Pupil Masks for Spectrophotometry of Transiting Exoplanets

TL;DR

This paper introduces a novel pupil mask design to enhance spectrophotometric stability in space telescopes, effectively reducing photometric variations caused by pointing jitter and mirror deformation during exoplanet transit observations.

Contribution

It proposes a new block-shaped pupil mask and an optimization methodology to significantly improve photometric stability in spectrophotometry of transiting exoplanets.

Findings

Achieves $10^{-5}$ stability with small jitter

Achieves $10^{-6}$ stability with very small jitter

Discusses effects of optical aberrations and mask imperfections

Abstract

Spectrophotometric stability, which is crucial in the spectral characterization of transiting exoplanets, is affected by photometric variations arising from field-stop loss in space telescopes with pointing jitter or primary mirror deformation. This paper focuses on a new method for removing slit-loss or field-stop-loss photometric variation through the use of a pupil mask. Two types of pupil function are introduced: the first uses conventional (e.g., Gaussian or hyper-Gaussian) apodizing patterns; whereas the second, which we call a block-shaped mask, employs a new type of pupil mask designed for high photometric stability. A methodology for the optimization of a pupil mask for transit observations is also developed. The block-shaped mask can achieve a photometric stability of $10^{-5}$ for a nearly arbitrary field-stop radius when the pointing jitter is smaller than approximately $0.7 \lambda/D $ and a photometric stability of $10^{-6}$ at a pointing jitter smaller than approximately $0.5 \lambda/D $. The impact of optical aberrations and mask imperfections upon mask performance is also discussed.