Latest Mission Status Report

22 months ago, NASA's Cassini spacecraft left Earth to begin its seven year odyssey to the beautiful ringed planet, Saturn. Early tomorrow morning, after swinging around the inner Solar System and completing two flybys of the planet Venus, Cassini will briefly return home for a third boost in speed which will kick it away from the Sun and towards Jupiter and Saturn.

The spacecraft, launched on its mission to Saturn in October 1997, will make its closest approach to Earth at an altitude of 1,166 km (725 miles, or about five times higher than the Space Shuttle's orbit) over the eastern South Pacific at -23.5 degrees latitude and 231.5 degrees longitude. It may be visible from small islands in that area, such as Pitcairn Island or Easter Island.

Although the primary purpose of this Earth flyby is to increase the spacecraft's speed by borrowing some energy from our planet - a manoeuvre known as a gravity assist - the encounter will also be of considerable interest to scientists from the UK. Nine of Cassini's 12 scientific instruments will make observations of the Earth-Moon system during the spacecraft's passage, including studies of Earth's magnetic environment and images of the Moon. UK scientists are involved with a number of the science instruments which will be switched on during this brief encounter.

One of the most significant events prior to the flyby was yesterday's successful deployment of the 11 metre long boom to which the two magnetometer sensors of Cassini's dual technique magnetometer instrument (MAG) are attached. Principal scientific investigator for MAG is Professor David Southwood of Imperial College, London and one of the co-investigators is ICL's Dr.Michele Dougherty.

The MAG instrument was turned on 44 hours before the closest approach to the Earth and scientists at Imperial College are already very excited about the data they are receiving from the instrument whilst the spacecraft is making its way towards the Earth. The flyby is extremely important to them since it can be used as an instrument calibration exercise, since the magnetic field of the Earth is very well known. Of prime scientific interest will be data from the interaction between the solar wind and Earth's magnetic field and plasma environment. In particular, studies of the enormous tadpole-shaped magnetotail, which stretches millions of kilometres 'downwind' on the planet's leeward side, will be carried out.

The Cassini Plasma Spectrometer (CAPS) instrument, with its Ion Beam Spectrometer and Electron Spectrometer, was turned on today about 16 hours before closest approach to Earth. Dr. Andrew Coates of Mullard Space Science Laboratory is the team leader for the Electron Spectrometer part of this instrument, while Rutherford Appleton Laboratory is also involved. CAPS is investigating how the electrically charged particles of the solar wind interact with our magnetic planet. "We know a lot about Earth's magnetic field, so this will be an ideal opportunity to calibrate our instrument in preparation for arrival at Saturn," said Dr. Coates.

The Earth flyby will also provide an opportunity to check out some of the other instruments. The Radio and Plasma Wave Science (RPWS) instrument will be tested during studies of low frequency waves in the sea of charged particles surrounding the Earth. Dr Hugo Alleyne and the late Dr. Les Woolliscroft of the University of Sheffield provided data compression software for the RPWS experiment.

Also undergoing calibration during the flyby will be the wide and narrow angle cameras of Cassini's Imaging Science Subsystem (ISS). Although no images of the Earth will be taken, about a dozen views of the half Moon will be snapped in visible and infrared light using various configurations of filters. As the Moon comes into Cassini's view, the cameras will obtain shots of both the illuminated and dark hemispheres. Professor Carl Murray of Queen Mary and Westfield College, London is a member of the ISS team. He and his colleagues at QMW produced the ISS calibration software used during the flyby.

While most of the spacecraft's instruments have been switched off since launch in October 1997, the Cosmic Dust Analyser (CDA) instrument has been operating continuously since 25 March 1999. It is expected to continue sending back data for nearly another decade. The instrument has already detected a number of dust impacts, some of which seem to have originated beyond our Solar System. It seems likely that CDA's chemical analyser, which has been provided by the University of Kent, has returned the first data ever obtained on the composition of an interplanetary dust particle. Professor Tony McDonnell from Kent is one of the CDA investigators. Rutherford Appleton Laboratory also contributed to the design and manufacture of this instrument.

NEXT STOP JUPITER

Saturn is so far away that it will take Cassini six years and nine months to get there. Since there are no launch vehicles powerful enough to send such a huge spacecraft directly to Saturn, mission planners turned to the tried and tested technique of gravity assists. This enables an energy exchange in which the spacecraft gains speed and alters its flight direction while reducing the orbital velocity of the planet by a minute amount.

In order to benefit from this technique and reach the ringed planet, the 5650 kilogram Cassini had to be launched inward towards Venus. Only after completing two Venus flybys, a flyby of Earth and one of Jupiter, will the bus-sized spacecraft have accelerated sufficiently to reach Saturn.

The Earth swingby will bend Cassini's flight path so that it heads towards Jupiter. Passing about 9.7 million km (6 million miles) from the gas giant on 30 December 2000, it will use Jupiter's gravity to change course and speed for its final destination of Saturn.

Saturn is ten times further from the Sun than the Earth - about 1,430 million km (900 million miles). Cassini's arrival is scheduled for 1 July 2004. Over the following four years, it will conduct 27 different scientific investigations of the giant planet's atmosphere and magnetosphere, its magnificent rings, and sixteen of the known moons. The largest of these, Titan, is particularly fascinating since it has a thick, cloudy atmosphere which is mostly made of nitrogen but also contains hydrocarbons such as methane - similar to the atmosphere of the early Earth but much colder.

Cassini will complete more than 60 orbits of Saturn, including about 45 close flybys of Titan and about 20 flybys of some of the smaller, icy moons. This tour is made possible by using planet-sized Titan's gravity to alter Cassini's orbit each time the craft swoops to within a few thousand kilometres of the moon's orange cloud tops.

January 1 1999

Spacecraft Status:

The most recent spacecraft status is from the DSN tracking pass on Tuesday, 12/29, over the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is executing the Cruise 11 sequence normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:

On Thursday, 12/24, the Probe Support Avionics (PSA) prime status was reset. This activity follows each Probe Checkout (PCO).

On Sunday, 12/27, Instrument Checkout (ICO) began. The first ICO activities involved the successful maneuver of the Spacecraft to a High Gain Antenna (HGA) to Earth point attitude. Once two-way communications was established using the HGA, the Probe data from PCO #3 that was stored on the SSR was played back, and a realtime command to clear the AACS High Watermarks was uplinked to the spacecraft.

On Monday, 12/28, the Radio Science Subsystem (RSS) began ICO activities with Ultra Stable Oscillator Test #1. The test was extremely successful and was the first time ever for three frequencies (S-Band, X-Band, and Ka-Band) to be simultaneously downlinked from a single spacecraft and recorded on the ground.

On Tuesday, 12/29, RSS performed its second test, a repeat of USO test #1 but without Ka-band transmission.

Upcoming events:

The events planned for the next reporting period consist primarily of a continuation of the ICO activities. RPWS, MAG, CDA, MIMI, CAPS, INMS, UVIS, and continued RSS tests are the principal participants.

December 24 1998

Due to the Christmas and New Years Holidays, reporting periods for the next three weeks
will be slightly irregular. This week's report covers Friday (12/18) through Wednesday (12/23)
(inclusive).

Spacecraft Status:

The most recent spacecraft status is from the DSN tracking pass on Tuesday, 12/22, over the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is executing the Cruise 11 sequence normally.

Spacecraft Activity Summary:

On Friday, 12/18, two activities were performed. The third component of Periodic Engineering Maintenance (Reaction Wheel Portion) executed, and Instrument Flight Software was updated for MIMI, CDA, CIRS and RPWS in preparation for Instrument Checkout.

