Herschel was launched on 14 May 2009, and is now an operational ESA space observatory o ering unprecedented observational capabilities in the far-infrared and submillimetre spectral range 55 671 m. Herschel carries a 3.5 metre diameter passively cooled Cassegrain telescope, which is the largest of its kind and utilises a novel silicon carbide technology. The science payload comprises three instruments: two direct detection cameras/medium resolution spectrometers, PACS and SPIRE, and a very high-resolution heterodyne spectrometer, HIFI, whose focal plane units are housed inside a superfluid helium cryostat. Herschel is an observatory facility operated in partnership among ESA, the instrument consortia, and NASA. The mission lifetime is determined by the cryostat hold time. Nominally approximately 20,000 hours will be available for astronomy, 32% is guaranteed time and the remainder is open to the worldwide general astronomical community through a standard competitive proposal procedure.

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Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy

The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submil- limetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 × 25 pixels, each, and two filled silicon bolometer arrays with 16 × 32 and 32 × 64 pixels, respectively, to perform integral-field spectroscopy and imaging photom- etry in the 60−210 μm wavelength regime. In photometry mode, it simultaneously images two bands, 60−85 μ mo r 85−125 μ ma nd 125−210 μm, over a field of view of ∼1.75 � × 3.5 � , with close to Nyquist beam sampling in each band. In spectroscopy mode, it images afi eld of 47 �� × 47 �� , resolved into 5 × 5 pixels, with an instantaneous spectral coverage of ∼ 1500 km s −1 and a spectral resolution of ∼175 km s −1 . We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the performance verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions.

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The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory

We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.

Star Formation in the Milky Way and Nearby Galaxies

The Spectral and Photometric Imaging REceiver (SPIRE), is the Herschel Space Observatory`s submillimetre camera and spectrometer It contains a three-band imaging photometer operating at 250, 350 and 500 mu m, and an imaging Fourier-transform spectrometer (FTS) which covers simultaneously its whole operating range of 194-671 mu m (447-1550 GHz) The SPIRE detectors are arrays of feedhorn-coupled bolometers cooled to 03 K The photometer has a field of view of 4' x 8', observed simultaneously in the three spectral bands Its main operating mode is scan-mapping, whereby the field of view is scanned across the sky to achieve full spatial sampling and to cover large areas if desired The spectrometer has an approximately circular field of view with a diameter of 26' The spectral resolution can be adjusted between 12 and 25 GHz by changing the stroke length of the FTS scan mirror Its main operating mode involves a fixed telescope pointing with multiple scans of the FTS mirror to acquire spectral data For extended source measurements, multiple position offsets are implemented by means of an internal beam steering mirror to achieve the desired spatial sampling and by rastering of the telescope pointing to map areas larger than the field of view The SPIRE instrument consists of a cold focal plane unit located inside the Herschel cryostat and warm electronics units, located on the spacecraft Service Module, for instrument control and data handling Science data are transmitted to Earth with no on-board data compression, and processed by automatic pipelines to produce calibrated science products The in-flight performance of the instrument matches or exceeds predictions based on pre-launch testing and modelling: the photometer sensitivity is comparable to or slightly better than estimated pre-launch, and the spectrometer sensitivity is also better by a factor of 15-2

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The Herschel-SPIRE instrument and its in-flight performance

▪ Abstract This review surveys the observed properties of interstellar dust grains: the wavelength-dependent extinction of starlight, including absorption features, from UV to infrared; optical lum...

https://www.ifa.hawaii.edu/users/reipurth/reviews/draine.pdf

Interstellar dust grains

Mechanisms operating in the cryovacuum are required to rotate filter and dichroic wheels, to tilt gratings and to flip in the beam of an internal calibration source. The design proposed here is based on similar mechanisms flown successfully on the liquid helium cooled European ISO-satellite and being presently under qualification for ESA's cooled HERSCHEL-satellite. Their main characteristics are high reliability during the 10 year lifetime in space, high precision and low heat dissipation in the cryovacuum.

Cryomechanisms for positioning the optical components of the mid-infrared instrument (MIRI) for NGST

The flight model of ISOPHOT has been completed and delivered to ESA. The pre-flight calibration verified the high performance specifications for the far-infrared detector channels. At times, limiting factors in orbit may be high-energy-radiation induced noise and responsivity drifts after passage through the radiation belts, and signal drifts following large incident flux changes.

