When two space-age technologies come together…almost (The KAO and the Space Shuttle)
The best, deep-space optical observatories are mounted high in tall mountains. This to avoid the light distortion caused by denser atmosphere at lower levels. Even so, infrared light—light that travels easily across vast distances in space—is quickly absorbed by slight amounts of water vapor. To get the clearest infrared images without actually going into space is to mount a telescope on an aircraft that can operate above 41,000 feet above sea level.
In 1965, NASA converted a Convair 990 airliner, the Galileo Observatory, for astronomical observations. In 1973, that aircraft was destroyed in a mid-air collision during a landing at Moffett Naval Air Station (Moffett Federal Airfield today).
Later that year, NASA selected and specially modified and outfitted a Lockheed C-141 Starlifter (N714NA, S/N 6110) with a 36-inch optical telescope mounted on a stabilized platform to serve as a high-altitude observatory. The aircraft was named the Gerard P. Kuiper Airborne Observatory (KAO).
This was at the same time that the Space Shuttle Columbia was preparing to make its first orbital flights. Concerned about the heat of reentry, it was determined that the KAO C-141 could be used to take “Infrared Imagery of the Shuttle” (IRIS) to collect high resolution infrared images of the Shuttle’s underside during reentry to obtain accurate heating data.
How it was supposed to work.
The C-141 would be positioned at an altitude of 45,000 feet, and as the Shuttle began reentry at an altitude of 400,000 feet over the Pacific near Hawaii. The C-141 would be required to fly a very precise track so that IRIS could collect images of the Shuttle.
To prepare for this mission, the KAO had actually tested IRIS using an SR-71 as the target aircraft. The first attempts on first two Shuttle flights, STS-1 and STS-2, failed primarily due to ground communication issues that did not put the KOA in the correct position.
On STS-3, IRIS achieved partial success, obtaining an image of about 60% of the Shuttle. There was a slight misalignment between the tracking telescope and the imaging telescope causing the partial image. This image, however, resulted in enough useful information to confirm that KOA infrared temperatures were within 75 degrees F of the 2960 F values of the onboard surface thermocouple—a variance of less than three percent.
IRIS was flown on STS-4, but an image of the Shuttle was not acquired due to an undetermined equipment malfunction. IRIS was discontinued after STS-4.
The KAO continued as an observatory platform until 1995. It provided the first sightings of the rings of Uranus (1977), and determined that Pluto had an atmosphere (1988). Astronomers used KAO to detect water and organic molecules in the areas of star formation, and in the vast interstellar spaces. KAO was retired in 1995.
Like so many forgotten steeds, a working aircraft like C-141, S/N 6110, is easily forgotten while the fruits of its missions continue to be discussed. The aircraft can be seen parked off to the side of the airfield at Moffett Federal Airfield. Time and neglect have not treated it well.
KAO has been replaced with a Boeing 747-based airborne observatory called the Stratospheric Observatory for Infrared Astronomy (SOFIA), which has been fully operational since 2010.
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