WASHINGTON — A delay in the launch of NASA’s Psyche asteroid mission is forcing another asteroid mission hitching a ride to revise its plans.
Janus, a NASA smallsat mission selected in 2019, will launch two identical spacecraft as secondary payloads on the Falcon Heavy rocket whose primary payload is Psyche. After a series of Earth flybys, each Janus spacecraft was to fly by different binary asteroids, designated 1996 FG3 and 1991 VH.
However, the mission’s principal investigator said June 8 that mission plan is no longer possible. Speaking at a meeting of NASA’s Small Bodies Assessment Group (SBAG), Dan Scheeres of the University of Colorado noted that mission plan assumed Psyche launched in August of this year as previously planned. NASA announced May 23 that the mission’s launch had been delayed to no earlier than Sept. 20 to provide more time for testing the spacecraft’s software.
With the revised launch date, he said it’s no longer possible for the spacecraft to perform those Earth flybys with the existing spacecraft design. “Those flybys were essential for setting up our flybys of our target binaries, 1991 VH and 1996 FG3,” he said.
He said it is possible for Janus to reach one of the original binary asteroid targets, 1996 FG3, if the mission launches between Oct. 7 and 10. That would be near the end of the new launch window for Psyche, which closes Oct. 11. In that scenario, the mission would send both spacecraft to 1996 FG3, allowing it to achieve its threshold science goals.
“We have no ability to influence the launch dates or the targeting of the launch vehicle, and that arises from our status as a rideshare,” he said.
The mission team is now looking for alternative asteroids that the spacecraft could visit if it can’t fly by either of its original destinations. Scheeres said they have found “multiple asteroids” the spacecraft could visit, depending on the day the mission launches. He did not disclose which ones are under consideration, but said some violate current mission constraints such as flyby speed or communications data rate. “Many of these constraints can be accommodated, it just takes a little bit more work,” he said.
Those plans depend on the ability of Psyche to launch during the revised launch window. During an earlier presentation at the SBAG meeting, Carol Polanskey, a co-investigator on the Psyche mission at the Jet Propulsion Laboratory, said work continues to upgrade the simulation environment needed for software testing.
“We have a new JPL flight software architecture that needs to be blended with the heritage Maxar simulation capabilities,” she said. Maxar built the Psyche spacecraft bus. “That has proven to be a little more challenging than we anticipated, so we have put a lot of resources in tackling this.”
She said the problem should be resolved in the “near future” but wasn’t more specific. “The project is very motivated to launch in that window,” she said. “We are doing everything possible to get into that second launch opportunity.”
Should Psyche and Janus miss that second window, Polanskey suggested the mission could return to its original plan to launch in 2023 before it moved up a year. “We’ve haven’t really looked at what that would imply,” she said.
Rideshare woes
NASA selected Janus as one of three missions in its Small Innovative Missions for Planetary Exploration, or SIMPLEx, program of low-cost planetary science smallsat missions, with a cost cap of $55 million each. All three have now suffered issues with their plans to launch as rideshare payloads.
The Psyche launch originally was going to carry both Janus and Escape and Plasma Acceleration and Dynamics Explorers (EscaPADE), a smallsat mission to study the interaction between the solar wind and the Martian atmosphere. However, a change in launch vehicles for Psyche from the Falcon 9 to Falcon Heavy changed the mission trajectory enough to no longer make it viable to accommodate EscaPADE, and NASA paused work on the mission in 2020.
EscaPADE found new life in 2021 when NASA approved a revised plan for the mission using Photon spacecraft buses from Rocket Lab, with greater propulsion capabilities than the original design. The twin EscaPADE spacecraft are now scheduled for launch in 2024, although NASA has not announced how they will get to Mars.
The third SIMPLEx mission, Lunar Trailblazer, is scheduled to be completed late this year, but will not launch until early 2025 because of delays in the primary payload of its rideshare mission, the Interstellar Mapping and Acceleration Probe (IMAP). Some lunar scientists have lobbied NASA to find an earlier ride for the mission, which will study the water distribution on the moon, because it could support other robotic and human lander missions.
Scheeres said in a discussion at the SBAG meeting that the issues Janus and other rideshare missions face illustrate one of the drawbacks of that approach for launching missions. “Having developed the spacecraft for a specific mission and then having at least part of that, and maybe all of it, taken away, highlights the fragility of having a very specific mission developed with no control over launch circumstances,” he said.
He suggested that rideshare payloads should have more say in the launch date than they do today. “Maybe there should be some accommodation for small adjustments to launch dates,” he proposed.
There are no plans, though, to take Janus off the Psyche launch and find an alternative means to space. A preliminary assessment, he said, found no other suitable missions that could accommodate Janus as a rideshare mission and could better meet the mission’s science goals.
“That’s not going to get us any closer to out original target binary asteroids,” he said when asked about the possibility of not launching on Psyche, “unless someone’s willing to spring for an independent launch for us, and I haven’t found any takers for that.”