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7.1 Overview  

Conceptually, for a given AOT the derivation of standard processed data (SPD) can be divided into three main stages:

• ramp processing: Integration ramps in V are reduced to signals in V/s.
• signal processing: Signals are corrected for instrumental effects and averaged over a given period in time.
• in-band power calibration: One or more FCS measurements that were collected according to the AOT logic are processed to determine calibration factors. These factors are used to convert the signals from the sky measurements to an in-band power (in W) on the detector for the selected filter band. In case FCS measurements cannot be applied, the conversion is based on a default detector responsivity.

SPD processing derives a record for each consecutive period in the sky measurement for which the power on the detector is expected to be constant:

• a staring measurement yields one SPD record;
• a chopped measurement yields 2 or 3 times the number of chopper cycles as SPD records depending on the chopper mode (2 for rectangular, 3 for sawtooth and triangular);
• a raster yields one SPD record per raster position;
• a PHT32 sky measurement contains one SPD record for each chopper plateau.

Apart from the mean in-band power, each record contains additional information such as the power uncertainty, median value, etc (see section 12.3).

The above description of SPD records applies to all AOTs except AOT P40 (PHT-S spectro-photometry). SPD for P40 contains signals (in V/s) instead of in-band powers (in W). In the processing level following SPD (see chapter 8) the PHT-S signal is directly converted to an astronomical flux (in Jy). This is a consequence of the absence of FCS measurements, filters, and apertures in the PHT-S subsystem.

Besides the SPD products that yield the processed data for the sky measurements a number of other products are derived based on non-sky internal measurements. The products refer to the following type of measurements (see section 3.3):

• FCS measurement. The resulting product is also referred to as a Calibration A (``Cal A'') file.
• Dark instrument configuration measurement. This measurement type is obtained with AOTs PHT05, PHT25, and PHT40 and is used to subtract dark signals (in case of PHT05 and PHT25) or to identify possible detector memory artifacts from a preceding measurement of a bright source (in case of PHT40)
• Cold FCS measurement. This type of measurement occurs in the absolute photometry AOTs PHT05 and PHT25 to correct for FCS straylight.