AIR-Spec Goes on a Test Run

Wednesday, August 9, 2017

With the eclipse nary a fortnight away, final instrument testing is gathering pace. A team led by Harvard University PhD student, Jenna Samra, met at NCAR's Research Aviation Facility in Broomfield, Co on Tuesday to perform one of their final tests before the big day. A modern-day Sk├Âll, this experiment will chase the eclipse from the confines of a Gulfstream V aircraft at close to 50,000 ft. On the ground, totality will last no more than 2 minutes 40 seconds; flying along the same path as the moon's shadow, AIR-Spec will extend this to 4 minutes. But more important than increasing the duration of totality, being at such high altitudes greatly reduces the absorbing effects of the Earth's atmosphere on the coronal light we hope to study.

The test flight was designed to mimic the conditions of the eclipse as closely as possible. With only a small window in the fuselage of the plane allowing sunlight to enter, the orientation of the plane relative to the Sun is all important. Flying west to east, at the same time of day as the eclipse, sunlight enters the aircraft at the correct angle to be collected by the instrument, while an adjustable mirror is used to perform the fine-precision pointing necessary to direct this light through the instrument and onto the detector. Keeping that image of the Sun positioned just right while traveling at 450 knots is no easy matter, however. The test flight confirmed the elaborate stability system that corrects for the jostling of the plane performed to the high standards required.

Of course, one thing the test flight cannot reproduce is the eclipse itself. The flight successfully demonstrated the pointing stability, the ability to adjust pointing to observe different regions of the corona, and the acquisition of photospheric data. Data from the corona itself will have to wait until August 21. Fingers crossed that all goes equally well that day!

Eclipse Instrumentation aboard the Gulfstream V aircraft