Status Report

Cassini Significant Events for 07/10/03 – 07/16/03

By SpaceRef Editor
July 18, 2003
Filed under , ,
Cassini Significant Events for 07/10/03 – 07/16/03

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, July 16. 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 .

On-board activities this week included a Radio and Plasma Wave Science
(RPWS) high frequency receiver calibration, conclusion of the RPWS
cyclic, a Magnetometer Subsystem (MAG) bus interface unit reset, MAG
power on reset, Cassini Plasma Spectrometer (CAPS) instrument
maintenance, ACS, CDS, Visual and Infrared Mapping Spectrometer (VIMS),
and Cosmic Dust Analyzer (CDA) flight software normalization, CDA and
VIMS Instrument Expanded Block (IEB) uplink, completion of the Reaction
Wheel Assembly (RWA)-4 articulation and checkout activity, Saturn Orbit
Insertion (SOI) demo sequence uplink to the SSR, and clearing of the
high water marks.

The normalization of ACS and CDS flight software loads on the SSR was in
preparation for the SOI Critical sequence demo. Old versions of flight
software had been kept in the prime partitions following ACS A8 and CDS
V9 checkout. All partitions now reflect the A8 and V9 copies.

The Spacecraft Operations Office (SCO) completed the Articulated
Reaction Wheel Mechanism (ARWM) and RWA-4 checkout activities this past
week. RWA-4 has now been moved by the ARWM to match the RWA-3 angular
momentum position and has been verified to be in the proper position.
There was a delay of two days during checkout activities due to
questions about the direction to be commanded for the ARWM. After
reviewing pre-launch special tests and the original problem failure
report on commanded direction, the correct direction was commanded and
verified by the remaining tests. A project briefing was held later in
the week where Reaction Wheels 1-2-4 were approved as the prime reaction

The Radio Science Subsystem (RSS) Solar Conjunction Experiment #2 (SCE)
concluded this week. Throughout the month of the experiment, the RSS
team was unable to move the Ka-Band Translator (KaT) frequency from its
current bad region. Given the uncertainty about future KaT performance,
Radio Science believes a re-scoped Gravitational Wave Experiment #3
(GWE) plan is appropriate and responsible given the Project’s policy of
minimizing time spent on reaction wheels. The team has suggested
observations only for the last 20 days of the currently allocated 40-day
interval. The re-scope does not affect GWE scientific objectives or
GWE3’s unique geometry for observations of the galactic center.

The official port#3 merged products were delivered to ACS/SCO as part of
Science Operations Plan implementation for tour sequences S7 and S8. A
wrap-up meeting for this process has been scheduled for July 30.

A Science Planning Team Project Briefing was held for cruise sequence
C40. The integrated product has been approved for implementation. At
the meeting it was decided that the first 2 hours of the new 20-day
GWE#3 would be allocated to ACS to perform an RWA bias. GWE now spans
2003-314T06:42:00 to 2003-334T06:05:00 SCET for a duration of
019T23:02, 37 minutes shy of 20.0 days.

A total of five Sequence Change Requests (SCR) was approved at a
Preliminary Sequence Integration and Validation SCR approval meeting for
C39. Two were corrections to items previously submitted and the other
three were reactions to the removal of the VIMS straylight activities,
which were moved from C39 to C40. Implementation of these SCRs was also
performed this week, and new input files sent back to the Sequence Team
lead by the affected teams.

Events this week for the S14 Science and Sequence Update Process (SSUP)
Verification and Validation (V&V) activity included PSIV2 subsequence
input port, default Live Movable Block (LMB) and trigger
Immediate/Delayed Action Program delivery, distribution of the full
merged sequence products with LMB requests included for the V&V PSIV2
phase, updated PSIV2 IEB loads sent to the Sequence Team lead by the
instrument teams, publication of updated Sequence Phase List of
Ancillary Files (SPLAF) products, conclusion of waypoint analysis and
report distribution, and PSIV2 IEB Command Packet File inputs to CDS.

System Engineering gave a presentation on the background, timeline,
goals and success criteria, test plan, and open issues for the Live
Update V&V. Live Update V&V is part of the SSUP real-time commanding
process. The V&V will operationally certify the processes, timeline,
and execution of commands in the Integrated Test Laboratory. Live Update
V&V will begin after the conclusion of SSUP V&V and will run from mid
August to mid September.

All teams and offices supported the Cassini monthly management review.

System Engineering (SE) assisted Science Planning and Mission Planning
in generating a SPLAF and associated Pointing Design Tool and Sequence
Generator configuration files for both Uplink V&V S14, and for C40. The
tools are still being refined, but appear to be time-savers for the
Operations Teams. Software Requirements Certification Review delivery
meetings were held for the VIMS v7.1, Ion and Neutral Mass Spectrometer
V6, and CAPS v4.0 instrument flight software (FSW). The FSW has been
delivered to the project software library and approved for processing to
uplink as part of the C39 sequence activities.

Delivery coordination meetings were held for BECON V1, Flight System
Dynamics Simulator V2.16, and a Cassini Information Management System
patch delivery V2.5.1. BECON, the Best fit conic gradient optimizer,
uses spacecraft and celestial body ephemeris data to construct the
Inertial Vector Propagator conic vector that minimizes the maximum
vector fit error over the time interval of the Probe Relay.

Cassini is a cooperative project of NASA, the European Space Agency and
the Italian Space Agency. The Jet Propulsion Laboratory, a division of
the California Institute of Technology in Pasadena, Calif., manages the
Cassini mission for NASA’s Office of Space Science, Washington, D.C.

SpaceRef staff editor.