LS1 and LS3 Crab Nebula count fluxes and PHA spectra were obtained
by exploiting the occultation by the Earth (as described in section 4.4)
when the source was pointed by one of the WFC and thus at the center of the
detectors fields of view. At the time of observations (autumn 1996), the
LLT threshold was set to step 1, corresponding to a calibrated value of 20 keV,
thus allowing the verification of the GRBM response functions down to low-energies.
The Crab Nebula measurements results
confirm the substantially good
calibration of LS1 and LS3 near-axis responses in the ratemeters and spectra
energy bands.