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2005.11.20

Fate of Hayabusa

JAXA/ISAS is trying to touch down Hayabusa (MUSES-C) onto the asteroid Itokawa this morning. Apparently some anomaly happened along the way and they are now trying to analyze the status. No detail information is released by JAXA as of this writing, so I'm trying to summarize what Mr. Matsuura wrote in his blog, who is a space journalist now in the press room of JAXA/ISAS.

All timeline below is in JST (GMT+9), as he wrote the message, not the timeline of the event itself.

04:54 JAXA confirmed Hayabusa received the decent command. Altitude 370m.
05:20 Altitude 250m. Hayabusa goes into autonomous operation mode.
05:30 Altitude 170m, velocity 10cm/s.
05:37 114m from the surface.
05:45 70m from the surface. Prof. Matogawa calls pressroom intermittently.

06:03 Hayabusa released the target marker, a bright small ball with about 880,000 names of people.

06:09 Hayabusa turned into ascent. Details unknown. Telemetry will arrive to Earth at 06:20. It was a miscommunication. It was a time Hayabusa might have turned into ascent.

06:37 Telemetry still not received. Parabola is now being switched from NASA DSN Gold Stone station to JAXA/ISAS Usuda station.

07:23 Prof. Matogawa addresses the media. The target marker has been released. It was confirmed Hayabusa went down to the altitude 17m with the autonomous mode. Shortly after, Hayabusa seems locked, not descending nor ascending (no Doppler shift in its beacon signal). Altitude of this event is unknown. Usuda station sent ascent command shortly after 7 o'clock, followed by the command to enter "Safe mode". No ascent observed as of this writing.

08:44 Situation not clear. Media briefing may be held around 9 o'clock.

08:51 Prof. Matogawa addressed the media. "Situation not improved. There were no responses to the ascent and safe mode commands sent from Usuda. No Doppler shift was observed. It requires two-way link. The landing site rotated away to the far side of the Earth but we still receives the beacon from Hayabusa, so the possibility of Hayabusa being stubbed into the surface of Itokawa is out. We keep receiving the beacon but it does not respond to the command from Usuda. We are trying to establish two way link using Hayabusa's low gain antenna. We just sent another command to switch to telemetry mode. We will know the result in 32 minutes."

09:36 Prof. Matogawa to the pressroom. They are now speculating the possibility of Hayabusa being stubbed onto the north pole of Itokawa. JAXA released interim timeline. The operator confirmed the release of the target marker at 05:46. Reading of the laser range finder was 17 m at 05:55.

09:45 The two-way communication link was reestablished at 09:32 using the low gain antenna. Hayabusa is not in safe mode now.

10:28 Prof. Matogawa addresses media again. "In about 10 minutes we expect the first telemetry data from Hayabusa. The press conference originally scheduled at noon would have to be cancelled. The project manager Prof. Kawaguchi would also like to postpone it until tomorrow." The media wanted to hold the press conference anyway. "The result of the analysis of what happened has to wait until tomorrow. Once we receive the telemetry, we will know whether it touched down, impactor has been ejected, and such. We will let you know the status immediately. I would like Prof. Kawaguchi to concentrate on his operation. Telemetry will arrive in every 40 minutes. I think I will give you the briefing in every hour or so. There were some speculations about why Hayabusa did not go into safe mode. While it was trying to touch down, it somehow hovered at a certain altitude (about 10 m) for a half hour. Hayabusa's movement was closely monitored by two-way Doppler signal but no shift has been observed. We speculated the temperature of Hayabusa went up considerably. The communication circuit might have experienced some kind of anomaly. It seems reasonable we re-established the communication once Hayabusa moved away from Itokawa." About the velocity monitoring with Doppler shift. "There are two methods, one is one-way Doppler shift using Hayabusa's signal, and two-way Doppler shift by measuring the response to the signal sent from Earth. Frequency of the signal from Hayabusa varies as the temperature of the communication circuit changes. Therefore we could not precisely measure the velocity without calibrations in one-way Doppler. To measure the velocity at a few cm/s, we need two-way Doppler."

12:12 Prof. Matogawa again. "Now we keep contact with Hayabusa with medium gain antenna. We started the communication with low gain antenna and enabled the medium gain. We will receive the house keeping data such as whether the impactor has been ejected, around 1 o'clock. We will also know whether Hayabusa touched down. I will come back immediately when I know." The media: "Then we will have a lunch break until 1 o'clock..." Matogawa: "No, I won't take a break. I don't know the entire picture but they (operation team) know the whereabouts of Hayabusa. It's not returned to the home position yet." He is still being interviewed by media as of 12:23.

