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LightSail Reboots: Sail Deployment Soon

It was a worrisome eight days, but LightSail has broken its silence with an evident reboot and return to operations, sending telemetry to ground stations and taking test images. We now have sail deployment possibly as early as Tuesday morning EDT (15:44 UTC), but according to The Planetary Society’s Jason Davis, much will depend on today’s intensive checkout.

Planetary Society CEO Bill Nye issued this statement on the spacecraft’s reawakening:

“Our LightSail spacecraft has rebooted itself, just as our engineers predicted. Everyone is delighted. We were ready for three more weeks of anxiety. In this meantime, the team has coded a software patch ready to upload. After we are confident in the data packets regarding our orbit, we will make decisions about uploading the patch and deploying our sails— and we’ll make that decision very soon. This has been a rollercoaster for us down here on Earth, all the while our capable little spacecraft has been on orbit going about its business. In the coming two days, we will have more news, and I am hopeful now that it will be very good.”


Image: LightSail-A back in August of 2014 during a testing period at Cal Poly. The craft is a three-unit CubeSat no larger than a loaf of bread, but it packs 32 square meters of sail inside. Four metal booms will, if all goes well, unfold the craft’s four triangular sails. Credit: The Planetary Society.

What we get from Davis is largely positive (see LightSail Team Prepares for Possible Tuesday Sail Deployment). The diminutive craft made twelve passes over the Cal Poly and Georgia Tech ground stations on Sunday, returning 102 data packets. You’ll recall that errant software was suspected in LightSail’s problems, with engineers crafting a software patch that they tried unsuccessfully to upload. The trick is that the satellite is tumbling, able to receive some commands and transmit data, but lacking the kind of stable downlink that would allow the software changes to be made. For that reason, the patch idea is now being abandoned.

Instead, a series of reboots will keep the beacon.csv file reset so that it doesn’t fill up and crash the system. Understandably, the LightSail team wants to begin sail deployment as soon as it is safe to do so. We should have a final decision on a possible Tuesday deployment by Monday night. We’re going to find out what effect the spacecraft’s tumble has on sail deployment the hard way. As Davis noted in an earlier post:

… the rotation rate has increased from -7, -0.1 and -0.3 degrees per second about the X, Y, and Z axes to 10.8, -7.3 and 2.9 degrees. The cause for the tumbling uptick currently unknown, but with the spacecraft’s attitude control system offline [see What Images Will We Get Back from the LightSail Test Mission?], sail deployment is likely to be a wild ride.

The best Tuesday ground pass window begins at 11:44 EDT. To keep up with the latest, follow Jason’s Twitter account @jasonrdavis, and we’ll see just how wild a ride it is. Remember, this mission is not designed to demonstrate controlled solar sailing, but serves as a test of the craft’s attitude control system and sail systems before it is pulled back into the Earth’s atmosphere. The tumbling we’re seeing now is obviously a concern because just next year the next LightSail mission is scheduled to perform controlled Earth-orbit sail flight. We’re going to need to find the bugs in this spacecraft’s attitude control system long before then.


Comments on this entry are closed.

  • Alex Tolley June 1, 2015, 10:44

    A little worrying that the team doesn’t know why the reboot occurred. Is this just random cosmic rays or other particle hits?

    If they cannot stop the tumbling, can the sail still be deployed? I gather that the orbital height (720km ?) will prevent the sail from acting as a drag that might stop the tumbling after deployment.

  • Cynthia Russ June 1, 2015, 12:04

    Hi, I was wondering if you could perhaps post an update on another mission with a similar form factor which was supposed to be flying by now: ExoPlanetSat?

  • Paul Gilster June 1, 2015, 12:35

    Cynthia, I’m tracking ExoPlanetSat and will have something on it in the near future. Thanks for asking.

  • Cynthia Russ June 1, 2015, 15:29

    Thank you Paul. Your site is stellar and you do an exceptional job.

  • Paul Gilster June 1, 2015, 16:49

    Very kind of you! Glad to have you as a reader.

