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# — Illustration of the geometry of an arsenic-doped silicon detector array. The light travels through 500 μ m of pure silicon (which may be anti-reflection coated) and then a transparent contact into a thin active layer (25 μ m for IRAC, 35 μ m for MIRI baseline material) of arsenic-doped silicon, followed by an even thinner (4 μ m for MIRI) blocking layer of pure silicon. Indium bump bonds, one per pixel, join evaporated contacts on the detectors and readout amplifiers to convey the photo-electrons generated in the active layer to the input of the amplifiers.

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Article
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The MIRI Si:As IBC detector arrays extend the heritage technology from the Spitzer IRAC arrays to a 1024 x 1024 pixel format. We provide a short discussion of the principles of operation, design, and performance of the individual MIRI detectors, in support of a description of their operation in arrays provided in an accompanying paper (Ressler et a...

## Contexts in source publication

Context 1
... layer is followed by an intrinsic blocking layer about 3 -4µm thick, with the second contact on it. This contact defines the pixel and is indium- bump-bonded to the input of the ROIC amplifier (see Figure 2). The bias voltage on the pixel is established between its individual contact and the buried common one whose bias is maintained through a V-shaped etched trough, aluminum-coated to make it conductive, and placed to one side of the array (Figure 1), although for illustration the figure shows it in the middle. ...
Context 2
... manufacture detector arrays, the detector wafers were diced and patterned with indium bumps, allowing them to be hybridized onto the readouts (Figure 2). Each detector is connected to the input of a source follower amplifier as shown in Figure 3. ...
Context 3
... explanation of this behavior is based on the geometry illustrated in Figure 2. The detectors are fabricated on a silicon substrate ∼ 500 µm thick that is transparent in the mid- IR. ...
Context 4
... arguments show that the cross artifacts must be associated with the interpixel gaps (see Figure 2). Optically, these gaps will act as narrow slits, with widths comparable to the wavelength of the light. ...
Context 5
... more detailed model shows that some of the light is diffracted beyond the angle for trapping by total internal reflection in the detector. In addition, some of the light escapes the detector wafer through the interpixel gaps into the space between the detector and the readout circuit (see Figure 2). This region acts like a lossy integrating cavity, and some of the light can re-enter the detector wafer through other interpixel gaps. ...

## Citations

... This non-linearity arises primarily due to the debiasing of the detectors as charge is accumulated on the amplifier integrating node. For details on the theory of the non-linearity on the MIRI detectors, see Rieke et al. (2015b). The linearity step adjusts the integration ramps so the output of the adjusted DN is a linear function of the input signal. ...
... Compared to simulations, the observed spectrum has more noise than expected in the at wavelengths λ 7µm (see Figure 9). We have not positively identified the source of this excess noise, but we note that it corresponds to wavelengths that show excess scattering along the rows and columns of the detector array in Figure 2. Radiation passes all the way through the detector substrate at these wavelengths and encounters multiple passes through its IR-sensitive layer and buried contact in addition to scattering along rows and columns between the Si detector substrate and its integrated readout (ROIC) (Rieke et al. 2015b;Gáspár et al. 2021). We speculate that these multiple passes introduce excess noise, and the light also scatters into a cross-like image structure with some flux Uncertainty estimate JWST MIRI/LRS spectrum L168-9b ...
Preprint
We present here the first ever mid-infrared spectroscopic time series observation of the transiting exoplanet \object{L 168-9 b} with the Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope. The data were obtained as part of the MIRI commissioning activities, to characterize the performance of the Low Resolution Spectroscopy (LRS) mode for these challenging observations. To assess the MIRI LRS performance, we performed two independent analyses of the data. We find that with a single transit observation we reached a spectro-photometric precision of $\sim$50 ppm in the 7-8~\micron~range at R=50, consistent with $\sim$25 ppm systematic noise. The derived band averaged transit depth is 524~$\pm$~15~ppm and 547~$\pm$~13~ppm for the two applied analysis methods, respectively, recovering the known transit depth to within 1~$\sigma$. The measured noise in the planet's transmission spectrum is approximately 15-20\% higher than random noise simulations over wavelengths $6.8 \lesssim \lambda \lesssim 11$ $\mu$m. We observed an excess noise at shorter wavelengths, for which possible causes are discussed. This performance was achieved with limited in-flight calibration data, demonstrating the future potential of MIRI for the characterization of exoplanet atmospheres.
