English: In 1969 a High Speed Interferometer (HSI) was designed and built to detect, identify, and measure trace constituents and pollutants in the atmosphere. An early version of the instrument conducted a ground-based study of the air above the Santa Monica Freeway. In 1973, the HSI was flown at a high altitude on two different types of aircraft: an Air Force NC-135 in February/March and three different flights on the Concorde 001 prototype in June. The photo above shows the instrument installed in the Concorde, along with equipment to record the tests. The photo below it is a diagram of the test setup on Concorde. Other photographs in the "325" photo album show equipment lining both sides of the aisle, being prepared for the test flights.

Data were collected from the Concorde flights in the upper troposphere and lower stratosphere. Light from the sun bounced off mirrors before entering the instrument and reaching the detector. The HSI covered the near infrared, or a wavelength of 2 to 8 microns. Results of the spectral analysis indicated that nitrous oxide, nitric oxide, nitrogen dioxide, carbon monoxide, carbon dioxide, methane, water vapor, and other compounds were present.

In addition to the ground-based tests and the flights mentioned above, tests were also conducted from a balloon over the Mojave Desert near Goldstone in 1974, and from a U2 airplane over Alaska in 1977. These early tests were conducted with the goal of flying an interferometer on the Space Shuttle. The High Speed Interferometer was a predecessor of the Atmospheric Trace Molecule Spectroscopy Experiment (ATMOS) which flew on four different shuttle flights, from 1985 to 1994.

H.S.I. Concorde; Interferometer; Historical Photo of the Month, August 2009

Task #108849

Requestor: J. Cooper