The figures 
and show examples of flat-field
frames for the two channels.
The flat-field error is likely to be the dominant source of noise in
most measurements at 
m. The availability of a
flat-field measurement is essential for all the direct observations
(AOT 1 and 4).
If a flat-field accuracy of 1 % is enough, the direct observation mode of CAM01 is the most efficient, and using the library flat-field frames is recommended.
Flat-field frames will be recorded during each orbit, with the 1.5
arcsec PFOV, with filters LW2 and LW3, with an accuracy of 1%, and
with filters SW1 and SW3, with an accuracy of 3%. They will be the
best library data to be used along this orbit with these filters. For
the other filters, using the library flat-field frames recorded during
the routine calibration operations is also recommended if there is no
need for an accuracy better than 1%, but it is also possible to ask
for a specific flat-field measurement with the desired filter; it adds
5 minutes to the observation (see section ). If a
better flat-field accuracy is needed, 2 possibilities must be
considered:
