R. Cole

VIS: the visible imager for Euclid

Euclid-VIS is the large format visible imager for the ESA Euclid space mission in their Cosmic Vision program, scheduled for launch in 2020. Together with the near infrared imaging within the NISP instrument, it forms the basis of the weak lensing measurements of Euclid. VIS will image in a single r+i+z band from 550-900 nm over a field of view of ~0.5 deg2. By combining 4 exposures with a total of 2260 sec, VIS will reach to deeper than mAB=24.5 (10σ) for sources with extent ~0.3 arcsec. The image sampling is 0.1 arcsec. VIS will provide deep imaging with a tightly controlled and stable point spread function (PSF) over a wide survey area of 15000 deg2 to measure the cosmic shear from nearly 1.5 billion galaxies to high levels of accuracy, from which the cosmological parameters will be measured. In addition, VIS will also provide a legacy dataset with an unprecedented combination of spatial resolution, depth and area covering most of the extra-Galactic sky. Here we will present the results of the study carried out by the Euclid Consortium during the period up to the Critical Design Review.

Euclid: ESA's mission to map the geometry of the dark universe

Euclid is a space-borne survey mission developed and operated by ESA. It is designed to understand the origin of the Universes accelerating expansion. Euclid will use cosmological probes to investigate the nature of dark energy, dark matter and gravity by tracking their observational signatures on the geometry of the Universe and on the history of structure formation. The mission is optimised for the measurement of two independent cosmological probes: weak gravitational lensing and galaxy clustering. The payload consists of a 1.2 m Korsch telescope designed to provide a large field of view. The light is directed to two instruments provided by the Euclid Consortium: a visual imager (VIS) and a near-infrared spectrometer-photometer (NISP). Both instruments cover a large common field of view of 0.54 deg2, to be able to survey at least 15,000 deg2 for a nominal mission of 6 years. An overview of the mission will be presented: the scientific objectives, payload, satellite, and science operations. We report on the status of the Euclid mission with a foreseen launch in 2019.

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.

NOMAD spectrometer on the ExoMars trace gas orbiter mission: part 2-design, manufacturing, and testing of the ultraviolet and visible channel

NOMAD is a spectrometer suite on board the ESA/Roscosmos ExoMars Trace Gas Orbiter, which launched in March 2016. NOMAD consists of two infrared channels and one ultraviolet and visible channel, allowing the instrument to perform observations quasi-constantly, by taking nadir measurements at the day- and night-side, and during solar occultations. Here, in part 2 of a linked study, we describe the design, manufacturing, and testing of the ultraviolet and visible spectrometer channel called UVIS. We focus upon the optical design and working principle where two telescopes are coupled to a single grating spectrometer using a selector mechanism.

The Command and Data processing Unit of the Euclid Visible Imager: impact of the data compression needs on the unit design

The Command and Data Processing Unit (CDPU) of the Euclid Visible Imager is one of the two warm electronics units of the instrument. It implements on one side the digital interface to the satellite, for telecommands acquisition and telemetry downloading, and on the other side the interface to the focal plane CCDs readout electronics, for science data acquisition and compression. The CDPU main functionalities include the instrument commanding, control and health monitoring. The baseline unit architecture is presented, reporting the results of the phase B1 study and of the trade-off activity carried out to check the performances of the SW implementation of two different lossless compression algorithms on the baseline target processor (LEON3-FT) and on a HW compressor.

Wavelength calibration of the JWST near-infrared spectrograph (NIRSpec)

The Near Infrared Spectrograph (NIRSpec) is one of four science instruments aboard the James Webb Space Telescope (JWST) that is to be launched later this decade. NIRSpec is sensitive in the wavelength range from 0.6 to 5.0 μm and operates at temperatures ≤ 40 K. It offers multi-object, fixed slit, and integral field spectroscopy with seven selectable dispersers. The on-ground spectrophotometric calibration of the instrument is performed by means of continuum and line emission lamps. NIRSpec also contains an internal calibration assembly (CAA) that will provide the wavelength and radiometric calibration in orbit. Due to thermal constraints, the CAA features low power tungsten filament lamps in combination with long-pass and Fabry-Perot-like interference filters, which need to be calibrated at instrument level. We will report on the wavelength calibration of the NIRSpec flight model and the CAA, carried out during the first cryogenic performance testing.

