Japanese scientists rescue lost Venus space probe with daring maneuvers

 

 The Japanese Aerospace Exploration Agency (Jaxa) appears to have successfully rescued the Akatsuki space probe five years after it missed its orbital rendezvous with Venus. Akatsuki (the word means “dawn” or “daybreak” in Japanese) launched in May 2010 and reached Venus by December of that year. The orbital insertion began properly, but the engines only fired for three minutes when a 10-minute burn was required to enter a stable Venusian orbit.
The diagram below, provided by Jaxa, shows the probe’s orbit since its failed insertion attempt. The science team on the ground eventually discovered that salt deposits had formed between the helium pressure tank and the fuel tank. This caused the fuel mixture to become too rich, which in turn damaged the combustion chamber and nozzle.

Akatsuki had missed its intended window, but Jaxa engineers had another trick up their sleeves. The orbital maneuver engine (OME) was badly damaged, but it wasn’t the only engine. Akatsuki also carried four attitude control thrusters — and while these provide a fraction of the power of a main engine, they could still be used to nudge the probe’s orbit over time.
Because Akatsuki was never designed to operate for 4.5 years, the researchers had to find a way to put the craft in long-term hibernation to conserve power. There’s no way for Akatsuki to enter its original low Venus orbit — the hydrazine attitude control thrusters can’t provide enough specific impulse. Instead, the new orbit would be elliptical. Even this plan was far from guaranteed. The only way for the hydrazine thrusters to drive the spacecraft into orbit was to burn them for 20 minutes straight — far longer than they were designed to function.

Artist’s depiction of Akatsuki with all four thrusters firing.

As of this writing, Akatsuki’s orbital insertion appears to be a success. Jaxa has cautioned that they won’t know for certain until Wednesday, but the probe’s early telemetry looks solid and the hydrazine thrusters functioned flawlessly — even producing more thrust than expected at some points.
The difference in orbit and the long delay between launch and today may limit some of the scientific observations that the probe can perform, but this is a truly impressive feat. The Akatsuki probe endured a much closer solar pass than originally anticipated, it survived for nearly five years post-launch, and if all goes well, it’ll be performing scientific observations later this week.