INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) is a currently operational space telescope for observing gamma rays. It was launched by the European Space Agency into Earth orbit in 2002, and is designed to detect some of the most energetic radiation that comes from space. It was the most sensitive gamma ray observatory launched until eclipsed by Fermi.

In mathematics, an integral assigns numbers to functions in a way that can describe displacement, area, volume, and other concepts that arise by combining infinitesimal data. Integration is one of the two main operations in calculus, with its inverse, differentiation, being the other. Given a function  of a real variable  and an interval  of the real line, the definite integral