This is a PSF FITS format we agree on for IACTs. This file contains the offset- and energy-dependent table distribution of the PSF.
This format is almost identical to the OGIP radial PSF format. The differences are that we don’t have the dependency on azimuthal field of view position, the units are different and the recommended axis order is different (to have uniformity across axis order in the IACT DL3 IRFs).
ENERG_HI– ndim: 1, unit: TeV
- True energy axis
THETA_HI– ndim: 1, unit: deg
- Field of view offset axis (see Field of view)
RAD_HI– ndim: 1, unit: deg
- Offset angle from source position
RPSF– ndim: 3, unit: sr^-1
- Point spread function value \(dP/d\Omega\), see Probability distributions.
Recommended axis order:
As explained in HDU classes, the following header keyword should be used to declare the type of HDU:
Example data file: TODO