  • William Collins June 1, 2015, 20:42

    Thanks for the update,Paul. I certainly hope that this very valuable project overcomes this “hiccup” on its way to successful completion of its mission.

  • ljk June 1, 2015, 21:20

    Speaking of the need for reliable software on spaceships:


  • ljk June 1, 2015, 21:24
  • J. Jason Wentworth June 1, 2015, 23:30

    If the boom deployment rate is controllable (being able to be programmed to occur at a desired speed), it would seem that the sail deployment wouldn’t be ruined by the spacecraft’s tumbling. Just as a spinning figure skater spins more slowly as she extends her arms, changing her angular momentum, a sufficiently slow deployment should reduce the spacecraft’s tumbling about all three axes. Also:

    After that (assuming a successful boom and sail deployment), the drag from the residual atmosphere should tend to stabilize the sailcraft in a “kite-like” attitude. If it stays up longer than expected (as NanoSail-D2 did), the solar photon pressure–together with infrared photons reflected/re-emitted from the Earth’s surface–might enable such a sail in just a slightly higher orbit to spiral away from Earth, to a higher orbit or (given enough time) to escape from the Earth altogether.

  • ljk June 3, 2015, 8:08

    LightSail Deployment Update: Panels Wednesday, Sails Friday

    Posted By Jason Davis

    2015/06/02 00:02 UTC

    Topics: LightSail

    LightSail Mission Managers have split the spacecraft’s sail deployment sequence into two segments, following an extended camera checkout period that wrapped up Tuesday. On Wednesday, the CubeSat’s deployable solar panels will be released, followed by an additional imaging session to verify all systems are go for sail deployment. The deployment itself is now targeted for Friday morning, during a ground station pass that begins at 12:47 p.m. EDT (16:47 UTC).

    When LightSail reached orbit, its solar panel deployment switches had been triggered, indicating the panels were possibly ajar or deployed. The four hinged panels are designed to open outward, clearing a path for solar sail deployment and positioning the onboard cameras for imaging.

    Full article here:


  • ljk June 4, 2015, 8:47

    Apparently LightSail’s solar panels have opened but no images yet:


  • Matt June 4, 2015, 21:32

    It looks like Lightsail A is having more struggles with basic operations. It has fallen silent again, probably because of battery problems. In the next few weeks it will process into an orbit with more sunlight. They expect that to restart communications and allow them to deploy the solar sail.


  • James M Essig June 6, 2015, 0:18

    I’ve been writing about space sailing craft for several years now. I have several series of books on the subject.

    There are very many ways to do light sails. I am pleased with The Planetary Society’s efforts. They are among the very first to develop and field real hardware. Now, if they can just get the software to work on the small craft, that will be awesome.

    This small craft may end up being an effectively Chicago Pile moment for going beyond the constraints of chemical rockets.

  • James M Essig June 7, 2015, 11:15

    Sailing on Sun-Light! Sailing on star-light! Sailing on the CMBR! Riding a beam of light! The Planetary Society Lightsail-1 is a beginning. I am fixated today on how The Planetary Society pulled this project off. Light-sailing is way too cool! I often like to muse that light sails are in a kind of wonderland of the exotic. They are not warp-drives, nor wormholes, yet they are propellant-less drives. Not only are they propellant-less drives, they need no on-board power source such as might be required of warp drives. Light sails do not even need to react off space-time. They are simple kinetic energy accruing devices of a most passive nature. As for hyper-spatial analogues of light-sails, I leave that for the mathematical Johnys of future times. Perhaps hyperspace is suffuse with real mass-less bosonic energy forms, maybe even low density electromagnetic radiation that can be used to propel one-way reflective, one-way transmissive sails. Yes, indeed, space travel is becoming lots of fun again.

  • Alex Tolley June 7, 2015, 17:36

    Jason Davis’ latest blog post on LightSail-1.
    Looks like we will know if the deployment was successful by Monday morning. There should be pictures too.

    No word on the issue of tumbling, but it cannot be too serious if telemetry is working.