ELOIS: an innovative spectrometer design using a free-form grating

Clercq, C. De; Moreau, Vincent; Jamoye, Jean-François; Marchi, A. Zuccaro; Gloesener, P.

doi:10.1117/12.2191345

Cited by 14 publications

(20 citation statements)

References 7 publications

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“…Even more so when considering the fast speed at the focal plane (F#2.1), wide spectral range, and associated 52.2 mm long input slit. As shown in [1], reaching adequate imaging performances does not require strong freeformity of the grating substrate. Indeed, the deviation to the best fitting sphere encountered over the 40 mm diameter useful area of the ELOIS VISWIR grating is merely <10 μm PtV while the slope deviation remains below ~1 mrad.…”

Section: Broadband Freeform Diffraction Gratingmentioning

confidence: 99%

The challenges of broadband performances within a compact imaging spectrometer: the ELOIS solution

Borguet¹,

Moreau²,

Santandrea

et al. 2021

International Conference on Space Optics — ICSO 2020

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ELOIS VISWIR is a science-grade, smallsat compatible, pushbroom hyperspectral payload covering the entire VISWIR spectral range (400-2450 nm) with over 200 contiguous 10 nm wide spectral bands. Its unique all reflective optical design enables covering a 70 km swath with 35 m ground sampling distance (GSD), while guaranteeing high imaging performances across the full field of view.At the core of the instrument, the spectrometer formula expands upon AMOS' state of the art Offner-based ELOIS VNIR long-slit spectrometer [1], including key features such as built-in slit de-magnification, and the use of a fine-tuned freeform diffraction grating enabling the appropriate compensation of the optical aberrations affecting the fast, F/2.1 focal plane.Besides its excellent imaging performances and advanced control of distortions, the ELOIS VISWIR delivers unparalleled throughput in a single optical chain thanks to the inclusion of leading-edge technical solutions including a broadband multi-blazed freeform diffraction grating, a variable dichroic beam-splitter plate, and high efficiency order sorting filters. In this paper, we discuss these key ingredients in the optical design of the ELOIS VISWIR spectrometer and report the optical performances of the manufactured optical components.

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Section: Broadband Freeform Diffraction Gratingmentioning

confidence: 99%

The challenges of broadband performances within a compact imaging spectrometer: the ELOIS solution

Borguet¹,

Moreau²,

Santandrea

et al. 2021

International Conference on Space Optics — ICSO 2020

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“…Currently the development of the Qualification Model is ongoing. The non-exhaustive applications are in agriculture, forestry, environment and water monitoring, natural resources and disaster management and coastal monitoring 19,25 .…”

Section: Eloismentioning

confidence: 99%

Hyperspectral innovation on instruments and technologies at the European Space Agency

Strese¹,

Ribes-Pleguezuelo²,

Marchi³

et al. 2021

International Conference on Space Optics — ICSO 2020

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Emerging spaceborne hyperspectral technologies answer a growing need to comprehend the Earth and its atmosphere. These technologies constitute a reliable source of information about Earth's environment. The near real-time distribution of Earth Observation (EO) information can be a requirement for certain applications, such as early warning and disaster management systems.The last few decades have shown an increasing interest in hyperspectral observation data. This pushed the development of hyperspectral instrument technologies, also towards the miniaturization of instrument elements, taking advantage of electronics, new detector developments, material processes, hyperspectral filters, optical free-form design manufacturing and verification, on-board calibration techniques, on-board data processing and machine learning for image resolution enhancement. In parallel, the advent of smaller-size instruments, with lower development and operation costs is desirable to feed new data usage ideas and markets.ESA actively participates in the development of hyperspectral instruments, each to satisfy specific performance needs. Its participation spans from the shaping of a vision for an instrument, to the initiation of projects and missions, through the support of development activities, on to the instrument launch and subsequent tasks.The first hyperspectral instrument launched by ESA in 2001 was CHRIS, whose purpose was to improve knowledge on spectral reflectance from the Earth. Since then, the understanding of hyperspectral data and its significance has strongly risen and a sound heritage on hyperspectral instruments and applications exists by now. As for recent developments, a hyperspectral imaging mission study in the context of the Copernicus Expansion has been initiated and targets the realization of an instrument for routine observations in the visible-to-shortwave infrared range. In particular, it addresses the management of natural resources and enhances services for food security, sustainable agriculture and raw materials.The degree of innovation, compactness, overall technical challenge and user needs can constitute the starting constraint for each development objective. The evolving technologies enable compactness and a better instrument performance to expand the scope of its use. In order to give a comprehensible overview of the current hyperspectral imagers and technologies, opportunities and challenges, this communication sheds light on different instrument characteristics and design concepts in a categorized view and provides the current status of key technologies.

