We developed, characterized, and verified an alignment procedure for the DESHIMA 2.0 instrument, an ultra wide-band spectrometer operating between 200--400 GHz, at the ASTE telescope. To this end, we mounted the warm optics, consisting of a modified Dragonian dual reflector system, on a motor controlled hexapod. Crucial in the alignment procedure is our sky chopper, which allows fast beam switching. It has a small entrance and exit aperture coupling to (cold) sky, which creates a measurable signal with respect to the warm cabin environment. By scanning the instrument beam across the entrance aperture of the sky chopper using the hexapod, we found the hexapod configuration that produced the lowest signal on our detectors, implying the beam is coupled fully to cold sky and not the warm cabin. We first characterized the alignment procedure in the laboratory, where we used a vat containing liquid nitrogen as the cold source behind the sky chopper. Then, we applied the alignment procedure to DESHIMA 2.0 at ASTE. We found that the alignment procedure significantly improved the aperture efficiency compared to previously reported values of the aperture efficiency of DESHIMA at ASTE, which indicates the veracity of the alignment procedure.
@article{arxiv.2501.14478,
title = {Alignment and optical verification of DESHIMA 2.0 at ASTE},
author = {A. Moerman and K. Karatsu and J. J. A. Baselmans and S. O. Dabironezare and S. Fujita and R. Huiting and K. Kohno and Y. Nishimura and F. Steenvoorde and T. Takekoshi and Y. Tamura and A. Taniguchi and S. J. C. Yates and B. R. Brandl and A. Endo},
journal= {arXiv preprint arXiv:2501.14478},
year = {2026}
}