European Twin-Telescope Mission Launched
By Michael A. Taverna
PARIS - Europe's pioneering Herschel and Planck telescopes, 20 years in the making, are finally en route to their orbital position 1.2 million kilometers (746,000 miles) from Earth, following a high-stakes dual liftoff.
The twin-satellite payload blasted off from Kourou, French Guiana, atop an Ariane 5 ECA booster at 10:12 a.m. local time (3:12 p.m. CET) on May 14. At 3:38 p.m. CET Herschel, the top passenger, separated from the Ariane 5 upper stage at an altitude of 1,150 kilometers over the east coat of Africa.
The Sylda support structure enclosing Planck ejected 1.5 minutes later, followed at 3:40 p.m. CET by Planck itself, at an altitude of 1,700 kilometers.
The spacecraft attitude control and telecommunications subsystems switched immediately thereafter and first signals were received by the European Space Agency's (ESA) 35-meter deep space antenna at New Norcia in Australia at 3:49 p.m. CET.
The satellites were injected into a highly elliptical orbit with an apogee of 1.2 million kilometers and a perigee of 270 kilometers. Following injection into transfer orbit, they will set out independently for the L2 Lagrange point, chosen because it is free of Earth, solar and lunar gravity effects. ESA engineers said both spacecraft appeared to be in nominal condition as they prepared for initial trajectory correction maneuvers. Once in geostationary transfer orbit, they will take about 60 days to reach final orbit.
The care with which the launch was prepared bespeaks the high stakes involved in the 1.3 billion euro ($1.7 billion) mission - the most ambitious European space science undertaking ever. Liftoff had initially been set for mid-April but was repeatedly delayed as engineers strove to eliminate each and every possible risk. The April launch date itself was more than a year later than initially planned, which was the result of technical headaches caused in particular by the mission's cutting-edge cryogenic cooler designs.
The mission was the second of the year for the Ariane 5 ECA and the first ever for Arianespace to the Lagrange points. Previous European missions to this position, such as Soho, were launched by American rockets.
The twin mission, built by Thales Alenia Space, will attempt to unveil the secrets of the darkest, coldest and oldest parts of the universe. Herschel, equipped with the largest mirror ever launched into space, will observe mostly uncharted parts of the infrared spectrum to study the birth of stars and galaxies and observe dust clouds and planet-forming discs around stars. Planck will map fossil radiation left over from the Big Bang and study exotic objects like dark matter and dark energy that continue to puzzle the science community.
The spacecraft will be the first to cover the spectrum between 55 and 672 microns, the first to detect objects as cool as 5-50 degrees Kelvin and the first to see through the "fog" caused by cosmic dust.
Ariane 5 ECA booster photo: ESA
