Nearly two-and-a-half years after launching into Earth orbit, The Planetary Society’s LightSail 2 solar sail mission is still going strong.
The spacecraft, which uses sunlight for propulsion, is currently operating in an extended mission to further advance solar sailing technology. The LightSail 2 team is gathering vital data about the performance of the spacecraft’s boxing ring-sized solar sail and using imagery to track its condition over time.
Ten new processed pictures from space have been added to the mission’s image library.
The Planetary Society shares mission data with NASA to assist three upcoming solar sail missions: NEA Scout, Solar Cruiser and ACS3. NEA Scout is scheduled to hitch a ride to lunar space as early as February 2022 on NASA’s Space Launch System rocket during the Artemis I test flight. Using the gentle push of sunlight for propulsion, NEA Scout will use its solar sail to leave the vicinity of the Moon and visit an asteroid.
LightSail 2 is the first small spacecraft to demonstrate controlled solar sailing. At its core, the spacecraft measures just 10 by 10 by 30 centimeters — about the size of a loaf of bread. Tucked inside the spacecraft for launch and deployed using long, tape measure-like metal booms, LightSail 2’s solar sails have an area of 32 meters (144 feet).
Sunlight has no mass, but it has momentum, which can be harnessed by a solar sail for propulsion. Future space missions like LightSail 2 could use solar sails to visit unique destinations and orbits throughout our solar system, making deep space exploration more affordable and accessible.
At LightSail 2’s altitude above Earth — currently about 687 kilometers — there is still enough atmosphere to counteract the thrust gained from solar sailing and slowly pull it back toward Earth. The spacecraft will eventually succumb to drag and reenter Earth’s atmosphere.
Thanks to optimized sail pointing over time, altitude decay rates during recent months have been the best of the entire mission. Thrust even occasionally overcame atmospheric drag, slightly raising the spacecraft’s orbit.
Additionally, below-average Sun activity has kept Earth’s upper atmosphere thin for much of the mission, creating less drag on the sail.
That has recently changed, with the Sun becoming more active and emitting significant solar flares. The LightSail 2 team believes that this activity is likely now causing higher orbital decay rates than those seen earlier in the mission.
Orbital decay modeling by Hugo Favila, a mechanical engineer and operations intern at The Planetary Society through the Zed Factor Fellowship, working with the LightSail 2 operations team, indicates that the spacecraft may stay in orbit for at least another year. This prediction, based upon matching models to the decay seen so far, has a lot of uncertainty, in part because it assumes no changes in major factors such as LightSail 2 staying healthy and atmospheric density staying the same.
There are signs that the spacecraft’s solar sail may be starting to degrade, although the extent is under study. The mission team will continue to track and analyze the sail’s condition, as the data could prove valuable to other solar sail missions. LightSail 2 monitors its sails using two fish-eye cameras mounted at the end of two solar panels.
Almost 30 months after liftoff, the mission continues to impress. For now, LightSail 2 will keep teaching the world about solar sailing, returning inspiring images and helping prepare for the next generation of solar sail missions.