WASHINGTON — NASA and the Japan Aerospace Exploration Agency have started discussions about how to recover the science lost with the failure of Japan’s Hitomi astronomy spacecraft in March, although there appear be limited opportunities by either agency to fly a replacement mission for the foreseeable future.

Speaking at forum here June 10 about U.S.-Japan cooperation in space science organized by the Japan Society for the Promotion of Science, Saku Tsuneta, director general of JAXA’s Institute of Space and Astronautical Science, said he was starting discussions with NASA officials about next steps after JAXA declared the Hitomi mission lost in April.

Hitomi, launched Feb. 17 and previously known as ASTRO-H, was a flagship x-ray astronomy mission for JAXA. The spacecraft included a number of instruments, including a Soft X-Ray Spectrometer (SXS) provided by NASA.

However, spacecraft controllers lost communications with Hitomi on March 26, and declared the spacecraft lost April 28. An investigation into the failure concluded a series of mistakes, including human error, caused the spacecraft to spin uncontrollably, snapping off its solar panels and an instrument boom. Tracking radars spotted several pieces of debris associated with the spacecraft.

Tsuneta said JAXA was working to both incorporate recommendations from the failure investigation as well as find ways to do the science Hitomi was to carry out. “My priorities are to fix the problem in the systems that led to the mishap — this is not easy, but this is going on — and to recover the Hitomi science with SXS with NASA,” he said. “One of the purposes for my trip here is to start discussions with NASA people about this.”

“We’re working with Dr. Tsuneta and others to figure out what is the right path going forward,” said Geoff Yoder, NASA’s acting associate administrator for science, in a later talk at the forum. “It’s very positive dialogue, but it’s premature to say the exact path yet.”

One challenge facing that effort is that there does not appear to be an opportunity to fly a full-fledged Hitomi replacement, led by JAXA, through the end of the 2020s. Hitomi was a large, or “strategic,” space science mission for JAXA, which that agency flies only every several years. JAXA has already planned the next several strategic missions, including a Mars mission in 2022 and a joint infrared astronomy mission with the European Space Agency slated for 2028.

Tsuneta suggested that he would not seek to disrupt that schedule to fly a Hitomi replacement. “These missions should reach the implementation phase as early as possible regardless of the problems with Hitomi,” he said.

Tsuneta offered no specific details about alternative mission concepts that could carry out at least some of the science planned by Hitomi. He said that there are no plans by any space agencies to fly a similar mission until an ESA mission called Athena, which he dubbed a “super ASTRO-H” but won’t launch until at least 2028.

“We cannot live without doing anything. JAXA has to start something to recover the science of SXS,” he said. “I hope that JAXA and NASA work together to make it happen.”

Should there be some kind of replacement mission for Hitomi, it should be relatively straightforward to build another SXS instrument. Richard Kelley, a senior astrophysicist at NASA’s Goddard Space Flight Center who worked on SXS, said at the forum there is some space-qualified hardware available from development of the model flown on Hitomi that could be used on a replacement.

“If we were to do a recovery mission, we would basically pick up from where we left off” rather than build a brand-new instrument, Kelley said.

Tsuneta, in his prepared remarks, apologized for the loss of Hitomi, saying both JAXA and the companies involved in developing Hitomi were “deeply aware” of their responsibilities in the mission’s failure. “We apologize for this deeply,” he said. “This is an embarrassing situation for us, but this is a fact and we have to accept this.”

There were no signs from either Japanese or American officials at the forum that the failure had put any serious strain on cooperation between the two nations in other space projects. “We appreciate the openness and transparency that our JAXA colleagues have shown,” Yoder said. “From our standpoint, we want to work with our colleagues and to work through this.”