Jason DavisMay 30, 2015

LightSail Team Prepares for Sail Deployment

Update, June 1: Tomorrow's solar sail deployment has been rescheduled to Wednesday to allow for additional image capture and downlink testing. A timeline will be posted as soon as it is confirmed.

LightSail is almost ready for its moment in the sun.

This afternoon, mission managers gave the go-ahead for a manual solar sail deployment as early as Tuesday, June 2 at 11:44 a.m. EDT (15:44 UTC), providing the spacecraft completes an arduous set of Monday preparations. Since waking up Saturday after eight days of silence, the spacecraft has been busy sending telemetry back to Earth, snapping test images and preparing itself for sail deployment.

LightSail 1 in the clean room
LightSail 1 in the clean room The LightSail 1 spacecraft sits in a Cal Poly clean room prior to a scrubbed day-in-the-life test on Aug. 20, 2014.Image: The Planetary Society

LightSail completed 12 ground station passes over Cal Poly and Georgia Tech Sunday, sending home 102 data packets. The team started the day with a ground-commanded reboot to reset a file overload vulnerability believed to have silenced the spacecraft two days after launch. On a subsequent ground pass, engineers attempted to upload a software patch designed to fix the problem once and for all, but were unable to maintain two-way communications. LightSail’s tumble rate has increased since it entered orbit May 20. It can receive certain commands and transmit data to the ground, but the data link is not stable enough for the team to log in and make software changes.

Because the primary goal of the test mission is sail deployment, the plan to apply the patch has been shelved. As a workaround, LightSail will be rebooted at least once per day to reset the contents of beacon.csv, the spreadsheet-like file that stores the spacecraft’s automated data chirps. Several successful reboots have already been completed.

Doppler shifts contained within LightSail's chirps have allowed engineers at Cal Poly and Georgia Tech to refine the spacecraft's position. It is now believed to be one of five ULTRASat spacecraft bunched together on the fleet’s orbital path. Our Mission Control Center page has been updated for the first time since launch day. It now shows the position of ULTRASat 8, believed to be a close match for LightSail. You can view all ten ULTRASat two-line element sets in the radio tracking section.

Also on Sunday, LightSail’s cameras were commanded to capture a series of test images. Telemetry indicated a power draw consistent with camera operation, and memory allocation counters for the cameras incremented as expected. On Monday, the team will attempt to download one of the images. It isn’t expected to show much—just a dark scene from the spacecraft’s innards. Only a partial download may be necessary to validate the camera is working before proceeding with the sail deployment sequence.

If the spacecraft continues to operate as expected through Monday, sail deployment could be scheduled for Tuesday morning. The deployment will be triggered during one of the first sunlit ground station passes of the day, when there are several subsequent passes over Cal Poly and Georgia Tech available. That currently works out to 11:44 a.m. EDT (15:44 UTC). A final go/no-go decision is expected Monday night.

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