Raw data format

SCUBA raw data (i.e. data in the format expected by the SURF task reduce_switch) has the following general layout:

STRUCT  <NDF>

   MORE           <EXT>           {structure}
      FIGARO         <FIGARO_EXT>    {structure}

      SCUCD          <SCUCD_ST>      {structure}
         
      SCUBA          <SCUBA_ST>      {structure}

      FITS(171)      <_CHAR*80>      'ACCEPT  = 'not used'           / ac...'
                                     ... 'WAVE_5  =                 ...','END'

   DATA_ARRAY(5,130,900)  <_REAL>   0.0102353,1.9114159E-6,0.0184784,
                                    ... 1.7097691E-5,0.01525085,1.841503E-5,0

It is a very simple NDF format with a single DATA_ARRAY and four extensions. The extensions are described in section . The DATA_ARRAY is three dimensional with the following meanings:

1. The size of the first dimension depends on the observing mode. For jiggle and noise observations it has size 5 corresponding to the demodulated data, variance on demodulated data, internal calibrator signal, variance on calibrator signal and data quality. For SCAN/MAP observations it has size 4 corresponding to the demodulated data, variance on demodulated data, internal calibrator signal and data quality (i.e. the calibrator variance is not stored for scan maps). The data quality is converted from a REAL number to a standard UBYTE quality (appendix ): if the quality is odd, this indicates the flatfield was set to zero so bit 1 is turned on (this is also done using the flatfield task), if the quality is greater than the value specified via the SPIKE_LEVEL parameter (i.e. there were more spikes in the individual sample than the specified threshold) bit 2 is turned on. For SKYDIP observations it has a size of SCUBA__N_TEMPS (see Appendix , usually 3) corresponding to the different temperatures measured (AMBIENT, SKY and COLD).

2. The second dimension corresponds to the number of bolometers observed. This should match the size of the BOL_CHAN and BOL_ADC arrays in the SCUBA extension.

3. The third dimension is the time axis and is equal to the total number of samples (of length EXP_TIME). This dimension must be greater than any value stored in the DEM_PNTR array. For a JIGGLE observation the size can be calculated (assuming the observation was not aborted early)