Venus or bust: Wayward Japanese spacecraft hurtles toward destiny

This weekend, the golf cart-sized Japanese spaceship named Akatsuki could become a national hero. Or it could end up a national disgrace.

Five years ago, the innovative ship took aim at Venus -- and missed. Rather than swinging into orbit Venus as planned, Akatsuki sailed past its target, becoming another embarrassment for a Japanese space-exploration program plagued with mishaps.

Now, Akatsuki is poised for a comeback five years to the day after its worst moment. At roughly 7 pm ET Sunday, the spacecraft will make a risky bid to orbit Venus and redeem its honor.

Japanese scientists have fashioned an ingenious rescue plan that takes advantage of Akatsuki's small thruster jets, which were never meant for the job of putting the spacecraft on an orbital course. Hopes are high. So are the stakes.

If it's orbiting Venus, Akatsuki "can make these spectacular discoveries," says James Green, NASA's head of planetary science. "And if it's not, we will miss them." Neither Europe nor the United States has a spacecraft around Venus, and it will be years before NASA sends one there, he says.

"There is kind of a cloud over (Japan's) planetary program," says planetary scientist Mark Bullock of the Southwest Research Institute, who is working closely with the mission. "Japanese prestige is very much on the line."

"Akatsuki" in Japanese means "dawn," a suitable name for a craft that marked a fresh start for a troubled space program. A Japanese spacecraft that launched in 1998 never made it to Martian orbit. Hayabusa, an ambitious mission that lifted off in 2003 to return a bit of an asteroid to Earth, suffered failure after failure but eventually brought home specks of asteroid dirt.

Akatsuki's battery of cameras is designed to scrutinize the complicated clouds and atmosphere of Venus, Earth's closest neighbor and near twin. After blasting off in May of 2010, the spacecraft was supposed to slow its pace seven months later to slip into orbit around Venus.

But a malfunctioning valve led to catastrophe. Temperatures rose dangerously high in the ship's main engine, totally destroying it. With the engine unable to curb the vehicle, it hurtled past Venus and began orbiting the sun. The Japanese team, project manager Masato Nakamura said then, was "bitterly disappointed." Then they set to work.

In the intervening years, Japanese engineers repeatedly tested the craft's puny thruster jets, which were only meant to control its orientation. Even so, the jets proved strong enough to set Akatsuki on the right path to rendezvous with Venus, and scientists inside and outside Japan are optimistic that the craft will reach its destination.

"Everything that could go wrong has already gone wrong," says University of Wisconsin, Madison, senior scientist Sanjay Limaye, who is helping with the mission. "The rest has been tested and verified and tested again and again."

"We are confident we can succeed" this time, says Takeshi Imamura of the Japan Aerospace Exploration Agency. A shrine has been set up in the spacecraft control room, Imamura says, and one program leader prays for success every day. And if this attempt doesn't work?

"During this operation, we will use all of the remaining fuel," Imamura says. "We have no other chance."