From Newsgroup: sci.space.news


Cassini Significant Events 
for 04/13/11 - 04/19/11

The most recent spacecraft telemetry was acquired on April 18 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/mission/presentposition/ .

Wednesday, April 13 (DOY 103)

A software patch to the Cassini Information Management System (CIMS)
Resource Checker (RC) was delivered and installed today. The RC is a CIMS
function that is called by CIMS, but can be altered without the need to
deliver a new version of CIMS. Several enhancements were provided to the RC
as part of this delivery, which are referenced in approved engineering
change request (ECR) 111264.

Files were uplinked to the spacecraft yesterday in support of S67 for the
end of sequence reaction wheels bias and for the swap from Reaction Wheel
Assembly (RWA) 3 to RWA-4 in preparation for S68. Files were verified as
properly received by the spacecraft and will start execution on DOY 115.

An item called "Cassini-Huygens Participating Scientist Announcement of
Opportunity" was released today on the European Space Agency (ESA) web site
as an invitation to submit proposals for Participating Scientist (PS)
positions on the Cassini-Huygens mission. This Announcement of Opportunity
was published jointly by ESA, NASA and the Italian Space Agency (ASI). For
more information link to:

http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=48621 .

Thursday, April 14 (DOY 104)

Seven instrument expanded block (IEB) files were radiated to the spacecraft
today over DSS-43 in support of the S68 background sequence. The S68
sequence will be uplinked on Wednesday, April 20, and go active on Monday,
April 25.

A kickoff meeting was held today for the S70 Sequence Implementation
Process. Port 1 for the first set of input files from the teams occurs April
29.

Friday, April 15 (DOY 105)

Orbit Trim Maneuver (OTM) #280 was performed today. This was the approach
maneuver setting up for the Titan 75 encounter on April 19. The Reaction
Control Subsystem (RCS) burn began at 6:00 PM PDT. Telemetry immediately
after the maneuver showed a burn duration of 13.125 seconds, giving a
delta-V of 0.0212 m/s. All subsystems reported nominal performance after the
maneuver.

Sunday, April 17 (DOY 107)

Non-targeted flybys of Aegaeon and Helene occurred today.

Monday, April 18 (DOY 108)

This week in science closed out the long (26 day) period focusing on the
Magnetospheric and Plasma Science (MAPS) instruments making measurements of
Saturn's magnetosphere. Five optical navigation images were acquired. The
Ultraviolet Imaging Spectrograph (UVIS) performed two more of its series of
repeated slews across the auroral oval of Saturn for 17 hours each, a
special set of observations that were coordinated with Hubble Space
Telescope observations of Saturn's aurorae. Just after periapsis, the Visual
and Infrared Mapping Spectrometer (VIMS) and the Composite Infrared
Spectrometer (CIRS) observed a stellar occultation of a star passing behind
Saturn to determine the hydrogen/helium ratio in Saturn's atmosphere. This
was followed by the Titan T-75 flyby.

T-75 is a pre-dusk, high altitude equatorial flyby across Titan's induced
magnetic tail downstream from the moon. The geometry for T-75 is ideal to
study the structure of the magnetotail and possibly the current sheet that
separates its two lobes. The Cassini Plasma Spectrometer (CAPS) pointing
will lead to important measurements of the ion and electron species escaping
from the moon as a result of its interaction with Saturn's magnetospheric
flow. UVIS obtained measurements of Titan's atmosphere at Extreme
Ultraviolet/Far Ultraviolet (EUV/FUV) wavelengths by sweeping its slit
across the disk of the moon. These data provide spectral and spatial
information on nitrogen emissions, H emission and absorption, absorption by
simple hydrocarbons, and the scattering properties of haze aerosols. This is
one of many such datasets gathered over the course of the mission to provide
latitudinal and seasonal coverage of Titan's middle atmosphere and
stratosphere. CIRS rode along with a slow UVIS scan across the surface to
determine seasonally changing surface temperatures at 19 microns.

Tuesday, April 19 (DOY 109)

Cassini flew by Titan today at an altitude of 10,053 kilometers and a speed
of 5.6 km/sec. Closest approach occurred at 2011-109T05:00:39, at a latitude
of 0.1 degree N. This was one of the two most important Titan flybys in the
entire extended mission for two of Cassini's science teams. The radio and
plasma wave science (RPWS) instrument team and the Cassini plasma
spectrometer (CAPS) instrument team will use this flyby to study how Titan's
and Saturn's magnetospheres interact with each other. For more information
link to: 

http://saturn.jpl.nasa.gov/mission/flybys/titan20110419/ .

The S68 final sequence approval meeting was held today. The background
sequence will go up to the spacecraft on Wednesday, Apr. 20, and will begin
execution on Monday, April 25.


A mission planning forum was held today to discuss the science objectives
for the F-ring and Proximal orbits. These orbits occur during the last year
of Cassini's Solstice mission and represent unique science opportunities.
Science objectives for these orbits include determining the mass of Saturn's
rings, mapping the internal structure of Saturn, and in-situ sampling of
Saturn's atmosphere. The information presented at the forum will be used by
the science and engineering teams to plan for the F-ring and Proximal
orbits.

The Science Forum for S70 was held today. Topics included an overview of
science planned for this sequence followed by highlights, unique activities,
and highest priority observations as described by the Target Working Team
(TWT) and Orbiter Science Team (OST) leads, with comments from the
Investigation Scientists and other instrument team representatives.

Visit the JPL Cassini home page for more information about the Cassini
Project: 

http://saturn.jpl.nasa.gov/

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