Herschel Space Observatory - PACS

The satellite consists of three instruments:

HIFI, the Heterodyne Instrument for the Far Infrared, a high-resolution spectrograph that operates in the range of 480 to 1250 GHz in five bands and 1410 to 1910 GHz in two additional bands.

PACS, the Photodetector Array Camera and Spectrometer, a bolometer array photometer and a photoconductor array imaging spectrometer operating at a wavelenght range between 60 and 210 µm.

SPIRE, the Spectral and Photometric Imaging Receiver, consisting of a 3-band imaging photometer and a Imaging Fourier Transform Spectrometer and will operate at wavelengths between 200 and 670 µm.

Herschel will be launched on 14 May 2009 together with Planck, another ESA scientific mission. Both satellites will separate shortly after launch and will be operated independently.

The institute of Astronomy has a substantial participation in the PACS instrument. The principle investigator of PACS is Albrecht Poglitsch from the Max-Planck-Institut für Extraterrestrische Physik (MPE) in Garching, Germany. Prof. Christoffel Waelkens is co-Principle Investigator of PACS.

Prior to launch, the instrument control center team is executing a suite of laboratory tests of the qualification models and the flight model of the instrument. These tests encompass detailed performance and calibration tests on instrument level, as well as integrated system tests with the instrument mated on the satellite. The team in Leuven is focusing on the testing of mechanisms and the spectrometer calibration.

Mechanism testing includes the verification of compliance to specifications and control loop optimisation of the grating and filter wheels, and of the Ge:Ga detector flashers and heaters. We design tests, define the measurements in the uplink logic, execute the tests, analyse data and follow-up the results with the engineering team.

The ground calibration of the instrument is crucial for the full calibration and understanding of the instrument in space. For the spectrometer we take care of the spectrophotometric calibration strategy, absolute radiometric calibration, relative spectral response calibration, flatfield determination, testing of observing modes, and characterisation of the Ge:Ga detector and cryogenic readout (CRE) behaviour.

In parallel to the testing of the instrument in the laboratory, a lot of work is devoted to the preparation of the launch and the in-orbit phase. A first version of the observing modes of the instrument have been delivered to ESA's Herschel Science Centre (HSC) to support the first round of proposals for the key programmes.

For the in-orbit calibration, a detailed plan is being prepared for the initial calibration during the commissioning and performance verification phases. The Leuven team is leading the work on fiducial stellar flux calibrators for the Herschel instruments and participates in the Herschel Calibration steering group. The preparation of the in-orbit spectrophotometric calibration of the PACS spectrometer is K.U.Leuven responsibility . Continuing our involvement in proton irradiation tests of the photoconductors in the cyclotron of Louvain-La-Neuve, we are working on the strategy for detector curing, and detection and correction for response changes due to cosmic particle hits. The corresponding data reduction pipeline steps are also developed in our group.

A substantial amount of work in Leuven is spent on the development of software in the common Herschel software system. A large part of the system is operational already, visible in the proposal submission functionality, and the data analysis system used for the analysis of instrument level data. The focus is now shifting to in-orbit operations functionality including the standard product generation pipelines, data access, access to housekeeping telemetry of all satellite subsystems and interactive data analysis tools for the observers. In these areas, our team has a leading role. On a system level, we deliver key personnel in the data processing system architecture group and the ground segment system engineering group.

Via a software development contract with ESA, we contribute to advanced data reduction functionality in the extended Herschel Data processing system.

With the broad wavelength range of approximately 60 to 670 um, Herschel will observe the so-called `Cold Universe'. Black bodies with temperatures between 5 and 50 K, peak at these wavelengths. Also the brightest molecular and atomic emission lines for gasses with temperatures between 10 and a few hundred Kelvin are emitted in the far-infrared.

With its photometric mapping capabilities, Herschel offers the possibility of unbiased surveys related to galaxy and star formation. With the spectroscopic instruments, a characterisation of (newly detected) objects will be possible.

Interesting results are to be expected in the field of Cosmology (i.e. discovery of proto-galaxies, formation of Galaxies), interstellar medium (spectroscopic studies of gas and dust) and star formation as well as in the field of our solar system, through the study of comets and planets.

The institute is leading the guaranteed time Herschel Key programme on the circumstellar environment in post-main-sequence objects, and is responsible for important parts of the guaranteed time Key Programmes on Stellar Disk Evolution; HIFISTARS: The physical and chemical properties of circumstellar environments around evolved stars; Water and related chemistry in the Solar system; Probing the origin of the stellar initial mass function (a wide-field Herschel photometeric survey of nearby star-forming cloud complexes), and the Open Time key programmes on Gas in Protoplanetary systems (GASP); Dust, Ice and Gas in Time (DIGIT) and Hi-GAL: the Herschel infrared Galactic Plane Survey.

	People involved

Christoffel Waelkens    Joris Blommaert    Wim De Meester    Katrina Exter    Rik Huygen    Christophe Jean    Sara Regibo    Pierre Royer    Bart Vandenbussche    Eva Bauwens   

	Related links

Herschel information at the ESA Science portal
The PACS consortium pages
PACS information at MPE, Garching