The Planck observatory was installed atop the launch vehicle’s core stage yesterday, marking a major step in the build-up of Ariane 5’s dual payload “stack.” This 1,950 kg. spacecraft will provide new information on the formation of galaxies and how the universe began. Planck is riding in the lower position of the payload stack on Ariane 5, and will be situated below the Herschel space telescope, which will be integrated next on the launch vehicle. Designed to make the most accurate maps ever of the microwave background radiation that fills space, Planck will scan the sky in nine wavelength bands. 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. Planck carries a telescope with an effective aperture of 1.5m, which directs microwave radiation onto the spacecraft’s two instruments. The Low Frequency Instrument’s array of 22 tuned radio receivers will image the sky in three frequencies between 30 GHz. and 70 GHz., while the High Frequency Instrument is to use 52 bolometric detectors that operate at six frequencies between 100 GHz. and 857 GHz.
Both Planck and Herschel will be deployed by Ariane 5 into very elliptical orbits, enabling these spacecraft to follow transfer trajectories for their 1.5 million kilometer voyages to the Sun-Earth system’s second Lagrange point (L2). The two spacecraft were built by Thales Alenia Space-led industrial teams for the European Space Agency’s space science program. A launch date announcement for this mission — Arianespace’s second of 2009 — is pending while additional checks are performed on the heavy-lift Ariane 5 ECA. The checks were decided after an anomaly was discovered during tests on a subassembly that is identical to equipment already installed on the Ariane 5 at Europe’s Spaceport.