B. Horeau

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).

CEA Bolometer Arrays: the First Year in Space

The CEA/LETI and CEA/SAp started the development of far-infrared filled bolometer arrays for space applications over a decade ago. The unique design of these detectors makes possible the assembling of large focal planes comprising thousands of bolometers running at 300 mK with very low power dissipation. Ten arrays of 16x16 pixels were thoroughly tested on the ground, and integrated in the Herschel/PACS instrument before launch in May 2009. These detectors have been successfully commissioned and are now operating in their nominal environment at the second Lagrangian point of the Earth-Sun system. In this paper we briefly explain the functioning of CEA bolometer arrays, and we present the properties of the detectors focusing on their noise characteristics, the effect of cosmic rays on the signal, the repeatability of the measurements, and the stability of the system.

A study on the use of the PACS bolometer arrays for submillimeter ground-based telescopes

A new kind of bolometric architecture has been successfully developed for the PACS photometer onboard the Herschel submillimeter observatory. These new generation CCD-like arrays are buttable and enable the conception of large fully sampled focal planes. We present a feasibility study of the adaptation of these bolometer arrays to ground-based submillimeter telescopes. We have developed an electro-thermal numerical model to simulate the performances of the bolometers under specific ground-based conditions (different wavelengths and background powers for example). This simulation permits to determine the optimal parameters for each condition and shows that the bolometers can be background limited in each transmission window between 200 and 450 microns. We also present a new optical system that enables to have a maximum absorption of the bolometer in each atmospheric windows. The description of this system and measurements are shown.

Qualification model of the space ISGRI CdTe gamma-ray camera

Abstract A new generation of large area semiconductor based γ-ray camera for astrophysics space application has been developed through the γ-ray IBIS (Imager on Board INTEGRAL Satellite) telescope program, on board the ESA INTEGRAL satellite. This instrument features a coded-mask aperture imaging system, active and passive shields and two detector arrays. The first one (ISGRI : INTEGRAL Soft Gamma-Ray Imager) is made of 16384 CdTe detectors (4×4xa0mm large, 2xa0mm thick) operating at room temperature and will operate between 15xa0keV and 1xa0MeV. The second detector array (PICsIT : Pixelated CsI Telescope) is made of 4096 CsI scintillators (9.2×9.2xa0mm large, 30xa0mm high) coupled to silicon PIN photodiodes working between 150xa0keV and 10xa0MeV. IBIS combine broad band energy, spectroscopic capabilities and high spatial resolution imaging (12xa0arcmin) over a wide field of view (∼20°×20°, 50% sensitivity). A “flight-like” model of the detectors has been built, integrated and successfully tested. After a description of the IBIS imaging principle, we will report results obtained with the qualification model of the ISGRI camera.

A laboratory test setup to study the stability of operation of the CdTe detectors within Astro-H HXI

Astro-H1 is a JAXA/NASA X-ray satellite launched in 17th Feb. 2016. The hard X-ray imager (HXI)2 is a Si/CdTe stacked detector system which is placed in the focus of a hard x-ray telescope. HXI constitute one of the four different instruments onboard Astro-H. We are presenting the current status of a stacked detector setup which consists of two mini-HXI double sided CdTe strip detectors (CdTe DSDs)|similar to those used in HXI|that are read out with the low-noise readout ASIC IDeF-X BD. We describe the configuration of the setup, its spectroscopic performance, and a long-term operation of the setup. The long-term test simulates the orbital operation of HXI using identical detector temperatures, bias voltages, and switch-on/switch-off cycles with the goal to study the detector stability and the evolution of its performance during operation.

Impacts of the radiation environment at L2 on bolometers onboard the Herschel Space Observatory

We present the effects of cosmic rays on the detectors onboard the Herschel satellite. We describe in particular the glitches observed on the two types of cryogenic far-infrared bolometer inside the two instruments PACS and SPIRE. The glitch rates are also reported since the launch together with the SREM radiation monitors aboard Herschel and Planck spacecrafts. Both have been injected around the Lagrangian point L2 on May 2009. This allows probing the radiation environment around this orbit. The impacts on the observation are finally summarized.

The High Energy Detector of Simbol‐X

The High Energy Detector (HED) is one of the three detection units on board the Simbol‐X detector spacecraft. It is placed below the Low Energy Detector so as to collect focused photons in the energy range from 8 to 80 keV. It consists of a mosaic of 64 independent cameras, divided in 8 sectors. Each elementary detection unit, called Caliste, is the hybridization of a 256‐pixel Cadmium Telluride (CdTe) detector with full custom front‐end electronics into a unique component. The status of the HED design will be reported. The promising results obtained from the first micro‐camera prototypes called Caliste 64 and Caliste 256 will be presented to illustrate the expected performance of the instrument.

The Euclid STM VIS focal plane assembly metrology: description of the method to measure the CCDs position and the flatness of the full camera

In the frame work of the ESA Euclid mission to be launched in 2021, the Euclid Consortium is developing an extremely large and stable focal plane for the VIS instrument. After an extensive phase of definition and study over 4 years made at CEA on the thermo-mechanical architecture of that Focal Plane, the first model (Structural and Thermal Model) has been assembled qualified and delivered to MSSL in June 2017. The VIS Focal Plane Assembly integrates 36 CCDs (operated at 153K) connected to their front end electronics (operated at 280K). This Focal Plane will be the largest focal plane (∼0.6 billion pixels) ever built for space application after the GAIA one. The CCDs are CCD-273 type specially designed and provided by the Teledyne e2v company under ESA contract. The Structural and Thermal Model is fully representative of the Flight Model regarding the thermo-mechanical architecture. The STM FPA thus integrates 36 CCDs representative of the flight model except for the detection function. We have implemented specific equipment in order to perform the metrology of the full FPA. It consists of the measurement of the flatness of the full camera as well as the determination of the position of its 36 CCDs. The purpose is to measure the dimension of the sensitive area and to localize each CCDs’ image area with an uncertainty of +/-50 µm in X- and Y-directions. These positions are then given at room temperature in the reference frame of the main FPA structure that is interfaced with the Euclid telescope. The metrology also implies the verification of the flatness of the focal plane in the range of +/-60 μm with an uncertainty of +/-10 μm. Indeed, we must check that the design and the assembly of the FPA meet this requirement that consists of considering that the full photosensitive area is included in a volume of 120 μm high. Based on a marble with a flatness of 10 μm and two motorized linear stages, the test bench combines a CCD camera and a confocal sensor. The camera allows localizing the four fiducial crosses of each CCD-273 and thus to define a grid of 9 equally spaced points on the image area. We can then measure thanks to the confocal sensor the flatness of the full sensitive area in 324 points across the FPA. In this paper, we describe the test bench and the method that we have validated for the STM program. We thus report the results for the STM FPA5 with an estimation of the uncertainty of +/-10 µm for the flatness measurement and around +/- 24 μm (including a coverage factor of 2 for a level of confidence of 95%) for the relative position of the CCDs, which corresponds to twice the pixel size of the CCDs. We finally indicate the improvement that we plan to implement to better estimate the CCDs position in the FPA coordinates.