13:42 Prof. Matogawa into the pressroom. "We still don't know whether it touched down or not. Hayabusa did go into the safe mode. We also know it now hovers further away from the home position. Hayabusa is now in safe mode, stabilizing itself with a gentle spin, with its solar array facing to the sun. Medium gain antenna transmits signal with an 18 degrees cone. We receive the house keeping data only when the Earth is within its cone. Hayabusa is broadcasting its house keeping data with medium gain antenna repeatedly.
We don't know why it entered into the safe mode. It is not clear whether it received the safe mode command from Earth or not. Hayabusa has an option of going into the safe mode from its autonomous mode. This could also be the case.
Low gain antenna transmits the signal into every direction. So we didn't know Hayabusa was rotating. It was not before we received the signal from medium gain antenna that we realized it is rotating.
Usuda station ends contact with Hayabusa around 14:55. We plan to establish the 3-axis attitude control before the contact through Usuda ends.
We hold the next DSN station, Madrid, Spain, from 17:25 to 22:00. After the next is Usuda, from 08:30 tomorrow morning to 14:55. We would like to establish the attitude control this afternoon.
Our current goals are 1) establish the attitude control and 2) attempt to go back to Itokawa again. We are evaluating which goal to perform and when."
Next briefing will be around 16:00, when Usuda station ends contact with Hayabusa.

14:40 Mr. Matsuura's personal speculation based on the press briefings by JAXA/ISAS: "I got the impression that we did not experience such a strange hovering nor going into safe mode during the last three descent operations.
It may as well be the consequences of the event specific to this operation, namely the touch down!?
It could be due to the touch down that Hayabusa lost the attitude and entered into the safe mode??
Safe mode means the probe is safe. Anyway we are not in the worst situation."

15:46 Prof. Matogawa says the project manager Kawaguchi will show up at 4pm. Regaining the 3-axis attitude control seems not completed in time during the Usuda station communication. Press briefing will start at 4pm.

