The Euclid Imaging Channels Instrument of the Euclid mission is designed to study the weak gravitational lensing
cosmological probe. The combined Visible and Near Infrared imaging channels will be controlled by a common data
handling unit (PDHU), implementing onboard the instrument digital interfaces to the satellite. The PDHU main
functionalities include the scientific data acquisition and compression, the instrument commanding and control and the
instrument health monitoring. Given the high data rate and the compression needs, an innovative architecture, based on
the use of several computing and interface modules, considered as building blocks of a modular design will be presented.
The NIP is a near infrared imaging photometer that is currently under investigation for the Euclid space mission
in context of ESA's 2015 Cosmic Vision program. Together with the visible camera (VIS) it will form the basis of
the weak lensing measurements for Euclid. The NIP channel will perform photometric imaging in 3 near infrared
bands (Y, J, H) covering a wavelength range from ~ 0.9 to 2 μm over a field of view (FoV) of ~ 0.5 deg<sup>2</sup>. With
the required limiting point source magnitude of 24 mAB (5 sigma) the NIP channel will be used to determine
the photometric redshifts of over 2 billion galaxies collected over a wide survey area of 20 000 deg<sup>2</sup>. In addition
to the photometric measurements, the NIP channel will deliver unique near infrared (NIR) imaging data over
the entire extragalactic sky, enabling a wide variety of ancillary astrophysical and cosmological studies. In this
paper we will present the results of the study carried out by the Euclid Imaging Consortium (EIC) during the
Euclid assessment phase.
Euclid-VIS is a large format visible imager under investigation for the ESA Euclid space mission in their Cosmic Vision
program. Together with the near infrared photometer (NIP) it forms the basis of the weak lensing measurements of
Euclid. VIS will image in a single r+i+z band from 550-920 nm over a field of view of ~0.5 deg<sup>2</sup>. Over 4 exposures
totalling 1800 sec, VIS will reach to V=24.9 (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 PSF over a wide surcey area of of 20000 deg<sup>2</sup>
to measure the cosmic shear from over 2 billion galaxies to high levels of accuracy, from which the cosmological
parameters will be measured. In addition, VIS will also provide a legacy deep imaging dataset of unprecedented spatial
resolution over the entire extra-Galactic sky. Here we will present the results of the study carried out by the Euclid
Imaging Consortium during the Euclid Assessment Phase.
Euclid is an ESA Cosmic Vision wide-field space mission concept dedicated to the high-precision study of Dark Energy
and Dark Matter. The mission relies on two primary cosmological probes: Weak gravitational Lensing (WL) and Baryon
Acoustic Oscillations (BAO).
The first probe requires the measurement of the shape and photometric redshifts of distant galaxies. The second probe is
based on the 3-dimensional distribution of galaxies through spectroscopic redshifts. Additional cosmological probes are
also used and include cluster counts, redshift space distortions, the integrated Sachs-Wolfe effect (ISW) and galaxy
clustering, which can all be derived from a combination of imaging and spectroscopy.
Euclid Imaging Channels Instrument of the Euclid mission is designed to study the weak gravitational lensing
cosmological probe. The combined Visible and Near InfraRed imaging channels form the basis of the weak lensing
measurements. The VIS channel provides high-precision galaxy shape measurements for the measurement of weak
lensing shear. The NIP channel provides the deep NIR multi-band photometry necessary to derive the photometric
redshifts and thus a distance estimate for the lensed galaxies.
This paper describes the Imaging Channels design driver requirements to reach the challenging science goals and the
design that has been studied during the Cosmic Vision Assessment Phase.
We present a first design study of the shutter mechanism to be implemented on the visible channel of the
Euclid imager. The main functionality of the shutter is to obscure the light during the detector read-out and
flat field calibration. Hence, the major design drivers are the number of open/close cycles of 160,000 and the
opening/closing time of 5 sec without introducing a too large uncompensated momentum disturbance. The
current design foresees to use two fully redundant actuators, which drive the shutter via a lever system. In case
of an actuator failure, the blocked actuator can be disengaged via a fail-safe system.
DUNE (Dark Universe Explorer) is a proposed mission to measure parameters of dark energy using weak gravitational
lensing The particular challenges of both optical and infrared focal planes and the DUNE baseline solution is discussed.