On Monday, 12/21, two additional activities were done. Occurring approximately every 6 months, Probe Checkout number 3 was conducted as planned, and following this a Flight Software update was performed for CAPS and INMS in preparation for Instrument Checkout.

Upcoming events:

Activities scheduled for the week of 12/24-12/29 (Thursday through Tuesday) include reset of the PSA (Probe Support Avionics) Prime status following Probe Checkout (PCO) on 12/24, beginning of Instrument Checkout (ICO) Period, switch to High Gain Antenna (HGA), High Watermark Clear, and playback of PCO data on 12/27, begin Radio Science Subsystem
(RSS) ICO activities and Ultra Stable Oscillator Test #1 on 12/28, and RSS Test B and playback of ICO data on 12/29.

December 18 1998

Spacecraft Status:

The most recent spacecraft status is from the DSN tracking pass on Thursday, 12/17, over the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is executing the Cruise 11 sequence normally. The Cassini spacecraft is presently traveling at a speed of approximately 66,338 kilometers/hour relative to the sun and has traveled approximately 1.079 billion kilometers since launch on October 15, 1997.

Spacecraft Activity Summary:

On Friday, 12/11, the Solid State Recorder (SSR-B) record and playback pointers were reset as planned.

On Sunday, 12/13, two planned of the three possible components of Periodic Engineering Maintenance were performed. All activities were nominal;the third component is planned for next week.

On Wednesday, 12/16, routine maintenance was performed on the Solid State Recorder (SSR-B) flight software partitions.

On Thursday, 12/17, an Instrument Flight Software update was performed for MIMI in preparation for Instrument Checkout.

Upcoming events:

Activities scheduled for the week of 12/18-12/24 include SSR Pointer Reset, Periodic Engineering Maintenance (Reaction Wheel Portion), and Instrument Flight Software update for CDA, CIRS and RPWS on 12/18, Probe Checkout, SSR Pointer Resets, and Flight Software update for CAPS and INMS on 12/21, and reset of the PSA (Probe Support Avionics) Prime status following Probe Checkout on 12/22.

December 11 1998

Spacecraft Status:

The most recent Spacecraft status is from the DSN tracking pass on Thursday, 12/10, over the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is executing the Cruise 11 sequence normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:

On Friday, 12/04, data was played back from the very successful Deep Space Maneuver. Following this, the record and playback pointers were reset as planned.

On Saturday, 12/05, the oxidizer side of Propulsion Module Subsystem (PMS) was successfully isolated by closing pyro valve PV24. This was a planned activity as part of the post Deep Space Maneuver (DSM) reconfiguration.

On Monday, 12/07, part two of the Cruise 11 sequence was successfully uplinked to the spacecraft. Following this activity, a calibration was initiated on the attitude control Stellar Reference Units (SRUs) but was halted by AACS fault protection. Flight engineers are investigating the cause for the test interruption. Once the cause is understood, the calibration test will be rescheduled.

On Wednesday, 12/09, the AACS High Watermarks were cleared.

On Thursday, 12/10, an update was performed to the Active IVP Vector to correct for the change in the trajectory due to the successful completion of the DSM. A post DSM update was also made to the on-board mass properties stored in AACS software. These are the final activities associated with the post DSM reconfiguration.

Upcoming events:

Activities scheduled for the week of 12/11-12/18 include an SSR Pointer Reset on 12/11, a Periodic Engineering Maintenance (BAIL and EGA portions) on 12/13, SSR FSW Partition Maintenance on 12/16, and Instrument flight software updates for CDA, CIRS, and RPWS on 12/17.

December 4 1998

Cassini/Huygens successfully completed its long-planned 90-minute firing of its onboard rocket engine on 3 December, setting the spacecraft on course for a second flyby of Venus in June - the next major milestone on the long voyage to Saturn. More...

Spacecraft Status:

The most recent Spacecraft status is from the DSN tracking pass on Thursday, 12/03, over the Madrid tracking station. The Cassini spacecraft is in an excellent state of health and is executing the Cruise 11 sequence normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:

On Saturday, 11/28, the Solid State Recorder (SSR-B) record and playback pointers were reset as planned (nominally once per week).

On Tuesday, 12/01, the Propulsion Module Subsystem (PMS) was successfully pressurized in preparation for Wednesday's Deep Space Maneuver (DSM).

On Wednesday, 12/02, the Deep Space Maneuver, a large maneuver required to shape the spacecraft trajectory to achieve the proper energy gain from the next Venus flyby, was sucessfully uplinked and executed. Nominal maneuver size was 449.97 m/s and was expected to take approximately 87 minutes to complete.

Maneuver activities began with a series of commands to reconfigure spacecraft heaters for the main engine burn. The next set of spacecraft activities was commands to open the cover for the main engine. After spacecraft telemetry confirmed that the cover had been successfully opened, a ground command was sent to activate the main engine burn sequence. The S/C first performed roll and yaw turns to reach the desired burn attitude. The main engine burn began slightly after 10:00 PM PST and completed 87 minutes 35 seconds later. The S/C then re-oriented itself to the nominal sun-point attitude, closed the main engine cover, and reconfigured for the nominal cruise state.

All S/C telemetry and radiometric data indicate that the maneuver was extremely successful. S/C carrier signal was tracked by the DSN throughout the maneuver. Burn time was within 1% of the nominal value, all propulsion system parameters were within expected ranges, and the attitude control system reports an excellent maneuver. Continued tracking by the DSN will
provide data for an updated navigation solution to be made available on Dec. 5.

On Thursday, 12/03, three activities occurred. The VIMS Decontamination Heaters were powered up for a 24 hour period, the AACS High Watermarks were cleared, and routine maintenance was performed on the Solid State Recorder (SSR-B) flight software partitions.

Upcoming events:

Activities scheduled for the week of 12/04-12/10 include data playback from the DSM and an
SSR Pointer Reset on 12/04, Propulsion Module Subsystem isolation on 12/05, uplink of the
C11 Sequence Part II and Stellar Reference Unit calibration on 12/07, AACS High
Watermark Clear on 12/08, and IVP Vector Update and Mass Properties Update on 12/10.

November 27 1998

Spacecraft Status:

The most recent Spacecraft status is from the DSN tracking pass on Tuesday, 11/24, over the Canberra tracking station. The Cassini spacecraft is in an excellent state of health and is executing the Cruise 11 sequence normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:

On Friday, 11/20, routine maintenance was performed on the Solid State Recorder (SSR-B) flight software partitions

On Saturday, 11/21, the Solid State Recorder (SSR-B) record and playback pointers were reset as planned (nominally once per week).

On Sunday, 11/22, three activities occurred. Science & Engineering Record (S&ER) 3 telemetry mode was installed into the CDS in preparation for the Instrument Checkout in January. An accelerometer calibration was performed. The accelerometer was powered up for this activity and will remain powered ON in preparation for the upcoming Deep Space Maneuver (DSM). The AACS High Watermarks were cleared as the last activity for this
day.

Upcoming events:

Activities scheduled for the week of 11/27-12/03 include: SSR Pointer Reset (11/28), Propulsion Module Subsystem (PMS) Pressurization & Playback (12/01), DSM Mini Sequence Uplink and Execution (12/02), Power on VIMS Decontamination Heaters, Active IVP Vector Update, and AACS High Watermark Clear (12/03), and SSR Memory Load Repair (12/03).

