Optical design and optical properties of a VUV spectrographic imager for ICON mission

Loicq, Jérôme; Kintziger, Christian; Mazzoli, Alexandra; Miller, Tim; Chou, Cathy; Frey, H. U.; Immel, T. J.; Mende, S. B.

doi:10.1117/12.2232588

Cited by 6 publications

(7 citation statements)

References 6 publications

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“…A detailed discussion of the optics can be found in Loicq et al (2016aLoicq et al ( , 2016b. The ray tracing of the instrument is presented in Fig.…”

Section: Opticsmentioning

confidence: 99%

“…In this condition, diffraction in the tangential plane upon reflection from the grating introduces an astigmatism that can compensate for the off-axis reflections from the spherical optics. As a result of these considerations the CZT design became quite asymmetrical with a relatively small M1 and a very much larger M2 (Loicq et al 2016a(Loicq et al , 2016b. Unfortunately, the accommodation of the large M2 proved to be mechanically difficult because it necessitated the mounting of all optical elements at a large distance from a conventional optical bench.…”

Section: Opticsmentioning

confidence: 99%

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The Far Ultra-Violet Imager on the Icon Mission

et al. 2017

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ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N 2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O + ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a Czerny-Turner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with

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“…A detailed discussion of the optics can be found in Loicq et al (2016aLoicq et al ( , 2016b. The ray tracing of the instrument is presented in Fig.…”

Section: Opticsmentioning

confidence: 99%

Section: Opticsmentioning

confidence: 99%

The Far Ultra-Violet Imager on the Icon Mission

et al. 2017

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“…Compared to other UV-instruments where spectral selection is achieved with gratings [5][6], the challenge of the development of such instrument lies mainly on the performances of the coating deposition on the optical mirror surfaces. The -multilayer technology [7][8] seems to be the most promising technology to realize such challenge.…”

Section: Coating Optical Designmentioning

confidence: 99%

Development of VUV multilayer coatings for SMILE-UVI instrument

Loicq

Fleury-Frenette

Blain

et al. 2019

International Conference on Space Optics — ICSO 2018

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The Ultraviolet Imager (UVI) instrument is a very challenging imager developed in the frame of the SMILE-ESA mission. The UV camera will consist of a single imaging system targeted at a portion of the Lyman-Birge-Hopfield (LBH) N2 wavelength band. The baseline design of the imager meets the requirements to record snapshots of auroral dynamics with sufficient spatial resolution to measure cusp processes (100 km) under fully sunlit conditions from the specified apogee of the spacecraft. To achieve this goal, the UVI instrument utilizes a combination of four on-axis mirrors with an intensified FUV CMOS based camera. The mirrors will be coated with spectral selective interferometric layers to provide most of the signal filtering. The objective of these filters is to select the scientific waveband between 160 and 180 nm. The combined four mirrors have to give an out-of-band rejection ratio as high as possible to reject light from solar diffusion, dayglow and unwanted atomic lines in a range of 10-8 -10-9. Different multilayer coatings are considered and optimized according to the πmultilayer equation for different H/L ratio and for different angles of incidence. Our theoretical evaluation shows a least a modification of the reflectance spectrum as a function of the angle of incidence, so that the optical beams hitting the different mirrors can have different optical properties depending on the optical fields and the distribution of the rays on the pupil. In this paper the effect of fields and coating homogeneity on the spectral throughput of the UVI instrument will be assessed and described.

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“…The FUV boresight shall be directed vertically 20 +/-0.5 degrees below the local horizontal in the nominal launch position. Optimisation process of the optical design is described in details into the reference [7]. Even if the spectral selection of the instrument is performed identically for both channels with the CZT, the objectives followed by both channel are different.…”

Section: B Optical Requirementsmentioning

confidence: 99%

“…Alignment achievements will be presented. Instrument concept design, tolerances and alignment cases simulations were presented on the paper [7].…”

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confidence: 99%

V-UV spectrographic imager (FUV) for Icon mission: from optical design to vacuum calibration

Loicq

Blain

Kintziger

et al. 2017

International Conference on Space Optics — ICSO 2016

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In the frame of this mission the Space Center of Liege was involved in the optical design optimization and related analysis, and VUV on ground calibration. The ICON mission (NASA) will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. Recent NASA missions have shown how dramatically variable the region of space near Earth is, where ionized plasma and neutral gas collide and react. This region, the ionosphere, has long been known to respond to space weather drivers from the sun, but in this century we have come to realize that the energy and momentum of our own low altitude atmosphere regularly affect the ionosphere with equal or greater magnitude. ICON will weigh the impacts of these two drivers as they exert change on our space environment. During the day, photoelectrons colliding with atmospheric neutrals, N2 and O, produce emissions and by observing the limb brightness of the N2 Lyman-Birge-Hopfield (LBH) band and of the OI 135.6 nm line, the density ratio of the neutral N2 and O atmospheric constituents can be retrieved. At night the recombination of O+ ions with ionospheric electrons also creates OI 135.6 nm emissions and the nighttime electron density can be estimated from the limb brightness of 135.6 nm. ICON FUV will measure the altitude distribution of the OI 135.6 nm and N2 LBH dayglow emissions at 157 nm and the altitude and spatial distribution of the OI 135.6 nm nightglow emissions. These quantities can then be used to determine dayside O and N2 densities and altitude profiles, and the nightside O+ densities in the F-region. The ICON-FUV instrument is based upon the IMAGE Spectrographic Imager (SI) [1] [2] [3]. Like this predecessor, ICON-FUV is a two-channel imager that uses a grating spectrometer for spectral discrimination [4] [5] [6]. The two channels are required to provide the daytime profiles of two wavelengths characterizing the N2 and O species (centered at 157 nm and 135.6 nm respectively). This grating type of spectrographic imager minimizes contamination by out-of-band light leaks that are a typical problem for non-grating type FUV cameras. The instrument is composed by two parts, a Czerny-Turner spectrograph selecting the science wavelengths. This spectrograph is then combined with two imagers respectively working in the two wavebands of interest. The challenge of this space instrument was to be designed for a very wide FOV (24° vertical by 18° horizontal).

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Optical design and optical properties of a VUV spectrographic imager for ICON mission

Cited by 6 publications

References 6 publications

The Far Ultra-Violet Imager on the Icon Mission

The Far Ultra-Violet Imager on the Icon Mission

Development of VUV multilayer coatings for SMILE-UVI instrument

V-UV spectrographic imager (FUV) for Icon mission: from optical design to vacuum calibration

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