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Mission Status 2008
Kevin V. Gilliland Stardust Spacecraft Team
June 26, 2008
All subsystems are nominal. Stardust-NExT made contact on Wednesday, and the next pass is scheduled for Friday.
TCM-22 executed successfully during Wednesday's pass. The maneuver was successful, and delivered the desired 1.82 m/s velocity change. Since the maneuver attitude was within 12 deg of our normal Earth point attitude, the on-board transmitter provided continuous carrier signal throughout the burn and all required turns. Upcoming passes will be used by Navigation to refine the estimate of the burn's accuracy. Small forces reconstruction indicates that the contribution of required turns were within 1 cm/sec of the predicted change in velocity. Including calibration maneuvers, this was the 39th TCM executed by the Stardust spacecraft. Background sequence SN012 is the active sequence; SN013 is on board and will become the active sequence Sunday, July 7th.
June 25, 2008
The Stardust-NExT Flight Team implemented a flawless TCM-22 that targets an Earth Flyby on January 14, 2009 and onto a trajectory to flyby the comet Tempel 1 on February 14, 2011. Initial results from the telemetry and doppler data indicate the spacecraft's performance was as expected. In the coming weeks additional tracking data will allow the Navigation Team to better determine the accuracy of the maneuver.
June 19, 2008
All subsystems are nominal. Stardust-NExT made contact on Monday, and two more passes are scheduled for Friday.
Background sequence SN012 is the active sequence; SN013 is in development. TCM-22 design is underway, and will execute on Wednesday, June 25. The maneuver will provide a change of velocity of 1.8 m/sec over approximately 98 seconds. The spacecraft will turn to the burn attitude using two single-axis turns. These turns are relatively slow (1.5 deg/min), fuel efficient, and impart less than 1 cm/sec of velocity change. Since the velocity change imparted by these turns must be accounted for in the maneuver sequence, single-axis turns are used to provide the most predictable turn behavior. Stardust's telecommunications subsystem will provide contact throughout the maneuver sequence with a carrier signal. Wednesday's maneuver will be the first ever for the spacecraft without the leadership of Tom Duxbury, JPL's Stardust Project Manager, who is retiring this week. We wish you well, Tom
June 6, 2008
All subsystems are nominal. Stardust-NExT made contact on Wednesday, and two more passes are scheduled for Saturday. Background sequence SN011 is the active sequence; SN012 has been uplinked, and will become the active sequence Sunday evening. SN013 is in development. While our rendezvous with Tempel-1 is more than 2 and ½ years away, our target is coming closer. At this time, the comet is approximately 5 AU from NExT. TCM-22 planning and design is underway, with a preliminary solution developed by the Navigation team. On June 25, we will execute the maneuver to target our Earth flyby in January 2009.
May 29, 2008
All subsystems are nominal. The most recent contact period ended this morning, and two more passes are scheduled for Saturday. Background sequence SN011 is the active sequence; SN012 is ready for uplink and will be sent next week. The spacecraft is now 1.69 AU from the Sun and 1.92 AU from the Earth. As TCM-22 approaches, the Navigation team will use the spacecraft's record of daily thruster firings to help design the maneuver. The contribution of each thruster firing's change in velocity of the spacecraft is modeled in flight software. These so-called small forces packets are sent down during every pass. The Aces and the Systems group have a remarkable record of delivering this data. Since January 30, 2006, the beginning of hibernation following the conclusion of Stardust's prime mission, 57,492 packets have been generated by the small forces model, and only 1 packet has been lost. In the nearly two-and-a-half years since the end of the prime mission, the record of thruster firings is 99.998% complete.
(The missing packet, by the way, was generated in February, 2007.) The chart shown below presents the small forces data summed as daily totals. (The range of 350 pulses per day was selected for clarity; there are a handful of data points with many more pulses per day generated during slews that are not shown.) The recent data shows a well-behaved and efficient controller.
May 22, 2008
All subsystems are nominal. The most recent contact period ended this afternoon. Two passes are scheduled for Saturday. Background sequence SN011 is the active sequence; SN012 has been developed and is awaiting approval for uplink. The spacecraft is 1.70 AU from the Sun. NExT reached its maximum distance from the Sun for this orbit yesterday. The range to Earth is 2.08 AU, and continues to decrease rapidly. The Stardust-NExT team wishes the best for the Phoenix team this weekend and their landing on Sunday afternoon.