... Nebular phase observations in the NIR and MIR provide unique and powerful constraints on models, including the density-dependent nucleosynthesis of intermediate mass elements, radioactive iron-group elements, and stable irongroup elements (Gerardy et al. 2007;Diamond et al. 2018;Dhawan et al. 2018;Hoeflich et al. 2021). The JWST Near Infrared Spectrograph (NIRSpec; Jakobsen et al. 2022) and Mid Infrared Instrument (MIRI; Rieke et al. 2015;Wright et al. 2015) give access to a wider range of elemental and ionic species than the optical. Lines are also typically less blended in the infrared, making it easier to derive line fluxes and abundance estimates, as well as to infer the geometry of the emission region from the line profile shape (e.g., Jerkstrand 2017). ...
Preprint
Full-text available
We present JWST near- and mid-infrared spectroscopic observations of the nearby normal Type Ia supernova SN 2021aefx in the nebular phase at $+255$ days past maximum light. Our Near Infrared Spectrograph (NIRSpec) and Mid Infrared Instrument (MIRI) observations, combined with ground-based optical data from the South African Large Telescope (SALT), constitute the first complete optical $+$ NIR $+$ MIR nebular SN Ia spectrum covering 0.3$-$14 $\mu$m. This spectrum unveils the previously unobserved 2.5$-$5 $\mu$m region, revealing strong nebular iron and stable nickel emission, indicative of high-density burning that can constrain the progenitor mass. The data show a significant improvement in sensitivity and resolution compared to previous Spitzer MIR data. We identify numerous NIR and MIR nebular emission lines from iron-group elements and as well as lines from the intermediate-mass element argon. The argon lines extend to higher velocities than the iron-group elements, suggesting stratified ejecta that are a hallmark of delayed-detonation or double-detonation SN Ia models. We present fits to simple geometric line profiles to features beyond 1.2 $\mu$m and find that most lines are consistent with Gaussian or spherical emission distributions, while the [Ar III] 8.99 $\mu$m line has a distinctively flat-topped profile indicating a thick spherical shell of emission. Using our line profile fits, we investigate the emissivity structure of SN 2021aefx and measure kinematic properties. Continued observations of SN 2021aefx and other SNe Ia with JWST will be transformative to the study of SN Ia composition, ionization structure, density, and temperature, and will provide important constraints on SN Ia progenitor and explosion models.
... JWST /MIRI (Bouchet et al. 2015;Rieke et al. 2015) imaging was obtained with the F560W (5.6µm), F770W (7.7µm), and F1500W (15.0µm) filters with both the BRIGHTSKY and SUB128 subarray modes. Our analysis was done on the SUB128 subarray data where the full starburst ring was observable in the field of view (FoV: 14.1 × 14.1 ). ...
Preprint
Full-text available
We present James Webb Space Telescope (JWST) imaging of NGC 7469 with the Near-Infrared Camera (NIRCam) and the Mid-InfraRed Instrument (MIRI). NGC 7469 is a nearby, $z=0.016317$, luminous infrared galaxy (LIRG) that hosts both a Seyfert Type-1.5 nucleus and a circumnuclear starburst ring with a radius of $\sim$0.5 kpc. The new near-infrared (NIR) JWST imaging reveals 65 star-forming regions, 36 of which were not detected by HST observations. Nineteen of the 36 sources have very red NIR colors that indicate obscurations up to A$_{\rm{v}}\sim7$ and a contribution of at least 25$\%$ from hot dust emission to the 4.4$\mu$m band. Their NIR colors are also consistent with young ($<$5 Myr) stellar populations and more than half of them are coincident with the MIR emission peaks. These younger, dusty star-forming regions account for $\sim$2$\%$ and $\sim$10$\%$ of the total 1.5$\mu$m and 4.4$\mu$m luminosity of the starburst ring, respectively. The addition of these young regions confirm the age bimodality seen in the star-forming regions of the ring. Moreover, we have increased the number of young sources by a factor of four, raising the total percentage of the young population to $\sim$40$\%$. These results illustrate the effectiveness of JWST in identifying and characterizing previously hidden star formation in the densest star-forming environments around AGN.
