Olivier Boulade

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

The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESAs 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.

MegaCam: the new Canada-France-Hawaii Telescope wide-field imaging camera

MegaCam is an imaging camera with a 1 square degree field of view for the new prime focus of the 3.6 meter Canada-France-Hawaii Telescope. This instrument will mainly be used for large deep surveys ranging from a few to several thousands of square degrees in sky coverage and from 24 to 28.5 in magnitude. The camera is built around a CCD mosaic approximately 30 cm square, made of 40 large thinned CCD devices for a total of 20 K x 18 K pixels. It uses a custom CCD controller, a closed cycle cryocooler based on a pulse tube, a 1 m diameter half-disk as a shutter, a juke-box for the selection of the filters, and programmable logic controllers and fieldbus network to control the different subsystems. The instrument was delivered to the observatory on June 10, 2002 and first light is scheduled in early October 2002.

DUNE: the Dark Universe Explorer

Understanding the nature of Dark Matter and Dark Energy is one of the most pressing issues in cosmology and fundamental physics. The purpose of the DUNE (Dark UNiverse Explorer) mission is to study these two cosmological components with high precision, using a space-based weak lensing survey as its primary science driver. Weak lensing provides a measure of the distribution of dark matter in the universe and of the impact of dark energy on the growth of structures. DUNE will also include a complementary supernovae survey to measure the expansion history of the universe, thus giving independent additional constraints on dark energy. The baseline concept consists of a 1.2m telescope with a 0.5 square degree optical CCD camera. It is designed to be fast with reduced risks and costs, and to take advantage of the synergy between ground-based and space observations. Stringent requirements for weak lensing systematics were shown to be achievable with the baseline concept. This will allow DUNE to place strong constraints on cosmological parameters, including the equation of state parameter of the dark energy and its evolution from redshift 0 to 1. DUNE is the subject of an ongoing study led by the French Space Agency (CNES), and is being proposed for ESAs Cosmic Vision programme.

The Herschel/PACS 2560 bolometers imaging camera

The development program of the flight model imaging camera for the PACS instrument on-board the Herschel spacecraft is nearing completion. This camera has two channels covering the 60 to 210 microns wavelength range. The focal plane of the short wavelength channel is made of a mosaic of 2×4 3-sides buttable bolometer arrays (16×16 pixels each) for a total of 2048 pixels, while the long wavelength channel has a mosaic of 2 of the same bolometer arrays for a total of 512 pixels. The 10 arrays have been fabricated, individually tested and integrated in the photometer. They represent the first filled arrays of fully collectively built bolometers with a cold multiplexed readout, allowing for a properly sampled coverage of the full instrument field of view. The camera has been fully characterized and the ground calibration campaign will take place after its delivery to the PACS consortium in mid 2006. The bolometers, working at a temperature of 300 mK, have a NEP close to the BLIP limit and an optical bandwidth of 4 to 5 Hz that will permit the mapping of large sky areas. This paper briefly presents the concept and technology of the detectors as well as the cryocooler and the warm electronics. Then we focus on the performances of the integrated focal planes (responsivity, NEP, low frequency noise, bandwidth).

Submillimeter bolometers arrays for the PACS/Herschel spectro-photometer

Since 1997, CEA/SAP and CEA/LETI/SLIR have been developing monolithic Si bolometer arrays sensitive in the far infrared and submillimiter range for space observations. Two focal planes, 32x64 and 16x32 pixel arrays, are designed and manufactured for the PACS (Photodetector Array Camera and Spectrometer) instrument of the Herschel observatory, to be launched in 2007. The two arrays cover respectively the 60-130 μm and 130-210 μm ranges. The goal of these large bolometer arrays is to achieve observations in a Background limited NEP around 10-16 W.Hz-1/2. The detector physics and manufacture techniques of the different stages of these arrays are first presented. Then we describe the read-out and multiplexing cold electronics (300mK) that make possible several functional modes (temporal and fixed pattern noise reduction,...). The latest experimental measurements carried out with the complete detector system at the nominal temperature are presented and performances are discussed.

Development of MegaCam, the next-generation wide-field imaging camera for the 3.6-m Canada-France-Hawaii Telescope

MegaCam is the new wide-field imaging camera currently being built for the new prime focus of the 3.6m Canada-France- Hawaii Telescope. The camera will offer a 1 square degree field of view and is built around a mosaic of 40 2K by 4.5K CCD devices. The delivery of the CCDs is proceeding along the schedule, the project passe dits final design review and the realization phase started, for an expected delivery to CFHT in Summer 2001.

The Euclid VIS CCD detector design, development, and programme status

The focal plane array of the Euclid VIS instrument comprises 36 large area, back-illuminated, red-enhanced CCD detectors (designated CCD 273). These CCDs were specified by the Euclid VIS instrument team in close collaboration with ESA and e2v technologies. Prototypes were fabricated and tested through an ESA pre-development activity and the contract to qualify and manufacture flight CCDs is now underway. This paper describes the CCD requirements, the design (and design drivers) for the CCD and package, the current status of the CCD production programme and a summary of key performance measurements.

Ultralow dark current CdHgTe FPAs in the SWIR range at CEA and Sofradir

We report here first results carried out at CEA and Sofradir to build ultra low dark current focal plane arrays (FPA) in the short wave infrared range (SWIR) for space applications. Those FPAs are dedicated to very low flux detection in the 2μm wavelength range. In this purpose, Sofradir has designed a source follower per detector readout circuit (ROIC), 384x288, 15μm pitch. This ROIC has been hybridized on different HgCdTe diode configurations processed at CEA-LETI and low flux characterisations have been carried out at CEA-SAp at low temperature (from 60 to 160K). Both ion implanted p/n and n/p diodes have been evaluated. The metallurgical nature of the absorbing layer is also examined and both molecular beam epitaxy (MBE) and liquid phase epitaxy (LPE) have been processed. Dark current measurements are discussed in comparison with previous results from the literature. State of the art dark currents are recorded for temperatures higher than 120K. At temperatures lower than 100K, the decrease in dark current saturates for both technologies. In this regime, currents between 0.4 and 0.06 e/s/pixel are reported.

Status of the mid-infrared E-ELT imager and spectrograph METIS

METIS is one the first three instruments on the E-ELT. Apart from diffraction limited imaging, METIS will provide coronagraphy and medium resolution slit spectroscopy over the 3 – 19μm range, as well as high resolution (R ~ 100,000) integral field spectroscopy from 2.9 – 5.3μm, including a mode with extended instantaneous wavelength coverage. The unique combination of these observing capabilities, makes METIS the ideal instrument for the study of circumstellar disks and exoplanets, among many other science areas. In this paper we provide an update of the relevant science drivers, the METIS observing modes, the status of the simulator and the data analysis. We discuss the preliminary design of the optical system, which is driven by the need to calibrate observations at thermal IR wavelengths on a six-mirror ELT. We present the expected adaptive optics performance and the measures taken to enable high contrast imaging. We describe the opto-mechanical system, the location of METIS on the Nasmyth instrument platform, and conclude with an update on critical subsystem components, such as the immersed grating and the focal plane detectors. In summary, the work on METIS has taken off well and is on track for first light in 2025.

Megacam: the next-generation wide-field imaging camera for CFHT

MEGACAM is the next generation wide-field camera to be used at the prime focus of the 3.6 m CFHT telescope. This instrument, which will cover a full 1 square degree, is designed around a mosaic of 36 to 40 2K X 4K CCDs. such a large detector requires new approaches for the hardware as well as the software, and will have major impacts on the telescope structure, optics and operations. We present in this paper several novel ideas and techniques that will be implemented as part of this challenging project.