Spectral energy distribution

Detector for spectral energy distribution

The count rates observed from a given astronomical radiation source have no simple relationship to the flux from that source, such as might be incident at the top of the Earth's atmosphere. This lack of a simple relationship is due in no small part to the complex properties of radiation detectors.

These detector properties can be divided into

• those that merely attenuate the beam, including
  1. residual atmosphere between source and detector,
  2. absorption in the detector window when present,
  3. quantum efficiency of the detecting medium,
• those that redistribute the beam in detected energy, such as
  1. fluorescent photon escape phenomena,
  2. inherent energy resolution of the detector.

The type of detector required to measure a spectral energy distribution changes based on the portion of the electromagnetic spectrum being observed.