PAOS (Physical Optics Simulator) performs physical optics propagation simulations using Fourier optics and the Fresnel approximation to model the behavior of optical fields through complex optical systems. It combines paraxial ray tracing with wavefront propagation methods to analyze diffraction, wavefront aberrations, and imaging effects in user-defined optical configurations. The package accepts configurable input systems via files or interfaces, supports modeling of apertures, optical elements, and aberrations, and outputs propagated fields and related diagnostic data. PAOS includes command-line and library interfaces along with interactive notebooks for exploration and visualization of simulation results. Its modular design allows users to apply different propagation and aberration models, generate surface error fields, and retrieve metrics such as wavefront properties and optical system responses.

ExoSim 2 (Exoplanet Observation Simulator 2) makes spectro-photometric observations of transiting exoplanets from space, ground, and sub-orbital platforms. It is a complete rewrite of ExoSim (ascl:2002.008); it is implemented in Python 3 and uses object-oriented design principles. The package follows a three-step workflow: the creation of focal planes, the production of Sub-Exposure blocks, and the generation of non-destructive reads (NDRs). ExoSim 2 has demonstrated consistency in estimating photon conversion efficiency, saturation time, and signal generation. The simulator has also been validated independently for instantaneous read-out and jitter simulation, and for astronomical signal representation.

ExoRad 2.0, a generic point source radiometric model, interfaces with any instrument to provide an estimate of several Payload performance metrics. For each target and for each photometric and spectroscopic channel, the code provides estimates of signals in pixels, saturation times, and read, photon, and dark current noise. ExoRad also provides estimates for the zodiacal background, inner sanctum, and sky foreground.

RAPOC (Rosseland and Planck Opacity Converter) uses molecular absorption measurements (i.e., wavelength-dependent opacities) for a given temperature, pressure, and wavelength range to calculate Rosseland and Planck mean opacities for use in atmospheric modeling. The code interpolates between discrete data points and can use ExoMol and DACE data, or any user-defined data provided in a readable format. RAPOC is simple, straightforward, and easily incorporated into other codes.