Ariane 5 ECA launches with Herschel and Planck observatories

by Chris Bergin
Arianespace’s Ariane 5 ECA launch vehicle has lifted off to place two space telescopes into orbit on Thursday, launching from the European Spaceport in French Guiana at 13:12 GMT. The dual launch marks the opening lifespan of the Herschel and Planck observatories, which has a price tag of 1.9 billion Euros.

Arianespace is planning to launch six to eight times this year, with Thursday’s dual launch marking the second mission of 2009.


The first mission of 2009 was the February 12 launch, which placed the HOT BIRD 10 and NSS-9 telecommunications satellites into geostationary transfer orbits. They were accompanied by a pair of Spirale piggyback passengers, which are demonstrators for a French early warning defense system.

The Ariane 5 ECA will loft Herschel and Planck off the planet, before they separate from the upper stage and head independently towards the L2 Lagrangian point of the Sun-Earth system – a gravitational stability point suspended in space some 1.5 million kilometres from Earth in the opposite direction to the Sun.

With a liftoff mass of 3,300 kg., Herschel will be the largest space telescope of its kind ever launched. Its ability to detect space radiation at far infrared and sub-millimeter wavelengths will help scientists to determine how the first galaxies were created, and how they evolved into their present-day form.

The 1,800-kg. Planck spacecraft will analyze radiation remnants that filled the universe immediately after the Big Bang, which are observed today as the Cosmic Microwave Background. Data from Planck will provide answers on the universe’s creation, and how it is expected to develop in the future.

Thales Alenia Space built both Planck and Herschel for the European Space Agency, working with one of the largest industrial teams ever assembled for this type of project.

The Planck spacecraft will ride in the lower position in the Ariane 5’s payload “stack.” It has a height and maximum diameter of 4.2 meters, and carries a telescope with a 1.5-meter primary mirror. Herschel is riding on Ariane 5 in the upper payload slot. The tubular-shaped spacecraft is 7.5 meters high and 4 meters wide

Herschel’s extremely smooth surface of its 3.5-m-diameter primary mirror – made of lightweight silicon carbide – is almost one and a half times bigger than that of Hubble’s, and six times bigger than that of its predecessor ISO launched by ESA in 1995.

With its huge light-collection capability and set of sophisticated detectors cooled to the vicinity of absolute zero by over 2000 litres of superfluid helium, Herschel will look at the faintest and farthest infrared sources and peer into the as-yet uncharted far infrared and submillimetric parts of the spectrum.

Herschel will be able to see through the opacity of cosmic dust and gas and observe structures and events far away that date back to the early Universe – such as the birth and evolution of early stars and galaxies – ten thousand million years ago, in an effort to determine exactly how it all started.

Closer by, within our galaxy, Herschel will also observe extremely cold objects, such as the clouds of dust and interstellar gases from which stars and planets are formed, and even the atmosphere around comets, planets and their moons in our own solar system.

Featuring a 1.5 m telescope and instruments sensitive to microwave radiation, Planck will measure temperature variations in the very early Universe. It will monitor the so called Cosmic Microwave Background, the relic of the very first light ever emitted in space about 380 thousand years after the Big Bang, when the density and temperature of the young Universe had decreased enough to finally allow light to separate from matter and travel freely in space.

Herschel’s detectors will be cooled down to 0.3 degrees above absolute zero. Planck’s detectors will reach even colder temperatures, just 0.1 degrees above 0 K.

With its ‘heart’ operating at unprecedented low temperatures, Planck will deliver unrivalled sensitivity and resolution. By measuring the tiny fluctuations in the temperature of the microwave background radiation, scientists will extract at least 15 times more information about the Universe’s origin, evolution and future than with its most recent predecessor.

The satellite is planned to take some 500 thousand million of raw samples to produce a set of multi-million-pixel sky maps that will also help scientists to understand the Universe’s structure and account as never before for all of its constituents.

Planck will be able to determine the total amount of atoms in the Universe, infer the total density of dark matter – an elusive component still inaccessible to direct observations but ‘visible’ through its effects on the surroundings – and even shed new light on the nature of the mysterious dark energy.

Herschel and Planck also represent a tremendous technological challenge that has been overcome by ESA thanks to the mobilising of over 100 industrial partners and institutes in Europe, the United States and elsewhere.

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