NASA has selected two small astrophysics missions for launch in 2017, the agency announced April 5.

The selections are the latest in NASA’s small explorer program line, a series of competitively selected, cost-capped astrophysics missions. NASA picked one standalone mission, which will fly aboard a dedicated spacecraft, and one mission of opportunity, which will be hosted aboard the international space station.

The standalone mission is the Transiting Exoplanet Survey Satellite (TESS), an exoplanet hunter similar to the Kepler telescope. The principal investigator for the $200 million mission is George Ricker of the Massachusetts Institute of Technology.

The hosted mission is an X-ray observatory called the Neutron Star Interior Composition Explorer, or NICER. NICER will observe superdense neutron stars from its perch on the space station. The principal investigator for the $55 million mission is Keith Gendreau of NASA’s Goddard Space Flight Center in Greenbelt, Md.