Ultraviolet imaging detectors for the GOLD mission

Siegmund, Oswald H. W.; McPhate, Jason B.; Curtis, T.; Jelinsky, Sharon R.; Vallerga, J. V.; Hull, Jeffrey S.; Tedesco, James M.

doi:10.1117/12.2232219

Cited by 10 publications

(8 citation statements)

References 4 publications

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“…The EMUS detector is a photon-counting, open-face microchannel plate (MCP) imaging device with a cross-delay line (XDL) anode readout provided by UCB-SSL. The detector electronics is a hybrid of SSL implementations used in the GOLD instrument (McClintock et al 2020;Siegmund et al 2016) and the Ionospheric Connection Explorer Extreme Ultraviolet spectrometer (ICON-EUV) (Sirk et al 2017). The MCP stack, detector body, and enclosure are identical to that used by GOLD, except: the MCP rectangular active area mask was replaced by a larger circular mask, the circular UV transmissive window in the reclosable door was replaced by a larger rectangular one to accommodate the oblique illumination from the internal lamp, and the pump port aperture was enlarged to increase conductance.…”

Section: Detector Descriptionmentioning

confidence: 99%

The Emirates Mars Ultraviolet Spectrometer (EMUS) for the EMM Mission

et al. 2021

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The Emirates Mars Mission (EMM) Hope probe was launched on 20 July 2020 at 01:58 GST (Gulf Standard Time) and entered orbit around Mars on 9 Feb 2021 at 19:42 GST. The high-altitude orbit (19,970 km periapse, 42,650 km apoapse altitude, 25° inclination) with a 54.5 hour period enables a unique, synoptic, and nearly-continuous monitor of the Mars global climate. The Emirates Mars Ultraviolet Spectrometer (EMUS), one of three remote sensing instruments carried by Hope, is an imaging ultraviolet spectrograph, designed to investigate how conditions throughout the Mars atmosphere affect rates of atmospheric escape, and how key constituents in the exosphere behave temporally and spatially. EMUS will target two broad regions of the Mars upper atmosphere: 1) the thermosphere (100–200 km altitude), observing UV dayglow emissions from hydrogen (102.6, 121.6 nm), oxygen (130.4, 135.6 nm), and carbon monoxide (140–170 nm) and 2) the exosphere (above 200 km altitude), observing bound and escaping hydrogen (121.6 nm) and oxygen (130.4 nm).EMUS achieves high sensitivity across a wavelength range of 100–170 nm in a single optical channel by employing “area-division” or “split” coatings of silicon carbide (SiC) and aluminum magnesium fluoride (Al+MgF2) on each of its two optical elements. The EMUS detector consists of an open-face (windowless) microchannel plate (MCP) stack with a cesium iodide (CsI) photocathode and a photon-counting, cross-delay line (XDL) anode that enables spectral-spatial imaging. A single spherical telescope mirror with a 150 mm focal length provides a 10.75° field of view along two science entrance slits, selectable with a rotational mechanism. The high and low resolution (HR, LR) slits have angular widths of 0.18° and 0.25° and spectral widths of 1.3 nm and 1.8 nm, respectively. The spectrograph uses a Rowland circle design, with a toroidally-figured diffraction grating with a laminar groove profile and a ruling density of 936 gr mm−1 providing a reciprocal linear dispersion of 2.65 nm mm−1. The total instrument mass is 22.3 kg, and the orbit-average power is less than 15 W.

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Section: Detector Descriptionmentioning

confidence: 99%

The Emirates Mars Ultraviolet Spectrometer (EMUS) for the EMM Mission

et al. 2021

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“…Spectra are recorded using a microchannel plate (MCP) detectors equipped with cesium iodide photocathodes and cross‐delay line (XDL) anodes (Siegmund et al, 1993; Siegmund et al, 2016). The detectors, which are contained within vacuum housings with doors that can be opened and closed by command, have a 27.0 × 32.0 mm ( x, y ) active area where x is the dispersion (across slit) direction and y is the imaging (along slit) direction.…”

Section: Instrument Designmentioning

confidence: 99%

“…Because the GOLD detectors process one event at a time, there is an upper limit to the allowable instantaneous count rate across the entire 2‐D array, which is set by the electronics processing time or “global dead time” of ~τ = 10 −6 s. Events that arrive in times less than 10 −6 s after an initial event are simply ignored (Siegmund et al, 2016). This results in a correctable nonlinear response in which the “true” count rate is related to the observed count rate by

C_{G - italictrue} = \frac{C_{G - obs}}{1 - τ \cdot C_{G - italicobs}} .

