The Planetary Society has announced LightSail, a plan to sail a spacecraft on sunlight alone by the end of 2010. The new solar sail project, boosted by a US$1 million anonymous donation, was unveiled at an event on Capitol Hill in Washington, D.C on the 75th anniversary of the birth of Planetary Society co-founder Carl Sagan, a long-time advocate of solar sailing.

LightSail is an innovative program that will launch three separate spacecraft over the course of several years, beginning with LightSail-1, which will demo that sunlight alone can propel a spacecraft in Earth orbit. LightSails-2 and 3, more ambitious still, will reach farther into space. Taking advantage of the technological advances in micro- and nano-spacecraft over the past five years, The Planetary Society will build LightSail-1 with three Cubesat spacecraft. One Cubesat will form the central electronics and control module, and two additional Cubesats will house the solar sail module. Cameras, additional sensors, and a control system will be added to the basic Cubesat electronics bus.

LightSail-1 will have four triangular sails, arranged in a diamond shape resembling a giant kite. Constructed of 32 square meters of mylar, LightSail-1 will be placed in an orbit over 800 kilometers above Earth, high enough to escape the drag of Earth's uppermost atmosphere. At that altitude the spacecraft will be subject only to the force of gravity keeping it in orbit and the pressure of sunlight on its sails increasing the orbital energy.

Lightsail-2 will demonstrate a longer duration flight to higher Earth orbits. LightSail-3 will go to the Sun-Earth Libration Point, L1, where solar sails could be permanently placed as solar weather stations, monitoring the geomagnetic storms from the Sun that potentially endanger electrical grids and satellite systems around Earth. James Cantrell, CEO of Strategic Space Inc, is Project Manager of LightSail-1. Stellar Exploration will build the spacecraft in San Luis Obispo, California. Other team participants include the Cubsesat development group at California Polytechnic University, San Luis Obispo, and a team at Russia's Space Research Institute.