During the part marked in orange, it will transmit data back to Earth. During the part of the orbit colored blue, TESS will observe the sky. COASTING IN SPACE The TESS satellite’s unusual 13.7-day orbit uses the moon’s gravity to stabilize it, so it needs little fuel.

Many of TESS’ planets won’t face the same uncertainty.

A recent paper posted at showed that Kepler 452b, an Earth-sized planet that orbits a sunlike star at the same distance Earth orbits the sun, may be a mirage (SN: 8/22/15, p. And not all those confirmations may stick. Because Kepler’s stars were so far and so dim, some of its planet candidates were confirmed as actual planets only by statistics rather than by other telescopes. That follow-up will help TESS avoid some of Kepler’s pitfalls. “Photons are our currency - the more, the better,” she says. The brighter the star, the easier it is to determine its planet’s characteristics, such as its mass and whether it has an atmosphere, Seager says. TESS will focus on 200,000 stars that are a few hundred light-years away at most, and shine between 30 to 100 times brighter on average than Kepler’s. Most of the planets found by Kepler orbit stars 1,000 light-years away or farther. Once in orbit, the spacecraft will trace an unusual, elliptical path between Earth and the moon that will enable it to observe at least 85 percent of the sky - 350 times as much sky as Kepler saw. TESS will be the first NASA science mission launched on the SpaceX Falcon 9 rocket. The TESS mission is “a whole new opening for exoplanet studies,” MIT astronomer Sara Seager, TESS’ deputy science director, said during a news conference describing the upcoming launch. Its size is partly due to the fact that it was designed to launch on NASA’s small Taurus rocket, but will instead launch on a larger SpaceX Falcon 9 on April 16. SMALL BUT MIGHTY NASA’s next exoplanet hunting telescope, TESS, is only 1.5 meters tall (shown here with engineers).

Spacex launches nasa planet-hunting s