There is also a local count rate limitation that is due to the finite time required for individual pores in the MCP to recover after a photon event and is proportional to MCP stack resistance.…”

Section: Instrument Designmentioning

confidence: 99%

“…The high‐gain MCP detectors in the GOLD instrument have a finite lifetime due to MCP charge depletion, or gain fatigue, which lowers detector quantum efficiency as a function of total accumulated counts (Sahnow et al, 2011; Siegmund et al, 2016) This effect is most significant for OI—135.6 nm radiation, which produces local count rates that are an order of magnitude higher than those from LBH (Figure 6). Sensitivity changes are tracked and corrected during ground processing using images of a miniature Pen‐Ray® cold cathode “flat field” lamp located within each channel.…”

Section: Instrument Designmentioning

confidence: 99%

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Global‐Scale Observations of the Limb and Disk Mission Implementation: 1. Instrument Design and Early Flight Performance

et al. 2020

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The Global-scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere-thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating atmospheric tides and waves. GOLD employs an instrument with two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by Société Européenne des Satellites (SES) and located in geostationary orbit at 47.5°west longitude (near the mouth of the Amazon River). They make images of atomic oxygen 135.6 nm and N 2 Lyman-Birge-Hopfield (LBH) 137-162 nm radiances of the entire disk that is observable from geostationary orbit and on the near-equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here, we provide an overview of the instrument and compare its prelaunch and early flight measurement performance. Direct comparison of LBH spectra of an electron lamp taken before launch with spectra on orbit provides evidence that both cascade and direct excitation are important sources of thermospheric LBH emission. Plain Language Summary The Global-scale Observations of the Limb and Disk (GOLD) is aNational Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere-thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating tides on time scales as short as 30 min. GOLD employs two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by SES and located in geostationary orbit at 47.5°west longitude (near the mouth of the Amazon River). They make images of atomic oxygen 135.6 nm and N 2 LBH radiances of the entire disk that is observable from geostationary orbit and on the near-equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here we describe the GOLD instrument including its optical system and detector. Its performance was characterized in the lab before launch. We compare measurements of laboratory sources made then to observations of the thermosphere after launch and find good agreement.

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“…Background rates can be exceeding low (<0.05 events cm -2 sec -1 ) 13 , MCPs are inherently radiation hard and have low sensitivity to gamma ray flux 14 . Electronic readout MCP sensors have been used as photon counting, imaging, event time tagging detectors for a number of astronomical 8,15,16 , remote sensing 17 , time resolved biological imaging 18 , photoelectron emission spectroscopy 1 and night time sensing 19 applications. The development of large area, high performance, photon counting, imaging, timing detectors also has significance for "open faced" configurations for UV and particle detection in space astrophysics, mass spectroscopy and many time-of-flight applications.…”

Section: Mcp Detectors and Readoutsmentioning

confidence: 99%

Microchannel plate detector technology potential for LUVOIR and HabEx

Schindhelm

Green

Siegmund

et al. 2017

UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XX

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Microchannel plate (MCP) detectors have been the detector of choice for ultraviolet (UV) instruments onboard many NASA missions. These detectors have many advantages, including high spatial resolution (<20 µm), photon counting, radiation hardness, large formats (up to 20 cm), and ability for curved focal plane matching. Novel borosilicate glass MCPs with atomic layer deposition combine extremely low backgrounds, high strength, and tunable secondary electron yield. GaN and combinations of bialkali/alkali halide photocathodes show promise for broadband, higher quantum efficiency. Cross-strip anodes combined with compact ASIC readout electronics enable high spatial resolution over large formats with high dynamic range. The technology readiness levels of these technologies are each being advanced through research grants for laboratory testing and rocket flights. Combining these capabilities would be ideal for UV instruments onboard the Large UV/Optical/IR Surveyor (LUVOIR) and the Habitable Exoplanet Imaging Mission (HABEX) concepts currently under study for NASA's Astrophysics Decadal Survey.

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Ultraviolet imaging detectors for the GOLD mission

Cited by 10 publications

References 4 publications

The Emirates Mars Ultraviolet Spectrometer (EMUS) for the EMM Mission

The Emirates Mars Ultraviolet Spectrometer (EMUS) for the EMM Mission

Global‐Scale Observations of the Limb and Disk Mission Implementation: 1. Instrument Design and Early Flight Performance

Microchannel plate detector technology potential for LUVOIR and HabEx

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