ISOPHOT: the imaging photopolarimeter for the Infrared Space Observatory

A chopper acts as an optical switch within the entrance optics of the PACS instrument onboard the ESA Space Observatory HERSCHEL to discriminate the light of faint celestial sources from a large background flux, which is basically due to the thermal radiation of the only moderately cooled 3.5mtelescope (≈ 80K). This chopper primarily consists of a small electrically driven tilting mirror with a high position accuracy for the full range of elongations up to ±9◦ to be operated at 4K with a power dissipation of less than 4mW. At a chopping frequency of up to 10Hz in square wave modulation scheme a duty cycle of 80% is to be achieved. After a pre-development phase at MPIA, which resulted in an optimized and cold tested prototype, the industrial optimization and implementation of the PACS chopper started in 2000 in a cooperation with the company Zeiss (Oberkochen). We focus on the new design of the chopper and its critical components, including the recently developed double-stage flexural pivots as high reliable bearings of the chopping mirror axis. The monolithic CuBe2 layout has to resist vibration loads of up to 45g during the launch of the ARIANE 5 carrier and to guarantee for an accurate motion in a cryogenic environment during a lifetime of at least 3 years in space, which corresponds to 630 Mio cycles of the chopper. Other components like the cryomotor and the rotor will be considered with respect to the selection of optimal materials, the reliability of mechanical linkages and the compensation of thermal stresses within the whole multi-material chopper assembly. I. HERSCHEL SATELLITE In 2007 ESA will launch the HERSCHEL satellite (formerly known as FIRST) as another cornerstone mission of its ”Horizon 2000 long term programme” [1]. This multi-user device will be the biggest and most powerful infrared observatory of its time. With a wavelength coverage between 60 and 670μm it will be sensitive especially in the far-infrared and submillimeter region, thus exploring radiation in a very unknown range of the electromagnetic spectrum. Scientific objectives, which will be addressed by HERSCHEL, range from the exploration of the distant universe and the question how first stars and galaxies were born, across the formation of planetary systems up to the investigation of our own solar system. 3.5m primary mirror sun shield + collector cryostat + scientific instruments

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A cold focal plane chopper for Herschel-PACS - critical components and reliability

FIRBACK is one of the deepest cosmological surveys performed in the far infrared, using ISOPHOT We describe this survey, its data reduction and analysis We present the maps of fields at 175µm We point out some first results: source identifications with radio and mid infrared, and source counts at 175µm These two results suggest that half of the FIRBACK sources are probably at redshifts greater than 1 We also present briefly the large follow-up program

Firback far infrared survey with iso: data reduction, analysis and first results

The first set of compact sources observed in the ISOPHOT 170 μm Serendipity Survey is presented From the slew data with low (I100μm ≤ 15 MJy/sr) cirrus background, 115 well-observed sources with a high signal-to-noise ratio in all detector pixels having a galaxy association were extracted Of the galaxies with known optical morphologies, the vast majority are classified as spirals, barred spirals, or irregulars The 170 μm fluxes measured from the Serendipity slews have been put on an absolute flux level by using calibration sources observed additionally with the photometric mapping mode of ISOPHOT For all but a few galaxies, the 170 μm fluxes are determined for the first time, which represents a significant increase in the number of galaxies with measured Far-Infrared (FIR) fluxes beyond the IRAS 100 μm limit The 170 μm fluxes cover the range 2 <∼ F170μm <∼ 100 Jy Formulae for the integrated FIR fluxes F40−220μm and the total infrared fluxes F1−1000μm incorporating the new 170 μm fluxes are provided The large fraction of sources with a high F170μm/F100μm flux ratio indicates that a cold (TDust <∼ 20 K) dust component is present in many galaxies The detection of such a cold dust component is crucial for the determination of the total dust mass in galaxies, and, in cases with a large F170μm/F100μm flux ratio, increases the dust mass by a significant factor The typical mass of the coldest dust component is MDust = 1075 ± 05 M , a factor 2–10 larger than that derived from IRAS fluxes alone As a consequence, the majority of the derived gas-to-dust ratios are much closer to the canonical value of ≈ 160 for the Milky Way By relaxing the selection criSend offprint requests to: M Stickel ? Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) are MPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena, Imperial College London Correspondence to: stickel@mpia-hdmpgde teria, it is expected that the Serendipity Survey will eventually lead to a catalog of 170 μm fluxes for ≈ 1000 galaxies

Dietrich Lemke

Papers

Cryomechanisms for positioning the optical components of the mid-infrared instrument (MIRI) for NGST

ISOPHOT: the imaging photopolarimeter for the Infrared Space Observatory

A cold focal plane chopper for Herschel-PACS - critical components and reliability

Firback far infrared survey with iso: data reduction, analysis and first results

The ISOPHOT 170 μ m serendipity survey. I. Compact sources with galaxy associations