SOFIA: The Airborne Infrared Observatory [Gallery]

SOFIA on the ground, in the evening, before one of the two science missions I took part in.

SOFIA, as well as the DC-8 and the ER-2s and all the other aircraft based at Palmdale are impeccably maintained, a testament to the dedication and pride of their NASA caretakers.

SOFIA’s 2.7 meter telescope, cavity and door, open during a test flight. The tufts highlight the airstream around the cutout. It was feared that that the huge “organ pipe” hole might create turbulence that impedes flight characteristics and vibrations that reduce the lifetime of the fuselage. None of these fears turned out to be true. Notice the slightly thicker aft fuselage around the cutout as a consequence of additional structural members to compensate for the hole.

Mission director Charlie Kaminski is about to start the mission briefing. Everybody flying on the aircraft attends, and topics include science objective, weather, flight track, as well as the ubiquitous safety notices and the reminders for everybody to take their food out of the fridge at the end of the flight.

The 747 SP is basically an airplane from the 1970s, and it has the vast array of dials and steam gauges to prove it. It is also flown with a three person crew, the third position being the flight engineer. However, the SOFIA 747 SP was upgraded with a glass cockpit in the mid 2000s, as can be seen from the panels in front of the two pilots. The systems and their indicators remained unchanged, though, leading to an interesting mix of old and new technologies in the cockpit.

The SOFIA cabin, viewed towards the telescope. The picture is taken from the guest/educators console, and the two people seen directly in front of it are the mission director (left) and the flight planner (right). In front of them, standing in front of their consoles, are the instrument team. To their left are the telescope people.

Looking aft towards the telescope. The grey ring is the aft bulkhead in which the telescope is mounted. The blue structure is the telescope and its counterweight. The silver box in the center is the FIFI-LS instrument. The white plastic bag with the face drawn on it located on top of the instrument indicates coolant flow :-) The whole structure, telescope and instrument, moves around inside the bulkhead when the telescope controller is active and the 747 flies through turbulence.

A glimpse on to the flight planner’s display. The screen shows the planned track as well as the actually flown route. The two might diverge because of unexpected winds and the inability to crab (because that would change the heading, which in turn determines the observation target), or because minor adjustments are made to the observation schedule.

To make it easier for the instrument cooling system, the air conditioning system in the cabin is usually turned down. Sixteen degrees centigrade or less are typical. These leads to interesting variations of headwear.

Everybody is exhausted (and cold) towards the end of the ten hour mission (in the middle of the German guests’ biological night), using the business class seats at the front of the cabin to take a nap.

The FIFI-LS instrument. It is a basically a one cubic meter box that weighs several hundred kilograms. It is very rugged because of the required precision and stability of the optical path inside (see below) and the fact that it has to be able to be able to withstand a 9G impact in case of an accident.

Part of the inside of the FIFI-LS instrument.

SOFIA sits quietly on Palmdale’s apron, taken care of by the ground crew, shortly after the landing of science mission 249 in October 2015.