The two GIS detectors have different spatial characteristics and background. It should be possible, however, to make a combined light curve from GIS2 and GIS3 data which, when analyzed, would not yield misleading timing results. It is possible to combine two energy spectra from GIS2 and GIS3 3.3 and to superpose GIS2 and GIS3 images taking account of the correct detector responses, after they are separately extracted from separate events files. Nearly all GIS data have been taken in PH mode with standard bit assignments. The rare exceptions are non-standard PH mode, used to increase temporal resolution, or MPC mode used for very bright sources.
Temporal resolution depends on bit rate and bit assignment.
Combining data with different bit rates is acceptable, provided the highest temporal resolution is not required throughout. Data taken in LOW bit-rate can be used. This will be important only if accurate fluxes are required and for temporal analysis. To obtain the correct flux, a correction will be needed for the electronic deadtime. The data taken with the standard bit-assignment have 128 spectral channels, as opposed to the ordinary 1024.