Venus Probe's Problems May Cause Japan to Scale Back

SAN FRANCISCO ? The failure of a Japanese probe to enter orbit around Venus last week will likely cause the nation's space program to dial back its ambitions a bit, a mission scientist said.

Researchers are still working hard to figure out what caused the Akatsuki spacecraft to overshoot Venus on the night of Dec. 6. But the miss ? coupled with the 2003 failure of Japan's only other interplanetary effort, the Nozomi mission to Mars ? has already imparted some key lessons, the scientist said.

"Our score is zero wins, two losses," Takehiko Satoh, of the Japan Aerospace Exploration Agency (JAXA), told SPACE.com here yesterday (Dec. 16) at the 2010 fall meeting of the American Geophysical Union. "We have to be more conservative to plan our next planetary mission, so it will never fail in any aspect."

Overshooting Venus

After more than six months of interplanetary travel, the $300 million Akatsuki spacecraft ? whose name means "dawn" in Japanese ? got within 342 miles (550 kilometers) of Venus the night of Dec. 6. It began firing its thrusters in an orbital-insertion burn, to slow the craft enough to let the planet's gravity snag it.

The thrusters were supposed to fire for 12 minutes, but an unexpected pressure drop in the fuel line caused them to conk out after only 2.5 minutes, JAXA officials have said. As a result, the spacecraft sailed right on past Venus, scuttling its mission to study the planet's climate and weather in unprecedented detail. [Gallery: Beneath the Clouds of Venus]

Mission scientists don't know the root cause of the problem, Satoh said.

"The pressure decrease was the direct cause," he said. "But we don't know why the pressure shut down."

Previous speculation that a collision with some sort of impactor caused Akatsuki's problems is almost certainly off the mark, Satoh added.

"That's highly unlikely," he said.

Akatsuki scientists want to get a handle on what exactly went wrong by February at the latest, Satoh said. That's because the team wants Akatsuki to perform an orbit-correction burn in April.

The idea is to position the spacecraft for another run at Venus when the probe gets close enough again, which should happen in about six years, Satoh said. That attempt would likely take place between November 2016 and January 2017.

Keeping their fingers crossed

The Akatsuki team is cautiously optimistic that the probe will make good on its next attempt six years from now, said Satoh, who is the principal investigator for one of the spacecraft's infrared cameras.

The probe likely has enough fuel left to make a second orbital-insertion burn, he added, since it used so little on the first attempt.

Akatsuki's battery should be able to hold out for another six years, and the probe's shielding should be good enough to protect it from damaging radiation during its annual 200-day trips around the sun, Satoh said.

If the team can fix the fuel-line problem, the probe may well redeem itself down the road. Satoh said that scientists can draw inspiration from Japan's Hayabusa asteroid-sampling mission, which looked to be dead and gone but made a triumphant return to Earth, carrying bits of space rock as planned.

"Everybody thought Hayabusa was unrecoverable," Satoh said. "We now share that never-give-up-spirit with the Hayabusa team."

Dialing some ambitions back

Whether or not Akatsuki makes a comeback six years from now, the probe's initial failure will have a big impact on how JAXA plans future planetary missions, Satoh said.

The space agency will likely hew to more conservative ideas in the near future, he said. Satoh is involved with a working group considering a future Mars mission, and he used the Red Planet as an example of what he meant.

"With Mars exploration, so many scientists want a big lander or a big rover," he said. "If we had previous successes with planetary orbital insertions, we might say, OK, we'll try something big. But now, maybe we can do an orbiter and a very small lander or a small rover."

Nothing, in other words, on the scale of NASA's car-sized Curiosity rover, which is slated to land on the Red Planet in August 2012.

"We can dream of that," Satoh said with a laugh. "But it must be in the farther future."

He also said Japan may want to consider collaborating more with NASA and the European Space Agency, to learn from those agency's successes.

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