16:00 Hayabusa project manager Prof. Kawaguchi entered into the pressroom.
Kawaguchi: "Hayabusa started descent operation at 9pm last night. It actually started the descent long before but we declared at 9pm at the altitude of 1km.
We successfully aimed the probe to the target, better than our last rehearsals.
Around 4:30 this morning we started the "perpendicular descent " phase, at altitude of 400 to 500 m, along the line between Earth and Itokawa. The velocity was about 10 cm/s.
It had been very smooth. We presume we had controlled the spacecraft at an order of 1 cm/s precision.
It took about an hour to the altitude 54 m. We sent GO at 4:55. This was the prescheduled altitude. We cut the wire which held the target marker. At the altitude of 40 m the spacecraft braked by 6 cm/s, which released the target marker. We calculated the marker reached onto the surface of Itokawa 400 seconds later.
At 35 m we switched the altitude monitor from radar?LIDAR to the laser range finder. It was the first time for us to use the laser range finder, but it worked pretty well.
The spacecraft then took pictures of the marker and it followed the marker autonomously, which also went very well.
At 55 m Hayabusa went into hovering mode using the laser range finder.
Then it went down slowly until 17 m, when the spacecraft aligned itself to the surface of Itokawa. The communication with the high gain antenna was stopped at that point. We switched to the beacon mode and watched the altitude with Doppler information.
From that point on, we only have Doppler information at hand now.
We speculate the spacecraft had descended at 2 to 3 cm/s with the trajectory parallel to the surface of Itokawa. We observed it stayed at 10 m for about a half hour. Combined with other data, we do not think Hayabusa had touched down.
Staying longer near the surface of Itokawa, the temperature of the spacecraft goes up due to the sun light reflection from the surface. We sent ascent command at 7am from NASA station.
At this point the angle between the Sun and the solar array went too large and this caused the Hayabusa to go into safe mode. We don't know why at this point.
We tried every effort during the communication time window from the Usuda station to stop the spinning of the spacecraft but we still do not regain the 3-axis control. We will try again tomorrow. As a consequence, we still not downloaded the data in the data recorder.
The spacecraft evacuated from Itokawa at rather high speed, so it is now about 100 km away from Itokawa. It will take several days to bring it back near Itokawa.
We need to check the status of the sensors because the spacecraft stayed longer near the surface. We will check them in a couple of days.
We were so close to the success, and we maintained the spacecraft in a deep space at a very high precision without the (reaction) wheels. This is a very big step forward.
We are also pleased that we successfully delivered the target marker which carries the names of so many people.
We plan to test the probe. Then we'd like to try the touch down again to get the sample of the surface. We have another target marker on board."
Mainichi: "Tell us the reason you don't think there was a touch down."
Kawaguchi: "The spacecraft has a software which will be triggered by the distortion of the sampler horn. We know this has not been triggered based on the telemetry received at Usuda.
However the spacecraft went into ascent mode autonomously, so there had been some turbulence such as some part of the spacecraft touched the surface of Itokawa. We don't know precisely at this point."
Kyodo: "What is the reason for the horizontal drift?"
Kawaguchi: "It is a speculation at this point that the spacecraft had drifted horizontally. At very low altitude it does not follow the target marker. It free-falls onto the surface. There is a possibility that the spacecraft may drift horizontally when it cuts the chasing mode of the target marker, which is an expected operation. We thought it should then be in a free fall."
Tokyo: "You think the spacecraft was in visual contact with the target marker?"
Kawaguchi: "We think so. We think this is a smoking gun evidence that the target marker has landed. We still do not declare it until the data is downloaded.
The separation of the marker, descent speed, the marker being photographed and tracked, were all monitored in real time."
NHK: "You say it did not touch down. How about the altitude?"
Kawaguchi: "By integrating the descent rate, the amount of the descent looks like the spacecraft went inside Itokawa. This is a tentative number and not conclusive. It actually did not go inside Itokawa. There is a possibility as the spacecraft moves horizontally with the rotation of Itokawa that we might have this kind of data. Rationally."
NHK: "The software was not triggered means the impactor was not ejected. Are you really sure the spacecraft did not touch down?"
Kawaguchi: "You are right. Even if some portion of the spacecraft touched the surface of Itokawa, I do not want to declare it as a 'touch down'."
NHK: "Why you think the altitude was 10 m?"
Kawaguchi: "Actual measurement we had was 17 m. We also know that the spacecraft was in descent after this measurement. We speculate it was at about 10 m."
NHK: "Why it lost the attitude?"
Kawaguchi: "We don't know yet. While it aligns to the surface, the logic to go into safe mode because of the angle between the solar arrays and the Sun was tuned off. Afterwards we turned on the logic. We still don't know what happened in between."
NHK: "You did not receive the status of ascent in real time. Did it go in the safe mode?"
Kawaguchi: "It was just at the handing over from the NASA DSN and the Usuda station. We realized these events when we received the signal at Usuda."
Gekkan Tenmon: "How long was it during the horizontal drift? You sent the ascent command from Earth, and you are supposed to send the stop command but you didn't. Why?"
Kawaguchi: "The duration of the drift was monitored to be about 30 minutes. Then we sent the ascent command and it arrived to the spacecraft 16 minutes later. So it should have been longer than 30 minutes.
We did not send the stop command because the recovery from the safe mode was our priority."
Gekkan Tenmon: "What about the remaining fuel?"
Kawaguchi: "We consumed fair amount. It is one of our concerns for the future operations. But we would like to try one more chance."
Jiji: "Would it be on time for the descent on November 25?"
Kawaguchi: "If we are to try again on the 25th, we need to hurry. There are so many things we need to consider. Also we can try the touch down operation only when the NASA DSN backup is available. There are not so many chances. We think we need to exploit the chances. But we also need to think again if there are damages in the spacecraft."
NHK: "The sensor for obstacles, which would have triggered the abort operation, was not actually triggered?"
Kawaguchi: "No, it didn't."
Unknown: "The whole world is watching this operation. Do you have any comments for not being able to touch down, and for your intention to try again?"
Kawaguchi: "It was a pity. We need to check the status of the spacecraft with very limited chances. On the other hand we have firmly established the spacecraft maneuver which had not been possible during the last two rehearsals. Autonomous descent and the attitude control with the laser range finder was a big milestone.
We thought we had cleared all the technical challenges, but we encountered some unknown event. We think Hayabusa is a success as a robot probe. It did not actually touch down but it is a good mark as for the engineering. We strongly want to try again."
Unknown: "What was the impact of the reaction wheels?"
Kawaguchi: "We originally planned the last minutes descent without the attitude thrusters. Because of the malfunction of the reaction wheels, the spacecraft had to go through the small turbulence due to the thrusters. It affected today's event in some way. Pending on the analysis of today's data, we are even thinking to thrust the spacecraft downwards onto Itokawa."
Tokyo: "What temperature Hayabusa could endure? Do you have the data how hot it was?"
Kawaguchi: "We think the circuits which were turned on and generated heats were in critical condition. There may be some effect due to the temperature. We originally did not plan to stay near Itokawa for such long period of time. We still do not have the estimate of the temperature. Some circuits might be at 100 deg C because the surface was 100 deg C."
