German researchers are playing important roles in the Herschel and Planck astronomy missions
Final assembly of the Herschel PACS Focal Plane Unit Today, two of Europe's most ambitious and complex astronomy missions, Herschel and Planck, were launched. The two spacecraft are now on their way to orbits around the second Lagrange point (L2) of the Sun-Earth system, where they will conduct their observations.
German involvement in Herschel and Planck is financed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) using funds from the German Federal Ministry of Economics and Technology (Bundesministeriums für Wirtschaft und Technologie; BMWi). Researchers from a number of German scientific institutions are playing important roles in these missions.
Herschel/PACS at the Max Planck Institute for Extraterrestrial Physics
The Max Planck Institute for Extraterrestrial Physics (Max-Planck-Institut für extraterrestrische Physik; MPE) is based in Garching. Its main research topics are astronomical observations at wavelengths such as the far infrared, X-ray and gamma ray spectral regions, which are only accessible from space because of the absorbing effects of Earth's atmosphere.
Albrecht Poglitsch is the Principal Investigator for the Photodetector Array Camera & Spectrometer (PACS) on Herschel. PACS consists of a colour camera and an imaging spectrometer. Within its wavelength range (55–210 microns), the PACS camera is the first instrument capable of obtaining the complete spatial (imaging) and spectral information of a target simultaneously. The PACS spectrometer has a lower resolution than that of Herschel/HIFI, but it is perfectly suited to seeing young galaxies and the gas clouds from which stars form.
PACS operates either as a special camera (photometer) in two colours simultaneously, or as a spectrometer. The PACS consortium includes institutes from Belgium, Austria, France, Italy and Spain.
Germanium-gallium photoconductor arrays
Speaking about the challenge of constructing PACS, Dr Poglitsch said: "Building PACS was more than just one challenge: working in the far infrared is still a pioneering effort, largely due to the fact that there are no sensitive detectors available on the market – in other words, you have to develop them yourself. Because we wanted to achieve the best sensitivity that the overall system allows, we even had to implement two different technologies in the photometer and in the spectrometer branches of the instrument."
Describing the advanced technologies developed for PACS, Dr Poglitsch continued: "The mechanically-stressed photoconductor detector arrays in the spectrometer, manufactured by ASTEQ GmbH (Kelkheim, Germany), are the largest ever built. The same is true for the bolometer arrays, provided by CEA (Saclay, France). The optics – jointly designed by MPE and our prime contractor, Kayser-Threde GmbH (Munich) – were originally considered impossible by many experts and now work fully within the specifications. The optical chopper – necessary to subtract background light – can perform hundreds of millions of high-precision movements during its lifetime. It was developed at Carl Zeiss AG (Oberkochen, Germany) in collaboration with our partner institute, MPIA (Max-Planck-Institut für Astronomie; Heidelberg). To see all these new developments work together in one instrument and produce new, exciting scientific results will be a great reward after more than ten years of joint effort by the PACS instrument consortium."
Planck software development at the Max Planck Institute for Astrophysics
The Max Planck Institute for Astrophysics (Max-Planck-Institut für Astrophysik; MPA) is also based in Garching. Its main research topics are in the areas of stellar evolution, stellar atmospheres, supernova physics, astrophysical fluid dynamics, high-energy astrophysics, galaxy structure and evolution, the large-scale structure of the Universe, and cosmology.
MPA Planck team
Scientists and engineers at MPA developed the software needed for data processing and information exchange while the Planck instruments were being developed and wrote the simulation programs required for testing the data processing routines and the systems for analysis of the observation data. They are also building a database to store the data after they have been processed.
Torsten Enßlin is the MPA Planck Group Leader and a Planck Associate. He explains the mission: "Planck will permit precise measurements of fundamental cosmic properties. It will allow us to listen to the very first heartbeats of our Universe and to improve our understanding of the emergence of space, matter and energy. Planck will give us a full sky view of many astrophysical objects such as our Milky Way and galaxy clusters, at mostly unexplored wavelengths and with polarisation information. And it will hopefully reward the huge efforts of all Planck development teams around the globe during the last decade."
