The LWS calibration strategy

The calibration strategy of LWS was developed prior to the launch of ISO through setting up and understanding the instrument on-ground tests. The strategy was followed in operations and was largely executed successfully. However difficulties in combining calibration time with target visibility, and one hardware problem (the long wavelength Fabry-Pérot (FPL) tracking), had an impact on the detailed schedule of the performance verification (PV) phase. When ISO entered routine operations, the calibration was not complete and two PV revolutions had been surrendered for later use. This paper describes the evolution of the calibration strategy in the context of the ISO mission from the perspective of the LWS Instrument Dedicated Team (LIDT) based in VilSpa, and the extended LWS instrument team based at consortium institutes. Its aim is to draw up a set of lessons learned which may be useful for future missions.