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“…For Earth Observation, the mission type is oriented towards the observation and characterization of Earth surfaces such as forests and agricultural lands with in mind the goal of improving food security, agriculture and land characterization. The observation of large Earth spatial elements requires a spatial resolution better than 30 m / 2 detector pixels; instruments such as CHIME 12 , a hyperspectral imager for the environment scheduled for the mid-2020, or ELOIS 13 , a free-form spectrometer for Earth observation, are looking for comparable spatial resolutions. The spatial resolution for our Earth observation spectro-imager must be then lower than 30 m / 2 detector pixels.…”

Section: Spectro-imager For Earth Observationmentioning

confidence: 99%

MOEMS-based spectro-imagers for Earth and Universe Observation

Vachey

Zamkotsian

Benard

et al. 2021

International Conference on Space Optics — ICSO 2020

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MOEMS-based instruments could be the next stepping stone in ground-based and space telescopes for Universe and Earth Observation. Targeted instruments are next generation multi-object spectrographs, as MOEMS can be used as reconfigurable slit masks at the MOS entrance, allowing increased instrument compacity and new observational modes such as SNR optimization. For Earth Observation, the use of MOEMS acting like programmable slit masks also allows a dynamic removal of the bright sources in the field of view, therefore enhancing the global SNR of the instrument. We propose a MOEMS-based spectro-imager named BATMAN, using a Digital-Micromirror-Device (DMD) to split the light between its imaging and spectrograph arms. This instrument is intended to be installed at the TNG telescope in the Canary Islands in 2022. This concept has been extended for space Universe and Earth Observation. A new MOEMS-based spectro-imager for Earth Observation has been designed, with constraints of wide 2D field-ofview (3°x1°), image quality (< 2 pixels = 11 μm) and compacity (Fig. 1). The instrument is panchromatic with a medium spectral resolution between 1000 and 2000, fitting in a 80 cm x 80 cm x 40 cm box. A 3-mirror solution for both imaging and spectrograph arms has been designed, using only aspheric surfaces, allowing for easier alignment and tolerancing. The compact design contains a convex grating to disperse light. In order to optimize the spectrograph efficiency, this convex grating must be blazed at the right angle for maximizing the light in the first order of diffraction. For Universe Observation, a new design for a DMD-based high-resolution spectro-imager has been done. For the spectrograph, the large 370 -950 nm wavelength range is divided into 4 channels for a spectral resolution of 15 000, all with an image quality of under two pixels. Moreover, the 3-mirror design of the instrument allows for a high throughput in comparison to classical systems which use catadioptric optics. These results show the great interest of MOEMS-based spectro-imagers for space Earth and Universe Observation.

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ELOIS: an innovative spectrometer design using a free-form grating

Cited by 14 publications

References 7 publications

The challenges of broadband performances within a compact imaging spectrometer: the ELOIS solution

The challenges of broadband performances within a compact imaging spectrometer: the ELOIS solution

Hyperspectral innovation on instruments and technologies at the European Space Agency

MOEMS-based spectro-imagers for Earth and Universe Observation

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