November 20 1998

Spacecraft Status:

The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 11/18, over the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is executing the Cruise 11 sequence normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:

On Sunday, 11/15, the Solid State Recorder (SSR-B) record and playback pointers were reset as the last activity in the C10 sequence.

On Wednesday, 11/18, an update to the Active Spacecraft IVP (Inertial Vector Propagator) Vector was made in preparation for the Deep Space Maneuver (DSM) which occurs on Dec 2 (Dec 3 UTC).

Upcoming events:

Activities scheduled for the week of 11/20-11/26 include: Solid State Recorder Flight Software Partition Maintenance on 11/20, SSR Pointer Reset on 11/21, Installation of the Science & Engineering Record (S&ER) 3 telemetry mode into the CDS in preparation for the Instrument Checkout in January, Accelerometer Calibration, and AACS High Watermark Clear on 11/22, a window for possible Accelerometer Bias Parameter Update on 11/23, and AACS Parameter Update prior to the DSM on 11/25.

November 13 1998

Spacecraft Status:

The most recent Spacecraft status is from the DSN tracking pass on Monday, 11/09, over the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is executing the Cruise 10 sequence normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:

On Friday, 11/06, routine maintenance was performed on the Solid State Recorder (SSR-B) flight software partitions.

On Saturday, 11/07, Part 1 of the Cruise 11 sequence was successfully uplinked to the spacecraft.

On Monday, 11/09, a housekeeping activity was performed which reads out a set of AACS Attitude Estimator measurements not available in regular engineering telemetry, and the Solid State Recorder (SSR-B) record and playback pointers were reset

Upcoming events:

Activities scheduled for the week of 11/13-11/19 include initiation of the C11 sequence, SSR Pointer Reset on 11/15, and update active to Spacecraft Vector on 11/18. Ranging passes will occur on 11/13 and 11/15.

November 6 1998

Spacecraft Status:

The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 11/04, over the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is executing the C10 sequence normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:

On Monday, 11/02, three activities were performed: the Delta-V Estimator Flight Software Update was sent up to the spacecraft, the Solid State Recorder (SSR) record and playback pointers were reset, and the AACS High Water marks were cleared.

On Tuesday, 11/03, Part 1 of the SSR-A Power Off was performed. Powering off the SSR will enhance the overall life expectancy of the unit. Part one consisted primarily of a complete memory test prior to the power off commands.

On Wednesday, 11/04, Part two of the SSR-A Power Off was performed and the VIMS Decontamination Heaters were powered up for a 24 hour period.

Upcoming events:

Activities scheduled for the week of 11/06-11/12 include SSR FSW Partition Maintenance on 11/06, uplink of the C11 sequence on 11/07, and AACS Attitude Estimator Memory Readout and SSR Pointer Reset on 11/09.

October 30 1998

Spacecraft Status:

The most recent Spacecraft status is from the DSN tracking pass on Monday,10/26, over the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and is executing the C10 sequence normally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:

On Monday, 10/26, three activities were performed. The Remote Engineering Unit Memory Read Out (MRO) for the Main Engine Cover was combined with Real-time Engineering Mode (RTE)158 in a final test for their use in support of the Deep Space Maneuver scheduled for 12/3/98.

This was followed by a housekeeping activity which reads out a set of AACS Attitude Estimator (ATE) measurements not available in regular engineering telemetry. Finally, routine maintenance was performed on the Solid State Recorder (SSR) flight software partitions.

Upcoming events:

Activities scheduled for the week of 10/30 - 11/05 include the Delta-V Estimator Flight Software Update, SSR Pointer Reset, and AACS High Water Mark Clear on 11/02, and SSR-A Power Off parts 1 & 2 and Power On VIMS Decontamination Heaters on 11/03, 04. Ranging passes are scheduled for 10/30 and 11/03.

October 23 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Monday,10/19, over Goldstone. The Cassini spacecraft is
in an excellent state of health and is executing the C10 sequence normaly. The speed of the spacecraft can be viewed on the
"Where is Cassini Now?" web page.

Spacecraft Activity Summary:
On Monday, 10/19, two activities were performed. An update was performed to the Active IVP Vector to correct for the
normal accumulation of inaccuracies due to Spacecraft motion. This was followed by a test of Real-time Engineering Mode
(RTE)158 for it's use in support of the Deep Space Maneuver (currently scheduled for 12/3/98). On Wednesday, 10/21, the Solid State Recorder (SSR) record and playback pointers were reset.

Upcoming events:
Activities scheduled for the week of 10/23 - 10/29 include:
DSM Preparation Test (date tentative), AACS ATE MRO, and SSR FSW Partition Maintenance on 10/26, and an SSR
Pointer Reset, 10/28. Ranging passes are scheduled for 10/23 and 10/29.

October 16 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Monday, 10/12, over Madrid. The Cassini spacecraft is in
an excellent state of health and is executing the C10 sequence nominally. The speed of the spacecraft can be viewed on the
"Where is Cassini Now?" web page.

Spacecraft Activity Summary:
Saturday, 10/10, routine maintenance was performed on the SSR flight software partitions. Sunday, 10/11, quarterly Periodic Instrument Maintenance was performed as planned on board the spacecraft. This activityinvolves 11 out of the 12 onboard instruments and runs for a 24 hour period. Wednesday, 10/14, the Solid State Recorder (SSR) record and playback pointers were reset.

Upcoming events:
Activities scheduled for the week of 10/16 - 10/22 include:
Active IVP Vector Update and RTE 158 Test on 10/19, and an SSR Pointer Reset on 10/21.

October 9 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 10/07, over Goldstone. The Cassini
spacecraft is in an excellent state of health and is executing the C10 sequence nominally. The speed of the spacecraft can be
viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:
Monday, 10/05, a housekeeping activity was performed which reads out a set of AACS Attitude Estimator (ATE) measurements not available in regular engineering telemetry. Wednesday, 10/07, four activities took place: the Solid State Recorder (SSR) record and playback pointers were reset; a CDS Flight Software Patch was sent to the spacecraft to avoid backup CDS resets resulting from science telemetry mode transitions; uplink was performed of the SAF Alt Mode Table, which loads 3 alternate versions of where science data are collected from the instruments in the SAF 248 telemetry mode in preparation for Instrument Checkout; and the AACS High Watermarks were cleared.

Upcoming events:
Activities scheduled for the week of 10/09 - 10/15 include:
SSR FSW Partition Maintenance on 10/10, Periodic Instrument Maintenance on 10/11, and an SSR Pointer Reset on 10/14.
Ranging passes occur on 10/13 and 10/14.

October 2 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Monday, 09/28, over Madrid. The Cassini spacecraft is in
an excellent state of health and is executing the C10 sequence nominally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:
On Sunday, 09/27, three activities took place. A housekeeping activity was performed which reads out a set of AACS Attitude Estimator (ATE) measurements not available in regular engineering telemetry. This was followed by the clearing of AACS High Watermarks and routine maintenance performed on the SSR flight software partitions. On Wednesday, 09/30, the Solid State Recorder (SSR) record and playback pointers were reset.

Upcoming events:
Activities scheduled for the week of 10/02 - 10/08 include:
Ranging passes on 10/04, AACS ATE MRO on 10/05, CDS FSW Patch, Uplink of SAF Alt Mode Table, Clear AACS High Watermark, and SSR Pointer Reset all on 10/07.

