The Japanese spacecraft Hayabusa has not had the best of all lives. It was destined to have a quick spin around the near solar system, visiting asteroid Itokawa, collecting some dust and rock samples trailing in its wake and then return back home, dropping off the samples canister and cremating in the upper atmosphere.
But no. Apparently, once the probe was at the asteroid, it decided it might like to stay. One by one each of the four ion engines that do most of the work propelling the spacecraft shut down. The chemical propellant that powers the shorter lasting but much more powerful normal thrusters leaked into space. The reaction wheels that correct the probe’s direction from any perturbations closed down, leaving just one operational.
In 2007, the probe’s departure from the asteroid was postponed until this year. When the last of the ion engines shut down last November, it looked like the probe would get its wish – it sent back lots of pictures of the asteroid, but no actual bits. In fact, due to the failure of the collection systems, it isn’t even known whether or not a single pebble was netted. Then things started to turn.
Engineers on the ground were able to rig up a system that allowed two of the ion engines to negotiate enough working components to function as one. The lack of a strong chemical thruster simply meant corrections and alterations for the trajectory would be over a longer timescale. The existence of just the one reaction wheel meant… well… fingers crossed.
The probe has now left the asteroid three years late and is headed back to Earth orbit. Due to the length of the extension of stay, it is not known whether the batteries in the samples canister still function (they are needed to deploy a parachute in order to avoid a repeat of another space dust collection mission, which went splat, as well as activate a navigation beacon so it can be found – even if it goes splat). The probe will therefore arrive at Earth, turn over to bask the canister in the rays of the Sun to warm it, then push the thing into the atmosphere before launching onwards to its own fiery death.
The canister is expected to attempt a landing at the Woomera Test Facility, Australia on June 13th at 11pm local time.
…and I guess this would be a suitable article to mention that part 10 of Universe Today’s 13 things that saved Apollo 13 is up and it is Duct Tape.