WASHINGTON — A delay in the launch of NASA’s Psyche asteroid mission is forcing another asteroid mission to hitch a ride to rethink 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 overflights on Earth, each Janus spacecraft had to fly through several binary asteroids, designated 1996 FG3 and 1991 VH.
However, the mission’s principal investigator said on June 8 that the mission plan is no longer possible. At a meeting of NASA’s Small Bodies Assessment Group (SBAG), Dan Scheeres of the University of Colorado noted that the mission plan assumed Psyche would launch in August this year as previously planned. NASA announced on May 23 that the mission’s launch had been delayed until September 20 to allow more time for testing the spacecraft’s software.
With the revised launch date, he said it is no longer possible for the spacecraft to perform those Earth flights with the existing spacecraft design. “Those flybys were essential to setting up our flybys of our target binaries, 1991 VH and 1996 FG3,” he said.
He said it may be possible for Janus to reach one of the original binary asteroid targets, 1996 FG3, if the mission launches between October 7 and 10. That would be near the end of the new launch window for Psyche, which closes on October 11. In that scenario, the mission would send both spacecraft to 1996 FG3, reaching its science threshold goals.
“We have no influence on the launch dates or the targeting of the launch vehicle, and that stems from our rideshare status,” he said.
The mission team is now looking for alternative asteroids that the spacecraft could visit if it can’t fly past one of its original destinations. Scheeres said they found “multiple asteroids” that the spacecraft could visit, depending on the day the mission launches. He has not disclosed which are being considered, but said some violate current mission restrictions, such as airspeed or communications data rate. “A lot of these limitations can be accommodated, it just takes a little more work,” he said.
Those plans depend on Psyche’s ability to launch during the revised launch window. In an earlier presentation at the SBAG meeting, Carol Polanskey, a co-investigator on the Psyche mission at the Jet Propulsion Laboratory, said work is underway to upgrade the simulation environment needed for software testing.
“We have a new JPL flight software architecture that needs to be combined with the historical Maxar simulation capabilities,” she said. Maxar built the Psyche spacecraft bus. “That turned out to be a little more challenging than we expected, so we’ve put a lot of resources into tackling this.”
She said the issue should be resolved in the “near future,” but wasn’t more specific. “The project is very motivated to start in that window,” she said. “We are doing everything we can to capitalize on that second launch opportunity.”
Should Psyche and Janus miss that second window, Polanskey suggested the mission could revert to its original plan to launch in 2023 before moving it up a year. “We didn’t really look at what that would entail,” she said.
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 run into issues with their plans to launch as rideshare payloads.
The launch of the Psyche was originally supposed to carry both Janus and Escape and Plasma Acceleration and Dynamics Explorers (EscaPADE), a small 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 altered the mission trajectory enough to render it unviable to house EscaPADE, and NASA interrupted work on the mission in 2020.
EscaPADE found new life in 2021 when NASA approved a revised plan for the mission using Rocket Lab’s Photon spacecraft buses, with greater propulsion capabilities than the original design. The twin spacecraft EscaPADE is now slated for launch in 2024, although NASA has not announced how they will go to Mars.
The third SIMPLEx mission, Lunar Trailblazer, is due to be completed by the end of this year but won’t launch until early 2025 due to 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 water distribution on the moon, as it could support other robotic and human lander missions.
Scheeres said in a discussion at the SBAG meeting that the problems facing Janus and other rideshare missions illustrate one of the drawbacks of that approach to mission launches. “Having developed the spacecraft for a specific mission and then taking at least some of it, and maybe all of it, underscores the vulnerability of having a very specific mission developed without control over launch conditions,” he said. he.
He suggested that rideshare payloads should have more to say about the launch date than today. “Maybe there should be some room for minor adjustments to the launch dates,” he suggested.
However, there are no plans to take Janus off the Psyche launch and find an alternative means of space. A preliminary assessment, he said, found no other suitable missions that could accommodate Janus as a rideshare mission and better meet the mission’s scientific goals.
“That won’t get us any closer to our original target binary asteroids,” he said when asked about the option not to launch on Psyche, “unless someone is willing to jump for an independent launch for us, and I don’t have one.” found to qualify.”