Integral will be launched by a Proton rocket, Russia¹s largest operational
launch vehicle. A powerful launcher is absolutely essential to put the heavy
spacecraft into an unusually high Earth orbit which is crucial for the
scientific success of the mission.
The characteristics of the Proton are impressive: The total length of
four-stage booster is more than 57 metres, its total lift-off mass is almost
700 tonnes. The Proton has served as the primary heavy-lift launch vehicle
for Russian unmanned space programs for over 30 years. Used in more than 230
launches it has a reliability record of over 90 %.
Russia provides the launcher for Integral free of charge but in return
observation time. An arrangement between ESA and the Russian Space Agency
(RSA) was signed in November 1997 and later approved by the Russian
government in September 1999. The arrangements states that RSA shall be
responsible for placing the satellite in the desired orbit using a Proton
launcher, while ESA is responsible to deliver a satellite compatible with
the launcher. In October 1999 a launcher adaptation contract was signed to
ensure proper interfaces of the launcher with the satellite.
The Integral launch is planned for April 2002 from the Baikonur Cosmodrome
in the Republic of Kazakhstan, about 2100 kilometres south-east of Moscow,
Russia. The rocket is assembled horizontally and thus the satellite also has
to be integrated in this position. This required some modifications in the
spacecraft¹s service module. The launcher with its payload is then rolled
out of the assembly building, raised to vertical and moved to the launch
The first stage of the booster has six engines. They ignite 1.6 seconds
before lift-off. Two minutes into flight the ignition of the four engines of
stage two occurs. About 4 minutes later the stage three main engine ignites.
These three booster stages use nitrogen tetroxide and asymmetrical
dimethylhydrazine as propellants. They place the upper section with the
spacecraft into a low parking orbit.
About 50 minutes later the upper stage is ignited. It is powered by
restartable, liquid oxygen/synthetic kerosene propulsion system. The upper
stage puts the satellite into a 51.6 degrees inclined and highly eccentric
transfer orbit with a perigee altitude of about 700 kilometres. After the
upper stage burn end the satellite will separate. Then Integral¹s own
propulsion system will bring the spacecraft to the operational 72 hours
orbit with its initial perigee height of 9'000 kilometres and the apogee
height of 155'000 kilometres. The perigee height increases throughout the
mission to about 31'000 kilometres after 5 years. In addition to the orbit
shape, also the inclination changes drastically to 86.5 degrees after 5
The high and eccentric orbit guarantees long periods of uninterrupted
observation with nearly constant background and away from trapped radiation
in Earth¹s proton and electron belts. 90 % of the time spent in the orbit
provided by the Russian rocket can be used for scientific observations above
an altitude of 40'000 kilometres. The orbital period with its 72 hours being
a multiple of 24 hours guarantees an optimal coverage pattern from the
ground stations that can be kept for all revolutions and allows repetitive
working shifts on ground.
In its four-stage configuration Proton is regularly used to launch
spacecraft into geosynchronous trajectories. As a three-stage vehicle it
primarily launches large space station type payloads into low earth orbit.
In November 1998 a Proton rocket put the first component for the
International Space Station (ISS) into orbit. In the future the Proton will
be a crucial asset in deploying ISS.
Production of the first two-stage Proton model started in 1962. The
four-stage rocket was originally developed to flyby the Moon with a manned
capsule. Today International Launch Services, a joint venture between the
Russian companies Khrunichev and RSC Energia and American Lockheed Martin
commercially market launch services of western satellites on the Proton. In
April 1996 an Astra broadcast satellite was the first Western spacecraft to
be carried by a Russian Proton rocket, others followed as the Iridium
satellites for mobile telephony.