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Mission Status 2011

Tim Larson, Stardust-NExT Project Manager

February 11, 2011 - E-3 Days

The spacecraft has continued the 2 hour imaging loop today and will continue into tomorrow. The spacecraft has been performing well, and the DSN continues to provide outstanding support for our downlinks. The Navigation Advisory Group meeting was held tonight for TCM 33. The NAG agreed that the best course of action is to deliver a maneuver design based on an OD solution that weights the latest available opnavs the most. The opnavs received today are all at 0.25 pixel quality, and have moved the solution since yesterday’s opnav solution. The science team believes that we are seeing the nucleus signal starting to come through, and these latest opnavs are the best indication of the nucleus location.

The maneuver design is being finalized, and will be around a 170 km maneuver. The TCM 33 burn is scheduled for 8:30 PM PST Saturday. After that, the final opnav set will be shuttered at 02:30 AM PST Sunday morning. This is the final data that will be used to deliver the comet ephemeris and Time of Arrival estimate for the encounter sequence update. This sequence will be uplinked Sunday evening.

February 10, 2011 - E-4 Days
The spacecraft continued its 2 hour imaging sequence until about 10:30 AM PST today. At that time the the CCD heater was turned on in preparation for the camera bake. The bake was executed successfully at around 5:30 PM PST. This is the last bake before encounter. The approach images to date show that the contamination has not been returning between bakes, thus contamination is not expected to be a factor in the flyby images. The CCD heaters will be turned off at 04:30 PST tomorrow and the 2 hour imaging will continue after a 6 hour cool down period. The two hour imaging cadence will continue until 16:30 PST with shorter image exposures to account for the brightening comet and for improved spatial resolution for the final opnavs.

The data cutoff for TCM 33 is at 14:30 PST tomorrow, utilizing the first two sets of post-bake images. The NAG for TCM 33 will be held at 21:30 PST tomorrow, immediately followed by the project decision meeting. The TCM will be executed at 20:30 PST on Saturday evening. The downlink and AOS performance has continued to be good with excellent support from the DSN stations.

The navigation solutions continue to improve and the solution uncertainties continue to shrink as the comet brightens in the opnav images. The science team begins arriving tomorrow, and the photometry group will be working over the weekend to support the selection of the autonav brightness threshold for encounter.

February 9, 2011 - E-5 Days

The spacecraft spent another day executing the 2 hour imaging loop. By the end of today’s DSS 14 pass, the downlink had caught up with all of the image playback. The spacecraft will continue the 2 hour imaging through about noon tomorrow, when the camera and spacecraft will prepare for the final pre-encounter Navcam bake. The bake will occur around 5:00 PM Pacific, and after the appropriate cool down period, the 2 hour imaging will resume. There are 2 70m tracks scheduled in addition to the 34 m antennas prior to the TCM 33 data cut-off. This will ensure all the images are down in time to support the TCM 33 design. TCM 33 is scheduled for 8:30 PM PST on Saturday, Feb 12.

The navigation team continues to receive ground based data. Magdalena Ridge in New Mexico, Siding Spring in Australia, LaSilla in Chile, and Mauna Kea in Hawaii have all contributed Tempel 1 observations. With the appropriate data reductions, all are agreeing well. The Opnavs continue to improve, with several recent images showing the comet in a single image, eliminating the need to coadd multiple images to detect the comet signal. This is leading to ~1/2 pixel uncertainties, and shrinking error estimates. The ground and s/c based comet observations are agreeing well.

February 8, 2011 - E-6 Days
The two hour imaging cycle started yesterday evening. The Navcam has been performing well, and all images have been acquired as planned (8 images every two hours, with approximately 50 minutes of downlink every two hours). We now have 24 hour DSN coverage, with at least one 70 m pass per day. The higher data rates over the 70 m antennas enables the image downlink to ‘catch up’. The images received today show much lower background noise due to the new spacecraft orientation and low mirror angles. The comet was even detected in some single images without having to coadd multiple images. The current activities will continue until Thursday afternoon, when the final camera bake-out is scheduled. After the bake and a cool down period, the imaging will resume until Saturday evening, followed by TCM 33.

February 7, 2011 - E-7 Days
TCM 32 executed beautifully this afternoon. This was a 0.56 m/s maneuver, moving the s/c approximately 370 km in the b plane, and used about 69 grams of fuel. The maneuver attitude was off earth, but the Doppler residuals before and after the burn, show a very accurate magnitude performance.  The next maneuver is on Saturday, February 12, with the data cut-off on Friday evening, February 11. The two hour imaging loop will start up tonight, with a set of 8 images taken every two hours.

February 3, 2011
The spacecraft is healthy and continues to operate as expected. A trajectory correction maneuver, TCM 31, was executed at 21:00 UTC on Monday, January 31. This 2.6 m/s maneuver adjusted the spacecraft trajectory for the desired flyby point of comet Tempel 1 on February 14. This was the first maneuver based on ground and optical navigation data. The spacecraft continues to acquire daily optical navigation image sets. The next planned maneuver will be executed on Monday, February 7, at 23:00 UTC. This maneuver will be based on a data cut-off on February 2. The spacecraft will turn to the final comet approach orientation, with the +x side of the spacecraft facing the comet direction. Right after the TCM on February 7, the spacecraft will begin imaging the comet every 2 hours as it continues its approach for the flyby. These images will provide optical navigation data as well as frequent comet monitoring, and will be used to design the final approach maneuver that will be executed on February 12, two days before the flyby.

Upcoming events – all Stardust-NExT:
February 7 – TCM 32
February 12 – TCM 33
February 13 – Uplink of final flyby sequences and parameters
February 14 – Closest approach to Tempel 1 a little after 20:30 PST
February 15 – first images of the comet are received on the ground around 00:00 PST

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