The Pointing and Tracking System of AIMS

The Accurate Infrared Magnetic field Measurements of the Sun (

Aims

is the world’s first instrument dedicated to spectropolarimetric observations of the solar mid-infrared Mg I line at 12.32um. To achieve high spectral resolution, it employs a Fourier Transform Infrared Spectrometer (FTIR) at the Coudé focus of a one-meter off-axis Gregorian telescope supported by an alt-azimuth mount. To meet the requirements of the FTIR operation, the pointing and tracking system must achieve a pointing accuracy with a RMS error less than 10.0″and a tracking accuracy with a RMS error less than 1.0″over 30 minutes. In this paper, we present the design and implements of the pointing and tracking system for AIMS, which addresses the key challenges caused by its unique optomechanical structure. The adopted control strategy and its realization are described in detail. High-precision pointing of

Aims

is achieved by establishing a pointing model using a fifth-order polynomial. High-precision tracking is realized by detecting tracking errors through local solar photospheric images and adjusting the guiding optical path in real time. Our tests demonstrate that the pointing and tracking system achieves a pointing RMS error of 7.5″ and a tracking RMS error of 0.67″, while maintaining stable tracking for over 30 minutes. It has operated stably and reliably since the trial observations of AIMS, providing essential support for the acquisition of a large volume of scientific data.