Numerical simulators are fundamental tools for the design and optimisation of missions and instruments.
I am and I've been involved in the development of different simulators, some of them are now publicly available.
Generic instrument simulators
The Generic instrument independent point source simulator. It's been used to build the radiometric models in the following missions: ARIEL, EXCITE.
Refactored version of the end-to-end time domain simulator for the exoplanet transit observations.
Mission dedicated tools
Radiometric model simulator for the ARIEL space mission.
Wrapper of ArielRad and TauREx to produce ARIEL simulated data-set of entire planetary populations.