continued today with teams delivering
their inputs for the second of three ports for the S44 sequence. The files
were merged and reports were sent out to the teams for review and
resolution. AACS will perform end-to-end pointing and the first Reaction
Wheel Assembly Bias Optimization Tool analysis on this product. The third
and final port is scheduled for June 18.

Thursday, May 22 (DOY 143)

An encounter strategy meeting was held today to cover the period between
May 28 and July 31, Titan flybys T44 and T45, and maneuvers 158-160.

In addition to the IEB files for S41, sequence leads also sent command
files for Radio and Plasma Wave Science (RPWS) direction finding for
periapsis science enhancement. The RPWS file has been registered on-board
the spacecraft and will start executing on 146T16:15. The only remaining
IEB - ISS S41 IEB Load to the SSR, part 2 - will be radiated tomorrow.

Science Planners have delivered the hand-off package to Uplink Operations
for the S43 background sequence. The final sequence development process for
this sequence will begin on Tuesday, May 27.

Friday, May 23 (DOY 144):

Thanks to a very accurate OTM-156 orbit determination solution and maneuver
execution, OTM-157 has an estimated magnitude of 2 mm/sec, which is less
than the minimum RCS maneuver magnitude, with a deviation from the targeted
aim point of less than 400 meters. Science Planning reviewed the
no-maneuver solution and has determined that there is no impact to science.
Therefore, OTM-157, scheduled for Sunday, May 25, has been cancelled.

The Ultraviolet Imaging Spectrograph (UVIS) led a joint Optical Remote
Sensing (ORS) instrument campaign to image the northern aurora of Saturn
today. In addition, the Visual and Infrared Mapping Spectrometer (VIMS)
gathered information on Saturn's atmospheric dynamics.

Saturday, May 24 (DOY 145):

Non-targeted flybys of Pallene, Atlas, and Janus occurred today.

Sunday, May 25 (DOY 145):

Following the gathering of more VIMS data on Saturn's atmospheric dynamics,
the Composite Infrared Spectrometer (CIRS) led a joint ORS observation of a
Tethys solar eclipse. VIMS watched a star as it was occulted by the rings,
and ISS looked at some satellites to improve orbit estimation accuracy. As
the spacecraft moved though periapsis, ISS and UVIS led high priority
observations of a Saturn solar occultation.

Congratulations to the Phoenix Flight Team today on their successful entry,
descent, and landing operations!

Monday, May 26 (DOY 147):

Sequence leads successfully uplinked the S41 background sequence today.

As the spacecraft moved outbound from periapsis, ISS led a joint ORS
observation of Janus by means of limb sounding in the mid-IR, CIRS
performed a Saturn limb integration to obtain stratospheric thermal
structure, VIMS performed more measurements of the global dynamics of
Saturn, and ISS wrapped up the day with an observation of Enceladus.

Tuesday, May 27 (DOY 148):

The Cassini-Huygens Analysis and Results of the Mission (CHARM)
teleconference for May was titled The History of Saturn's Rings.

Coming Up:

"Naked Science 5: Saturn's Secrets" will air for the first time
this Sunday, June 1, at 3:00 PM Pacific Time, on the National Geographic
Channel. Many images from Cassini will be shown.
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