Q: Did Mr. Nakamura send the commands during the second touchdown, too?
Nakamura: That's right. I was in charge at the time. Seems like I'm jinxed, right?
Sugiura: I was also in Sagamihara, preparing for communication system failures.
Q: At that point, it still wasn't time for Mr. Sugiura to play your part, right? Of course, things got difficult after that.
Sugiura: That's right. After the second successful touchdown on December 8th, 2005, we lost communication with the probe. I received an urgent phone call, and I was told to help find Hayabusa.
I was also told to make rescue operation software, and I was up all night that day creating the software with another team member. Throughout December, I made countless minor adjustments to the software based on the operation results. Professor Kawaguchi said that we would definitely find the probe. I'm sure the professor understood that recovering a probe with which communication has been lost is difficult, but he seemed confident. He said various things from the beginning that were based on the assumption that we would be able to restore the probe operations.
Q: As someone who sent commands, what was it like when there was no response from the probe?
NEC Networks & System Integration,
Sunao Kawada
Kawada: We experienced a long-term lack of responses from our Mars probe Nozomi as well, so I guess you could say we were used to this problem. Of course, problems like that are never supposed to happen. At the time, we weren't too pessimistic. We knew Hayabusa was on the antenna radar. It just wasn't responding.
Sugiura: Because Professor Kawaguchi told me there was no reason we wouldn't be able to find the probe, I feel that I was able to concentrate on the recovery operations without being distracted by too much worrying. I did my best not to think of the situation as an emergency.
Matsuoka: I knew that, as long as the probe was not destroyed by the low temperature, sunlight would strike the solar cells at some point, and then a response would definitely come.
Nakamura: As I mentioned before, there was a rule that I was the one on duty whenever anything important happened and, sure enough, I was on duty when communication was lost in December, as well as when it was restored in January. On January 23rd, 2006, a small radio wave peak appeared on the screen of the analyzer for received waves. Hayabusa had come back to us.
Sugiura: When communication was restored, I was working in Usuda space center. The person in charge at Usuda station kept looking at the screen. Suddenly, a small radio wave peak that might have just been noise popped up. I still clearly remember someone saying "Is this Hayabusa?" and the response that "This must be it."
NEC Networks & System Integration,
Yousuke Nakamura
Nakamura: To tell the truth, even though everyone else seemed confident, I still thought that recovering the probe was a miracle.
Matsuoka: To be honest, although I was sure that the probe would respond, I also suspected deep down inside that, since communication had been lost, then the mission was over. I think the fact that no one on the Sagamihara operations team gave up made all the difference. Their refusal to give up led to Hayabusa's recovery.
Sugiura: Even though communication was restored, communication was only possible at first for a few minutes out of every 30 minute period, and that caused all kinds of trouble. At first, this was one-bit communication. Hayabusa has a function that switches the carrier level between two levels, and we used this function for one-bit communication to gain an understanding of the probe's status and gradually correct it.
Matsuoka: As I mentioned earlier, our original plan was to have Hayabusa depart from Itokawa early in December and return to Earth in 2007, but we missed our return timing during the period communication was lost, and we decided not to think about the return until after we found the probe. Until we found the probe, we wouldn't be able to tell which parts of it were broken and would therefore not be able to plan the returning orbit to Earth. Of course, I also knew that the hard days of work would start again once we found Hayabusa, (laughs) but we eventually found the probe and restarted operations.
