An array of wide-field telescopes known as the Transiting Exoplanet Survey (TESS) will launch in 2017 to conduct the first space-based survey of the entire sky in the search for habitable planets orbiting other stars. TESS will search for planets that pass between Earth and their own stars, causing a change in the observed light from the star—what’s called the transit method.
Ground-based telescopes have used this method to find exoplanets in previous surveys, which have found mostly gas giants similar to Jupiter. Smaller, rocky planets like Earth and Mars are better prospects for life, but they are also harder to spot.
The Kepler space telescope, launched in 2009, has identified some smaller worlds among its 115 confirmed discoveries, such as Kepler-37b, a rocky planet about the size of Earth’s moon with an average temperature of 800 degrees F. However, Kepler is searching for planets around only 100,000 stars in a relatively small slice of the sky. TESS will cover about 400 times as much area.
"It will identify thousands of new planets in the solar neighborhood, with a special focus on planets comparable in size to the Earth," said the project’s principal investigator George Ricker of MIT, in a release. Once it has identified those planets, TESS’s instrument package will allow it to study their orbits, masses, densities, and the chemical composition of their atmospheres.
NASA announced funding for the MIT-led project on April 8 through its Explorers Program, the goal of which is to fund more frequent science missions at relatively low cost per mission. The program imposes a $200 million budget cap on satellite missions like TESS and a $55 million limit on space station missions. Since 1958, the program has launched 90 missions.
Because it takes about 13 billion years for light to reach Earth from the most distant galaxies in the universe, those images provide a glimpse into the universe's past. A million miles above Earth, the James Webb Space Telescope will study the oldest light in the universe to understand how galaxies formed after the Big Bang.
As cosmic objects move farther away, our view of their light shifts toward the red end of the spectrum; light from very distant objects is shifted into the infrared spectrum, which makes infrared telescopes like Webb ideal for studying the oldest objects in space.
The more light telescopes collect, the more deeply they can see into the sky. Webb will collect a lot of light: Its 6.5-meter (21-foot) segmented mirror is too wide to fit on a rocket, so it will fold up like origami alongside a sun shield the size of a tennis court, both of which will unfurl once Webb reaches orbit.
Webb has a projected lifespan of five years, but scientists hope it will last up to 10. However, repairs, like those that have kept its predecessor, Hubble, flying since 1990, will be impossible for Webb. "It's four times higher than the moon, so the day that it stops operating it's just going to stay there," says Ray Villard, news director for the Space Telescope Science Institute.
Some scientists consider that a risky proposition. Webb's price tag has grown from its original $1 billion budget to about $8.8 billion, forcing NASA to take money from other projects, like the Wide-field Infrared Survey Telescope commercial flights to the International Space Station, to foot the bill.
In response, researchers have tried to pack Webb with as many instruments for as many studies as possible — adding further expense. With Webb, space science is putting most of its eggs in one very expensive basket that can't be repaired if it breaks.