By Jim Melvin
CLEMSON, South Carolina – Clemson University scientist Donald Liebenberg has personally witnessed and researched 26 total solar eclipses over the past 60-plus years.
Liebenberg, who has been an adjunct professor in the College of Science’s department of physics and astronomy since 1996, has literally travelled all over the world to enter the path of totality of solar eclipses. He has studied them from the ground, on ships in the middle of oceans, and in airplanes. He even watched one eclipse from the cabin of a Concorde supersonic airliner, where he was able to remain within the window of totality for an astounding 74 minutes.
The Concorde eclipse on June 30, 1973 above Africa was his ninth eclipse. His 26th eclipse was March 9, 2016 aboard the cruise ship MS Vollendam off the coast of Indonesia.
All told, Liebenberg has spent more than two and a half hours in totality, which surpasses anyone else on Earth.
The upcoming Aug. 21, 2017 event over Clemson will mark Liebenberg’s 27th eclipse. He has also witnessed several other eclipses that were nearly – but not quite – in the path of totality.
Today is the ninth chronicle of all 26 of Liebenberg’s eclipse adventures on our Eclipse Over Clemson blog. Most segments will focus on one eclipse. But during a few of the installments, Liebenberg will describe more than one eclipse, so that we will have time to visit them all before the arrival of Aug. 21.
However, the Concorde eclipse was too grand for just one segment, so it has been broken into two parts. Part 2 is chronicled below. Part 1 appeared last week.
Please sit back and continue to enjoy this amazing adventure.
FLIGHT ON THE CONCORDE / PART 2
Eclipse No. 9: June 30, 1973
Totality: 74 minutes
Where: Over Africa
Weather conditions: beautifully clear, dark skies
Our first test flight was in early May 1973, and for that flight I believe Ed Brown came over with me. I had helped him make arrangements to bring his wife along, as well. The U.S. Air Force had provided me with its standard flight suit that was fire resistant and had useful pockets.
The test flight plan was to provide sun-tracking, and so the photoelectric sensors were set for that. All went well, and we took off with the thrust of the low altitude engines, climbed and reached the altitude when Captain Andre Turcat began using the high altitude engines, and then shifted into supersonic flight. We made mercury fringe calibrations of the FPI and determined they were not affected by the vibrations of takeoff and flight. We tracked the sun and demonstrated stabilization of the image. We were very pleased that this instrument, which had been so quickly put together, performed very well.
While we were at work in Toulouse, Art Cox and others in the Los Alamos Scientific Laboratory (LASL) were preparing for the NC-135 flight, with Marvin Hoffman taking charge of our telescope and equipment. Cox was also calculating flight paths for the Concorde, and we communicated by phone. The French had set up a phone line at Aerospatiale that put me in direct contact with an English-speaking operator for direct connection to Los Alamos.
Four other groups were on the Concorde flight, in addition to a photographer at a navigator window. Pierre Lena of the Paris Observatory fielded an infrared measurement to look at the thermal corona. Alain Soufflot, also of the Paris Observatory, and Don Hall of Kit Peak Solar Observatory also participated. John Beckman of Queen Mary College of London made measurements in the far infrared of the chromosphere emission. John Bego of the Astrophysical Institute of Paris operated a camera to capture the white light corona. P.C. Wright of Aberdeen University operated an instrument to observe atmospheric changes during the eclipse using a passenger window.
Another sun-tracking test flight, about a week before the eclipse, was also successful.
We flew to Las Palmas, Canary Island, on June 27. Upon arrival, I noted a large French transport aircraft had also come along. This plane carried technicians and a spare Concorde 001 engine. The Rolls-Royce plant in England had shut down the current engine production to build a spare engine, and they also provided technicians to install it, if needed. I found this to be very impressive, and it indicated that the French-British Aerospatiale Group did not want us to fail. On June 28, we conducted a practice flight for sun-tracking and to travel part of the planned eclipse path. My measurements were good. We were ready for the eclipse.
Finally, the long-anticipated day arrived. On June 30, we took off at a precise time to reach altitude and intercept the eclipse totality so that our fuel would carry us most of the way across Africa to eventually land in Fort Lamy, Chad. Totality overtook us while flying at Mach 2.08, which was more than twice the speed of sound.
The speed at any altitude is controlled partly by the temperature of the aluminum alloy skin, since the Concorde design is similar to a commercial aircraft and not to the U.S. titanium skin SR71 supersonic plane. My equipment was operating well but the tracking did not stay locked in. I collected the pressure scanning fringe data throughout totality and would later devise a method to extract the time dependent data. The onset of totality was stretched by the Concorde’s speed. More than a minute before totality, the corona was already visible and the chromosphere could be seen for some seconds. After totality, the corona was observed even longer due mainly to better dark adaptation achieved during totality.
The corona was astoundingly brilliant. This is what I wrote in my notebook at the time:
“(The) Concorde ready to intercept the fleeting shadow. Poised like a falcon at the runway awaiting the time 10:08 UT to fly up and snare the shadow. The long months of preparation are about complete, the challenge nearly to be met, the corona to be viewed against the purple sky of space, darkened still further to reveal in full contrast the ethereal white of the solar corona. These raiments must only enhance the diety of the sun. But will we know more about the cloth, can we feel the threads with the instruments we have? That is the challenge for we Earth-bound tailors. We have our tape measure.”
On eclipse day, we took off from Las Palmas at 10:08 UT (Universal Time). We intercepted the totality and stayed within it for 74 minutes before descending and landing in the African nation of Chad.
As we came in for landing, I could see native Africans waving their hands or throwing stones, as they had done since ancient times to get the moon to release the sun. Of course, this tradition has continued for centuries, since it has been successful in every case, thus far.
When the data were analyzed, we found several regions where there was a fairly clear five-minute variation of intensity of the FeXIV line. The periodicity did not last in one location for more than a few periods, and the intensity variation was not large but clearly there. These observations were the first to find a periodic intensity fluctuation in the solar corona. Now, some 44 years later, we know there are many more periodic actions in the corona. And my own continuing observations in retirement have indicated periodicities of about 15-25 seconds in the FeXIV emission line.
We packed and shipped 16 boxes of equipment back to LASL. I received a letter of commendation from Dr. Edgar Piret, the American ambassador to France. We published preliminary results.
At 74 minutes, our group aboard the Concorde set a record for the amount of time spent in totality that has never been broken. To say the least, it was an experience I will never forget. Though most people will never witness an eclipse from such a high and fast-moving perch in the sky, I urge you not to miss the one coming this August. Even watching it from the ground will be one of the grandest experiences of your life.
Up next: Eclipses 10-11