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

ISOPHOT, the photometer for ESA's Infrared Space Observatory ISO, will use extrinsic photo-conductors for astrophysical research at wavelength ranging from 3 to more than 200 μm. Doped silicon detectors will be applied as single pixels, linear and two dimensional arrays for photometry, polarimetry, mapping and in a low resolution spectrometer. Two dimensional arrays of doped germanium are foreseen as far-infrared cameras. During phase B of the project breadboard models of the most critical detectors have been built and tested with cryogenic multiplexing readout electronics.

Focal Plane Arrays For The Isophot Experiment

The Infrared Space Observatory's (ISO) photometer experiment ISOPHOT provides 4 sub-systems, as described in LEMKE 1985, which optimizes the different ways of photometric measurements. They allow multiband - multiaperture photopolarimetry, multicolor - polarimetric imaging and spectrophotometry. In order to cover the wide wavelength range 2.5...240μm five different detector materials have to be used. They are arranged according to their application as 2D-arrays, linear arrays and single detectors, a total of 223 detectors are present, see tab. 1.

Detectors and arrays of ISO's photopolarimeter

The array camera and spectrometer PACS to be flown aboard the European 3.5 m infrared space telescope FIRST will apply a cold focal plane chopper. Its development has to meet ambitious goals, such as large chopper throws, high operational accuracy in several modes, very low heat dissipation in the cryogenic environment, sufficient rigidity to meet the ARIANE5 launch conditions and a long lifetime thereafter. The prototype development of such a chopper and test results under cryovacuum conditions are reported here.

Focal plane chopper for the PACS instrument aboard the far-infrared space telescope FIRST

We have studied potential effects of the ISO spacecraft orbital radiation environment on the transmission of infrared interference filters and filter materials. To simulate the critical proton radiation within the earth radiation belts and its influence on the materials at cryogenic temperatures the samples were cooled to LHe temperature and subjected to an Am-241 (alpha) -radiation source (approximately 4.1 MeV) mounted inside a cryostat. The dose per hour absorbed in a 20 micron thick layer, the mean penetration depth for the (alpha) particles, was about 25 krad (Si). The substrates Ge, ZnSe, and CaF2 and three tested ISOPHOT interference bandpass filters (3.21-3.37 micrometers and 2-50 micrometers even after a total dose of approximately 0.5 Mrad (Si), which is more than 100 times the expected total dose for ISOPHOT. The multilayer interference blocking coating on sapphire used on all ISOPHOT far infrared filters to block the wavelength range 1.7-6.7 micrometers showed no degeneration either. The organic far infrared antireflex coating materials polyethylene deposited on a quartz substrate, and a 15 micrometers thick parylene foil used as field lens coating, were investigated in the wavelength range of 16-300 micrometers . Our data suggests a slightly reduced transmission < 6% after 350 krad (Si) exposure.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Alpha-radiation tests on the transmission of cryogenically cooled infrared filter materials used in ISOPHOT

Cost and schedule risks in space projects can be minimized by applying technical concepts successfully flown previously to the subsequent missions. Examples from the development of three cold infrared instruments are discussed: ISOPHOT on ISO, PACS on HERSCHEL and MIRI on JWST. The progress achieved over two decades in the development of opto-mechanical elements like cold focal plane chopper and cold filter wheels will be demonstrated. While the instruments became larger and more complex, eventually the development consortia grew up to 20 institutes involved per instrument, requiring increasing resources for interface handling and coordination activities.

Dietrich Lemke

Papers

Focal Plane Arrays For The Isophot Experiment

Detectors and arrays of ISO's photopolarimeter

Focal plane chopper for the PACS instrument aboard the far-infrared space telescope FIRST

Alpha-radiation tests on the transmission of cryogenically cooled infrared filter materials used in ISOPHOT

Lessons learnt and implemented: from ISO- to HERSCHEL- and JWST-instrumentation