ENERGY_RESP represents the instrument response matrix for a spectral instrument. Its structure is as follows:
ENERGY_RESP <EXTENSION>
VERSION <CHAR*80>
ENERGY <LIST>
DATA_ARRAY(N) <_UBYTE, _UWORD or _INTEGER>
ENERGY_SPEC(NEN) <_REAL>
ENERGY_BOUNDS(NEN+1 <_REAL>
CHANNEL <LIST>
DATA_ARRAY(N) <_UBYTE, _UWORD or _INTEGER>
CHANNEL_SPEC(NCH) <_REAL>
CHANNEL_BOUNDS(NCH+1) <_REAL>
RESPONSE <LIST>
DATA_ARRAY(N) <_REAL>
Basically, this is a set of three lists: ENERGY, CHANNEL and the RESPONSE value which maps between the two, together with a VERSION string which defines the epoch or version number of the response (important in case it changes). The ENERGY and CHANNEL lists are stored, for compactness, as indices, with translation into actual values specified by the ENERGY_SPEC and CHANNEL_SPEC arrays. (i.e. ENERGY index 1 corresponds to energy ENERGY_SPEC(1)). ENERGY_BOUNDS specifies the boundaries of the energy space channels, and CHANNEL_BOUNDS the energy values corresponding to the instrument channel boundaries.
Response values map spectral fluxes in photon/(cm**2*s) per energy bin onto count/s per channel - they therefore correspond to effective areas as a function of energy for each channel.
In the case of a SPECTRAL_SET, which contains a set of parallel spectra, the ENERGY_RESP is an array of structures (one for each spectrum in the set) each component having the structure shown above.