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.

/pdf/herschel-space-observatory-an-esa-facility-for-far-infrared-3pdcouv7zo.pdf

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.

/pdf/the-photodetector-array-camera-and-spectrometer-pacs-on-the-16nlmaj1la.pdf

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

/pdf/the-herschel-spire-instrument-and-its-in-flight-performance-3wv4kydzfn.pdf

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

The imaging photopolarimeter ISOPHOT on-board the European satellite ISO houses 144 background detectors of Si:Ga, Si:P, Ge:Ga and stressed Ge:Ga, all sampled by newly developed cold read-out electronics. There is large temporal radiation damage to most of these detectors on the daily passage through the earth's radiation belts. In addition the Ge:Ga detectors exhibit a continuous responsivity increase caused by the cosmic radiation far off the earth. Effective curing procedure shave been developed to heat out these effects. The in-flight sensitivities achieved are close to the pre-flight predictions for most channels. At 100-200 micrometers cirrus confusion is a serious limit for the detection of faint objects on large parts of the sky. The cold filter wheel carrying 56 optical elements, such as filters, apertures and polarizers, as well as the focal plane chopper, operate with high precision and very low power consumption. Due to an effective cold internal baffle system the measured near-field straylight was close to the pre- flight theoretical prediction based on APART simulations. THe sun and moon straylight at 25 and 175 micrometers was measured during several solar eclipses. Drift and transients of the detectors, non-linearities of the preamplifiers, ionizing radiation effects and a complex optical path make the photometric calibration of this instrument challenging. Because most of these effects are reproducible, a calibration accuracy of < 30 percent is already available for most photometric modes. Examples of observations, including the 175 micrometers Serendipitous Sky Survey, will highlight the capabilities of the instrument.

ISOPHOT: in-flight performance report

Sub-threshold operated lead-salt lasers for calibration of IR-astronomy detectors

The ISOPHOT Serendipity Survey utilized the slew time between ISO’s pointedobserv ations with strip scanning measurements of the sky in the far-infrared at 170 μm. From the slew data with low (I100μm ≤ 15 MJy/sr) cirrus background, 115 well-observedsources with a high signal-to-noise ratio in all four detector pixels having a galaxy association were extracted. The integral 170 μm fluxes measured from the Serendipity slews have been put on an absolute flux level by using a number of calibrator sources observedwith ISOPHOT’s photometric mapping mode. 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 measuredFIR fluxes beyondthe IRAS 100 μm limit. The vast majority of the galaxies are morphologically classifiedas spirals. The large fraction of sources with a high F170μm/F100μm flux ratio indicates that a very cold (T < 20 K) dust component is present in many galaxies. The typical mass of the coldest dust component is MDust = 107.5±0.5 M⊙, a factor 2 – 10 larger than that derived from IRAS fluxes alone. As a consequence, the gas-to-dust ratios are much closer to the canonical value of ≈ 160 for the Milky Way. By relaxing the selection criteria, it is expectedthat the Serendipity survey will eventually leadto a catalogue of 170 μm fluxes for ≈ 1000 galaxies.

ISOPHOT 170 μm Serendipity Sky Survey: The First Galaxy Catalogue

We present results of a far-infrared molecular cloud mapping program which utilizes the PHT-P photometer and PHT-C cameras of the ISOPHOT instrument. ISO has enabled us to study the emission of very cold dust, Td < 15 K. The multi-wavelength observations between 3.6–200 μm allow to discern emission of different grain components, and to construct spectral energy distributions for embedded young stellar objects at far-IR wavelengths where their emission is at maximum. The extension up to 200 μm and the multi-filter coverage of the 60–200 μm wavelength range are essential improvements for study of physical properties of young stellar objects.

ISOPHOT Far-Infrared Survey of Nearby Molecular Clouds

We observed the reflection nebula NGC7023 at var- ious positions using wide and narrow band photometry centred on the 7.7 and 11.3 m PAH emission features and wide band photometry at 20 and 25 m. No significant variations have been detected over the nebula in the 7.3 and 20 m continuum relative to the total emission in the 6-15 m range (hereafter ). This result supports the hypothesis that most of the continuum emission in both bands come from very small grains. In contrast, the 7.7 and 11.3 m PAH emission features show clear variations. We find that in weaker radiation fields of the nebula the 11.3 and 7.7 m features are not the domi- nant emission components in the 6-15 m range. The 11.5 m band increases whereas the 11.3 m emission feature decreases relative to in the outer parts of the nebula. The effect can be explained by increased hydrogenation of PAH molecules.

http://aa.springer.de/papers/6315002/230l313.pdf

Dietrich Lemke

Papers

ISOPHOT: in-flight performance report

Sub-threshold operated lead-salt lasers for calibration of IR-astronomy detectors

ISOPHOT 170 μm Serendipity Sky Survey: The First Galaxy Catalogue

ISOPHOT Far-Infrared Survey of Nearby Molecular Clouds

Very small grain emission in NGC 7023