Chase The Sun - Concorde 001 and the 1973 Solar Eclipse

30th June 1973 was the date when Concorde 001 was used to “chase the sun”. More precisely, there was a Solar Eclipse that day, with the track of the moon’s shadow running across Africa. For anyone standing on the ground the totality (complete eclipse) would only last a few minutes. But by using an aeroplane, flying along with the shadow, it was possible to extend this to a much longer duration. The snag was that the aircraft had to be supersonic...

At the time I was in the middle of a research studentship with the Astrophysics Group at Queen Mary College, London University. My supervisor (Dr John Beckman) and some others were wishing to make far-infrared observations of the eclipse to learn about the sun. He put two and two together and came up with the answer - Concorde! He initially contacted the British Aircraft Corporation who were running the UK side of the development and asked if we could use their prototype (002). Although they initially thought it was a good idea, they backed out when they realised that we needed to make some holes in the roof to insert crystal quartz windows to observe the sun at these Terahertz frequencies. So he then approached the French and asked if we could use their prototype (001). They agreed.

Although in an Astrophysics group, my real interest was in the engineering of the experimental equipment. As John’s student at the time I took on the task of designing and making the electronics to control the measurement system and collect the data. This set me on a course for the south of France and a number of flights at Mach 2!

My first view of 001 in the Concorde Hall in the factory.

Having spent some months developing and testing at QMC I flew to Toulouse at the start of May 1973. The French side of the Concorde project was based at the Aerospatiale factory there. The first few weeks at Toulouse involved testing the instrument on a very-low-speed trolley outside the building.

Is it working OK?
This photo shows the QMC system being tested outside the factory building.
Left-to-right the people are: Jim Lesurf, Jim Hall (RSRE), Tony Marston.

Once these tests ensured the system was working correctly, the instrument was fitted into Concorde, and connected into its electrical power systems, etc

Standing on the wing!

QMC weren’t the only research team using 001 at the time. There were also researchers from Los Alamos in the USA, two groups from France, and one from Aberdeen University. The UK work was also supported by RSRE which was one of the UK's government research laboratories of the period (now amalgamated into the Rutherford Appleton Laboratory). In addition there was already an ongoing project run by Dr Jim Birch of the UK National Physical Laboratory.

Researchers in the room QMC and NPL used as a Lab at the factory.
Jim Birch on the left, John Beckman and Tony Marston from QMC on the right.

At the time we were asked not to mention the NPL work to anyone else. This was because it wasn’t using Concorde to observe a Solar Eclipse. Jim Birch was making observations on the upper atmosphere because some people had worried that routine supersonic civil flights might damage the stratosphere and lead to an environmental problem. So the NPL were investigating this to see if there was anything to worry about.

This was my first trip out of the UK. When I went, I had no knowledge of French Language. So I had to pick up the words and phrases I needed by trying to communicate with the people around me. John Beckman did speak French. However after a few weeks some of the workers used to turn to me to find out what he had said! This was because he spoke with a well-educated - i.e. posh - French accent. Whereas I had just learned how the words sounded when spoken by the people in Toulouse. I am still not sure how much this was because I had adopted the local way of speaking, or if they were just French workers enjoying winding up an English ‘professor’...

André Turcat, the chief test pilot for 001, being interviewed at Toulouse.
For some reason I tend to think of this picture as being ‘A study in noses’...

I went on a number of test flights in 001 from Toulouse. These tended to fly out over the Atlantic, and go supersonic above the ocean. For our tests Concorde then flew along the horizontal towards or away from the sun whilst I worked on the instrument. In service Concorde became the symbol of luxury travel. But working on the prototype was rather less luxurious.


The QMC instrument installed in the cabin of Concorde 001. Note the dark opening in the roof which holds the quartz window of the cabin.

The plane only had a few seats in the main cabin. These were all ‘military style’ seats with full belts to aid protection in the event of a crash. (Although I doubt they’d help much if you hit something at Mach 2!) When the plane took off the thrust from the Olympus engines gave it a high acceleration. It also rotated to a steep angle of attack to get enough lift. The result was that I’d hang out of the seat as if it were attached to the ceiling! And when working on the instruments I’d find that the pilots would have fun putting 001 though semi-aerobatic moves to test the plane itself. Once I was trying to undo a bolt with a screwdriver. The pilots put the plane into a zero-gee fall. The bolt didn’t rotate, I did. My feet came off the deck and I went though about 30 degrees before the pilots pulled back on the controls and I fell onto the deck! On another occasion the rest of the experimenters had failed to manage to get the signal detector working, but decided not to tell me. So I spent over an hour working in this funfair environment worried that something was seriously wrong. I was told that I looked green when I came down the boarding gangway at the end of the flight. In level flight, Concorde was like a magic carpet with almost no turbulence or waggling. But the test flights were sometimes rather more ‘entertaining’.

