The goal was to achieve an accuracy of between 10 and 20% of a resolution element for the two gratings. An accuracy of 10% was hoped for the LW grating as this is used by the FP wavelength calibration.
The errors expected on the wavelength calibration of the grating are shown in Table 7.4. It lists the requirements on ISO, what has been achieved in ground tests and during operations.
|Obtained on||;SPMlt;1 LVDT||;SPMlt;0.5 - 1.0 LVDT||2.0 LVDT|
|Flight Achieved||1 LVDT||0.5 - 1 LVDT|
The limitation on the grating wavelength calibration accuracy appear to come from pointing, see section 5.7.
The wavelength calibration stabilisation is very good. A slight shift was seen in the wavelength calibration between PV and rev 450 of about 1 LVDT which was corrected by an update of the calibration files.
For the two FPs the relevant information is shown in Table 7.5.
|Obtained on ground|