NASA may build replacement instrument for Japanese astronomy mission


WASHINGTON — NASA is considering building a replacement for an instrument lost on a Japanese X-ray astronomy satellite earlier this year that could fly on another Japanese spacecraft.

In a presentation to the astrophysics subcommittee of the NASA Advisory Council’s science committee July 20, Paul Hertz, director of NASA’s astrophysics division, said the Japanese space agency JAXA has approached NASA about contributing a copy of its Soft X-Ray Spectrometer (SXS) for a new version of Japan’s Hitomi spacecraft.

JAXA launched Hitomi, also known as ASTRO-H, in February. The spacecraft and its instruments, including the NASA-build SXS, were working well until spacecraft controllers lost contact with Hitomi on March 26. JAXA attempted to recover the spacecraft but declared the mission lost a month later. JAXA later blamed the failure on a series of technical problems with the spacecraft exacerbated by human error.

JAXA leadership is now talking about building a copy of Hitomi that could launch around the end of the decade. “JAXA has announced their intent to study a rebuild of Hitomi,” Hertz said, referring to that new spacecraft as ASTRO-H2. NASA, he said, is now studying developing a “build-to-print” version of the SXS for that new spacecraft.

Hertz said NASA would have to cover the cost of rebuilding the instrument. A rough estimate of building a new SXS, taking into account using the existing design and any available spare parts, is about $70 to 90 million, to be spent from 2017 through 2021.

“I don’t know if my budget would go up if we decided to do that,” Hertz acknowledged. However, even if NASA received no additional funding, he believed it could be fit into the astrophysics budget by adjusting funding for other programs, similar to what the agency does already to account for other changes in its overall budget. “In my assessment, these kinds of changes do not cause grievous harm to our programs. The impacts are acceptable.”

JAXA has not formally agreed to develop ASTRO-H2, but the agency is seeking government approval as soon as possible. “They’re asking for permission to reprogram money in their current fiscal year budget. They want to get started this calendar year,” Hertz said, which would allow for a launch around 2020.

Because of the speed of that decision-making process, Hertz asked for advice from the astrophysics committee as soon as possible. He said he was meeting with JAXA officials again in early August to discuss the status of an ASTRO-H2 mission and NASA’s participation in it.

Committee members, in the discussion that followed Hertz’s talk, had no issues with flying SXS again from a scientific standpoint, noting that there are no similar X-ray astronomy missions planned by any nation until Europe’s Athena mission in the late 2020s. Hertz added that SXS, during its brief time in operation on Hitomi, worked better than expected, reducing any concerns about its performance.

Some, though, worried about the checkered history of efforts to launch an instrument like SXS on a Japanese spacecraft. A similar instrument was included on Japan’s ASTRO-E spacecraft, which was lost in a launch failure in 2000. Another instrument was flown on the ASTRO-E2, or Suzaku, spacecraft launched in 2005, but that spacecraft lost its entire supply of liquid helium coolant days after launch, preventing the instrument from working.

“We need to be very careful about investing our money and giving our instruments to someone who then has these kinds of failures,” said one unidentified committee member during the discussion.

Hertz said that JAXA had requested insights from NASA in how to improve their mission assurance efforts, and that NASA agreed to share its knowledge with them. “We’re not satisfied with merely making sure the previous mistakes can’t happen again,” he said. “We intend to work with JAXA to review best practices and the state of the art in managing these complex systems.”

“NASA doesn’t want to get into a partnership,” he said later in the discussion, “unless we’re confident it’s going to result in a successful mission.”