A formal Agreement between the European Space Agency and the Russian Space Agency confirms that a Russian Proton launcher will lift ESA's Integral satellite into space in 2001. In return, Russian astronomers will have about a quarter of the observing time on Integral, as it examines gamma-ray sources in the Universe.
The Agreement, signed in Moscow on 18 November 1997 by ESA's Director General Antonio Rodotà, and his Russian counterpart Yuri Koptev, also assures a place for Russian astronomers in Integral's science team supervising the instrumental and astonomical aspects of the mission. The Agreement is the culmination of five years of study and negotiation that began when scientists and engineers were first defining Integral, even before its selection in 1993 as a medium-size mission to be included in ESA's science programme.
In April 2001, the four-stage Proton rocket will put Integral's mass of nearly 4 tonnes into a very high orbit. Orbiting the Earth every 48 hours, never approaching closer than 46 000 kilometres, Integral will avoid the Earth's radiation belts and will be capable of observing the Universe for 24 hours a day.
Integral's mission team has managed to reduce costs substantially through the use of an adapted version of the service module (bus) of ESA's XMM X-ray astronomy spacecraft, due for launch in 1999. NASA will take part in the mission too, with ground stations in its Deep Space Network helping to maintain 24-hour operation. With astronomical instruments provided by teams led by European scientists, Integral will be a thoroughly international mission under ESA leadership.
Instruments of advanced design will make Integral the first gamma-ray astronomical mission to provide sharp images of gamma-ray sources in the cosmos and accurate measurement of gamme-ray energies. It will far surpass the recent Compton Gamma-Ray Observatory (NASA, 1991) and Granat (Russia, 1989). These in turn were big improvements on ESA's COS-B (1975), which pioneered gamma-ray astronomy twenty years ago. ESA returns to this branch of space astronomy at a time of high excitement. Gamma-ray astronomy offers special insights into some of the most violent events in the Universe, including gamma-ray bursts and activity close to black holes.