ESA Science & Technology - Publication Archive

The James Webb Space Telescope (JWST; Gardner et al. 2006) will be a large, cold, infrared- optimized space telescope designed to enable fundamental breakthroughs in our understanding of the formation and evolution of galaxies, stars, and planetary systems (see Astro 2010 white papers by Gardner et al., Stiavelli et al., Meixner et al., G. Rieke et al., & Sonneborn et al.). In the current white paper, we describe the great potential of JWST in the theme of Galaxy Assembly.

The study of transiting exoplanets has provided most of the key data to date on the properties of exoplanets, such as direct estimates of their mass and radius (e.g.Charbonneau 2007), and spectral diagnostics of their atmospheres (e.g. Swain et al. 2008). The Hubble Space Telescope (HST) and Spitzer Space Telescope (SST) have both played lead roles in making the demanding, high S/N observations of light curves, and spectra of transiting exoplanets. Ground-based surveys have so far provided the candidate targets for space-based characterization studies. The study of transiting exoplanets requires the extraction of a differential signal from high S/N observations so the James Webb Space Telescope (JWST), by virtue of its 25 m² collecting area (~50x SST), will open up a new discovery space for transiting exoplanet science. Specifically, it will enable the characterization of intermediate and low mass exoplanets. The goal of this white paper is to provide an informational briefing for the panel on the expected capabilities of JWST for observations of exoplanet transits, in particular the characterization of transiting lower mass planets (d M_Nep).

Before addressing how JWST can detect "First Light" we need to define what we mean by such term. First light is the appearance of the first stars (Population III) or mini-AGNs in the Universe. JWST is incapable of detecting individual Population III stars directly but could detected them as SNae, thought to be ultra-bright pair instability SNae or, even, Gamma Ray Bursts. The recent detection of the superluminous SN2006gy of absolute magnitude -22 (Smith et al. 2007, astro-ph/0612617) and detectable to z=20 and beyond highlights the appeal of this approach as a very effective way to identify the location of very high-z objects.

The aim of this paper is to outline the expected JWST performance in addressing first light and reionization science questions that are found to be of interest today. These are some of the most challenging and interesting questions in modern astronomy, and are key drivers for the design of the JWST. Nevertheless, because these early epochs are difficult to observe, even JWST is unlikely to provide complete answers.

The Hubble Space Telescope (HST) has contributed significantly to studies of dark energy. It was used to find the first evidence of deceleration at z=1.8 (Riess et al. 2001) through the serendipitous discovery of a type 1a supernova (SNIa) in the Hubble Deep Field. The discovery of deceleration at z>1 was confirmation that the apparent acceleration at low redshift (Riess et al. 1998; Perlmutter et al. 1999) was due to dark energy rather than observational or astrophysical effects such as systematic errors, evolution in the SNIa population or intergalactic dust. The GOODS project and associated follow-up discovered 21 SNIa, expanding on this result (Riess et al. 2007). HST has also been used to constrain cosmological parameters and dark energy through weak lensing measurements in the COSMOS survey (Massey et al 2007; Schrabback et al 2009) and strong gravitational lensing with measured time delays (Suyu et al 2010).

The James Webb Space Telescope (Gardner et al. 2006} will have the capability to make significant, early progress in extrasolar planet studies. The JWST instrument complement features several coronagraphs that will be able to conduct programs imaging debris disks, and conduct searches to directly detect gas giant exoplanets.

A report to NASA recommending addition or optimization of the James Webb Space Telescope capabilities to maximize astrobiology science return.

JWST has many 'nascent capabilities' that could be developed to optimize their value for astrobiology at little cost or detriment to other JWST science. Here we summarize recommendations to the JWST project to ensure a wide variety of key astrobiological contributions.

This document will be used as an input to the new call for ideas for the Cosmic Vision programme. The objective is to make a survey of potential interplanetary transfers between the Earth and the outer planets Saturn, Uranus and Neptune for the timeframe 2025-2035. The main mission is probe release, either simple to the target planet, or double if it is possible in terms of mass. Two launchers have been contemplated: Soyuz-Fregat and Ariane 5 ECA, both launched from Kourou. A first step in the analysis has been to find all potential transfers following well known and efficient sequences. The second step carried out was to filter out the huge amount of solutions by applying a system margin approach. This approach allowed to conclude whether or not a specific mission (simple vs double) with a specific launcher and target planet was feasible.

The International X-ray Observatory (IXO) is a candidate mission in the ESA Space Science Programme Cosmic Visions 1525.

IXO is being studied as a joint mission with NASA and JAXA. The mission is building on novel optics technologies to achieve the required performance for this demanding astrophysics observatory. The European X-ray optics technology baseline is the Silicon Pore optics (SPO), which is being developed by an industrial consortium. In a phased approach the performance, environmental compatibility and industrial production aspects are being addressed. As a back-up technology ESA is also investigating slumped glass optics, which forms the baseline for the NASA approach.

The paper, which was presented at the SPIE Astronomical Telescopes and Instrumentation 2010, presents a summary of the ESA-led optics technology preparation activities and the associated roadmap.

