New flux = Measured flux / (1 $+$ %age IP )

IP = %age polarisation $\ast$ cos (4$\ast$waveplate - 2$\ast$ IP angle)

where %age polarisation and IP angle vary linearly with elevation.

This is an approximation of

Actual flux = measured flux - mean flux $\ast$ %age IP

where IP = P $\ast$ (1 $+$ cos (4 WP - 2 THETA ) ) because the mean flux can not be calculated trivially since the bolometers are jiggling on and off the source

This routine corrects the data point for each bolometer by looking up the IP data in the supplied array. Only one set of bolometers can be processed at any one time (since the elevation of the array changes during the observation). The routine should be called repeatedly for each time/elevation.

ELEVATION = DOUBLE (Given)

NUM_CHAN = INTEGER (Given)

NUM_ADC = INTEGER (Given)

N_BOLS = INTEGER (Given)

WPLATE_ANG = REAL (Given)

BOL_CHAN (N_BOLS) = INTEGER (Given)

BOL_ADC (N_BOLS) = INTEGER (Given)

BOL_IP_DATA( 8, NUM_CHAN, NUM_ADC ) = REAL (Given)

BOL_DATA (N_BOLS) = REAL (Given and returned)

BOL_VAR ( N_BOLS ) = REAL (Given and returned)

STATUS = INTEGER (Given and returned)

• The elevation of each bolometer is assumed to be the elevation of the central bolometer.

• Output variance is calculated

• degrees are used throughout since this simplifies the calculations when the gradients and ThetaZero are specified in degrees (or inverse degrees for the slope) from the input IP file.