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Mission Update

Europe's Herschel space telescope joins its Planck observatory co-passenger on the Ariane 5 launcher

May 4, 2009

The second of two passengers to study the cold depths of space has been integrated on the Ariane 5 launcher, marking a major new step in preparations for Arianespace’s upcoming heavy-lift mission.

During activity performed in Ariane 5’s Final Assembly Building at the Spaceport, Herschel was installed in the upper position of the launcher’s payload “stack.”  It is mated atop the SYLDA payload dispenser system, which previously was installed over the mission’s lower passenger – the Planck observatory.

With Herschel and Planck now integrated on Ariane 5, preparations for Arianespace’s May 14 launch from French Guiana move into their final phase – with several peculiarities for the pioneering dual space science mission.

This includes a “top-up” of Herschel’s cryostat cooling system with liquid helium, which is now underway and will continue into next weekend.  The cryostat will keep the temperature of Herschel’s scientific instrument detectors close to absolute zero (–273ºC), enabling the space telescope to provide an unprecedented view of the “cold universe” during observations made in far-infrared and sub-millimeter wavelengths.

Members of the Herschel team initially filled the cryostat with liquid helium during operations in April, which were performed in the Spaceport’s S5 payload preparation facility.  The current top-up serves several purposes: ensuring the liquid helium is maintained at a low temperature, replacing any loss that occurred since the initial loading, and filling any volume created when vacuum is applied to the cryostat.

Once the liquid helium top-up is completed, the Herschel/Planck stack will be encapsulated inside Ariane 5’s protective fairing, completing the launch vehicle’s integration.  

Herschel will be the largest space telescope ever launched, with its 3.5-meter diameter mirror providing astronomers a better understanding of the formation of stars and galaxies. 

Planck also will study the cold cosmos.  The data from its telescope, which has an effective aperture of 1.5 meters, will help determine the universe’s fundamental characteristics – including the rate at which it is expanding.  

Both Planck and Herschel were built by Thales Alenia Space-led industry teams for the European Space Agency.  After their launch by Ariane 5, the two spacecraft will follow trajectories for 1.5 million-kilometer voyages to the Sun-Earth system’s second Lagrange point (L2).  Planck’s mass at liftoff will be approximately 1,920 kg., while Herschel will weigh about 3,400 kg. at launch.

• Arianespace’s official launch kit has more details on this Ariane 5 mission.