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Upper Atmosphere Observation—Interview with Makoto Taguchi, Associate Professor at NIPR.

Nikon lenses at both poles

How do you observe something like this that happens so high above the earth ?


© NIPR

At present, observation is conducted mainly by remote sensing methods using optical instruments and radar. By using a rocket, it has become possible to directly measure the variety of atoms, quantity of electrons and status of the electromagnetic field existing on a flight course. However, the launch costs are quite high and observation is possible only for the short time period during a flight. With optical instruments and radar, regular and long-term observations of large areas are possible. Most of my observations are conducted with optical instruments. By measuring the light from the upper sky with an optical instrument called an All-Sky Camera (ASC), I can photograph the entire sky in one 180° image and observe what is occurring. I use an instrument called a Fabry-Perot Imager (FPI) to carefully analyze every minute detail in the data. By observing light interference found in the data, I can determine the wind speed and temperature of atmosphere up to about 300km above the earth.

When did such studies begin ?

Observation of the aurora at Syowa Station in Antarctica began in the 1950s. In the beginning, film was used and long exposure times were required due to the film's low sensitivity. Since 1997, however, observation has been conducted with the highly sensitive CCD of the ASC. It can take pictures of fast-moving aurora without shaking as it selects light with specific wavelengths. And it captures these images with exposures within 2 seconds.

Where are the observations conducted ?

Mainly at the Antarctic and Arctic regions, just as the name of the institute indicates. In the Antarctic, over 20 countries including Japan have more than 30 observation stations, but only a small portion of them conduct observations of aurora. NIPR has observation instruments at the South Pole station, in Norway and in Ireland, with Syowa Station utilizing more equipment than any other facility. About 40 people stay throughout the winter at Syowa Station every year to conduct various scientific observations. At present, there are two members in charge of observation related to the upper atmosphere. Enormous amounts of data obtained by our observations are sent to Japan and analyzed daily.

The ASC uses a Nikon lens, doesn't it ?


© NIPR

Yes. At present, we use mainly three observation instruments: the ASC, the ASI (All-Sky Imager) and the FPI. All of our lenses are made by Nikon. We have asked other makers to produce observation instruments for us before, but the light quantity and resolution in the peripheral view field decreased dramatically. At that time, we found a Nikon lens that was used for the previous ASC kept in a storehouse. It was a very fast 6mm f/1.4 lens with a 180° field of view. Although it had been in storage for a long time, it had a perfect optical performance. To re-utilize this lens for the new ASI, we decided to consult with its manufacturer, Nikon and Nikon Engineering (in Japanese language only). As a result, the first camera is now being used at the South Pole station. After that, three ASIs of the same type were produced, and are in use in both the Arctic and Antarctic, as well as an equatorial area. At present, newly-innovated ASCs are being produced. They are planned to be sent to Syowa Station and to Iceland to observe the aurora at both poles at the same time.

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