Concorde 001 at Toulouse just before one of the test flights.

After the test. Happy researchers disembarking.

During the project we were able to fly to and from home whenever we wished. Because we were using Concorde for the experiment the UK/French Governments and their, then, state-owned airlines made travel easy. If there was a free 1st class seat we were give it if we turned up at the gate. Alas, the Paris-London hop was so short that it was a rush to eat the excellent meal before landing!

On 27th June we flew down to Gran Canary Airport (Canary Islands) which was where the actual eclipse flight would commence as it was near the track of the total eclipse. Concorde flew down from Toulouse first, carrying the instruments. We followed in an old Caravelle airliner that Aerospatiale used as a transport for the engineers who accompanied 001 in its flights around the world. Although that Caravelle was old, it was very well maintained. Some of the best aviation engineers in France would give it a careful checkup before each time they flew in it. This included senior engineers going round kicking the tyres, etc, to make quite sure!

The flight down to the Canaries in the Caravelle was livened up by the pilots playing a trick. Half way there they reduced engine power without warning and announced (in French) that we’d run out of fuel due to the headwind. Fortunately I didn’t know what the fuss was about as my French wasn’t good enough to find out until the joke was over. But there was indeed a strong headwind as there was also a huge dust storm over Africa which we could see from the Caravelle.

One of the first tasks when we arrived was to find somewhere safe to put a dewer of 100 litres of Liquid Helium. This was needed to cool down the InSb Far-Infrared Detector used for our measurements. However it needed to be kept out of the sunlight and not be disturbed. We did spot a shed near the runway with a jeep in it. Since this was the only nearby shelter we duly started shoving the jeep out of the shed. At that point some uniformed military guards started running towards us and pointed their guns at us! It turned out that the jeep belonged to the Commander of the airport. (This was in the days when Spain was essentially a military dictatorship under General Franco.) Fortunately, after some discussions in a weird mix of English, French, and Spanish we got permission to use the shed. This was helped along by us pointing out that if left in the sun the dewer might explode. If not, it might still lose all its contents and the high-publicity project would then have been ruined. So a lack of co-operation might not have looked good for the governments involved.

A short time before the eclipse flight my supervisor and some of the other experimenters climbed up onto the top of Concorde’s cabin and proceeded to give the observation windows a final clean and polish. Perhaps one of the strangest episodes of window cleaning in the history of astronomy or aviation!

Researchers cleaning the observation windows in the cabin roof just prior to takeoff.
John Beckman on the left. I think one of the people on the right is Don Liebenberg of the LASL group.

As 001 taxied out to take off on 30th July the runway became busy with a series of Spanish Air Force fighters. These were Messerschmitt fighters of the same design as used during World War II. One after another these took off. At the time it seemed like the Spanish were saying, “We could delay your take off if we wanted to, you know!” However despite this, Concorde took off at the correct time. It then flew along the eclipse track, eventually landing in Fort Lamy, Tchad some hours later. Shortly after 001, the Caravelle took off carrying the service engineers.

Concorde 001 taking off on 30th June 1973 for the eclipse flight.

The Caravelle support plane taking off to follow 001 to Tchad.
If you look carefully at the bottom-left part of the photo you can just see Concorde
after it has turned to fly towards the eclipse track.

Overall, the QMC experiment was a success. There was a minor mechanical problem with the scanning system in the interferometer used to collect spectra. But it was still possible to get good results which were duly published in Nature. These show some of the first Far Infra Red observations of the limbs of the sun and demonstrated a behaviour called ‘limb brightening’. (Beckman, Lesurf, and Ross. Submillimetre brightness spike at the solar limb. Nature V254 March 5 1975, pages 38-39.) How much impact that had on understanding the Sun. I can’t say. I was just an engineer. By then I was well into making systems for other measurements. I still know the French words for screwdriver and inverter, though...

Jim Lesurf (ex-QMC student)
24th September 2011