The total solar eclipse that took place on June 30, 1973 was a long one. A bunch of scientists aboard Concorde 001, however, made it the longest observed total eclipse ever by following the path of totality. This is how aviation met astronomy to make this incredible feat possible…
Do you know who an umbraphile is? Literally meaning shadow lover, the word is used to describe a person who loves eclipses. Umbraphiles often travel to witness these eclipses, even planning years in advance to be at the right place at the right time. They are also called eclipse chasers, a term that nicely encapsulates what they actually do during an eclipse.
For some in astronomy, chasing an eclipse is normal. The larger the duration of the eclipse, the better for them as it affords them more opportunity to learn about the phenomenon and what goes on during the eclipse.
On June 30, 1973, a total solar eclipse took place with the path of totality passing through the breadth of Africa. While it was already on the longer side, with observers on the ground capable of getting a maximum of 7 minutes and 4 seconds of totality, astronomers were always looking to maximise it further, if possible.
The idea
In 1972, an idea occurred to Paris Observatory astronomer Pierre Lena — why not use a supersonic Concorde to essentially race the solar eclipse across the face of the Earth? (British astronomer John Beckman had independently arrived at the same idea, but hadn’t been able to get the necessary permissions.) Lena pitched his idea to French test pilot Andre Turcat over lunch at a restaurant inside Toulouse Airport.
Impressed with what he had heard, Turcat took the idea to his bosses at Aerospatiale. While it was provisionally approved and they agreed to cover the cost of the mission, it wasn’t until February 1973 that they received their final go ahead.
Planning phase
With just four months to go for the eclipse, the researchers and aviation staff went into overdrive. While those involved with flying the machine began customising the Concorde for the purpose and charting out the course of the flight, the researchers involved planned for the tests that they might be able to carry out, bearing in mind the limitations of conducting the experiments while inside an aircraft travelling at speed.
There were a total of seven astronomers from France, Britain, and the U.S. on board, including Lena and Beckman (yes, he found room onboard too!). There were five others aboard the Concorde — a flight mechanic, two radio navigators, and Turcat flying the craft with another pilot.
The flight
On June 30, 1973, the Concorde 001 took off from Las Palmas, Gran Canaria, in the Spanish Canary Islands in pursuit of the solar eclipse. On the day, the path of totality was about 250 km wide with the moon’s shadow moving at the rate of 2,400 km/h.
Despite all the test flights, there was a tense atmosphere on board as the Concorde intercepted the moon’s shadow over northwest Africa. The entire crew eagerly awaited entering totality, which the Concorde shortly managed — a success for all the precise planning and engineering.
Once plunged into the darkness, Turcat kept the Concorde on course, even as the astronomers employed the specially made rooftop potholes to witness the phenomenon and perform their experiments. The Concorde reached a little over Mach 2 (twice the speed of sound, over 2,400 km/h) at one point and then flew at 2,200 km/h along the path of totality.
Landing and completion
Flying in the same direction as that of the moon’s shadow, they kept up with it for as long as possible. But with the landing site in Chad fast approaching, the researchers quickly wrapped up their experiments, before gazing out to steal some glances for themselves.
In all, the overall exercise was able to extend the duration of totality for those on board to 74 minutes! Having got more than 10 times the time that a ground observer might have got, the experimenters had studied the sun’s corona, its chromosphere, and the intensity of the sun’s light from above the Earth’s atmosphere (they were flying at 17,000 m for much of the flight).
The collaboration of different disciplines served as an important example of how experts from varied fields can bring their vast knowledge together to push the boundaries of human knowledge further. While this wasn’t the last such flight to observe an eclipse (not even for a Concorde), it certainly still remains the one that provided for the longest observed solar eclipse.
First published in The Hindu In School
