| Ken'ichi Okamoto |
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Chairperson (Yasuoka):
Prof. Okamoto, thank you very much.
There were many technical issues and he worked out the issue one by one. As an international joint research venture, TRMM was a tremendously successfulexample. I attend many international conferences. The successful PR results were often cited, not from the Japan side, but from the US side, for example by NASA people. I could be very proud when attending conferences and am very appreciative of this. Then I would like to invite questions from the floor.
Questioner 1:
This is the same question as I asked before. Usually one might think that it may be easy to bring the ground radar to space. However, according to your presentation there were many requirements, such as scanning and attaining the swath width of 215 km. Apart from the observation on the ground radar, I would like to ask when you came to have confidence that you could measure the precipitation from space and what kind of idea led to such confidence.
Okamoto:
As I also mentioned in the presentation, we were not sure at first. As the study progressed, we increased in confidence. In the first place I did the calculations and evaluated the effect of the ground clutter based on the radar equations. We considered the antenna pattern characteristics and calculated precipitation echoes and S/C ratio. I thought it possible to achieve and presented the results at IAF conference in 1979. CRL was a good place and when I said it had the possibility of success, they trusted me. Even though I was young, they had the atmosphere for providing me with the budget. We constructed the airborne precipitation radar and did the experiment. It was very difficult to go through, but finally we could make a new rain rate retrieval algorithm and find a way to eliminate the ground clutter by the combination of sidelobe and short pulse. We gradually came to understand such problems and had confidence. Finally speaking, I was not sure about the reliability of the system on the satellite. I was quite worried about the reliability issue. I thought the satellite group might be consisted of quite nervous people, though I myself was very nervous. I worried that the NASDA people would say NO to the project. On the contrary, Mr. Tanaka said to promote the project, but the other people were not so positive about it. However, Mr. Tanaka and Mr. Shibato said we should do that. I thought NASDA was a very strange place. There were pessimists, and on the contrary there were such people as Mr. Tanaka. He and Mr. Shibato said they should promote the project and were the original supporters. Though I didn't know much about a satellite, but I became confident about the satellite. As Dr. Fugono mentioned, I was quite pleased to see the typhoon image that was the same as that of the airplane experiment. I was quite assured.
Questioner 2:
You analyzed the precise 3-D precipitation data for a long time and achieved good results. From the point of view to conserve the global environment, I would like to hear your opinion about what work should be done in the future, especially in the development of the algorithm.
Okamoto:
The last slide shows GPM and this is very important. The USA is playing the major role in this project, but Japan's side is behind. ve have to try hard and have to catch up with the US side. As for the precipitation radar, fortunately we had major achievements in the TRMM. The radar hardware is not everything, and we have to take an initiative in developing PR algorithms also. GPM is a very important mission. The global precipitation will be observed for every 3 hours. On the governmental side, they would say that they have no budget and that the safety of Japan and the acquisition of information are more important. I think it is very important to keep the highest level in the science and technology field where Japan can do the highest contribution to the world. I am not sure this example is a good one, but Kashima Antlers has become strong owing to Mr. Zico. As for the radar algorithm, we are in the highest level in the world. As for the radiometer, we have no achievement at all now, but we have to contribute to the radar and radiometer combined algorithm.
Questioner 3:
In your presentation, I was surprised that you have overcome and achieved many requirements. My question is how long you took to develop the technologies for achieving the requirements. Next question is what was the difficult point in communicating with the scientists who presented the requirements.
Okamoto:
These user's requirements were presented by NASA. We worked very hard to do the feasibility study in 1987. After that, the CRL couldn't get enough national budget for a certain time. Though we had a little budget, we made the bread board model with the help of manufacturers. This situation continued for about three years. In the end, it took three years to do the feasibility study for the requirements. During this time we had a chance to communicate and discuss with Prof. Matsuno and Prof. Sumi of the University of Tokyo. They were the end user of this project. The requirements we presented did not match ones that they had thought of. For example, they required the definite figure for the accuracy of the rainfall rate. To achieve this requirement, we had to use the radar which was calibrated accurately. Actually in TRMM radar the accuracy was improved to }0.5 dB, about 17%, using active radar transponder. When we compare the accuracy of the ground radar with that of the TRMM radar, the accuracy of the ground radar was worse than that of TRMM. I had a good experience that the requirements from the end user provided the upgrade of the system. I understood that it was very important to have an interaction with end users.
Questioner 4:
The first question is about the hardware. I think a high sensitive detector should be used, so I would like to ask what kind of detector was used. The second question is as follows. As Dr. Fugono mentioned before, because the system of the organization was very different between Japan and the US, the collaboration almost collapsed. It was the personal trust that continued the collaboration. As the collaboration becomes as large as that of this project, I assume that there must be something other than the personal trust. I would like to ask what the motivating force for the success of the project was.
Okamoto:
Radar was highly sensitive, so the point was how to decrease the noise from the receiver. We used the frequency of 13.8 GHz; therefore it was rather easy to reduce the noise. NEC had the high potential for developing the new semiconductor device, so the new device with the noise figure of 1.5 dB could be developed. We also used the PIN diode phase sifter. This was very difficult to develop, so we had earnest discussions with Mr. Nishikawa of NEC - I am not sure if he attended today. Finally we could develop a good device. Then I think the trust of each person is very important. And at the same time there is another crucial factor. I think it very important that each person has an intention of never giving up. The personality is also very important. Another factor was that we were very lucky. Many people helped us. In addition to this, we all worked very hard to achieve this work. Also the trust of each person was substantial.
When we negotiate with the Americans, we never tell a lie. Usually we Japanese have a tendency of saying YES, even though we can't do something. When we cannot do the thing, we should say that we cannot. When I made a presentation at NASA about 35 GHz and 13.8 GHz dual-frequency radar, the total weight of the two radars was over 750 kg. The engineer who attended the meeting booed and said it was impossible to load on a satellite. Some people went out of the room. I didn't know what to do, but I couldn't tell a lie. Finally one of the radar was loaded on a satellite. Not to tell a lie is very important to make a relationship of mutual trust.
Chairperson:
Thank you very much. This was an excellent example of making a success of a big project. I think that there were probably many failures leading up to this success. However, they finally got good results, so I think this achievement is very deserving of the Takeda Award. Please show our appreciation to three awardees by clapping and cheering.
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