The DUNE visible Focal Plane Array (VFP) consists of 36 large format red-sensitive CCDs, arranged in a 9x4 array
together with the associated mechanical support structure and electronics processing chains. Four additional CCDs
dedicated to attitude control measurements are located at the edge of the array. All CCDs are 4096 pixel red-enhanced
e2v CCD203-82 devices with square 12 μm pixels, operating from 550-920nm. Combining four rows of CCDs provides
a total exposure time of 1500s. The VFP will be used in a closed-loop system by the spacecraft, which operates in a drift
scan mode, in order to synchronize the scan and readout rates. The Near Infrared (NIR) FPA consists of a 5 x 12 mosaic
of 60 Hawaii 2RG detector arrays from Teledyne, NIR bandpass filters for the wavelength bands Y, J, and H, the
mechanical support structure, and the detector readout and signal processing electronics. The FPA is operated at a
maximum temperature of 140 K for low dark current of 0.02-/s. Each sensor chip assembly has 2048 x 2048 square
pixels of 18 μm size (0.15 arcsec), sensitive in the 0.8 to 1.7 μm wavelength range. As the spacecraft is scanning the sky,
the image motion on the NIR FPA is stabilized by a de-scanning mirror during the integration time of 300 s per detector.
The total integration time of 1500 seconds is split among the three NIR wavelengths bands. DUNE has been proposed to
ESA's Cosmic Vision program and has been jointly selected with SPACE for an ESA Assessment Phase which has led
to the joint <i>Euclid</i> mission concept.
The Dark UNiverse Explorer (DUNE) is a wide-field imaging mission concept whose primary goal is the study
of dark energy and dark matter with unprecedented precision. To this end, DUNE is optimised for weak gravitational
lensing, and also uses complementary cosmological probes, such as baryonic oscillations, the integrated
Sachs-Wolf effect, and cluster counts. Immediate additional goals concern the evolution of galaxies, to be studied
with groundbreaking statistics, the detailed structure of the Milky Way and nearby galaxies, and the demographics
of Earth-mass planets. DUNE is a medium class mission consisting of a 1.2m telescope designed to carry out
an all-sky survey in one visible and three NIR bands (1deg<sup>2</sup> field-of-view) which will form a unique legacy for
astronomy. DUNE has been selected jointly with SPACE for an ESA Assessment phase which has led to the
Euclid merged mission concept.
A feasibility study is presently led by CNES for the Dark UNiverse Explorer (DUNE), a space mission designed to
provide unprecedented constraints on dark matter and dark energy using weak gravitational lensing measurements over a
very large region of the sky (20 000 square degrees). To achieve this scientific goal, the instrument requires a stable 0.23
arc second FWHM PSF with very low ellipticity (6%) over a field of view of 0.55 square degree. To perform the survey
we adopted the drift scan mode which brings many advantages in this type of mission but adds the unusual requirement
of a zero distortion optical design. We will present the optical performances of a 1.2 meters Korsch three mirror
telescope concept (called NODI for NO DIstortion) where the third mirror works with an atypical large magnification
and a slightly curved focal surface to obtain zero distortion over an annular 1.7 degrees field of view. A mosaic of 64
CCD detectors of 8 Mega pixels each is shown to pave the curved focal surface without significant degradation of the
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 ESA's Cosmic Vision programme.
A well-adapted spectrograph concept has been developed for the SNAP (SuperNova/Acceleration Probe) experiment. The goal is to ensure proper identification of Type Iz supernovae and to standardize the magnitude of each candidate by determining explosion parameters. The spectrograph is also a key element for the calibration of the science mission. An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented in this paper. The spectrograph concept is optimized to have high efficiency and low spectral resolution (R~100), constant through the wavelength range (0.35-1.7μm), adapted to the scientific goals of the mission.
Mission requirements, the baseline design, and optical systems budgets for the SuperNova/Acceleration Probe (SNAP) telescope are presented. SNAP is a proposed space-based experiment designed to study dark energy and alternate explanations of the acceleration of the universe’s expansion by performing a series of complementary systematics-controlled astrophysical measurements. The goals of the mission are a Type Ia supernova Hubble diagram and a wide-field weak gravitational lensing survey. A 2m widefield three-mirror telescope feeds a focal plane consisting of 36 CCDs and 36 HgCdTe detectors and a high-efficiency, low resolution integral field spectrograph. Details of the maturing optical system, with emphasis on structural stability during terrestrial testing as well as expected environments during operations at L2 are discussed. The overall stray light mitigation system, including illuminated surfaces and visible objects are also presented.
We present the baseline telescope design for the telescope for the SuperNova/Acceleration Probe (SNAP) space mission. SNAP’s purpose is to determine expansion history of the Universe by measuring the redshifts, magnitudes, and spectral classifications of thousands of supernovae with unprecedented accuracy. Discovering and measuring these supernovae demand both a wide optical field and a high sensitivity throughout the visible and near IR wavebands. We have adopted the annular-field three-mirror anastigmat (TMA) telescope configuration, whose classical aberrations (including chromatic) are zero. We show a preliminary optmechanical design that includes important features for stray light control and on-orbit adjustment and alignment of the optics. We briefly discuss stray light and tolerance issues, and present a preliminary wavefront error budget for the SNAP Telescope. We conclude by describing some of the design tasks being carried out during the current SNAP research and development phase.
