Explorers Program

Starting with Explorer 6, it has been operated by NASA, with regular collaboration with a variety of other institutions, including many international partners.

Explorer 1 was launched on the Juno I on 1 February 1958, becoming the first U.S. satellite, as well as discovering the Van Allen radiation belt.

NASA continued to use the name for an ongoing series of relatively small space missions, typically an artificial satellite with a specific science focus.

Explorer 6 in 1959 was the first scientific satellite under the project direction of NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland.

[3][4] The Interplanetary Monitoring Platform (IMP) was launched in 1963 and involved a network of eleven Explorer satellites designed to collect data on space radiation in support of the Apollo program.

[5] Over the following two decades, NASA has launched over 50 Explorer missions,[8] some in conjunction to military programs, usually of an exploratory or survey nature or had specific objectives not requiring the capabilities of a major space observatory.

[9] Later, NASA established the University-Class Explorer (UNEX) program for much cheaper missions, which is regarded as a successor to STEDI.

[15] The Explorer program Office at Goddard Space Flight Center, provides management of the many operational scientific exploration missions that are characterized by relatively moderate costs and small to medium-sized missions that are capable of being built, tested, and launched in a short time interval compared to larger observatories like NASA's Great Observatories.

These early missions were managed by the Small Explorer Project Office at Goddard Space Flight Center.

[15] NASA funded a competitive study of five candidate heliophysics Small Explorers missions for flight in 2022.

The proposals were Mechanisms of Energetic Mass Ejection – eXplorer (MEME-X), Focusing Optics X-ray Solar Imager (FOXSI), Multi-Slit Solar Explorer (MUSE), Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS), and Polarimeter to Unify the Corona and Heliosphere (PUNCH).