Abstract
We aim to measure the optical spectral shape of gamma-ray bursts (GRBs) in the prompt phase, in order to identify the emission mechanism (after Grossan et al. 2019, JHEA 23, 14). This requires measuring GRB emission within ~10 s, measuring in at least 3 spectral channels simultaneously, at high time-resolution. The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) can point and track any celestial target above the horizon in < 8 s, with autonomous response to Swift and other real-time GRB alerts with ≤ 7' position errors. With three electron multiplied CCD (EMCCD) cameras, the Burst Simultaneous Three-Channel Imager (BSTI) can measure emission at Sloan g',r', and i' filters simultaneously, down to ~0.1 s time resolution. We report our instrument design and on-sky performance during commissioning. We detected early emission from GRBs 200925B and 201015A, though prompt emission was not obviously detected. We report early spectral shape measurements, along with other automatic responses to GRB alerts. The system is currently operating regularly, though with reduced time-resolution due to equipment failures, soon to be repaired. We anticipate completion of commissioning d performance; we discuss challenges and future plans for completion of commissioning and beyond.