Computer-aided star pattern recognition with astrometry.net: in-flight support of telescope operations on SOFIA

SOFIA is an airborne observatory, operating a gyroscopically stabilized telescope with an effective aperture of 2.5 m on-board a modified Boeing 747SP. Its primary objective is to conduct observations at mid- to far-infrared wavelengths. When SOFIA opens its door to the night sky, the initial telescope pointing is estimated from the aircraft's position and heading as well as the telescope's attitude relative to the aircraft. This initial pointing estimate needs to be corrected using stars that are manually identified in tracking camera images; telescope pointing also needs to be verified and refined at the beginning of each flight leg. We report about the implementation of the astrometry.net package on the telescope operator workstations on-board SOFIA. This package provides a very robust, reliable and fast algorithm for blind astrometric image calibration. Using images from SOFIA's Wide Field Imager, we are able to display an almost instant, continuous feedback of calculated right ascension, declination and field rotation in the GUI for the telescope operator. The computer-aided recognition of star patterns will support telescope pointing calibrations in the future, further increasing the efficiency of the observatory. We also discuss other current and future use cases of the astrometry.net package in the SOFIA project and at the German SOFIA Institute (DSI).