September 24, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 09/23, over Goldstone. The Cassini spacecraft is in an excellent state of health and is executing the C10 sequence nominally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:
Two activities were performed on Wednesday, 09/23. First, routine maintenance was performed on the SSR flight software partitions, and a housekeeping activity was performed which reads out a set of AACS Attitude Estimator measurements not available in regular engineering telemetry.

Next, the quarterly Periodic Engineering Maintenance was performed as planned on board the spacecraft. This activity consists of 3 parts: the AACS BAIL Maintenance, the Reaction Wheel Assembly (RWA) exercise, and the Engine Gimbal Actuator (EGA) exercise.

Upcoming events:
Activities scheduled for the week of 09/25 - 10/01 include: SSR FSW Partition Maintenance, AACS High Watermark Clear, AACS ATE MRO, and ranging passes on 09/27, SSR Pointer Reset on 09/30.

September 18, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Tuesday, 09/15, over Goldstone. The Cassini spacecraft is in an excellent state of health and is executing the C10 sequence nominally. The speed of the spacecraft can be viewed on the " Where is Cassini Now?" web page.

Spacecraft Activity Summary:
On Monday, 09/14, routine maintenance was performed on the SSR flight software partitions, and a housekeeping activity was performed which reads out a set of AACS Attitude Estimator measurements not available in regular engineering telemetry.
On Tuesday, 09/15, a Remote Engineering Unit MRO for the Main Engine Cover was performed. This MRO is a test for an operation to be used for the Deep Space Maneuver. After the MRO, the Solid State Recorder (SSR) record and playback pointers were reset.

Upcoming events:
Activities scheduled for the week of 09/18 - 09/24 include a Periodic Engineering Maintenance, AACS High Watermark Clear, and SSR Pointer Reset on 09/23, and a Ranging Pass on 09/24.

September 11, 1998

Program Level Items:
The monthly Cassini Program status report to NASA Headquarters was held on 9/09 via videocon. A reorganization of the Cassini Program was announced on 9/08, effective immediately.

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Tuesday, 09/08, over Madrid. The Cassini spacecraft is in an excellent state of health and is executing the C9 sequence nominally. The C9 sequence will complete on 9/13, at which point the C10 sequence will begin. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:
On Monday, 09/07, the C10 sequence was uplinked to the spacecraft as scheduled.

On Wednesday, 09/09, the Solid State Recorder (SSR) record and playback pointers were reset. This housekeeping activity, done approximately weekly, maximizes the amount of time that recorded engineering data is available for playback to the ground should an anomaly occur on the spacecraft.

September 4, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 09/02, over Goldstone. The Cassini spacecraft is in an excellent state of health and is executing the C9 sequence nominally. The C9 sequence will complete on 9/13, at which point the C10 sequence will begin. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" web page.

Spacecraft Activity Summary:
On Wednesday, 09/02, three activities took place. Maintenance was performed on the SSR Flight Software Partitions. This activity, performed approximately every 2 weeks, repairs any SSR double bit errors (DBEs) which have occurred in the code-containing portions of the Flight Software partitions during the preceding period.

Secondly, a high-water mark maintenance activity was performed. This activity, scheduled approximately every two months over an available command/telemetry pass, clears the AACS high-water mark telemetry channels. These channels track the extremes of certain AACS values (hi or low) experienced since the last time the maintenance was performed.

Upcoming events:
Activities scheduled for the week of 04/09-10/09 include: Uplink of the Cruise 10 Sequence, (07/09) and SSR Pointer Reset (09/09).

September 4, 1998

The Cassini spacecraft remains in excellent health on its voyage to Saturn. Spacecraft operations have been normal with most tasks focused on routine maintenance activities. Early last month, the Cassini Program reduced -- earlier than planned -- the number of Deep Space Network communications antennas needed to collect navigation ranging data on the spacecraft, at least through the end of the calendar year. This frees up valuable time on the powerful 70-meter antennas for use by other space exploration projects. The Cassini program had been using 34-meter and 70-meter antennas in tandem at each of the three Deep Space Network complexes for spacecraft telecommunications and for gathering navigation ranging data on the spacecraft's position. But because of better-than-predicted ranging system performance and an improving telecommunications link due to the relative positions of Earth and Cassini, the 70-meter stations currently are not needed to augment the spacecraft ranging data collected with the 34-meter antennas. As the geometry between Earth and Cassini further improves, the program will temporarily give up the use of the 70-meter antennas for telecommunications, and will rely solely on the 34-meter antennas for an as-yet-undetermined period of time. Today, Cassini is travelling at about 81,770 kilometres per hour (about 50,800 miles per hour) and has travelled more than 900 million kilometres (about 560 million miles).

28 August, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 26/08, over Goldstone. The Cassini spacecraft is in an excellent state of health and is executing the C9 sequence nominally.

Spacecraft Activity Summary:
On Wednesday, 26/08 the Solid State Recorder (SSR) record and playback pointers were reset. This housekeeping activity, done approximately weekly, maximises the amount of time that recorded engineering data is available for playback to the ground should an anomaly occur on the spacecraft.

Upcoming events:
Activities scheduled for the week of 28/08 - 03/09 include: SSR FSW Partition Maintenance and SSR Pointer Reset, both performed on 02/09.

21 August, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Thursday, 20/08, over Madrid. The Cassini spacecraft is in an excellent state of health and is executing the C9 sequence nominally.

Spacecraft Activity Summary:
On Wednesday, 19/08, maintenance was performed on the SSR Flight Software Partitions. This activity, performed approximately every 2 weeks, repairs any SSR double bit errors (DBEs) which have occurred in the code-containing portions of the Flight Software partitions during the preceding period. Also on Wednesday, the Solid State Recorder (SSR) record and playback pointers were reset.

Upcoming events:
Activities scheduled for the week of 21/08 - 27/08 include: SSR Pointer Reset (26/08).

14 August, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 12/08, over Goldstone. The Cassini spacecraft is in an excellent state of health and is executing the C9 sequence nominally. The speed of the spacecraft can be viewed on the "Where is Cassini Now?" page.

Spacecraft Activity Summary:
Beginning on Friday, 07/08, the Cassini Program has been able to reduce the number of DSN stations needed to collect Navigation ranging data, at least through the end of the calendar year. For the last several months, dual 34 meter/70 meter DSN tracks have been needed for both spacecraft command/telemetry passes and ranging-only passes. Ground controllers have found that due to better than predicted ranging performance and an improving telecom link due to recently improved trajectory geometry, the 70 meter stations can be released from the ranging-only tracks. This release will free time on these unique and valuable DSN stations for use by other projects.

On Wednesday,12/08, an activity was performed to store RTE 158-enable and ATC6 parameter-update software on the Solid State Recorder (SSR). This software had been uplinked to the spacecraft several weeks ago, but only to active CDs memory. The storage of this software on the SSR makes the RTE 158 and ATC6 capabilities easily recoverable in the unlikely event of an anomaly with one of the CDS computers.

Upcoming events:
Activities scheduled for the week of 14/08 - 20/08 include: SSR FSW Partition Maintenance, and SSR Pointer Reset (19/08).

7 August, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Thursday, 06/08, over Madrid. The Cassini spacecraft is in an excellent state of health and is executing the C9 sequence nominally.

