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Explorers Missions Chart Link to IMAGE Mission Description Link to WMAP Mission Description Link to Swift Mission Description Link to THEMIS Mission Description Link to WISE Mission Description Link to TESS Mission Description Link to ICON Mission Description Link to SPHEREx Mission Description Link to MUSE Mission Description Link to HelioSwarm Mission Description Link to RHESSI Mission Description Link to GALEX Mission Description Link to IBEX Mission Description Link to NuSTAR Mission Description Link to IRIS Mission Description Link to IXPE Mission Description Link to PUNCH Mission Description Link to TRACERS Mission Description Link to COSI Mission Description Link to NICER Mission Description Link to GOLD Mission Description Link to Euclid Mission Description Link to XRISM Mission Description Link to AWE Mission Description Link to GUSTO Mission Description Link to SunRISE Mission Description Link to CASE Mission Description Link to EZIE Mission Description Link to EUVST Mission Description

Explorers Missions

Over the years, NASA has launched a series of “Explorer” spacecraft carrying a wide variety of scientific investigations. It is not only the longest running series of spacecraft, but has produced highly-durable (i.e., well-engineered) spacecraft as well.

Medium-Class Explorers (MIDEX)

Investigations characterized by definition, development, mission operations, and data analysis costs not to exceed $180 to $200 million total cost to NASA.

Missions in DevelopmentHelioSwarm | MUSE | SPHEREx
Operational MissionsACE | ICON | Swift | TESS | THEMIS
Past MissionsFUSE | IMAGE | RXTE (XTE) | WISE | WMAP (MAP)

Small Explorers (SMEX)

Investigations characterized by definition, development, mission operations, and data analysis costs not to exceed $120 million total cost to NASA.

Missions in DevelopmentCOSI | PUNCH | TRACERS
Operational MissionsIBEX | IRIS | IXPE | NuSTAR | RHESSI (HESSI)
Past MissionsAIM | FAST | GALEX | SAMPEX | SWAS | TRACE

University-Class Explorers (UNEX)

Investigations characterized by definition, development, mission operations, and data analysis costs not to exceed $15.0M (real year dollars) total cost to NASA. UNEX missions will be launched by a variety of low cost methods

Past MissionsCHIPS | SNOE

Missions of Opportunity (MO)

Investigations characterized by being part of a non-NASA space mission of any size and having a total NASA cost of under $55 million. These missions are conducted on a no-exchange-of-funds basis with the organization sponsoring the mission. NASA intends to solicit proposals for Missions of Opportunity with each Announcement of Opportunity (AO) issued for EX, UNEX, SMEX, and MIDEX investigations.

Missions in DevelopmentCASE | EUVST | EZIE | SunRISE
Operational MissionsAWE | Euclid | GOLD | GUSTO | NICER | TWINS | XRISM
Past MissionsCINDI | HETE-2 | Hitomi (ASTRO-H) | Suzaku (Astro-E2)

Internationals

Operational MissionsINTEGRAL