As we have discussed in section 2.3, the dependency of LS2 and LS4 efficiencies on source direction is much more distorted with respect to the simple 'absorbed' cosinusoidal geometrical form. Moreover, the urgency for a good description of LS1 and LS3 responses delayed the study of these two detectors, which is now a wok in progress.
The description of the efficiencies and spectral responses will
be obtained with the Monte Carlo model when it will be sufficiently refined. Neverthless, because the study on GRBM source localization capabilities (chapter 6)
is already in progress, we developed specific software that interpolates the calibration data basing on cubic spline inteprolations of the available measurements. The subtraction of spurious contributions is performed basing on the results of the analysis of LS1 and LS3 spectral responses.
Although this is a very preliminar nd rough method to estimate LS2 and LS4
efficiencies dependency on photon energy and direction, it allows to perform
an estimate of source direction basing on the ratio of the counts in each shield both in GRBM and AC bands. Results of these analysis are reported in Preger et al. (1999).