HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from R (≡λ/Δλ) 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews.
The HARMONI data reduction pipeline is currently being developed. Its goal is to transform raw observations into a fully calibrated, scientifically usable data cube. It is designed to be mostly run as an automated pipeline and to fit into the ELT data flow environment. Given the complexity of HARMONI we have developed an instrument numerical simulator, which simulates the instrument from the optical point of view and provides synthetic exposures simulating detector readouts of calibration exposures or of data-cubes containing astrophysical scenes. To develop the data reduction pipeline, it is often used with some effects disabled or amplified and with arbitrary data in input, which in turn gives access to the ground truth.
In this paper, we briefly present the HARMONI project, the pipeline and the instrument numerical simulator. We then explain how we use this instrument simulator to prototype and validate robust pipeline algorithms for each of the 44 scale/band combinations of the instrument, long before the it is built. We give examples of such algorithms (flat-fielding, wavelength, and geometrical calibrations, shift measurement, etc.). For each of them we detail the gain brought by the simulator, and how it has been used to provide feedback on the instrument design.