Status Report

NASA Cassini Significant Events for 07/01/04 – 07/07/04

By SpaceRef Editor
July 9, 2004
Filed under , , ,
NASA Cassini Significant Events for 07/01/04 – 07/07/04

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, July 7. 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 the successful completion of the
Saturn Orbit Insertion (SOI) Critical Sequence, playback of all SOI
telemetry and science data, Cassini’s first Titan flyby, and acquisition of
temperature and composition data for validation of the Titan atmospheric
model to be used by the Huygens probe when released in December 2004.

Solar Conjunction occurs when the Sun is between the spacecraft and Earth.
This year it will last from July 5 through July 11, and is a time of reduced
commanding and downlink capability. During this period the project will
uplink a command file consisting of 10 no-op commands sent every 5 minutes,
10 to 20 times daily. The purpose of the test is to accumulate statistics
for uplink reliability at decreased separation angles.

Just prior to the start of conjunction, a relative timed IDAP to modify the
telemetry mode was uplinked to the spacecraft. This allowed the instrument
teams to obtain real-time instrument “house keeping” data to confirm the
state of their instruments. The spacecraft is in a normal state and will
remain Earth pointed and quiescent throughout conjunction.

Preliminary port#2 of Science Operations Plan (SOP) Implementation of tour
sequences S31/S32 occurred this week. The delivered products were merged
and reports delivered to the implementation team.

The SOP Update process for S05 began this week, and the process for S04
completed. A handoff package was delivered to Uplink Operations. A
kick-off meeting was then held as part of the S04 Science and Sequence
Update Process, and the Sub-Sequence Generation integrated sequence products
were released to the Sequence Team (ST).

The integrated sequence products and DSN keyword file for S03 were released
to the ST for review, and the instrument teams delivered their instrument
expanded block spacecraft activity sequence files to the file repository.
The final sequence products for S03 will be available next week, and the
sequence approval meeting held the week after. S03 will go active on board
the spacecraft on July 30.

As reported last week, the Cassini Team successfully executed the SOI burn
on June 30, 2004. This main engine burn slowed the spacecraft by 626.17
meters per second or about 2254.2 kilometers per hour and allowed the
spacecraft to be captured by Saturn’s gravity field.

Unlike delta-V burns executed by other JPL spacecraft, Cassini’s SOI burn
was the first and only burn designed to achieve a change in the specific
energy of the spacecraft, instead of a change in the spacecraft velocity.
The “energy” algorithm used was proposed, developed, coded, and
flight-tested by the SCO and Navigation teams.

This maneuver was also unique in the history of JPL in that the burn
direction was changed continuously with time. The SOI “steering” rate was
about 0.008 degrees per second, for a total steering angle of about 46 deg.
This is very close to the rotation rate of the hour hand of a clock. By
“steering”, the main engine thrust tracked approximately the Saturn-relative
velocity of the spacecraft, and the efficiency of the SOI burn was improved.
Less propellant was used as a result.

Following SOI, the decision was made to cancel both Orbital Trim Maneuver
(OTM) 001, and 001a. It was determined that there was no significant
propellant savings or mission benefits to be gained by performing these

Raytheon, Cassini Outreach, and the Instrument Operations (IO) Imaging
Science Subsystem (ISS) team located at JPL were involved in the rapid
development and deployment of the public web site for Cassini raw ISS
images. The site was rolled out on SOI day. IO/ISS supplied design
expertise, image data and metadata, testing, and site documentation.

Mission Assurance conducted a pair of Risk Team meetings to reassess risk to
the probe mission. As a result, three new items were added to the
Significant Risk List (SRL). There are no red risks in the SRL. All
continue to be mitigated to either yellow or green. In addition, all risks
related only to the Cruise portion of the mission and SOI were officially

The flight team continues to be excited and energized by the number of
articles appearing regarding Cassini, and the interest and enthusiasm of the
public. During 64 hours surrounding the SOI period the total number of
website hits were as follows:

261,216,092 = Total for Cassini traffic

136,595,464 = Mission website (

124,620,628 = Portal (

Below are a number of links to additional information:

Three color-filter images of Titan from Cassini are today’s Astronomy
Picture of the Day.
If “today” for you is no longer July 6, 2004, then go to:


Saturn’s density waves were also APOD yesterday, July 5, and you can see
that picture at


A rerun of the Cassini launch was APOD for Saturday, July 3, and that shot
is at

An amazing image of the Encke Gap taken by Cassini is today’s Astronomy
Picture of the Day:
If “today” for you is no longer July 2, 2004, then go to:

SpaceRef staff editor.