Spacecraft Activity Summary:
On Friday, 31/7, several bus heaters were turned off as their heat was no longer needed. Also on Friday, several address ranges were changed in the AACS trickle Memory Readouts (MROs), allowing certain AACS telemetry channels to be collected on the ground whenever Cassini has a scheduled DSN telemetry pass. This address update will allow future cancellation of specially scheduled AACS Attitude Estimator (ATE) MROs. On Wednesday, 05/08, maintenance was performed on the SSR Flight Software Partitions. This activity, performed approximately every 2 weeks, repairs any SSR double bit errors (DBEs) which have occurred in the code-containing portions of the Flight Software partitions during the preceding period.

Upcoming events:
Activities scheduled for the week of 07/08 - 13/08 include: SSR Pointer Reset (12/08), and store RTE158-enable and ATC6 parameter-update software on SSR (8/12) (rescheduled from 01/08).

31 July, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Saturday, 25/07, over Madrid. The Cassini spacecraft is in an excellent state of health and is executing the C9 sequence nominally. Inertial attitude control is being maintained using the spacecraft's hydrazine thrusters (RCS system). The spacecraft continues to fly in a High Gain Antenna-to-Sun attitude. The downlink telemetry rate is presently 40 BPS.

Spacecraft Activity Summary:
Telemetry from the DSN track on Friday, 24/7, confirmed that the quarterly Periodic Instrument Maintenance (PIM) activity, performed on 23/07 and 24/07, completed as planned. Also on Friday, an SSR Flight Software Partition maintenance activity was performed. This activity, scheduled approximately every 2 weeks, repairs any SSR double bit errors (DBEs) which have occurred in the code-containing portions of the Flight Software partitions during the preceding period. On Wednesday, 29/07, the Solid State Recorder (SSR) record and playback pointers were reset. This housekeeping activity, performed approximately weekly, maximises the amount of time that recorded engineering data is available for playback to the ground should an anomaly occur on the spacecraft.

Upcoming events:
Activities scheduled for the week of 31/07 - 06/08 include: power off bus heaters (31/07), update address range for AACS trickle MRO data (31/07), store RTE158-enable and ATC6 parameter-update software on SSR (01/08), perform SSR FSW Partition Maintenance and SSR Pointer Reset (05/08), and perform an Attitude Estimator MRO (06/08).

24 July, 1998

Spacecraft Status:
The most recent Spacecraft status is from the DSN tracking pass on Wednesday, 22/07, over Goldstone. The Cassini spacecraft is in an excellent state of health and is executing the C9 sequence nominally.

Spacecraft Activity Summary:
On Wednesday, 22/07, Periodic Instrument Maintenance (PIM) began execution, as planned. This activity is carried out every three months by 11 of the 12 Orbiter instruments. This activity concludes Thursday (23/07). PIM results will be reported in next week's Significant Events Report.

Upcoming events:
Activities scheduled for the week of 24/07 - 30/07 include: SSR FSW Partition Maintenance (24/07) and an SSR Pointer Reset (29/07).

July 7, 1998

The Cassini spacecraft's routine flight operations schedule was dominated by light "housekeeping" and maintenance activities over the past month, with the spacecraft remaining in excellent health.

For telecommunications with Earth, Cassini switched from low-gain antenna 1 to low-gain antenna 2 as planned; the antenna selected depends on the relative geometry of the Sun, Earth and the spacecraft.

The quarterly periodic spacecraft engineering maintenance was performed, which includes activities to lubricate the reaction wheel assembly mechanisms, which are one of two systems on Cassini used to provide pointing control for the spacecraft. The assemblies are electrically powered wheels that are mounted in three orthogonal axes onboard Cassini. To rotate the spacecraft in any one direction, the appropriate wheel is spun in the opposite direction. More complicated manoeuvres may involve two or even three reaction wheels. There are four wheels; one serves as a backup. The quarterly maintenance also included lubrication of the actuators for the two duplicate main rocket engines, and a software clean-up of any bit errors that may have occurred in the spacecraft's attitude and articulation control subsystem during the quarter.

Cassini is travelling at more than 107,000 kilometres per hour (66,000 miles per hour) and has travelled more than 769 million kilometres (478 million miles) since it left Earth last October.

June 4, 1998

Now more than 20 million kilometres (about 12.5 million miles) beyond Venus, Cassini is zooming along at more than 129,300 kilometres per hour (about 80,000 miles per hour), having received a big boost in speed from the effects of Venus' gravity when the spacecraft flew past that planet in late April.

The international Cassini and Huygens team this week bids a fond farewell to Cassini Program Manager Richard J. ("Spe") Spehalski, who retires from Cassini's helm on June 5. Since 1992, Spehalski has managed the successful development, launch and operation of Cassini. Robert T. Mitchell, currently Project Manager of the Galileo Europa Mission, assumes the post of Cassini Program Manager on June 8.

Earlier this week, NASA bestowed its highest honour on Spehalski, awarding him the agency's Distinguished Service Medal for his leadership of NASA's two historic flagship planetary missions - Cassini, and the Galileo Mission to Jupiter, which he managed through final development and launch and early operations from 1988 to 1990.

"The Galileo and Cassini missions are the last great flagship planetary flights of discovery of the 20th century, and their success has been critical to support for a vigorous program of solar system exploration," said JPL Director Dr. Edward C. Stone, commenting on Spehalski's retirement. "JPL, NASA, and the nation owe Spe and the teams he led a debt of gratitude for their accomplishments."

Cassini remains in excellent health. So far, the spacecraft has traversed more than 675 million kilometres of space since launch on Oct. 15, 1997. The mission's operations schedule over the past month was dominated by a variety of engineering tests and routine maintenance activities on Cassini and the European Space Agency's (ESA) Huygens Titan probe. Tests and engineering analysis for the Huygens probe are performed at ESA's Huygens Probe Operations Centre (HPOC) in Darmstadt, Germany, via a telecommunications link to JPL. Last week, engineers conducted an in-flight calibration test that pointed the high-gain antenna 12 degrees from the Sun. Data from that test confirmed the excellent health of the Huygens probe radio receiver.

Cassini's international science team gathered for the 17th Cassini Project Science Group in Pasadena this week. The primary topics covered at the meeting were planned and proposed operation of the science instruments during the flight to Saturn, and plans for the approach to Saturn and the four-year mission in orbit at Saturn.

Cassini Significant Event Report For Week Ending 29/05/98

Spacecraft Status:

The Cassini spacecraft is presently travelling at a speed of approximately 135,000 kilometres/hour (~83,000 mph) relative to the sun and has travelled approximately 650 million kilometres (~403 million miles) since launch on October 15, 1997.

The most recent Spacecraft status is from the DSN tracking pass on Thursday, 05/28, over Canberra. The Cassini spacecraft is in an excellent state of health and is executing the C8 sequence nominally.

Inertial attitude control is being maintained using the spacecraft's hydrazine thrusters (RCS system). The spacecraft continues to fly in a High Gain Antenna-to-Sun attitude. It will maintain the HGA-to-Sun attitude, except for planned trajectory correction maneuvers, for the first 14 months of flight. See the Huygens Probe AGC Test, below, for a scheduled 12 degrees off normal HGA-to-sun line attitude period on 5/28.

Communication with Earth during early cruise is via one of the spacecraft's two low-gain antennas; the antenna selected depends on the relative geometry of the Sun, Earth and the spacecraft. The downlink telemetry rate is presently 40 bps.

For the next several months, due to increasing range from Earth and relatively high angles with respect to the Low Gain Antenna boresight, the DSN tracking passes for Cassini will be dedicated either to command and telemetry (for spacecraft activities and health monitoring) or to Navigation ranging data (for orbit determination). This approach manages the available telecommunications signal strength, directing it to either command/telemetry or Navigation, according to plan. Telecommunications performance will improve again this Fall.

