Louis D. FriedmanJun 25, 2010

LightSail 1 Passes Critical Design Review

LightSail 1, the Planetary Society's new ultra-light Cubesat-based solar sail spacecraft, has passed its Critical Design Review. At a two-day meeting in Pasadena, a team -- including JPL project veterans Bud Schurmeier, Glenn Cunningham, Viktor Kerzhanovich, and Aerospace Corporation's Dave Bearden -- reviewed the LightSail 1 project from soup to nuts and gave us the thumbs up to proceed with building the spacecraft's hardware and software.

Cunningham said "The design/development team looks outstanding," and that "the review presented some excellent work by the team." He and other reviewers made some specific recommendations concerning risk identification and management and suggested additional analyses that might be helpful.

Our 4.5-kilogram spacecraft is an amazing advance in technology -- analogous in my mind to the miniaturization of computers two decades ago. LightSail 1 has:

  • 10 solar panels -- four deployable arrays with panels on each side plus one panel on the top and one on the bottom of the spacecraft,
  • Two 2-megapixel cameras mounted at the end of two of the solar panels (only one camera is visible in the diagram),
  • Four Sun sensors mounted at the end of four of the solar panels,
  • Six tiny ultra-sensitive accelerometers that will provide a direct measure of the light-force,
  • A momentum wheel for attitude control (colored red in the diagram above),
  • Three single axis gyros (yellow),
  • Three torque rods (gray) also part of the attitude control system,
  • A battery (salmon-colored, looking like a laptop computer battery)

Below the empty space where the solar sail is stowed for launch there are four new deployer mechanisms invented by our team around which the Trac booms are wound. The sails themselves are 4.5 micron Mylar film, aluminized and seamed for rip-stop protection: the thinnest sail ever made for spaceflight.  It will provide a total area of 32 square meters (5.6 x5.6 meters).

At the top of the spacecraft is the slim avionics package consisting of the command, control and data handling circuit board, the payload interface board, the radio transceiver, and power regulator. And at the bottom is the whip antenna for UHF communications -- not just to our specialized tracking and command stations but to the whole world.

All of this capability would fit comfortably inside a carry-on suitcase. Each of these components represents advanced technology, but it is more than the manufacturing the spacecraft that makes LightSail 1 a big undertaking. We also have required system engineering, integration, and testing, and the software programming of the circuit boards that serve as the spacecraft's central computer. We will complete the building the spacecraft by the end of this year, but -- to increase our reliability and quality assurance -- we have stretched out our integration and test schedule so that it runs into the first quarter of 2011.

We will be ready for launch in the second quarter of 2011, and we are now evaluating several options for launch, including a piggyback on a NASA launch, Air Force, other national security space agencies, and possibly a foreign launch. We expect to have a firm decision on launch within a couple of months. Our launch requirement is more difficult than many other sail spacecraft concepts, as we insist that we must launch high enough to render atmospheric drag negligible.  A minimum altitude of 820 kilometers is necessary for pure solar sail flight.

One very special aspect of our solar sail team is its mix of experience and youth. Stellar Exploration, Inc. led by Tomas Svitek is where our spacecraft is being built. They work closely with the avionics team at California Polytechnic University, San Luis Obispo (CalPoly), who also supplies the basic Cubesat bus and the launch vehicle P-POD interface. The mission operations team is centered at Georgia Tech University under the direction of our mission manager, Dave Spencer. Primary mission control will be at CalPoly with backup at Georgia Tech. The project manager is Jim Cantrell of Strategic Space Systems, and I am the Program Director

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