... In this context, a key advance of autodiff over previous methods is that we can trivially account for pixel sampling/binning and detector nonlinearity. These will be important issues when considering that the JWST mid-infrared imager MIRI will have significant detector nonlinearity (Rieke et al. 2015), or where we may wish to look at saturated sources. While they do not address more complex optical systems, this method may be straightforwardly applicable to sensing non-common-path errors in coronagraphic images. ...
Article
The accumulation of aberrations along the optical path in a telescope produces distortions and speckles in the resulting images, limiting the performance of cameras at high angular resolution. It is important to achieve the highest possible sensitivity to faint sources, using both hardware and data analysis software. While analytic methods are efficient, real systems are better modeled numerically, but numerical models of complicated optical systems with many parameters can be hard to understand, optimize, and apply. Automatic differentiation or “backpropagation” software developed for machine-learning applications now makes calculating derivatives with respect to aberrations in arbitrary planes straightforward for any optical system. We apply this powerful new tool to the problem of high-angular-resolution astronomical imaging. Self-calibrating observables such as the “closure phase” or “bispectrum” have been widely used in optical and radio astronomy to mitigate optical aberrations and achieve high-fidelity imagery. Kernel phases are a generalization of closure phases valid in the limit of small phase errors. Using automatic differentiation, we reproduce existing kernel phase theory within this framework and demonstrate an extension to the case of a Lyot coronagraph, which is found to have self-calibrating combinations of speckles. which are resistant to phase noise, but only in the very high-wave-front-quality regime. As an illustrative example, we reanalyze Palomar adaptive optics observations of the binary α Ophiuchi, finding consistency between the new pipeline and the existing standard. We present a new Python package morphine that incorporates these ideas, with an interface similar to the popular package poppy , for optical simulation with automatic differentiation. These methods may be useful for designing improved astronomical optical systems by gradient descent.
... With the read out integrated circuits (ROICs) used in Spitzer, the noise was largely unchanged as the temperature decreased below 40 K. However, for JWST/MIRI prototype ROICs, the noise increased as the temperature decreased, 11,13 which is due primarily to nonthermal and nonrandom noise components that do not reduce with either multiple sampling or multiple observations. The inverse temperature dependence of the read noise for the prototype ROICs over such a broad temperature range was not troubling since the MIRI arrays would be operated at a fixed temperature, but this behavior indicated where some of the problems originated in the ROIC design and fabrication. ...
... The high quantum efficiency of the Si:As IBC devices, in combination with the extensive wavelength range covered (5-28 µm) gives these devices a unique advantage. 2,3 Other detectors, such as the Teledyne Imaging Sensors' LWIR HgCdTe detector have a relatively higher quantum efficiency, however, they cover a shorter wavelength range (the LWIR HgCdTe detector extends out to 13 µm). 4 It is important thus to understand the spectrophotometric response of the Si:As IBC device across the long wavelength range covered in order to maximize scientific output. ...
... The Si:As IBC detectors are grown on a silicon substrate. We show a representation of the architecture of the MIRI detector arrays in Fig. 1, which is based on [2,3,11,12]. Photons pass through the anti-reflection coating on the detector back side, into the substrate, and then through the buried contact, into the infrared-active layer (detection layer). ...
... The infrared-active layer is doped with arsenic to absorb the incoming photons, elevating photo-excited electrons from the impurity band into the conduction band. 3 Assuming a low level of minority acceptor impurities in this layer, an electric field can be maintained across it that causes the photoelectrons to migrate to the front of the detector. A thin, high purity layer (blocking layer) is grown over the front of the infrared-active layer. ...
