The Design and Performance of the Gondola Pointing System for the Sunrise II Balloon-Borne Stratospheric Solar Observatory

Friday, November 4, 2016

At one meter, the Sunrise Balloon-Borne Stratospheric Solar Observatory is the largest solar telescope to leave the earth. Its aim during its June 12 to June 17, 2013 flight was to study the magneto-convective processes of the sun at a resolution of better than 100 km.

Gondola Pointing System Design image
Recomputed histogram of the length of periods of continuous pointing within ±26 arc seconds of the target during the 2013 flight of Sunrise after compensating for commanded re-pointing.

To obtain this goal, the gondola and telescope are required to point to an accuracy of better than 26 arc seconds for extended periods of time. Pointing of the gondola and telescope was effected by the Sunrise Pointing System (PS). The PS takes pointing error signals provided by a Lockheed Intermediate Sun Sensor (LISS) and passes the data through a cascade of up to four digital biquadratic filters to calculate best voltages to move azimuthal and elevation motors. All filter settings can be modified in flight to adapt to changing conditions. Using this design, the Sunrise Pointing System achieved the required goal, pointing the gondola and telescope to better than 26 arc seconds for 60% of the flight and continuous time periods up to 99 minutes. In this paper we detail the design and performance of the PS during the 2013 flight.

Submitted to the Journal of Astronomical Instrumentation in November 2016.