Twinkling stars are a perfect backdrop to a romantic evening stroll. But as far as professional astronomers are concerned, twinkling is bad. These scientists routinely battle the effects of our atmosphere. The heat inversion layers that create the gently twinkling star can wreck havoc with basic observations. Putting a telescope in orbit, such as with the Hubble Space Telescope, is one solution. Another answer is to lift a telescope above the lower (and thickest) levels of the atmosphere. Such is the job of the Stratospheric Observatory for Infrared Astronomy (SOFIA) telescope, which is carried aloft on a modified Boeing 747.
The obvious problem with observing from the air is that you don’t have the stability afforded by ground-based observations. Enter pneumatics. An air suspension system from ContiTech Air Spring Systems, Hannover, Germany turned in an outstanding performance in the first test flight of SOFIA. By ensuring vibration-free operating conditions, the air suspension system enables the telescope to obtain perfect pictures from the stratosphere.
At an altitude of 14 km, the SOFIA project carries out research into the formation of stars and planetary systems as well as the origin of the solar system. At the heart of the research aircraft is a 17-tonne telescope that peers out at the universe through a hatch in the tail of the plane. The world’s largest infrared telescope, it has an extremely high spatial resolution. The telescope rests on a vibration-isolation system (VIS) consisting of an air spring system and silicon-oilfilled dampers.
In the five-and-a-half-hour test flight, the telescope, with all its subsystems, was tested for the first time under regular operating conditions. The air suspension system completed the test with flying colors. It demonstrated its ability to absorb vibrational interference emanating from the aircraft itself or from windflow when the hatch is open. Assisted by its control electronics and sensors, the air suspension system holds the telescope exactly in position relative to the plane’s fuselage. This ensures that the ultra-sensitive instrument is always aimed directly at the target of observation, the prerequisite for perfect images. The German SOFIA Institute (DSI) in Stuttgart reported that the vibration-isolation system “performed excellently when the plane was diving, climbing, and spiraling”.
ContiTech Air Spring Systems manufactures the existing system, composed of 24 single- and doubleconvolution air springs. ContiTech’s sales partner, CFM Schiller GmbH, from Roetgen in North Rhine-Westphalia, assumed full engineering responsibility, from design calculations through to final assembly at the NASA base.