On sky testing of the SOFIA telescope in preparation for the first science observations

Abstract

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is an airborne observatory that will study the universe in the infrared spectrum. A Boeing 747-SP aircraft will carry a 2.5 m telescope designed to make sensitive infrared measurements of a wide range of astronomical objects. In 2008, SOFIA's primary mirror was demounted and coated for the first time. After reintegration into the telescope assembly in the aircraft, the alignment of the telescope optics was repeated and successive functional and performance testing of the fully integrated telescope assembly was completed on the ground. The High-speed Imaging Photometer for Occultations (HIPO) was used as a test instrument for aligning the optics and calibrating and tuning the telescope's pointing and control system in preparation for the first science observations in flight. In this paper, we describe the mirror coating process, the subsequent telescope testing campaigns and present the results.

Stitching error calculation method for the slope data on a square subaperture

“…Generate a matrix of slope data with the order of magnitude of × − rad 1 10 6 for a test optical component first.…”

“…However, the interference testing method requires a flat reference, and most interferometers are sensitive to the measurement environment. As a result, the cost of a large-scale interferometer is greatly increased, and good environment control is required for testing [5,6]. In 1982, the subaperture measuring method was first introduced in interferometric metrology by C.J.…”