Four main effects limit the flux calibration accuracy:
The errors expected on the flux calibration of the grating are shown in Table 7.1. It lists the requirements on ISO, the accuracy achieved in ground tests and the flight objective.
What has been achieved in flight at the time of the OLP V6 delivery (April 97) is shown in table 7.2.
|5A||11.8||0.01||FP tied to grating LW sections|
|5B||14.0||0.01||FP tied to grating LW sections|
|5C||17.0||0.01||FP tied to grating LW sections|
|5D||24.0||0.01||FP tied to grating LW sections|
|6||27.0||0.01||FP tied to grating LW sections|
Flux reproducibility was checked by observing the standard HR6705 twelve times during various orbits. Fluxes between the various measurements agreed to within 6% for band 1, and 12 to 15 % for bands 2 to 4.
The accuracy expected on the flux calibration of the FP are the same as that on the grating, but add an extra 1 to 20% due to wavelength dependant leakage .