The microphone was handed to another pressroom in Tokyo.
Asahi: "What is your most worrisome point? Is the schedule of another touch down on 25th at this point? When do you plan to download the data? Is there any possibility that you find something tonight?"
Kawaguchi: "We need to analyze the phenomena at the final stage. We are not sure exactly what happened. We think we need to try again even if we need to thrust the spacecraft downwards. We think there would be no problem if the spacecraft acts as same as today.
On the other hand we would not be able to navigate the spacecraft to exactly the same point as today. There remains some uncertainty due to the different surface. We believe we can do it based on our experiences.
We still do not know if we can try again on the 25th. We want to keep the 25th as the target date.
We will not have another data until 2am tomorrow."
Asahi: "Are there any possibilities that some part of the spacecraft is damaged?"
Kawaguchi: "As of our knowledge we do not have a big damage. We need to analyze it in detail."
Asahi: "What was the time of the target marker reached to the surface?"
Kawaguchi: "Released at 5:46, separation at 40 m and at 10 cm/s, so it should land in 400 seconds. It should have been 5:50."
Mainichi: "You said the drift time was 30 minutes. What was your original plan?"
Kawaguchi: "8 minutes or so."
Yomiuri: "What do you mean by you cut the wire at 54 m and the separation of the target marker was at 40 m?"
Kawaguchi: "After the wire was cut, the marker did not separate until you slow down the spacecraft. At 40 m, it braked by 6 cm/s, then the marker was separated. We need this complicated procedure to release the marker at the exact velocity."
Yomiuri: "And it landed on the Muses Sea?"
Kawaguchi: "Yes."
Sankei: "What will be the next chance if you miss the 25th?"
Kawaguchi: "Hayabusa must leave Itokawa in early December. So we need to seek for candidates during the end November and early December. We are not able to decide on our own."
The microphone returned to Sagamihara, ISAS.
NHK: "Was it a speculation that the spacecraft had drifted on the surface? Were there any possibilities it stayed near the surface?"
Kawaguchi: "It is a speculation. To give a reasonable explanation of the negative altitude, we need some movement while it had not touched the surface. Only the rational explanation is the movement horizontal to the surface."
NHK: "Was it a free fall after 17 m? Were the thrusters not used?"
Kawaguchi: "It was a free fall with attitude control with the thrusters."
NHK: "You told us several abort conditions at the last briefing. At this point were there any possibilities of abort due to the loss of the signal from the laser range finder? Were there no obstacles on the surface?"
Kawaguchi: "No. It does not mean there were no obstacles but it did not sense the obstacles. At the time of releasing Minerva, the obstacle sensor actually sensed Minerva. We think the sensor is functional."
NHK: "Am I correct there would be no reason that Hayabusa gets abort near the surface?"
Kawaguchi: "It might have gone into the safe mode due to some other reason which is not so obvious."
NHK: "Didn't the laser range finder record the angle of the plane it observed?"
Kawaguchi: "No."
Sankei: "Both the ascent due to entering the safe mode and the ascent command sent from Earth were in effect?"
Kawaguchi: "That is correct."
NHK: "Which direction did Hayabusa move away from Itokawa?"
Kawaguchi: "We don't know. It should be along the line perpendicular to the Muses Sea. It depends on the surface condition. Also the safe mode points the attitude of the spacecraft towards the Sun, so we would not be able to stop the spacecraft with thrusters. Nevertheless we performed the reverse firing maneuver without knowing the precise orientation of the spacecraft, to stop drifting further away."
NHK: "You said the temperature rise you measured was about 20 deg C. How long did it take?"
Kawaguchi: "About 20 minutes. We had the similar condition for another 30 minutes, so we think the temperature was more than 80 deg C, 40 to 50 deg C increase in total."
NHK: "Wasn't it dragged on the surface of Itokawa?"
Kawaguchi: "We have no direct evidence that it touched the obstacle. Even if there were such contacts, we won't call it 'landing'."
NHK: "Wasn't the free fall of 30 minutes enough time for touch down?"
Kawaguchi: "It should be. It may be possible that it followed onto some slope."
Kyodo: "When would you decide you might have another try on the 25th?"
Kawaguchi: "It may be late that week. We will not postpone the decision until the very day."
Kyodo: "You said you would be able to touch down next time, given the same condition as today. What does that mean? Will you change some criteria?"
Kawaguchi: "We did not expect the final stage such hard, so we are somewhat curious. If the analysis does not come to conclusion, we would take a risk with downward acceleration to touch down. In other words, we would change the criteria."
The microphone turned back to Tokyo.
Unknown: "The fuel consumption seems very tight. Are there any possibilities that you scrap the returning to Earth and perform the sampling maneuver instead?"
Kawaguchi: "I think the possibility is remote. The mission includes the retrieval of the asteroid sample. Getting the sample and retrieving it are coupled."
Mainichi: "You said you made a good score in robotics. What is your score in 500 mark?"
Kawaguchi: "We are still in the middle of the mission. I would avoid answering that question. But I feel a kind of satisfaction on the outcome of the robotics maneuver."
Yomiuri: "Could you remind us what are the two engineering points?"
Kawaguchi: "In one phrase it is the navigation and guidance. We performed the operation with high precision, given the feedback from the past rehearsals. The newly achieved two are 1) the attitude and altitude control using the laser range finder, and 2) guidance of the spacecraft based on the image processing of the picture of the target marker."
Yomiuri: "That means once you download the data, you have quite high resolution images, don't you?"
Kawaguchi: "We are not sure because the spacecraft entered into the safe mode. But if successful, we should have the high resolution images."
The microphone returned to Sagamihara again.
Fuji TV: "When did you realize you did not have chance for touch down? What were your feelings?"
Kawaguchi: "At around 7am when we sent the ascent command, we felt we do not come to touch down. The atmosphere at the operation room was that they were curious for not having touch down at the final stage thus far. I myself was thinking 'this is a kind of difficult situation.'"
Gekkan Tenmon: "The remaining fuel at the arrival of Itokawa was 50 kg. When would you able to estimate the possibility of returning to Earth? How do you estimate the amount of the remaining fuel?"
Kawaguchi: "We can calculate the rough amount of the fuel based on the temperature and the pressure readings of the tank. There is a method of extremely low fuel consumption but it depends on the conditions of Hayabusa and the maneuver of returning it to Earth. Whether it can return to Earth depends on how we choose the safety factors. We need to evaluate.
It is not whether we can bring Hayabusa back to Earth or not. It is how we restrict our fuel consumption.
I myself feel it is very critical at this point."
Gekkan Tenmon: "What are the house keeping data?"
Kawaguchi: "Readings of the temperature, pressure of the fuel tank, currents and voltages of the circuits, for example."
Matogawa: "I would like to thank Hayabusa team for delivering the target marker ball with about 880,000 names of people on it, to Itokawa. It was me who proposed this PR event. It is kind of strange to thank to the colleague. I've been watching various exploration missions, but this one gives me the firm impression that we have entered into a new horizon of the solar system exploration since the comet Halley mission.
The team members may not be aware now, but looking closely from behind, I think Japanese space exploration is really moving into a new chapter."
Unknown: "When would be the next press conference?"
Matogawa: "We don't know at this point. We will schedule and let you know. I would like the operation team to have some rest. It would not be today. Maybe tomorrow or some time later."

