  The INTEGRAL/SPI, X-gamma-ray spectrometer (20 keV - 8 MeV) is an instrument
for which recovering source intensity variations is not straightforward and can
constitute a difficulty for data analysis. In most cases, determining the
source intensity changes between exposures is largely based on a priori
information. We propose techniques that help to overcome the difficulty related
to source intensity variations, which make this step more rational. In
addition, the constructed "synthetic" light curves should permit us to obtain a
sky model that describes the data better and optimizes the source
signal-to-noise ratios. For this purpose, the time intensity variation of each
source was modeled as a combination of piecewise segments of time during which
a given source exhibits a constant intensity. To optimize the signal-to-noise
ratios, the number of segments was minimized. We present a first method that
takes advantage of previous time series that can be obtained from another
instrument on-board the INTEGRAL observatory. A data segmentation algorithm was
then used to synthesize the time series into segments. The second method no
longer needs external light curves, but solely SPI raw data. For this, we
developed a specific algorithm that involves the SPI transfer function. The
time segmentation algorithms that were developed solve a difficulty inherent to
the SPI instrument, which is the intensity variations of sources between
exposures, and it allows us to obtain more information about the sources'
behavior.
