&lt;title&gt;Optical calibration of the FUV spectrographic imager for the IMAGE mission&lt;/title&gt;

Habraken, Serge; Houbrechts, Yvette; Renotte, Étienne; Hellin, Marie-Laure; Orban, Anne; Rochus, Pierre; Mende, S. B.; Frey, H. U.; Geller, S. P.; Stock, Joseph M.

doi:10.1117/12.366529

Cited by 4 publications

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“…The measurement of the FOV has to be related to two instrument reference frames, one centered at the detector and the other at the entrance aperture. These reference frames may be rotated with respect to each other, and thus, an additional measurement of a fiducial like a reference optical cube at the outside of the instrument body has to be performed to establish the relative orientation between the two reference frames [Habraken et al, 1999]. This requirement will be discussed in section 3.2.…”

Section: Aperture Size and Field Of Viewmentioning

confidence: 99%

Calibration and testing of wide‐field UV instruments

Frey

Mende

Loicq³

et al. 2017

JGR Space Physics

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As with all optical systems the calibration of wide‐field ultraviolet (UV) systems includes three main areas: sensitivity, imaging quality, and imaging capability. The one thing that makes UV calibrations difficult is the need for working in vacuum substantially extending the required time and effort compared to visible systems. In theory a ray tracing and characterization of each individual component of the optical system (mirrors, windows, and grating) should provide the transmission efficiency of the combined system. However, potentially unknown effects (contamination, misalignment, and measurement errors) can make the final error too large and unacceptable for most applications. Therefore, it is desirable to test and measure the optical properties of the whole system in vacuum and compare the overall response to the response of a calibrated photon detector. A proper comparison then allows the quantification of individual sources of uncertainty and ensures that the whole instrument performance is within acceptable tolerances or pinpoints which parts fail to meet requirements. Based on the experience with the IMAGE Spectrographic Imager, the Wide‐band Imaging Camera, and the ICON Far Ultraviolet instruments, we discuss the steps and procedures for the proper radiometric sensitivity and passband calibration, spot size, imaging distortions, flatfield, and field of view determination.

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Section: Aperture Size and Field Of Viewmentioning

confidence: 99%

Calibration and testing of wide‐field UV instruments

Frey

Mende

Loicq³

et al. 2017

JGR Space Physics

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“…OPTICAL CALIBRATION Optical calibration gathers many concepts described below [5]. Before flight the instrument has to be calibrated to characterize how it behaves and to know how close it works from the optical design.…”

Section: IIImentioning

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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