Hitomi / ASTRO-H
Ilustration of the Hitomi x-ray astronomy satellite, launched by JAXA Feb. 17 with instruments from NASA and other space agencies. Credit: JAXA/Akihiro Ikeshita

WASHINGTON — The Japanese parliament will decide by the end of the year whether to fund development of a replacement for the failed Hitomi astronomy satellite, the head of Japan’s space agency said Sept. 22.

In a speech at a Space Transportation Association luncheon here, Japan Aerospace Exploration Agency President Naoki Okumura said the ministry responsible for JAXA included funding to start work on a Hitomi replacement in a budget request recently submitted to the finance ministry to be considered by the Diet.

“Typically, in Japan the budget bill passes the Diet at the end of December,” he said. “So if everything goes well, that should happen in December.”

Hitomi, an X-ray observatory designed to be Japan’s flagship astronomy mission for this decade, successfully launched in February. However, the spacecraft suffered an anomaly in late March that caused the spacecraft to spin up. Efforts to restore contact with and control of the spacecraft failed, and JAXA declared the mission lost in late April.

An investigation later concluded that a chain of errors in the spacecraft’s attitude control system, compounded by human error, caused the spacecraft to spin up and its solar panels to break off, depriving the spacecraft of power.

“The technical problem was identified and the underlying causes of the problem, including sociological factors, were analyzed,” said Okumura, who was one of three JAXA officials who took a 10 percent pay cut for four months, starting in July, because of the anomaly. “All findings we got are open to the public.”

The loss of Hitomi was a setback to astronomers, who considered Hitomi one of the key X-ray astronomy missions of the next decade. “We strongly regret that we are not able to meet the expectations of the international community,” Okumura said. “It could have achieved a lot.”

That strong interest in Hitomi has led JAXA to consider flying a replacement, and also has included discussions with NASA about building a replacement for one of the spacecraft’s instruments, the Soft X-Ray Spectrometer. Okumura did not specifically address those talks, but said the agency is discussing the status of a replacement mission with NASA and other international partners.

Okumura discussed several other JAXA programs in his speech, such as the H-3 launch vehicle, which he said is on schedule to make its first flight in 2020. That rocket, a successor to the existing H-2, is designed to be a low-cost “internationally competitive” vehicle. “It will bring Japan into the transportation market as a mainstay launch vehicle,” he said, alongside the smaller Epsilon rocket.

Another major project is an upgraded version of its H-2 Transfer Vehicle cargo spacecraft, called HTV-X. It will featured enhanced capabilities and lower cost compared to the HTV, he said.

He said that JAXA is designing HTV-X to be upgraded for potential missions beyond Earth orbit, such as in cislunar space. He added, though, that Japan doesn’t have specific plans for human spaceflight beyond its role on the ISS through at least 2024.

“Currently the discussion hasn’t even started” about human spaceflight plans beyond the agency’s current policy, which runs through 2025, Okumura said. “The only thing that is decided about human exploration is to extend the ISS the program to 2024. Anything beyond that we do not know.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...