The International X-ray Observatory (IXO) is an L class mission candidate within the science programme Cosmic Vision 2015-2025 of the European Space Agency, with a planned launch by 2020. IXO is an international cooperative project, pursued by ESA, JAXA and NASA. By allowing astrophysical observations between 100 eV and 40 keV, IXO would represent the new generation X-ray observatory, following the XMM-Newton, Astro-H and Chandra heritage. The IXO mission concept is based on a single aperture telescope with an external diameter of about 3.5 m, a focal length of 20 m and a number of focal plane instruments, positioned at the focal point via a movable platform. A grating spectrometer, enabling parallel measurements, is also included in the model payload. Two parallel competitive industrial assessment studies are being carried out by ESA on the overall IXO mission, while the instruments are being studied by dedicated instrument consortia. The main results achieved during this study are summarised in this paper which was presented at the SPIE Astronomical Telescopes and Instrumentation 2010 conference.

The International X-ray Observatory (IXO) is an L class mission candidate within the science Programme Cosmic Vision 2015-2025 of the European Space Agency, with a planned launch by 2020. IXO is an international cooperative project, pursued by ESA, JAXA and NASA. By allowing astrophysical observations between 100 eV and 40 keV using a very large effective collecting area mirror and state-of-the art instruments, IXO would represent the new generation X-ray observatory, following the XMM-Newton, Astro-H and Chandra heritage.

This paper was presented at the SPIE conference on Astronomical Instrumentation 2010 conference.

The first flyby of an asteroid by a European spacecraft was a major success, both from the scientific and engineering points of view. This was the first planned scientific objective of ESA's Rosetta mission, and the optical navigation campaign, performed for the first time in Europe, gave results well beyond expectations.

Gaia is ESA's global space astrometry mission, designed to map one thousand million stars and hundreds of thousands of other celestial objects in our galaxy, so its camera will have to be something truly special.

In this first paper on the results of our Herschel PACS survey of local ultra luminous infrared galaxies (ULIRGs), as part of our SHINING survey of local galaxies, we present far-infrared spectroscopy of Mrk 231, the most luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the first time in a ULIRG, all observed far-infrared fine-structure lines in the PACS range were detected and all were found to be deficient relative to the far infrared luminosity by 1-2 orders of magnitude compared with lower luminosity galaxies. The deficits are similar to those for the mid-infrared lines, with the most deficient lines showing high ionization potentials. Aged starbursts may account for part of the deficits, but partial covering of the highest excitation AGN powered regions may explain the remaining line deficits. A massive molecular outflow, discovered in OH and ¹⁸OH, showing outflow velocities out to at least 1400 km s^-1, is a unique signature of the clearing out of the molecular disk that formed by dissipative collapse during the merger. The outflow is characterized by extremely high ratios of ¹⁸O/¹⁶O suggestive of interstellar medium processing by advanced starbursts.

Volume 518 of Astronomy & Astrophysics is a special feature devoted to the first science results obtained with Herschel, an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. It includes 152 articles dealing with various subjects based on the first few months of science observing. A few papers describe the observatory and its instruments, and the rest are dedicated to observations of many astronomical targets from bodies in the Solar System to distant galaxies.

Aims. This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009.

Methods. The instrument is a set of 7 heterodyne receivers that are electronically tuneable, covering 480-1250 GHz with SIS mixers and the 1410-1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s^-1.

Results. After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations.

SPIRE, the Spectral and Photometric Imaging REceiver, is the Herschel Space Observatory's submillimetre camera and spectrometer. It contains a three-band imaging photometer operating at 250, 350 and 500 mm, and an imaging Fourier-transform spectrometer (FTS) covering 194-671 mm (447-1550 GHz).

In this paper we describe the initial approach taken to the absolute calibration of the SPIRE instrument using a combination of the emission from the Herschel telescope itself and the modelled continuum emission from solar system objects and other astronomical targets. We present the photometric, spectroscopic and spatial accuracy that is obtainable in data processed through the "standard" pipelines.

The overall photometric accuracy at this stage of the mission is estimated as 15% for the photometer and between 15 and 50% for the spectrometer. However, there remain issues with the photometric accuracy of the spectra of low flux sources in the longest wavelength part of the SPIRE spectrometer band.

The spectrometer wavelength accuracy is determined to be better than 1/10th of the line FWHM. The astrometric accuracy in SPIRE maps is found to be 2 arcsec when the latest calibration data are used.

The photometric calibration of the SPIRE instrument is currently determined by a combination of uncertainties in the model spectra of the astronomical standards and the data processing methods employed for map and spectrum calibration.

Improvements in processing techniques and a better understanding of the instrument performance will lead to the final calibration accuracy of SPIRE being determined only by uncertainties in the models of astronomical standards.

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 mm, and an imaging Fourier-transform spectrometer (FTS) which covers simultaneously its whole operating range of 194-671 mm (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'× 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.

The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre 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 photometry in the 60-210 mm wavelength regime.

In photometry mode, it simultaneously images two bands, 60-85 mm or 85-125 mm and 125-210 mm, over a field of view of ~1.75'× 3.5', with close to Nyquist beam sampling in each band.

In spectroscopy mode, it images a field of 47" × 47", resolved into 5×5 pixels, with an instantaneous spectral coverage of ~1500 kms^-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.

Herschel was launched on 14 May 2009, and is now an operational ESA space observatory offering unprecedented observational capabilities in the far-infrared and submillimetre spectral range 55-671 mm. Herschel carries a 3.5 m 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 h 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.