On Thursday (at 13:12 UT) Arianespace will send into orbit two scientific satellites for the European Space Agency: the Herschel space telescope and the Planck scientific observatory. The launch process which will take these amazing new instruments from the ground into space takes less than an hour! I will be watching the event live from Cardiff (you can watch it here) and was curious as to how exactly it would unfold.
This post features some interactive charts that show the altitude, velocity and acceleration of the Ariane rocket as it progress through the air into space. You can click and drag to zoom in on a section of these charts. Move your mouse around inside them to get more information.
7 seconds after ignition of the main stage cryogenic engine, two solid-propellant boosters are ignited, and we have liftoff. The launch begins with a 6 second vertical climb. The onboard computers optimize the motion of the rocket in real time, in order to minimise fuel consumption. The main stage engine takes the launcher into an intermediate orbit before the end stage takes the payload into the final orbit. You can clearly see the change between the two stages on the velocity and acceleration graphs at about 9 minutes.
The main stage of the launcher will apparently fall back, just off the coast of Africa in the Atlantic Ocean. The launcher will remain at an altitude of about 852 kilometers travelling at about 10,000 meters/second! The fairing protecting the Herschel, Planck spacecraft is jettisoned shortly after the boosters.
By the end of the process, Herschel and Planck will be on their way to a placed called ‘L2’, a point in space where objects sit ‘behind’ the Earth with respect to the Sun (see diagram below). L2 is a good spot for space-based observatories because they are effectively ‘towed’ around in orbit with the Earth but remain roughly stationary with respect to it.
Herschel and Planck will not be alone at L2. The Wilkinson Microwave Anisotropy Probe is already there and the Gaia mission and James Webb Space Telescope will also be placed at L2.
The Herschel space telescope has two main objectives: observation of the “cold” Universe, in particular the formation of stars and galaxies; and studying the chemical composition of celestial bodies and the molecular chemistry of the Universe. Herschel’s mirror, at 3.5 meters in diameter, will be the largest ever deployed in space. It will wiegh over 3,400 kg at launch. For more info visit the ESA Herschel page.
Planck is designed to analyze the remnants of the radiation that filled the Universe immediately after the Big Bang, which we observe today as the cosmic microwave background. Planck will provide vital information concerning the creation of the Universe and the origins of the cosmic structure. It will weigh 1,920 kg at launch. For more info visit the ESA Planck page.
[More info in Ariancespace press release. Launch image: ESA-CNES-ARIANESPACE, L2 diagram: ESA/NASA]
Orbiting Frog 
Leave a Reply