Nanosatellites to Join the Search for Earthlike Exoplanets
In a joint effort, the Draper Laboratory and MIT have developed a nanosatellite, ExoPlanetSat, that's mission will be to locate potentially life supporting Earthlike planets beyond our solar system. It is scheduled to launch next year and complement NASA's much larger Kepler satellite and the French operated CoRot satellite.
ExoPlanetSat will use the same technology that the larger satellites use to detect alien worlds. Using a technique known as transit observation, the satellite will use its high performance optics to detect dimming of a star caused by an orbiting planet passing in front of it. By precisely measuring the drop in brightness researchers can determine the size of the orbiting planet, and by observing the amount of time an orbit takes, the distance of the planet from the star can be calculated. In order for these measurements to be accurate ExoPlanetSat must be extraordinarily stable. Photons coming from the target star must hit the same fraction of a pixel at all times. According to Sara Seager, a professor of planetary science and physics at MIT and participating researcher on the Kepler project, "Any disturbances that shake the spacecraft will blur the image and make the measurements unusable." To maintain stability, ExoPlanetSat is equipped with custom avionics and reaction wheels for attitude control. The imaging detector, which decouples from the satellite so it operates separately, is controlled by solar panel charged battery powered piezoelectric drives. The drives, according to Seager, "move the detector counter to the spacecraft so precisely the human eye cannot see the motion [which] is an order of magnitude better than any nanosatellite has demoed before."
At just 10cm wide by 10cm high and 30cm long, ExoPlanetSat is designed to observe just one star at a time. Kepler looks at some 150,000 stars, some of which it finds to be "scientifically interesting" but continues on without further observation. ExoPlanetSat and others like it will concentrate on these stars.
Although ExoPlanetSat cost $5 million, once they are in production they are expected to cost around $600,000 each. They are expected to have an orbital lifetime of one to two years. Seager and the other researchers involved hope to eventually have a fleet of the nanosatellites observing the nearest and brightest stars.
[via Technology Review]