Reading RESIK fits files

 Program for reading RESIK fits files (8 kB)

CALLING SEQUENCE:
  resik_read_fits_fast, fname_fits, dset, index, data

  where:
  1) fname_fits - fits file name (input)
  2) dset - data set to read. (input)
       (To read entire fits file content set dset to -1 -> resik_read_fits, fname_fits, -1, index, data)
  3) index - RESIK index structure (output see description below)
  4) data - RESIK data cube (output see description below)

  Description of RESIK index tags and data cube

  1) index - the RESIK index structure contains the following tags:

INSTRUMENT	STRING	INSTRUMENT NAME
OBSERVATION_TYPE	STRING	TYPE OF OBSERVATION
SPECTRA_UNITS	STRING	UNITS OF RESIK ABSOLUTE SPECTRA
WVL_UNITS	STRING	WAVELENGTHS UNITS
SPC_N	LONG	NUMBER OF SPECTRA IN THE FILE
BIN_N	INT	NUMBER OF BINS per RESIK CHANNEL
CHAN_N	INT	NUMBER RESIK CHANNELS
SPEC_ID	LONG	SPECTRUM NUMBER (starting from 0)
STIME_ST	STRING	SPECTRUM START TIME
STIME_CE	STRING	SPECTRUM CENTRAL TIME
STIME_EN	STRING	SPECTRUM END TIME
TIME_ST	DOUBLE	SPECTRUM START TIME - JULIAN TIME
TIME_CE	DOUBLE	SPECTRUM CENTRAL TIME - JULIAN TIME
TIME_EN	DOUBLE	SPECTRUM END TIME - JULIAN TIME
EXPDUR	FLOAT	SPECTRUM EXPOSURE DURATION IN SECONDS

  2) data - the RESIK data cube is a (256, 16, n) array where n is the number of spectra read by resik_read_fits.

  data(*, 0:3, *)     -      wavelengths of particular RESIK channels
  data(*, 4:7, *)     -      absolute RESIK spectra
  data(*, 8:11, *)     -     uncertaintees of RESIK spectra
  data(*, 12:15, *)     -      Level-0 data, RESIK spectra corrected for orbital background

  Using RESIK data within IDL environment (examples)

   Plotting single spectrum in selected channel with uncertainties

  1) plot resik spectrum for channel 1

  plot, data[*, 0, 0], data[*, 4, 0], yst=10, xra=[3.3, 3.9],xst=1
  errplot, data[*, 0, 0], data[*, 4, 0]*(1-data[*, 8, 0]), data[*, 4, 0]*(1+data[*, 8, 0])

  2) Plotting spectrum selected channel integrated over all spectra with uncertainties

  a) summing the array
   zz=total(reform(data[*, 4, *]),2)

  b) processing uncertainties (summation of assumed Gaussian dispersions)
   uu=sqrt(total(reform(data[*, 8, *]^2),2))/n_elements(index)

   plot,data[*, 0, *],zz,psym=10,xra=[3.3, 3.9],xst=1,yst=1
   errplot,data[*, 0, 0],zz*(1-uu),zz*(1+uu)