Small Innovative Missions for Planetary Exploration (SIMPLEx) is aplanetary exploration program operated byNASA. The program funds small, low-cost spacecraft for stand-alone planetary exploration missions. These spacecraft are intended to launch assecondary payloads on other missions and are riskier thanDiscovery orNew Frontiers missions.[1]
The program selects missions from multiple proposals and gives them some money to begin development. After early development they are analyzed to see if they are cost-effective and scientifically valuable during Key Decision Point-C. If they pass Key Decision Point-C, then they will move into full development. The missions must weigh less than 180kg.[2][3]
As of March 2025, three missions have launched and failed, one is scheduled to launch in 2025, and one has been postponed indefinitely.
On August 8, 2015, the first two SIMPLEx missions were selected: Q-PACE and LunaH-Map.[4] They were bothCubeSats and each had a maximum budget of $5.6 million.[5] Q-PACE launched on aVirgin OrbitLauncherOne as part of theELaNa 20 mission.LunaH-Map was a 6U CubeSat that was intended to maphydrogen on the Moon, but failed to enter lunar orbit. The mission launched as a secondary payload onArtemis I.[6][7]
Three SIMPLEx-2 missions were selected in 2019. Janus was going to launch withPsyche and fly past multiple binary asteroid, but was removed from that mission due to the Psyche spacecraft being delayed. Lunar Trailblazer launched with the IM-2 mission to study theMoon's geology and map itswater.[8] EscaPADE will send two small satellites toMars to study its magnetosphere.[2]
So far, three missions in the SIMPLEx program have launched and failed, one is postponed with no new launch date, and one is awaiting a new launch date.[9]
| Name | Selection | Target | Launching with | Launch date | Status |
|---|---|---|---|---|---|
| Q-PACE | SIMPLEx-1 | Earlyprotoplanetary disks | ELaNa Rideshare | 17 January 2021 | Failure |
| LunaH-Map | SIMPLEx-1 | Moon | Artemis I | 16 November 2022 | Failure |
| Janus | SIMPLEx-2 | Binaryasteroids | TBD | TBD | Postponed, spacecraft in storage |
| Lunar Trailblazer | SIMPLEx-2 | Moon | IM-2 | 27 February 2025[9] | Failure |
| EscaPADE | SIMPLEx-2 | Mars | New Glenn[10] | October-November 2025[11] (planned) | Planned |
Q-PACE is a 3U CubeSat that would have studied the interactions of small particles in space in order to better understand early protoplanetary disks. The mission launched on January 17, 2021 on Virgin Orbit'sLauncherOne as part of NASA'sELaNa program. Contact was never established with the CubeSat.[12][13]
LunaH-Map (Lunar Polar Hydrogen Mapper) is a 6U CubeSat that was to map Hydrogen on the Moon using aneutron spectrometer. This mission launched as one of ten secondary payloads on Artemis I. The mission was designed, built, and tested byArizona State University. It would have take over a year for LunaH-Map to reach its science orbit, after which its 60-day science mission would begin.[14][15] However, after it launched, the spacecraft’s propulsion system did not work properly, and it failed to enter lunar orbit. It did succeed in testing its neutron spectrometer.[16]
Janus will send two small spacecraft to explore binary asteroids. The two spacecraft were scheduled to launch withPsyche on aFalcon Heavy rocket. The two identical spacecraft (Janus A and B) are being built by Lockheed Martin and are powered by solar panels and rechargeable batteries.[17][18] The originally intended launch date for Psyche was August 1, 2022, but when that date was delayed to September 20, NASA had to replan the trajectories for the Janus spacecraft.[19] The Psyche launch was then moved to October 2023, but this new launch date will not allow Janus to complete its mission, so Janus was removed from the Psyche launch plan.[20]
The Lunar Trailblazer orbiter's mission was to study water ice on the Moon and determine how it formed, how common it is, and where it is. The small spacecraft should have been capable of looking inside permanently shadowed craters for water ice. The mission was managed by NASA's Jet Propulsion Laboratory.[21][22] The spacecraft was scheduled to be completed in 2022 and was launched on 27 February 2025 as a secondary payload onIM-2,Intuitive Machines' second lunar landing.[23][24] The original plan was to launch Lunar Trailblazer as a secondary payload with theIMAP mission in 2025, but since the spacecraft would have been ready years before it was scheduled to launch, NASA found an earlier launch opportunity.[12]
Soon after launch, NASA lost contact with the spacecraft.[9]
EscaPADE (Escape and Plasma Acceleration and Dynamics Explorers) will send two identical spacecraft toMars. The spacecraft has been built byRocket Lab and is based on itsPhoton spacecraft bus. EscaPADE will studyMars' magnetosphere and how it has led to Mars losing much of its atmosphere. The mission was originally going to launch with Janus and Psyche, but was removed from the Psyche launch manifest in 2020.[25][26][27] On February 9, 2023, NASA announced thatBlue Origin'sNew Glenn rocket would launch EscaPADE in late 2024. It would’ve been put on a trajectory to arrive at Mars eleven months later. It was listed as the only payload instead of being co-manifested with something.[10] The launch was later delayed to spring 2025 on account of delays with New Glenn.[28] It was postponed several times after that, and is currently expected to be launched in October or November 2025.[11]