Spacecraft Activity Summary

On Friday, 5/22, a memory readout (MRO) was performed of some data stored when the backup CDS computer underwent a reset at the end of April. The MRO showed that the reset occurred at exactly the same time as a switch in data modes from SAF142 (a high-rate data collection mode) and RTE40 (the standard 40bps realtime engineering mode). Analysis will indicate whether any additional MROs will be needed to complete the investigation of the event.

From Saturday, 05/23 through Tuesday 05/26, there were no changes to spacecraft configuration.

On Wednesday, 05/27, the Solid State Recorder (SSR) record and playback pointers were reset, according to plan. This housekeeping activity, done approximately weekly, maximizes the amount of time that recorded engineering data is available for playback to the ground should an anomaly occur on the spacecraft.

On Thursday, 05/28, a maintenance activity was performed on the SSR Flight Software Partitions. This activity, performed approximately every 2 weeks, repairs any SSR double bit errors (DBEs) which have occurred in the code-containing portions of the Flight Software partitions during the preceding period.

Also on Thursday, a Huygens Probe AGC Test mini-sequence was executed and the first of three data playbacks occurred during the DSN pass over Canberra. This test turned the Orbiter 12 degrees off its normal HGA-to-Sun line for 33 minutes hour and powered on the Probe electronics for 30 minutes to investigate unexpectedly low AGC values measured across the Probe-to-Orbiter umbilical link during the second inflight Probe checkout in 3/98.

The present hypothesis is that the lower AGC value was caused by higher solar noise during the second inflight checkout relative to the first, perihelion occurring the same day as the second checkout. The injection of noise thru the HGA feed has been demonstrated to cause a reduced Probe AGC value using the Engineering model for test at the Huygens Probe Operations Center (HPOC) in Darmstadt, Germany.

Thursday's test will allow the Solar effect to be demonstrated or ruled out. Huygens Probe reports that the first 7 minutes of the Probe AGC test data were transmitted to Earth during the DSN pass available for the test. The preliminary analysis of this first data set indicates that the Huygens radio receivers perform as expected in a radio noise free environment. The rest of the AGC test data will be transmitted to earth on May 30 and May 31. A full test report will be published when the complete data set will have been analyzed.

Upcoming events:

Activities scheduled for the week of 5/29 - 6/04 include Huygens Probe AGC Test playbacks #2 and #3 (of 3) (05/29 and 05/30), an AACS Attitude Estimator MRO (05/30), and an SSR Pointer Reset (06/03)

The 17th meeting of the Cassini Project Science Group will occur in Pasadena from 6/01 through 6/05. The primary topics will be cruise operations of the science instruments and plans for the future, including plans for Science Cruise (7/01/2002 to 7/01/2004) and Saturn Tour (7/01/2004 to 7/01/2008)

DSN Coverage:

Over the past week Cassini had 3 scheduled DSN tracks, occurring on 5/22, 5/24 (ranging only) and 5/28. In the coming week there will be 4 DSN track periods.

April 26, 1998

The Saturn-bound Cassini spacecraft successfully performed a flyby of the planet Venus this morning, coming about 284 kilometers (176 miles) from the Venusian surface. The flyby gave the Cassini spacecraft a boost in speed of about 7 kilometers per second (about 4 miles per second) to help the spacecraft reach Saturn in July 2004.

"All indications are that the spacecraft did exactly what we expected," said Deputy Program Manager Ronald Draper at NASA's Jet Propulsion Laboratory, Pasadena, CA. "Everything seems to be right on the mark." Cassini was launched from Cape Canaveral, FL, on October 15, 1997. Cassini was built by and its mission is managed by JPL. It is an international mission involving NASA, the European Space Agency and the Italian Space Agency.

NASA's Deep Space Network telecommunications antennas in California's Mojave Desert and near Madrid, Spain, tracked the spacecraft as it made its closest approach to Venus at 6:52 a.m., Pacific Daylight Time (Earth-received time). One-way light time to the spacecraft from Earth was about 7-1/2 minutes.

Leaving Venus, the spacecraft was moving at more than 141,000 kilometers per hour (87,000 miles per hour). Science instruments on the spacecraft searched for lightning in Venus's atmosphere during the flyby, and the radar instrument onboard was activated to test a bounced signal off Venus's surface.

Today, Cassini is about 136 million kilometers (about 85 million miles) from Earth. In its long trajectory to Saturn, Cassini will perform another flyby of Venus next June, one of Earth in August 1999, and one of Jupiter in 2000. All of the flybys impart more speed to the spacecraft to allow it to reach its final destination of the Saturnian system. After it enters orbit around Saturn in 2004, Cassini will study the ringed planet, its moons and ring system for at least four years. It will also deliver a scientific probe called Huygens to parachute to the surface of Saturn's largest moon, Titan.

March 27, 1998

Huygens Second In-Orbit Check-out

The second in-orbit check-out of the Huygens Probe will take place on Friday 27 March 1998. As the Cassini/Huygens spacecraft is currently flying with its 4-m diameter High-Gain Antenna pointed towards the Sun to shade the whole spacecraft and the Probe in particular, this second check-out is done "blind", i.e. with no radio link between the spacecraft and the Earth.

The Probe check-out data will be safely recorded on the Orbiter Solid State Recorder and will be played back to NASA's DSN at a slow downlink link rate through the Cassini Spacecraft Low-Gain Antenna throughout the week following the in-orbit activation. The first batch of data from this second check-out is expected to arrive on ground on 31 March, with the last batch expected on 7 April. It will take a few days for the Huygens operations team at ESOC to merge the data into a single data set and make it available for analysis. The Huygens engineers and scientists will provide a preliminary report on their findings about the health and status of the Huygens Probe and its six-instrument payload by mid-April

March 3, 1998

The Cassini spacecraft successfully performed the second scheduled trajectory adjustment of its mission last week, fine- tuning its flight path in preparation for its flyby of Venus on April 26. The trajectory adjustment needed was so minor that the maneuver was performed using Cassini's small hydrazine thrusters instead of the spacecraft's large main engine. Engineering data recorded during the thruster firing confirmed that the maneuver went as planned, with all spacecraft and ground components performing perfectly. A final trajectory adjustment prior to the Venus flyby is scheduled in early April.

Cassini remains in excellent health, flying at a speed relative to the Sun of approximately 137,000 kilometers per hour (about 85,000 miles per hour). It is slowly gaining speed as it feels the tug of gravity from Venus. The spacecraft will gain a significant boost in speed when it swings around Venus next month. Cassini has traveled approximately 362 million kilometers (about 224 million miles) since launch on October 15, 1997.

February 3, 1998

The Cassini spacecraft remains in excellent health as it travels on its Saturn-bound trajectory at a speed of approximately 120,000 kilometers per hour (about 75,000 miles per hour). The spacecraft has traveled more than 271 million kilometers (about 168 million miles) since launch last October 15.

Cassini continues to fly with its 4-meter (13-foot) diameter high-gain antenna pointed toward the Sun so that the rest of the spacecraft is shaded. It will maintain in this attitude, except during planned trajectory adjustments, for the first 14 months of flight as it travels through the inner solar system.

Radio communications with the spacecraft are currently through low-gain antenna 2, one of the spacecraft's two low-gain antennas. Low-gain antenna 2 is located at the end of the spacecraft opposite the high-gain antenna. The low-gain antenna that is selected for a given period depends on the relative geometry of the Sun, Earth and the spacecraft. The telemetry data rate from Cassini is currently 40 bits per second.

