|Mission type||Asteroids flyby|
|Operator||University of Colorado Boulder, NASA|
|Mission duration||4 years (planned)|
|Spacecraft||Janus Serenity and Mayhem|
|Launch mass||36 kg (×2)|
|Power||2 solar arrays and batteries|
|Start of mission|
|Launch date||No earlier than 20 September 2022|
|Launch site||Kennedy Space Center, LC-39A|
Janus is a planned dual space probe, called Serenity and Mayhem, that will each visit asteroids that would be chosen prior to launch date. The mission is expected to be launched in September 2022 as a secondary payload on Falcon Heavy together with the Psyche spacecraft. On 3 September 2020, Janus successfully passed Key Decision Point-C and was approved for the final design of hardware. The mission budget is limited to US$55 million.
The two small 36 kg spacecraft —which fall under the 180 kg mass limit for SIMPLEx missions — will conduct stand-alone planetary science missions. They will launch together on a Falcon Heavy as secondary payloads alongside NASA's Psyche spacecraft. The spacecraft is jointly developed by two teams, based at the University of Colorado Boulder (lead by Daniel Scheeres) and at Lockheed Martin (lead by Josh Wood). The two spacecraft, Janus A and B, also go by Serenity and Mayhem.
The Janus team plans to image the two asteroids in visible and infrared light, using the ECAM-M50 (visible) and ECAM-IR3a (infrared) cameras. These cameras were developed by Malin Space Science Systems and successfully used on the OSIRIS-REx asteroid sample return mission.
In 2020 NASA gave approval for the Janus mission to proceed to the next phase of development. The mission is managed by the Planetary Missions Program Office at NASA's Marshall Space Flight Center in Huntsville, Alabama, as part of the Solar System Exploration Program at NASA Headquarters in Washington, D.C. The program conducts space science investigations in the Planetary Science Division of NASA's Science Mission Directorate at NASA Headquarters, guided by NASA's agency priorities and the Decadal Survey process of the National Academy of Sciences. Janus is led by the University of Colorado Boulder, where the principal investigator (PI) is based, which will also undertake the scientific analysis for the mission. Lockheed Martin will manage, build and operate the spacecraft.
After riding along with the launch of NASA's Psyche mission in September 2022, the Janus twins will separate and complete an orbit around the Sun, before heading back toward Earth for a gravity assisted sling-shot into space in 2025, each going their separate ways to the two asteroids, (175706) 1996 FG3 and (35107) 1991 VH.
Because Psyche's launch date was moved from August 2022 to late September, new targets have to be chosen as Janus would be unable to visit the initially chosen asteroids (175706) 1996 FG3 and (35107) 1991 VH. Psyche's launch was again delayed on June 24, 2022 to an unspecified date after the end of 2022. The new targets and trajectories for Janus were not announced at that time.