Look up during the next few nights and you might see a spacecraft gliding across the starry skies.
After days of glitches and tension, Bill Nye "The Science Guy" and his team at the Planetary Society confirmed on Sunday that their plucky LightSail satellite had successfully unfurled its sails in Earth orbit. Now, sky-watchers can spot the spacecraft as it glides above Earth before atmospheric drag brings it to a fiery end sometime in the next 10 days.
While the mission is only a proof of concept, the success is a significant step towards a cost-effective way to explore the solar system.
Launched on May 20, LightSail weighs less than 11 pounds and is no bigger than a large loaf of bread. The miniature CubeSat satellite at its heart has experience ongoing battery power issues and twice lost communication with Earth, but ground controllers persevered and eventually engaged the deployment motor to unfurl the nearly 350-square-foot (32 square meters) Mylar sail.
The sail is just 4.5 microns thick—less than the width of even a very fine human hair—but its large surface area (the size of a spacious bedroom) allows the highly reflective sail to be pushed along by a "breeze" of photons, which make up light. This technique is much like the way mariners use canvas sails to catch wind as they make their way across the oceans.
In this case, the hope is for solar wind to accelerate a spaceship across the vast ocean of interplanetary space.
The big advantage over traditional chemical rockets, which create short but powerful bursts of thrust, is that solar sails keep accelerating as long as they're exposed to radiation from a star, achieving fast speeds without carrying fuel.
Solar sail technology was first successfully demonstrated in 2010 when Japan's IKAROS probe deployed a 14-meter-wide sail. Then NASA's tiny NanoSail-D, launched in November 2011, circled Earth for eight months before burning up in the atmosphere. But the dreams for solar sail propulsion goes back to the 1970’s, when the late astronomer and Planetary Society co-founder Carl Sagan first proposed and promoted the technology.
The Planetary Society plans to launch a more ambitious follow-up mission in the next year or so that can steer itself through space. A crowdfunding campaign on Kickstarter to raise funds for this second craft has been wildly successful, raising four times the original request.
Farther out, NASA-derived concepts propose sails up to 1,300 feet (400 meters) wide that could cover distances as great as 2 billion kilometers a year. There are even blueprints for a Texas-sized solar sail that could possibly travel to other star systems.
See For Yourself
LightSail has more modest goals for now, but provides a great chance for folks around the world to glimpse the spacecraft for themselves.
Because of its large size and shiny sails, expectations are that LightSail should be visible to the naked eye in many parts of the world as a faint star-like object that takes just a few minutes to glide across the sky.
Current estimates suggest the craft may reach only magnitude 4.8 in brightness, making viewing best suited to dark locations away from light-polluted cities. But it may flare brighter when sun glints off its surface at just the right angle. Check out this global map showing the current location of LightSail.
The best times to spot the spacecraft will be at dusk and dawn when you are in Earth’s shadow and the sun is below the horizon, yet still shining where LightSail is orbiting. The trick is knowing when and where to look up.
Specific times are available at the satellite tracking website heavens-above.com. Just plug in your location, click "update" at the bottom of the screen, and then use the LightSail tool to see a viewing timetable for the coming week. Clicking on a date will give you a sky chart to help show you where to look.
For example, on Wednesday, June 10, for the New York City area, LightSail will begin a visible flyby in the West at 3:18 a.m. EDT, reach a little more than halfway up the sky (56 degrees altitude) at 3:20 a.m. in the northwest, and set in the northeast at 3:24 a.m.
In the San Francisco area, on Wednesday, June 11, the solar sail craft should make a visible pass starting at 2:52 a.m. PDT a little more than halfway up the sky (52 degrees altitude) and set in the northeast at 2:56 a.m. PDT. Both of these are just one of two or more flybys visible from each location on a single night.
Will you be able to hunt down LightSail? The only way to know for sure is to go outside and look up!