Performance Simulation Tools for Space Telescopes Applied to the Ariel Space Mission

In designing and developing space instruments, fast and reliable tools are essential for validation and optimisation. Within the Ariel Space Mission framework, we have developed novel, versatile tools to estimate space instrument performance: ExoSim 2 and ArielRad.

ExoSim 2 is a time-domain simulator for exoplanet observations, capable of simulating exoplanetary transit, eclipse, and phase curve observations from both ground and space-based instruments. This simulation captures temporal effects such as correlated noise and systematics on the light curve, producing spectral images akin to actual observations. Developed for the Ariel Space Mission, ExoSim 2 assesses the impact of astronomical and instrumental systematics on astrophysical measurements and prepares the data reduction pipeline against realistic data sets. Its outputs can be utilised by various data reduction methods to determine the best pipeline strategy for removing systematics and to assess the confidence level of retrieved quantities. ExoSim 2 is a refactored version of the original ExoSim, featuring improved usability, customisability, and compatibility with Python 3.7+. It includes an installer, documented examples, and a comprehensive guide, allowing users to incorporate new functionalities through user-defined functions.

ArielRad is the Ariel radiometric model, which accurately predicts telescope performance for observing candidate targets across all mission photometric and spectroscopic channels. The software inputs a target description and a parameterisation of the payload, enabling the investigation of various design performances. ArielRad can simulate entire target lists, predicting the observing time and the resulting Signal-to-Noise Ratio (SNR) versus wavelength. By analysing 1000 candidate targets within a 20-minute timescale, it validates different observational strategies. The software architecture is based on ExoRad 2, which is publicly available and can be adapted for future space missions.

Together, ExoSim 2 and ArielRad provide comprehensive tools for the development, validation, and optimisation of space instruments, particularly within the Ariel Space Mission framework. Their versatility and robust performance make them valuable assets for current and future astronomical projects.