The Velocity Aberration Effect of the CSST Main Survey Camera

TL;DR

This paper simulates the velocity aberration effect on the CSST Main Survey Camera, quantifying how motion-induced geometric distortions affect image scale and position across the focal plane.

Contribution

It provides a detailed simulation-based analysis of velocity aberration effects specific to the CSST, including correction strategies for observational phases.

Findings

Aberration causes sinusoidal scale variations over an orbit.

Offsets of up to 0.94 pixels at the field center for 20-minute exposures.

Effect diminishes with increasing ecliptic latitude.

Abstract

In this study, we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera (MSC) of the Chinese Space Station Telescope (CSST) due to its motion. As anticipated by previous work, our findings indicate that the geometric distortion of light impacts the focal plane's apparent scale, with a more pronounced influence as the size of the focal plane increases. Our models suggest that the effect consistently influences the pixel scale in both the vertical and parallel directions. The apparent scale variation follows a sinusoidal distribution throughout one orbit period. Simulations reveal that the effect is particularly pronounced in the center of the Galaxy and gradually diminishes along the direction of ecliptic latitude. At low ecliptic latitudes, the total aberration leads to about 0.94 pixels offset (a 20-minute exposure) and 0.26 pixels offset (a 300-second exposure) at the edge of the field of view, respectively. Appropriate processings for the geometric effect during the CSST pre- and post-observation phases are presented.