The data obtained by SPI is background dominated. The background in each of the 19 independent detectors can vary with time in a different way due to, e.g., short-term variations due to solar activity, variations over the orbital period (related to the position of INTEGRAL in the orbit) or long-term variations over the mission duration.
The sensitivity of SPI is largely dependent on the background and on the correct identification of background photons. The background can be divided into the following main components: