As has been reported, it is estimated that part of a series of attitude and orbit control
commands to restore the Hayabusa from its safe-hold mode have not gone well, and
the functions of its major systems, including its attitude and communication network,
have significantly deteriorated.However, on Nov. 29, a beacon line through a low gain
antenna was restored.
On Nov. 30, we started a restoration operation by turning on and off the radio frequency
modulation through the autonomous diagnostic function.Subsequently, on Dec. 1,
telemetry data were acquired at 8 bits per second through the low gain antenna, although
the line was weak and often disconnected.According to the data transmitted so far, the
attitude and orbit control commands sent on Nov. 27 did not work well due to an
unknown reason, and either major attitude control trouble or a large electric power loss
seems to have occurred.It is estimated that the overall power switching systems for
many pieces of onboard equipment were reset as their temperature dropped substantially
due to the evaporation of leaked propellant, and also because of a serious discharge of
electricity from the batteries of many sets of onboard equipment and systems due to
declining power generation.Details are still under analysis.
On Dec. 2, we tried to restart the chemical engine, but, even though a small thrust was
confirmed, we were not able to restore full-scale operations. Consequently, the cause
of the anomaly on Nov 27 is still under investigation, and we suspect that one of the
causes could be the malfunction of the chemical engine.
On Dec. 3, we found that the angles between the axis of the onboard high gain antenna
(+Z angle) and the Sun, and also that with the earth, had increased to 20 to 30 degrees.
As an emergency attitude control method, we decided to adopt a method of jetting out
xenon for the ion engine operation.Accordingly, we immediately started to create the
necessary operation software.As we completed the software on Dec. 4, we changed the
spin speed by xenon jet, and its function was confirmed.Without delay, we sent an attitude
change command through this function.
As a result, on Dec. 5, the angle between the +Z axis and the sun, and the earth,
recovered to 10 to 20 degrees, and the telemetry data reception and acquisition speed
was restored to the maximum 256 bits per second through the mid gain antenna.
After that, we found that there was a high possibility that the projectile (bullet) for
sampling had not been discharged on Nov. 26, as we finally acquired a record of the
pyrotechnics control device for projectile discharging from which we were not able to
confirm data showing a successful discharge.However, it may be because of the impact
of the system power reset; therefore, we are now analyzing the details including the
confirmation of the sequence before and after the landing on Nov. 26.
As of Dec. 6, the distance between the Hayabusa and the Itokawa is about 550
kilometers, and that from the earth is about 290 million kilometers.The explorer is
relatively moving from the Itokawa toward the earth at about 5 kilometers per hour.
We are now engaging in turning on, testing, and verifying onboard equipment of the
Hayabusa one by one to start the ion engine.We currently plan to shift the attitude
control to one using the Z-axis reaction wheel, and restart the ion engine.The restart
is expected to happen no earlier than the 14th.We are currently rescheduling the plan
for the return trip to earth.We need to study how to relax the engine operation
efficiency.We will do our utmost to solve the problem with the attitude control (such as
the restoration of the chemical engine), then find a solution for the return trip.
Since Nov. 29, our reports have been limited due to difficulties in confirming telemetry
data. We apologize for any inconvenience.
We will inform you as soon as the ion engine is restarted.