May 15, 2008
All subsystems are nominal. The most recent contact period ended this morning, and two more passes are scheduled for Saturday. Background sequence SN011 is the active sequence; SN012 is in development. The spacecraft is 1.70 AU from the Sun. NExT's range to the Sun is changing very slowly, as it approaches the maximum for this orbit. The range to Earth is 2.14 AU, and decreasing rapidly. As we're approaching TCM 22, the team has a close eye on daily thruster firings. Thruster firing frequency is closely watched for two reasons: fuel used, and the change in our trajectory. We've been using an improved, more efficient controller for 6 months now. The controller was developed to reduce fuel use. Operating beyond the January, 2006, capsule return requires more careful fuel management than the prime mission. Since implementing the improved controller, we've realized at least 30% savings in daily fuel consumption. The spacecraft's predicted trajectory with the new controller was used to optimize the timing of TCM-22, and actual behavior is very close to the prediction. Since February, a slight increase in thruster firings was detected, and is likely due to a drop in fuel tank pressure. Even with this increase, the daily fuel use is still at least 30% below the daily use before the controller improvement. The team will begin design and testing of the TCM sequence in June.
May 8, 2008
All subsystems are nominal. The most recent contact period ended earlier this afternoon, and two more passes are scheduled for tomorrow. The command loss timer has been reduced from 45 days to 17 days, in keeping with our more frequent contacts. We will continue to have passes 3 or 4 days per week to prepare for our next maneuver.
During the past week, the free spaces in Stardust-NExT's memory were collected and combined. Periodically defragmentating the memory is necessary to prevent execessive processing times. Background sequence SN010 is the active sequence; SN011 is on board and will begin executing on the evening of May 11. SN012 is in development. SN012 is the sequence which will manage contact periods during TCM-22. The spacecraft is 1.70 AU from the Sun. The range to Earth is 2.18 AU, and decreasing rapidly. The spacecraft's distance to Earth is decreasing at nearly 1,000,000 miles per day. The spacecraft will fly by Earth in January, 2009. Saturday, May 10, Allan Cheuvront will give a presentation on Stardust's mission and comets at Exploration Place, a science museum in Wichita, Kansas.
May 1, 2008
All subsystems are nominal. The most recent contact period ended earlier this afternoon.
Stardust-NExT resumes regular DSN contacts, 3 or 4 days per week, in order to prepare for TCM-22 in June.
Background sequence SN010 is the active sequence. Sequence SN011 is on board and will begin executing on the evening of May 11. The spacecraft is 1.69 AU from the Sun, which is near the maximum range for this orbit. The range to Earth is 2.24 AU, and decreasing rapidly. The spacecraft will fly by Earth in January, 2009.
April 1, 2008
Stardust-NExT monthly contact occurred on March 31 and all subsystems are nominal. During this pass the team updated the sun cone parameter used when the spacecraft goes into sun coning. If the spacecraft loses attitude knowledge, due to a star camera problem, safe mode is invoked. In this case, the response is to cone about the sun using the sun sensors and the sun cone vector. Stardust had one occasion, October 2000, when sun coning was executed. Presently, the coning vector is (0,0,1) or Z-Axis (HGA) toward the sun. Since the MGA is off-pointed 7 degrees from the Z-Axis the earth will be in the field of view for a portion of the one hour cone period. For sun-probe-earth (SPE) angles greater than 20 degrees the carrier signal can not be detected. The largest SPE angle for the mission is 40 degrees. The sun cone vector was change to place the Z-Axis 25 degrees from the sun to ensure the carrier signal can be detected. The Stardust Comet Sample Return Mission Team received the 2008 National Air and Space Museum Trophy on April 3. The museum awards two trophy’s annually, one for Lifetime Achievement and the other for Current Achievement. Stardust is the recipient of the Current Achievement award. Sequence SN010 is the current background sequence. The kickoff for sequence SN011 was held during the team meeting on April 1. The next scheduled pass is Tuesday April 29, 2008.
