As already reported, Hayabusa was restored at the end of January and had
completed the attitude control to make its antenna aperture pointed to
the Earth by the beginning of March, using its Xenon cold gas thrusters
(neutralizers of the ion engines) aboard.
Since then, Hayabusa has maintained the attitude slightly offset to the
Sun but kept to the Earth within communication coverage via the above
mentioned Xenon thrusters. It has worked very well and the radio
communication with the ground stations has been established through the
medium gain antenna everyday by now.
From March to April, the spacecraft performed so called baking operation
to exclude any volatile liquid potentially left inside the spacecraft by
making the temperature as highest as possible. There had not been
confirmed any gas that came out, however, the project team was sure that
the baking operation was completed practically.
From the end of April to the middle of May, Hayabusa had undergone the
ion engines functional verification to make sure if the performance of
the engines are in order toward the return cruise. The engines B & D
were driven and the results showed they are in a very good shape and
retained the nominal performance as that before arrival to Itokawa. The
engine C test was postponed to next January when the distance to the Sun
becomes closer, since the high voltage power supply as well as TWTA for
the thruster have high sensitivity to the temperature. The project team
thinks the engine C should also work normally. The engine A has been and
will be left for reserve.
The return cruise is possible even by two engines. And the Xenon gas
left aboard satisfies the Xenon gas required for the cruise.
From two weeks before, Hayabusa lowered its spin rate down to 0.2 rpm
whose period is about 5 minutes now, aiming at reducing the Xenon gas
consumption required for the attitude control.
Currently, there is no problem for the communication as well as the
operation. However, the project team is anticipating a few issues that
need to be clarified through ground experiment and flight history. As
soon as it becomes more clear, the project will make another news
release about it in a few months.
The spacecraft was seriously injured and operating it and making it
resume cruise are still very hard things. Nevertheless, the project team
is sure to try it as best as they can.