"With the launch of the Planck satellite, a dream comes true", says Rashid Sunyaev, MPA director, a pioneer of cosmic microwave background research and a Planck Co-investigator. "Planck will provide the most precise data on the early Universe ever. We have never been so close to the Big Bang.”
"We will understand the past of our Universe and take a glance at its future", adds Sunyaev’s colleague Simon White, also an MPA director and Planck Co-investigator. "Will it keep on expanding for ever, or some day collapse back upon itself? What is the nature of the mysterious dark energy causing this expansion? Planck will give answers to many important questions in cosmology. The spacecraft is the most powerful tool for studying the cosmic microwave background ever developed."
Herschel/HIFI at the Max Planck Institute for Solar System Research
The Max Planck Institute for Solar System Research (Max-Planck-Institut für Sonnensystemforschung; MPS) is based in Katlenburg-Lindau. Its main research topic is the investigation of the Solar System, in particular the environments of Earth, the other planets, and comets, as well as the Sun, its heliosphere and their interaction with the interstellar medium.
MPS is involved in the HIFI instrument on Herschel, providing acousto-optical spectrometers in collaboration with the University of Cologne.
HIFI, a high-resolution spectrometer, is designed to observe previously unexplored wavelengths. With its high spectral resolution – the highest ever in the range of wavelengths it covers – HIFI will observe an unprecedented level of detail. It will be able to observe and identify individual molecular species in the vastness of space, and study their motion, temperature, and other physical properties. This is fundamental to the study of comets, planetary atmospheres, star formation and the development of galaxies.
HIFI can produce high-resolution spectra of thousands of wavelengths simultaneously. It covers two bands (157–212 microns and 240–625 microns), and uses superconducting mixers as detectors. It was designed and built by a consortium led by the Netherlands Institute for Space Research (SRON). The consortium includes institutes from France, Germany, USA, Canada, Ireland, Italy, Poland, Russia, Spain, Sweden, Switzerland and Taiwan.
Last look: Herschel on top of the launcher
Herschel
Herschel is the largest-ever infrared space observatory. Equipped with a 3.5 metre diameter reflecting telescope and instruments cooled to close to absolute zero, it will observe at wavelengths that have never previously been explored. In recent decades, infrared astronomers have unveiled tens of thousands of new galaxies and have made surprising discoveries such as the huge amounts of water vapour that fill our Galaxy. Yet there is still much more to be discovered. Astronomical objects such as other planetary systems, or processes like the birth of galaxies in the early Universe, can best be studied with infrared telescopes situated in space and therefore freed from the restrictions imposed by Earth’s atmosphere.
Herschel carries three instruments. The Heterodyne Instrument for the Far Infrared (HIFI) is a very-high resolution spectrometer. The Photodetector Array Camera and Spectrometer (PACS) is an imaging photometer and medium resolution grating spectrometer. The Spectral and Photometric Imaging Receiver (SPIRE) is an imaging photometer and an imaging Fourier transform spectrometer.
Herschel will seek answers to important questions in modern astronomy and cosmology, including how galaxies formed and evolved in the early Universe, how stars form and evolve and their relationship with the interstellar medium. The mission will also investigate the chemistry of our Galaxy and the molecular chemistry of planet, satellite and comet atmospheres in the Solar System.
Planck
Planck at the Guiana Space Centre
The Planck mission will receive and characterise the Cosmic Microwave Background (CMB) radiation using sensitive radio receivers operating at very low temperatures. These receivers will determine the black body equivalent temperature of the background radiation and will be capable of distinguishing temperature variations of about one millionth of a degree Celsius. These measurements will be used to produce the best ever maps of variations in the CMB radiation field.
Planck carries two instruments, the Low Frequency Instrument (LFI), an array of radio receivers, and the High Frequency Instrument (HIFI), an array of microwave detectors that use bolometers (heat detectors).
Planck will seek answers to fundamental astronomical questions, including whether or not it can be conclusively shown that the early Universe passed through an inflationary phase, and investigate the nature of the dark matter that dominates the present Universe. The mission will also attempt to determine more precise values for cosmological parameters such as the Hubble constant.