This milestone, which occurred yesterday, clears the way for final preparation and arming of the launch vehicle – and will be followed by Ariane 5’s roll-out to the launch pad on May 13 for its liftoff from the Spaceport in the morning hours of May 14.

The fairing protects Ariane 5’s passengers during the launcher’s climb-out through the atmosphere’s dense layers, and it will be jettisoned approximately four minutes into the mission.

(In the photo at right, the payload fairing is partly visible at top as it descends over the dual passenger “stack.”  The Herschel space telescope is in the upper position, while the Planck observatory is encapsulated inside the canister-shaped SYLDA dispenser below it.)

Thursday’s launch with Herschel and Planck will be Ariane 5’s 44th mission, with the launcher carrying a total payload of just over 6,000 kg.  The weight includes approximately 5,320 kg. for the two spacecraft, plus their integration hardware and the SYLDA dual-payload dispenser system.

After being deployed in sequence during the 28-minute-long mission, both Herschel and Planck will follow 1.5 million-kilometer voyages to the Sun-Earth system’s second Lagrange point (L2), where they will perform their scientific observations.

As the largest space telescope ever launched, Herschel will provide astronomers with their best views of the universe at far-infrared and sub-millimeter wavelengths.  Its 3.5-meter-diameter mirror is designed to gather data for studies of the formation of stars and galaxies, and to investigate the relationship between the two.

The Planck observatory will map the sky in nine wavelength bands, using a telescope with an effective aperture of 1.5 meters.  This information will help determine the universe’s fundamental characteristics – including the overall geometry of space, the density of normal matter and the rate at which the universe is expanding.

Both Planck and Herschel were developed in European Space Agency-managed scientific programs, and the two spacecraft were produced by Thales Alenia Space-led industry teams.