Output Image Format

HDU 0 CCDIMAGE

Image of spectra projected onto the CCD with the PSF, with optional noise. The readout noise is always Gaussian, but the photon noise could be Poisson (default) or Gaussian (if –gaussnoise option was used.)

Header keywords:

  • SIMDATA = True

  • PREPROC = True

  • GAIN = CCD gain in electrons/ADU

  • RDNOISE = CCD amplifier readout noise in electrons

  • SIMNOISE = “Gaussian”, “Poisson”, or “None”

HDU 1 IVAR

If noise was added to the CCD, this contains the pixel inverse variance if the noise was treated as Gaussian (even if the photon shot noise is Poisson).

HDU 2 PHOTONS

NOTE : The format of this HDU will likely change to match the format of input spectra (flux plus FLUXUNIT keyword instead of PHOTONS). This has not yet been implemented.

Optional HDU with binary table giving the photon spectra projected onto the CCD after all throughputs were applied. Extraction code should produce this before any calibrations. There is one row per spectrum, with columns:

  • PHOTONS[nwave]

  • WAVELENGTH[nwave]

HDU 3 XYWAVE

Optional HDU with x,y vs. wavelength of spectral traces on CCD. There is one row per spectrum, with columns:

  • X[nwave]

  • Y[nwave]

  • WAVELENGTH[nwave]