For about the next month, there will be an increase in the amount of telecommunications time allotted to Cassini by NASA's Deep Space Network to meet the data needs of spacecraft navigators as they prepare for two long-scheduled trajectory refinements. In late January, Deep Space Network antennas were trained on Cassini about four times a week. In February, those episodes of tracking will be approximately doubled. The adjustments will be made in preparation for Cassini's flyby of the planet Venus on April 26. The additional data gathered through the extra telecommunications time are used to refine knowledge of the spacecraft's location, which will aid navigators in setting precise parameters for the trajectory adjustments, such as the duration of thruster firings.

January 8, 1998

Having clocked in more than 200 million kilometers (124 million miles) since launch last Oct. 15, the Cassini spacecraft remains in excellent health as it progresses on its long flight path to Saturn. The Cassini flight team has nearly completed all scheduled spacecraft configuration activities for the mission's early phase. Onboard software stored in the command data subsystem has been directing spacecraft activities as scheduled. The spacecraft's attitude in space is being maintained using the spacecraft's small hydrazine thrusters. For the first 14 months of flight, Cassini will fly so that its 4-meter-diameter (13-foot) high-gain antenna always faces the Sun, shading most of the spacecraft from the more intense sunlight that characterizes the inner solar system. Throughout this period, spacecraft communications are conducted through one of Cassini's two low-gain antennas; the antenna selected depends on the relative geometry of the Sun, Earth and spacecraft. In December and through January and beyond, periodic instrument maintenance and health checks, along with other routine spacecraft "housekeeping" activities, dominate Cassini's schedule. Cassini spacecraft operations and science team personnel continue to develop software command "loads" that will direct spacecraft activities and scientific instrument observations later in the mission. Today Cassini is traveling at a speed of more than 109,200 kilometers per hour (67,800 miles per hour) and is more than 22,450,000 kilometers (13,950,000 miles) from Earth. It is 27,500,000 kilometers (17,088,000 miles) from Venus, where the spacecraft will perform its first gravity-assist maneuver on April 26. As the spacecraft swings around Venus, the planet's gravity will boost Cassini's speed for the next phase of the journey to Saturn.

December 3, 1997

Now seven weeks and more than 113 million kilometers (about 70 million miles) flown since its perfect launch on Oct. 15, the Cassini spacecraft remains in excellent health as it travels smoothly along the first leg of its nearly seven-year-long flight path to Saturn. The temporary covers that protected many of Cassini's sensitive instrument optics and other detectors during launch have been shed over the past few weeks, and the ground operations team at JPL reports that the spacecraft has successfully deployed antennas and other mechanisms that had been stowed for launch. Cassini's instruments and operating systems are operating normally. This month, the spacecraft will remain relatively quiet, with periodic system health checks and routine maintenance operations scheduled. Telecommunications with Cassini are conducted through the antennas of NASA's global Deep Space Network, with complexes located in California's Mojave Desert, in Tidbinbilla, Australia, and near Madrid, Spain. Telecommunications with the spacecraft are routed to and from the Cassini mission operations area located in JPL's Space Flight Operations Facility. Today, Cassini is traveling at about 97,900 kilometers per hour (about 60,200 miles per hour) and is more than 16 million kilometers (about 10 million miles) from Earth.

November, 1997

Mission adjustments

10 November, 1997

A major milestone for the Cassini program was accomplished successfully on November 9 when Cassini spacecraft controllers performed the spacecraft's first planned trajectory correction maneuver. The maneuver required an adjustment of only 2.7 meters per second (about 8 miles per second) to fine-tune the spacecraft's flightpath. "The operations team was very professional and we are all delighted with the maneuver results," said Cassini Deputy Program Manager Ronald Draper, adding that the spacecraft performed "very, very nicely." The main engine burn lasted 34.6 seconds and was visible in real-time telemetry from the spacecraft. During the maneuver, the spacecraft was turned away from the Sun and performed a 63-minute thermal test. Reverse turns oriented Cassini back to the Sun following the burn and thermal tests. Later this week, the magnetosphere imaging cover will be released. This is the first instrument ever designed to produce an image of a planetary magnetosphere. It will measure the composition, charge state and energy distribution of energetic ions and electrons; detect fast neutral particles; and conduct remote imaging of Saturn's magnetosphere. Spacecraft health remains excellent as Cassini continues its voyage, with its first gravity assist, or swingby, of the planet Venus planned for April 26, 1998. This maneuver will help Cassini gain velocity to make possible its long journey and arrival at Saturn in 2004. The spacecraft's velocity relative to the sun is at about 26 kilometers per second (about 59,250 miles per hour). Cassini is now more than 9 million kilometers (almost 6 million miles) from Earth.

29 October 1997

The Cassini spacecraft continues its journey through space in excellent health on its way to the planet Saturn while ground controllers perform checks on various flight systems. "The spacecraft is operating beautifully," said Cassini Deputy Program Manager Ronald Draper.

Cassini's three plasma wave antennas have been deployed successfully. In addition, controllers verified that the Langmuir probe deployment during Cassini's launch phase was successful. The probe, which measures electron density and temperature, is part of the radio and plasma wave science instrument that will conduct investigations of Saturn's magnetic environment.

Controllers successfully transitioned from low-gain antenna number one to low-gain antenna number two, increasing signal strength by several decibels. This change between the two low- gain antennas on the spacecraft was planned due to changing geometry requirements caused by the relative movement of Earth and the spacecraft. Several transitions between the two antennas will be accomplished during the mission. Data from the first instrument maintenance sequence that were stored onboard the spacecraft were transmitted to Earth; early indications show good information.

The spacecraft's velocity relative to the Sun is at about 26.5 kilometers per second (about 59,400 miles per hour). Cassini is now more than 4.7 million kilometers (more than 3 million miles) from Earth.

NASA JET PROPULSION LABORATORY

24 October 1997

Huygens is alive and well, in space

Tests carried out on 23 october 1997, by ESA's Space Operations Centre (ESOC) in Darmstadt,Germany, confirm that ESA's Huygens probe is in excellent condition, following its launch on 15 October aboard NASA's Cassini spacecraft. The dual Cassini-Huygens mission is now en route for Saturn, by way of Venus. In 2004, Huygens will plunge into the atmosphere of Saturn's enigmatic moon Titan.

"It all went very smoothly, " said Jonh Dodsworth, ESOC's flight operations Director, "We had the option to continue checks on 26 October in case of difficulty, but we don't need to. That's good news".

ESOC established connection with the Huygens probe at 10:09 hrs, Central European Time on 23 October, using NASA's link to Cassini. Thanks to ESOC's new flight operations system, engineers and scientists responsible for the mission could check quite quickly that Huygens is alive and well in all respects.

ESA's project management team, and representatives of the contractors who built Huygens, were able to report that the engineering system and subsystems are all performing nominally.

The principal investigators from Europe and the USA, in charge of the six instruments on Huygens, were also present for the tests. Each experiment was checked for functionality :

- HASI to analyse Titan's atmosphere and weather

- DWE to measure wind speeds during the descent

- GCMS to analyse chemical compounds on Titan

- ACP to break down aerosols for chemical analysis

- DISR to produce images and spectra of Titan

- SSP to determine the nature of Titan's surface.

"Six experiments, six green lights", said Jean-Pierre Lebreton, ESA's project scientist.

