In complementing NASA’s larger “flagship” missions, the Discovery Program’s main objective is to enhance our understanding of the solar system by exploring the planets, their moons, and small bodies such as comets and asteroids. The program also seeks to improve performance through the use of new technology and broaden university and industry participation in NASA missions. Discovery Program missions are designed and led by a principal investigator, who assembles a team of scientists and engineers, to address key science questions about the solar system.

NASA Discovery Programs

Previous Discovery Program Missions

*Mission: Launch Date, Description

Near-Earth Asteroid Rendezvous (NEAR): 2/17/96, first spacecraft to orbit and land on an asteroid, entered orbit around asteroid Eros 2/14/00

Mars Pathfinder: 12/4/96, demonstrated a low-cost method of delivering a set of science instruments and the first rover to the surface of Mars, landed on Mars 7/4/97

Lunar Prospector: 1/6/98, enabled scientists to create detailed maps of the gravity, magnetic properties and chemical composition of the Moon's entire surface

Stardust: 2/7/99, collected interstellar dust and comet dust during a close encounter with comet Wild 2 and returned the particles to Earth on 1/15/06 for analysis

Genesis: 8/8/01, spent two years collecting atoms of solar wind before returning them to Earth on 9/8/04 for analysis

Comet Nucleus Tour (CONTOUR): 7/3/02, intended to visit and study two comets, but contact lost 8/15/02

Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER): 8/3/04, first Mercury orbiter, examined Mercury from orbit from 3/18/11 to 4/30/15

Deep Impact: 1/12/05, propelled a projectile into comet Tempel 1 on 7/4/05, creating a crater and yielding information about the internal composition and structure of a comet.

Dawn: 9/27/07, orbited protoplanet Vesta and dwarf planet Ceres, largest bodies in the main asteroid belt, to study conditions and processes at the dawn of our solar system

Kepler: 3/6/09, used a unique telescope to find more than 1,000 planets around stars beyond our solar system, spacecraft repurposed as K2 mission in 2014

Gravity Recovery and Interior Laboratory (GRAIL): 9/10/11, put twin satellites into orbit around the Moon 12/31/11 to study the Moon's interior and its thermal history


Lucy, expected to launch 10/21, will visit a main belt asteroid and six Jupiter Trojan asteroids (asteroids trapped by Jupiter’s gravity in two swarms that share the planet’s orbit, one leading and one trailing).

Psyche, expected to launch 10/23, will explore the intriguing asteroid, known as 16 Psyche, which is thought to be comprised mostly of metallic iron and nickel, similar to Earth’s core.

Missions of Opportunity

The Discovery Program also includes "missions of opportunity" that enable the U.S. science community to participate in non-NASA missions or to use an existing NASA spacecraft for a new investigation. Five missions of opportunity selected by the Discovery Program are the Analyzer of Space Plasma and Energetic Atoms instrument on the European Space Agency's Mars Express mission; The Moon Mineralogy Mapper on India's Chandrayan-1 mission; the EPOXI mission repurposing the Deep Impact spacecraft; the Stardust New Exploration of Tempel 1 mission using the Stardust spacecraft; and the Strofio spectrometer instrument on the European Space Agency's Bepi Colombo mission to Mercury.