SOFIA en route to Germany

On 17 September 2011 SOFIA, the airborne observatory, flew from Palmdale, California to Cologne, Germany. Author and science writer Alexander Stirn was on board. This is his log.

0.24am: “A star, we have a star,” shouts telescope engineer Randy Grashuis with delight. Although it is still daylight outside, SOFIA’s camera has registered its first heavenly body. Stars are important for getting bearings in the sky, but the main thing is that their light serves as a fixed point which can be used to firmly align the telescope regardless of the movements of the plane.

1.01am: “It’s not looking so good,” comes a voice from the corner where the scientists are sitting. Although we are flying at an altitude of up to 43,000 feet (13.1 kilometres) there is still a relatively large amount of water in the atmosphere. Water vapour is the enemy of the infrared astronomers: it swallows up the interesting frequencies. The water vapour measurements are indicating 35 micrometres, the optimum value at this altitude would be five micrometres. At ground level, in the Atacama Desert, for example, where the air is as dry as dust, the value is more than 300 micrometres.

1.37am: Forty minutes later than expected SOFIA provides the first useable spectra. “Good work, Randy,” is the praise from Jürgen Stutzki, a physicist at the University of Cologne and one of the scientific directors of the GREAT consortium. Ideally, the spiky lines should have a clear hump in their centre. In IC342, the star-forming region being observed today, this curve is very weak, however. “This source is really challenging,” says Stutzki. “It’s really painful.”

2.25am: Time is running out for the astronomers. In barely 25 minutes, southwest of Iceland, SOFIA must end its slight left bank which ensures that IC342 remains in the telescope’s field of view. Its path is obstructed by a no-fly zone.

2.43am: “Ten minutes remaining,” radios Mission Director Charlie Kaminski over the plane’s own communication system. Groans.

2.48am: “Five minutes,” says Kaminski. Someone replies: “Oh, oh.”

2.52am: “One minute!” – “My God!”

2.53am: Right on time, SOFIA steers onto its intended course. The telescope is clamped down. And that’s the end of IC342. “We always come up against the time limit,” says Rolf Güsten, head of the GREAT project from the Max Planck Institute for Radio Astronomy in Bonn. “But it would be much worse if we ran out of work during the journey.”

5.15am: “Four minutes left.” – “Wow!” With Galaxy M82, the second object on the transfer flight, the astronomers are experiencing the same problems. “It’s a brutal business,” says Urs Graf, a physicist at Cologne University and one of the team which developed GREAT. “It is therefore all the more important that all observations are precisely planned and specified down to the very last detail.”

6.06am: Mission Director Charlie Kaminski gives the order to close the hatch in the fuselage again.

6.13am: “This is NASA 747 Heavy, say again!” On the deck above, pilot Troy Asher is contending with the dense, completely unfamiliar air traffic over Europe, with the radio equipment and the accents of the air traffic controllers. He finally manages it.

6.49am: The Boeing 747SP makes a hard landing as it comes down to earth on runway 14L at Cologne/Bonn airport. SOFIA has arrived in Germany.