The project manager for Huygens is Hamid Hassan. In Darmstadt he too declared himself pleased with the check-out of the Huygens systems, subsystems and instruments. "We will now let Huygens go back to sleep, except for the planned six monthly checkouts" Hassan said. The probe will remain in that condition for the seven-year journey to Saturn. But we now have every reason to expect a successful outcome to this unprecedented mission".

23 October 1997

Successful first Huygens in-orbit check-out

The complete check out of the Huygens Probe and of its six experiments was performed successfully today, Thursday 23 October 1997, from the ESA Operations Centre (ESOC) located in Darmstadt (D). The Probe was powered on by Cassini exactly on time, at 9:45 a.m. CET, following a pre-programmed sequence loaded on board the Orbiter. A pre-defined check-out was run, which allowed comparison with data previously obtained during check-outs performed on the ground before launch. The evaluation of the data obtained, which were analysed by the 20 scientists working together with the ESOC Flight Control Team, Project and Industry Teams, evidenced the healthy state of the Probe system and of the experiments after launch. The results obtained today do not evidence the need to make use of the contingency check-out window next Sunday, October 26. The next in-flight check-out of the Probe system will therefore be performed in March 1998.

17 October, 1997

Cassini-Huygens Status

The status of the Cassini spacecraft after launch is excellent. The mission is proceeding nominally as planned. The Huygens Probe is presently still un-powered, it will be shortly powered on at L+8, on Thursday, October 23, when the first contact with the Operations Centre will take place at 9:15 a.m. CET. A short check-out will be conducted in order to verify the spacecraft condition and especially the battery relays status. The overall Probe status will be assessed by the project team and the experiments representatives, gathered at the European Space Agency Operations Centre (ESOC) in Darmstadt (D).

15 October, 1997

Successful Launch of Cassini-Huygens Mission

ESA's latest and farthest venture into the Solar System began at 10:43 Paris time on 15 October. The American Titan IVB/Centaur launcher sent NASA's large Cassini spacecraft on its way to Saturn. Cassini carries ESA's probe Huygens as well as the High Gain Antenna provided by ASI, the Italian Space Agency. In 2004, the Huygens Probe will plunge into the thick atmosphere of Saturn's largest moon, Titan . About 500 representatives of the scientific, engineering and industrial teams in Europe, which created the Huygens Probe, were present at Cape Canaveral for the Cassini-Huygens launch. They saw the powerful boosters of the Titan launcher light up the pre-dawn sky. The launch sequence concluded with the completion of the second firing and separation of the Centaur upper stage rocket. NASA's ground station at Canberra, Australia, obtained good signals from Cassini an hour after launch. The European Space Operations Centre (ESOC) at Darmstadt will monitor the condition of the Huygens spacecraft. Their report is expected in 8-10 days' time. The next major event will be the swingby of Cassini-Huygens at Venus on 21 April 1998. This is the first of a sequence of "gravity-assist" operations at Venus, the Earth and Jupiter, to accelerate the spacecraft towards Saturn. ------------------------------------------------------------------------

Countdown for October 15 launch, 4:43 a.m. EDT

Update: Oct. 15, 05:26 a.m. EDT

Cassini and Huygens have successfully separated from the Centaur and are now on their way to Venus.

Update: Oct. 15, 05:12 a.m. EDT

The Centaur Main Engine 2 has just been fired according to telemetry data received by the Diego Garcia ground station. It will inject the Centaur/Cassini on the proper hyperbolic orbit.

Update: Oct. 15, 04:55 a.m. EDT

The solid rocket boosters have just separated.

Update: Oct. 15, 04:50 a.m. EDT

Stage II has successfully ignited.

Update: Oct. 15, 04:47 a.m. EDT

The Titan IV B has successfully lifted-off. The solid boosters have separated.

Update: Oct. 15, 04:43 a.m. EDT

The countdown is at T-1 and counting. One minute to lift-off.

Update: Oct. 15, 04:41 a.m. EDT

The countdown is at T-3 and counting down the last three minutes.

Update: Oct. 15, 04:38 a.m. EDT

The countdown is at T-5 and counting down the last five minutes. Program is GO for launch.

Update: Oct. 15, 04:30 a.m. EDT

The countdown is at T-8 and holding. Status check is complete and all systems are GO. Mission is GO for launch.

Update: Oct. 15, 04:25 a.m. EDT

The countdown is at T-15 and holding; a pre-programming 10-minute hold has just started. The Launch Manager will poll the Mission Director for the final Program "GO" at the end of the hold period. Upper altitude winds are GO for launch.

Update: Oct. 15, 03:55 a.m. EDT

The countdown is at T-45 and counting. Tanking operations are proceeding 30 minutes ahead of scheduled time. Everything is green for launch at the present time.

Update: Oct. 15, 03:35 a.m. EDT p>The countdown is at T-65 and counting. The weather briefing announced scattered low level and high level clouds, upper level conditions improving, a perturbation approaching and probability of launch at 80 %. The dispersion model is still ok.

Update: Oct. 15, 03:15 a.m. EDT

The launch countdown is proceeding nominally. LH2 tanking is at 95 %. Probability of launch is still at 80 %.

Update: Oct. 15, 02:45 a.m. EDT

The launch countdown is proceeding nominally, slightly ahead of time. LH2 tanking is just about to start. Presently there is an 80 % probability of launch at 4:43 a.m.; both the upper altitude winds and the dispersion model are green and no problem is evidenced by the safety models.

Update: Oct. 15, 02:30 a.m. EDT

The launch countdown is proceeding nominally. LO2 tanking is at 75% and LH2 chilldown has already started.

Update: Oct. 15, 02:00 a.m. EDT

The launch countdown is proceeding nominally at L-162. LO2 chilldown has started and tanking will follow shortly.

Update: Oct. 15, 00:50 a.m. EDT

The launch countdown is proceeding nominally at L-230, less than four hours to expected lift-off. The spacecraft conditions are nominal, meterological conditions are presently favourable. The countdown has presently entered a 50 minutes programmed hold period.

Update: Oct. 14, 9:43 p.m. EDT

The launch countdown is proceeding nominally at T-360 = L-420. The Mobile Service Tower is being pulled back at this very moment.

Update: Oct. 14, 9:00 p.m. EDT

The launch countdown has started on time at 7:37 p.m. EDT. Launch operations are proceeding nominally, UES door has been opened and the Mobile Service Tower is about to be pulled back.

13 October, 1997 (9:00 AM EDT)

STATUS REPORT from Kennedy Space Center

The launch of NASA's Cassini spacecraft aboard an Air Force Titan IV/Centaur rocket has been postponed until Wednesday, Oct. 15.

The primary issue was upper level wind conditions which had the potential of blowing debris outside safe impact limit lines. The recycle involves moving the mobile service tower back into position around the rocket, detanking the Centaur upper stage, and restarting launch processing.

The Cassini spacecraft requires no significant turnaround activity to prepare for the next launch attempt. During the countdown, a non-critical software error was detected in the Cassini software testbed at the Jet Propulsion Laboratory. The testbed reverifies software identical to that installed on the spacecraft. The software in which the error was found is used in the early cruise phase of the mission but is not critical to launch. The issue is expected to be resolved before the launch attempt on Wednesday. The weather forecast on Wednesday has only a 20% chance of not meeting the launch weather criteria. Upper level wind conditions at 40,000 feet are expected to weaken and gradually shift to the west. At launch time, there will be scattered clouds, a temperature near 78 degrees, a relative humidity of 93 percent with surface winds from the East, 13 - 17 knots.

Prof. Manuel Grande
Last updated: 1 July 2004