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French researcher at the science bar
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In the early 1970s, a new generation of Soviet satellites called Prognoz was developed. Their primary mission was to monitor solar activity and its influence on the interplanetary environment.
“I began to get much more involved in cooperation with the Soviets through the Prognoz 5 and 6 programmes,” adds Jean-Loup Bertaux. This time, it was the French researcher who took the initiative to get into direct contact with the great Russian astrophysicist Joseph Shklovsky and close the deal—albeit in a rather unorthodox way.
“As part of the French-Russian space cooperation agreement, a meeting was held every autumn to review programmes in progress and in the pipeline. In 1971, the gathering took place in Tbilisi, Georgia.
I was at the bar one evening when I heard some colleagues from another French laboratory, the CESR space radiation research centre, talking about the performance of a new series of Soviet satellites called Prognoz. I immediately realized these satellites could help us resolve the mysteries surrounding the results of the OGO-5 mission.”
The American OGO-5 satellite studied the Earth’s geocorona, a cloud of hydrogen atoms that surrounds our atmosphere, extending to 10 or more Earth radii, in other words a diameter of 50 to 100,000 kilometres.
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Beyond this cloud, OGO-5 observed a faint light in all directions, but researchers were unable to explain what was causing it. One hypothesis was that streams of atomic hydrogen from interstellar space were being illuminated by the Sun. The only way to confirm this hunch was to make observations from beyond the geocorona, since its own hydrogen would distort the data. At an apogee of 200,000 kilometres, the Prognoz satellites offered an ideal vantage point.
Joseph Shklovsky.
“Vladimir Kurt, our regular contact on the Russian side, had broken a bone in his foot playing football and couldn’t make the meeting. So I went straight to Shklovsky myself and suggested the idea of flying a French Lyman-alpha photometer on one of the Prognoz satellites. He agreed without hesitation!”
And that is how a young French researcher, just 29 years old, after chatting with colleagues over a drink, managed in just a few hours to place his experiment with one of the greatest Soviet scientists of the time…
The experiment was the first to measure the angle of arrival and temperature of interstellar hydrogen, and to demonstrate that solar wind is more intense in the Sun’s ecliptic plane than at its poles. This remarkable achievement paved the way for prolific scientific cooperation that continues today. The French SWAN instrument on the SOHO solar observation satellite is one recent example. SWAN utilizes the method demonstrated with Prognoz and used by French researcher Rosine Lallement to predict the distance to the heliopause, the boundary area where the interstellar wind meets the solar wind.