Prof. Kawaguchi returned to the operation without answering to further questions. The time slot opened for the Madrid station communication, and the team needs to establish the 3-axis control anytime soon.

This will conclude my (Matsuura's) posting for today from Sagamihara, JAXA/ISAS.

[ The translator will not be available for the
[ next Hayabusa mission due to his schedule.
[ Please follow Matsuura's blog from now on.
[ Robotic English translations are available at
[ Google. Thank you for your interest to this
{ article. 5thstar, signing off. ;-)

References:

「はやぶさリンク」:着地はできず。88万人のターゲットマーカーの投下には成功
「はやぶさリンク」:臼田局可視中の、三軸制御確立は間に合わず
「はやぶさリンク」:タッチダウンできていた?
「はやぶさリンク」:実はセーフ・モードに入っていた、予想よりもイトカワから離れていた
「はやぶさリンク」:次の情報は午後1時過ぎぐらい
「はやぶさリンク」:セーフモードに入らなかった理由、ドップラー変位による速度測定について
「はやぶさリンク」:双方向通信回復
「はやぶさリンク」:ビーコンは受信できている。双方向通信が確立していない
「はやぶさリンク」:午前9時頃に説明がある、かも
「はやぶさリンク」:トラブル発生

「はやぶさリンク」:地上局アンテナ切り替え
「はやぶさリンク」:上昇開始
「はやぶさリンク」:ターゲットマーカー放出
「はやぶさリンク」:より一層降下
「はやぶさリンク」:降下継続

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今朝、小惑星探査機「はやぶさ」は「イトカワ」への第1回目着陸・試料採取に挑んだ。ターゲットマーカの投下に成功したものの、着陸は「イトカワ」から約10mまで近づいた所で姿勢が乱れ、上昇し、あと一歩の所でできなかった。 素晴らしいじゃないですか、JAXAさん。 ....... [Read More]

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