Tag Archives: Hitomi

Japan’s troubled space agency

Link here. The article describes how JAXA has pulled some remarkable successes out of the jaws of failure, but in describing these stories it made me realize how many of these failures have occurred, far more than one should expect. Just consider:

  • Nozomi failed to enter Mars orbit when its main engine did not fire as planned. The mission was a total loss.
  • Akatsuki failed to enter Venus orbit when its main engine did not fire as planned. The mission has been partly saved by the use of the spacecraft’s attitude thrusters to put it into Venus orbit five years late.
  • Hayabusa-1 had enormous problems, and was barely able to return to Earth with barely any asteroid samples, as had been the plan.

This list is essentially Japan’s entire interplanetary program since 2000, all of which failed in some significant way. The recovery of Akatsuki and Hayabusa-1 were hailed as great achievements, but in retrospect they both indicated a serious quality control problem in Japan’s space program. The loss of their most recent science X-ray telescope, Hitomi, when a software error caused the spacecraft to breakup in orbit only one month after launch, illustrated this again.

Problems with attitude system doomed Hitomi

A series of failures in the attitude system on Japan’s X-ray space telescope Hitomi led to its destruction.

The problem started when the satellite’s inertial reference unit detected Hitomi was rotating around its Z-axis at 21.7 degrees per hour. The spacecraft was actually stable at the time, mission managers from the Japan Aerospace Exploration Agency said Friday. The satellite’s attitude control system commanded Hitomi’s reaction wheels, rapidly-spinning devices which control the pointing of the spacecraft with momentum, to counteract the spin. The action caused the satellite to rotate in the opposite direction as the faulty inertial reference unit indicated, officials said. Momentum accumulated inside the reaction wheel system, and magnetic torquers aboard the satellite were unable to unload the building momentum, which neared the reaction wheels’ design limit.

Hitomi’s computers recognized the dangerous situation and put the satellite into safe hold a few hours later. The satellite tried to stabilize using the craft’s hydrazine-fueled rocket thrusters to aim its solar panels toward the sun. But the trouble was not over, and the spacecraft’s solar sensor was unable to find the sun. Struggling to correct the growing spin rate, small rocket firings inadvertently caused Hitomi to rotate faster due to a bad setting in the thruster system, JAXA officials said.

Air Force: Hitomi not hit by space junk

The Air Force has concluded that the Japanese X-ray telescope was not hit by debris, and that its problem was thus likely caused by some internal engineering failure.

What exactly happened remains unclear. Moreover, Japanese engineers still hope they may be able to save the spacecraft, as they are periodically still getting some intermittent signals from it.

Video suggests Hitomi tumbling in orbit

Video taken by an amateur astronomer of Hitomi shows it spinning out of control, another indication that something catastrophic occurred to the newly launched X-ray telescope.

The video shows an object that looks like Hitomi, which lost contact Saturday with the Japan Aerospace Exploration Agency (JAXA), shining and then turning extremely dark in short intervals. The wild changes in brightness might mean its sunlight-reflecting side is moving turbulently. “The fact that it is rotating with extreme variations in brightness indicates that it is not controlled and that some event caused it to begin its rotation,” Paul Maley, a former NASA flight controller who observed Hitomi from the ground in Arizona, was quoted as saying.

Debris spotted near Hitomi

U.S. military observations have detected debris near the Japanese X-ray telescope Hitomi that has failed to respond to communication signals.

The U.S. Joint Space Operations Center on Sunday said it has spotted five objects floating near Japan’s brand new Hitomi X-ray astronomy satellite that lost communication with Earth the previous day. In a Twitter post, the center, which tracks objects in orbit, said it identified five pieces of “break up” debris in the vicinity of the satellite.

None of this sounds encouraging.

No communications with new Japanese X-ray telescope

Bad news: Engineers have not been able to establish communications with Japan’s new X-ray telescope, Hitomi, since it was launched last month.

The JAXA announcement is very terse, and somewhat unclear, as its wording suggests that communications were not scheduled to begin until yesterday, even though the spacecraft was launched February 17. To me that does not sound right. Regardless, failure to establish communications at the beginning of a flight is usually a very bad thing, as it usually means something fundamental failed at launch and is thus difficult to fix or overcome.