Inventory of Forward Operators in HD(CP)²
| Forward Operator | Simulated Device |
| BaLiFOp | backscatter Lidar |
| COSP | ISCCP, CALIPSO, CloudSat, MODIS |
| MC-UNIK | Pyranometer |
| PAMTRA | Passive and active microwave instruments |
| Polarimetric Radar | Polarimetric radar at microwave band |
| RADVOP | Scanning radars from 3 GHz to 40 GHz |
| SATSIMS | ISCPP |
| SORBIT | arbitrary sun-synchronous orbiters (NADIR) |
| VISOP | SEVIRI on MSG |