The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.
The SuperNova/Acceleration Probe (SNAP) will measure precisely the cosmological expansion history over both the acceleration and deceleration epochs and thereby constrain the nature of the dark energy that dominates our universe today. The SNAP focal plane contains equal areas of optical CCDs and NIR sensors and an integral field spectrograph. Having over 150 million pixels and a field-of-view of 0.34 square degrees, the SNAP NIR system will be the largest yet constructed. With sensitivity in the range 0.9-1.7 μm, it will detect Type Ia supernovae between z = 1 and 1.7 and will provide follow-up precision photometry for all supernovae. HgCdTe technology, with a cut-off tuned to 1.7 μm, will permit passive cooling at 140 K while maintaining noise below zodiacal levels. By dithering to remove the effects of intrapixel variations and by careful attention to other instrumental effects, we expect to control relative photometric accuracy below a few hundredths of a magnitude. Because SNAP continuously revisits the same fields we will be able to achieve outstanding statistical precision on the photometry of reference stars in these fields, allowing precise monitoring of our detectors. The capabilities of the NIR system for broadening the science reach of SNAP are discussed.
A well-adapted spectrograph concept has been developed for the SNAP (SuperNova/Acceleration Probe) experiment. The goal is to ensure proper identification of Type Ia supernovae and to standardize the magnitude of each candidate by determining explosion parameters. An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented in this paper. The spectrograph concept is optimized to have very high efficiency and low spectral resolution (R~100), constant through the wavelength range (0.35-1.7μm), adapted to the scientific goals of the mission.
The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square-degree field sensitive in the visible and near-infrared wavelength regime. We describe the requirements for the instrument suite and the evolution of the focal plane design to the present concept in which all the instrumentation -- visible and near-infrared imagers, spectrograph, and star guiders -- share one common focal plane.
The Supernova / Acceleration Probe (SNAP) is a proposed space-borne observatory that will survey the sky with a wide-field optical/near-infrared (NIR) imager. The images produced by SNAP will have an unprecedented combination of depth, solid-angle, angular resolution, and temporal sampling. For 16 months each, two 7.5 square-degree fields will be observed every four days to a magnitude depth of <i>AB</i>=27.7 in each of the SNAP filters, spanning 3500-17000Å. Co-adding images over all epochs will give <i>AB</i>=30.3 per filter. In addition, a 300 square-degree field will be surveyed to <i>AB</i>=28 per filter, with no repeated temporal sampling. Although the survey strategy is tailored for supernova and weak gravitational lensing observations, the resulting data will support a broad range of auxiliary science programs.
The SuperNova/Acceleration Probe (SNAP) mission will require a two-meter class telescope delivering diffraction limited images spanning a one degree field in the visible and near infrared wavelength regime. This requirement, equivalent to nearly one billion pixel resolution, places stringent demands on its optical system in terms of field flatness, image quality, and freedom from chromatic aberration. We discuss the advantages of annular-field three-mirror anastigmat (TMA) telescopes for applications such as SNAP, and describe the features of the specific optical configuration that we have baselined for the SNAP mission. We discuss the mechanical design and choice of materials for the telescope. Then we present detailed ray traces and diffraction calculations for our baseline optical design. We briefly discuss stray light and tolerance issues, and present a preliminary wavefront error budget for the SNAP Telescope. We conclude by describing some of tasks to be carried out during the upcoming SNAP research and development phase.
The SuperNova / Acceleration Probe (SNAP) is a space-based experiment to measure the expansion history of the Universe and study both its dark energy and the dark matter. The experiment is motivated by the startling discovery that the expansion of the Universe is accelerating. A 0.7~square-degree imager comprised of 36 large format fully-depleted <i>n</i>-type CCD's sharing a focal plane with 36 HgCdTe detectors forms the heart of SNAP, allowing discovery and lightcurve measurements simultaneously for many supernovae. The imager and a high-efficiency low-resolution integral field spectrograph are coupled to a 2-m three mirror anastigmat wide-field telescope, which will be placed in a high-earth orbit. The SNAP mission can obtain high-signal-to-noise calibrated light-curves and spectra for over 2000 Type Ia supernovae at redshifts between z = 0.1 and 1.7. The resulting data set can not only determine the amount of dark energy with high precision, but test the nature of the dark energy by examining its equation of state. In particular, dark energy due to a cosmological constant can be differentiated from alternatives such as "quintessence", by measuring the dark energy's equation of state to an accuracy of ± 0.05, and by studying its time dependence.