| 1. |
- Griffin, M. J., et al.
(författare)
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The Herschel-SPIRE instrument and its in-flight performance
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518, s. L3-
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Tidskriftsartikel (refereegranskat)abstract
- 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 0.3 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 2.6'. The spectral resolution can be adjusted between 1.2 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 1.5-2.
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| 2. |
- Greaves, J. S., et al.
(författare)
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Extreme Conditions in a Close Analog to the Young Solar System: Herschel Observations of ∈ Eridani
- 2014
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 791:1
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Tidskriftsartikel (refereegranskat)abstract
- Far-infrared Herschel images of the is an element of Eridani system, seen at a fifth of the Sun's present age, resolve two belts of debris emission. Fits to the 160 mu m PACS image yield radial spans for these belts of 12-16 and 54-68 AU. The south end of the outer belt is approximate to 10% brighter than the north end in the PACS+SPIRE images at 160, 250, and 350 mu m, indicating a pericenter glow attributable to a planet "c" From this asymmetry and an upper bound on the offset of the belt center, this second planet should be mildly eccentric (e(c) approximate to 0.03-0.3). Compared to the asteroid and Kuiper Belts of the young Sun, the is an element of Eri belts are intermediate in brightness and more similar to each other, with up to 20 km sized collisional fragments in the inner belt totaling approximate to 5% of an Earth mass. This reservoir may feed the hot dust close to the star and could send many impactors through the Habitable Zone, especially if it is being perturbed by the suspected planet is an element of Eri b, at semi-major axis approximate to 3 AU.
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| 3. |
- Greaves, J. S., et al.
(författare)
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EXTREME CONDITIONS IN A CLOSE ANALOG TO THE YOUNG SOLAR SYSTEM : HERSCHEL OBSERVATIONS OF is an element of ERIDANI
- 2014
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 791:1, s. L11-
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Tidskriftsartikel (refereegranskat)abstract
- Far-infrared Herschel images of the is an element of Eridani system, seen at a fifth of the Sun's present age, resolve two belts of debris emission. Fits to the 160 mu m PACS image yield radial spans for these belts of 12-16 and 54-68 AU. The south end of the outer belt is approximate to 10% brighter than the north end in the PACS+SPIRE images at 160, 250, and 350 mu m, indicating a pericenter glow attributable to a planet c From this asymmetry and an upper bound on the offset of the belt center, this second planet should be mildly eccentric (e(c) approximate to 0.03-0.3). Compared to the asteroid and Kuiper Belts of the young Sun, the is an element of Eri belts are intermediate in brightness and more similar to each other, with up to 20 km sized collisional fragments in the inner belt totaling approximate to 5% of an Earth mass. This reservoir may feed the hot dust close to the star and could send many impactors through the Habitable Zone, especially if it is being perturbed by the suspected planet is an element of Eri b, at semi-major axis approximate to 3 AU.
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| 4. |
- Muller, T., et al.
(författare)
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Herschel celestial calibration sources
- 2014
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 37:2, s. 253-330
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Tidskriftsartikel (refereegranskat)abstract
- Celestial standards play a major role in observational astrophysics. They are needed to characterise the performance of instruments and are paramount for photometric calibration. During the Herschel Calibration Asteroid Preparatory Programme approximately 50 asteroids have been established as far-IR/sub-mm/mm calibrators for Herschel. The selected asteroids fill the flux gap between the sub-mm/mm calibrators Mars, Uranus and Neptune, and the mid-IR bright calibration stars. All three Herschel instruments observed asteroids for various calibration purposes, including pointing tests, absolute flux calibration, relative spectral response function, observing mode validation, and cross-calibration aspects. Here we present newly established models for the four large and well characterized main-belt asteroids (1) Ceres, (2) Pallas, (4) Vesta, and (21) Lutetia which can be considered as new prime flux calibrators. The relevant object-specific properties (size, shape, spin-properties, albedo, thermal properties) are well established. The seasonal (distance to Sun, distance to observer, phase angle, aspect angle) and daily variations (rotation) are included in a new thermophysical model setup for these targets. The thermophysical model predictions agree within 5 % with the available (and independently calibrated) Herschel measurements. The four objects cover the flux regime from just below 1,000 Jy (Ceres at mid-IR N-/Q-band) down to fluxes below 0.1 Jy (Lutetia at the longest wavelengths). Based on the comparison with PACS, SPIRE and HIFI measurements and pre-Herschel experience, the validity of these new prime calibrators ranges from mid-infrared to about 700 mu m, connecting nicely the absolute stellar reference system in the mid-IR with the planet-based calibration at sub-mm/mm wavelengths.
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