Homotopia, or, Reading Sagas on an Industrial Estate

ABSTRACT What are the psychological forces that imbue certain spaces with emotional power? Michel Foucault described one such space as “heterotopia.” Heterotopias are places of extreme color and diversity, where the magical coming-together of usually contradictory forces exerted profound influence on people’s emotions. This article presents spaces in Old Norse literature where it is not difference and strangeness that have dramatic impact, but rather sameness and familiarity. The term “homotopia” is proposed to describe such spaces. Scenes depicting two particular farmsteads from the sagas, Helgafell and Hlíðarendi, are considered as homotopias. Moreover, with reference to Karl Marx’s theory of labor alienation, it is argued that homotopias have the potential to serve as political propaganda, convincing workers that their workplaces are not sites of exploitation, but are instead objects of aesthetic enjoyment. With this political purpose in mind, literary artifacts from the Old Norse-speaking world are integrated into an intellectual genealogy arriving at the present day. In closing it is therefore suggested that some of the homotopias of the Íslendingasögur provide parallels with the homotopian industrial estates and strip malls of late capitalism.

Thermomechanical architecture of the VIS focal plane for Euclid

One of the main challenges for current and near future space experiments is the increase of focal plane complexity in terms of amount of pixels. In the frame work of the ESA Euclid mission to be launched in 2020, the Euclid Consortium is developing an extremely large and stable focal plane for the VIS instrument. CEA has developed the thermomechanical architecture of that Focal Plane taking into account all the very stringent performance and mission related requirements. The VIS Focal Plane Assembly integrates 36 CCDs (operated at 150K) connected to their front end electronics (operated at 280K) as to obtain one of the largest focal plane (∼0.6 billion pixels) ever built for space application after the GAIA one. The CCDs are CCD273 type specially designed and provided by the e2v company under ESA contract, front end electronics is studied and provided by MSSL. In this paper we first recall the specific requirements that have driven the overall architecture of the VIS-FPA and especially the solutions proposed to cope with the scientific needs of an extremely stable focal plane, both mechanically and thermally. The mechanical structure based on SiC material used for the cold sub assembly supporting the CCDs is detailed. We describe also the modular architecture concept that we have selected taking into account AIT-AIV and programmatic constraints.

Optical telescope BIRT in ORIGIN for gamma ray burst observing

The ORIGIN concept is a space mission with a gamma ray, an X-ray and an optical telescope to observe the gamma ray bursts at large Z to determine the composition and density of the intergalactic matter in the line of sight. It was an answer to the ESA M3 call for proposal. The optical telescope is a 0.7-m F/1 with a very small instrument box containing 3 instruments: a slitless spectrograph with a resolution of 20, a multi-imager giving images of a field in 4 bands simultaneously, and a cross-dispersed Échelle spectrograph giving a resolution of 1000. The wavelength range is 0.5 μm to 1.7 μm. All instruments fit together in a box of 80 mm x 80 mm x 200 mm. The low resolution spectrograph uses a very compact design including a special triplet. It contains only spherical surfaces except for one tilted cylindrical surface to disperse the light. To reduce the need for a high precision pointing, an Advanced Image Slicer was added in front of the high resolution spectrograph. This spectrograph uses a simple design with only one mirror for the collimator and another for the camera. The Imager contains dichroics to separate the bandwidths and glass thicknesses to compensate the differences in path length. All 3 instruments use the same 2k x 2k detector simultaneously so that telescope pointing and tip-tilt control of a fold mirror permit to place the gamma ray burst on the desired instrument without any other mechanism.

Optical ground support equipment for the alignment of JWST-NIRSpec

The alignment of the JWST NIRSpec spectrograph will use a customised set of optical light sources, imagers and wavefront sensors, which form part of the Optical Ground Support Equipment (OGSE). This has been developed by the Mullard Space Science Laboratory (MSSL) and the Centre for Advanced Instrumentation (CfAI) to be used at the Astrium GmbH, Ottobrunn (Germany) during NIRSpec integration. This paper describes the five precision illumination sources which form a key part of NIRSpec OGSE, and the optomechanical design of the three Shack-Hartmann wavefront sensors used.