Preprint
Full-text available
The Mid-Infrared Instrument MIRI on-board the James Webb Space Telescope uses three Si:As impurity band conduction detector arrays. MIRI medium resolution spectroscopic measurements (R$\sim$3500-1500) in the 5~$\mu m$ to 28~$\mu m$ wavelength range show a 10-30\% modulation of the spectral baseline; coherent reflections of infrared light within the Si:As detector arrays result in fringing. We quantify the shape and impact of fringes on spectra of optical sources observed with MIRI during ground testing and develop an optical model to simulate the observed modulation. We use our optical model in conjunction with the MIRI spectroscopic data to show that the properties of the buried contact inside the MIRI Si:As detector have a significant effect on the fringing behavior.
... The original efforts are largely successful in describing the properties of these improved devices at the longer wavelengths. However, testing of detectors with these thicker layers showed that the behavior of responsivity vs. bias voltage requires introduction of a diffusion length of ∼ 2.5 µm (rather than the negligible diffusion length in the original theory), or the response at low bias and wavelengths near the peak of response would fall short of measurements (Rieke et al. 2015). This change is required because at wavelengths 15 µm, most of the photons are absorbed in the first ∼ 10 microns of the infrared-active layer. ...
... This paper complements the evaluation of the long wavelength behavior of Si:As IBC detectors described in Rieke et al. (2015). We will discuss both the short wavelength QE and the imaging artifacts. ...
... Our model of the short wavelength response of Si:As IBC detectors uses the parameters of the MIRI "baseline" devices as described above and in more detail by Love et al. (2004Love et al. ( , 2005Love et al. ( , 2006; Ressler et al. (2008); Rieke et al. (2015); Ressler et al. (2015). We assume that the wavelength-dependent response is determined through a combination of (1) the absorption characteristics of the Si:As, (2) the anti-reflection coating on the entrance surface, (3) the optical characteristics of the buried contact, and (4) geometric factors. ...
Preprint
Arsenic doped back illuminated blocked impurity band (BIBIB) silicon detectors have advanced near and mid-IR astronomy for over thirty years; they have high quantum efficiency (QE), especially at wavelengths longer than 10 $\mu$m, and a large spectral range. Their radiation hardness is also an asset for space based instruments. Three examples of Si:As BIBIB arrays are used in the Mid-InfraRed Instrument (MIRI) of the James Webb Space Telescope (JWST), observing between 5 and 28 $\mu$m. In this paper, we analyze the parameters leading to high quantum efficiency (up to $\sim$ 60\%) for the MIRI devices between 5 and 10 $\mu$m. We also model the cross-shaped artifact that was first noticed in the 5.7 and 7.8 $\mu$m Spitzer/IRAC images and has since also been imaged at shorter wavelength ($\le 10~\mu$m) laboratory tests of the MIRI detectors. The artifact is a result of internal reflective diffraction off the pixel-defining metallic contacts to the readout detector circuit. The low absorption in the arrays at the shorter wavelengths enables photons diffracted to wide angles to cross the detectors and substrates multiple times. This is related to similar behavior in other back illuminated solid-state detectors with poor absorption, such as conventional CCDs operating near 1 $\mu$m. We investigate the properties of the artifact and its dependence on the detector architecture with a quantum-electrodynamic (QED) model of the probabilities of various photon paths. Knowledge of the artifact properties will be especially important for observations with the MIRI LRS and MRS spectroscopic modes.
... In this context, a key advance of autodiff over previous methods is that we can trivially account for pixel sampling/binning and detector nonlinearity. These will be important issues when considering that the JWST mid-infrared imager MIRI will have significant detector nonlinearity (Rieke et al. 2015), or where we may wish to look at saturated sources. While they do not address more complex optical systems, this method may be straightforwardly applicable to sensing non-common-path errors in coronagraphic images. ...
Preprint
The accumulation of aberrations along the optical path in a telescope produces distortions and speckles in the resulting images, limiting the performance of cameras at high angular resolution. It is important to achieve the highest possible sensitivity to faint sources such as planets, using both hardware and data analysis software. While analytic methods are efficient, real systems are better-modelled numerically, but such models with many parameters can be hard to understand, optimize and apply. Automatic differentiation software developed for machine learning now makes calculating derivatives with respect to aberrations straightforward for arbitrary optical systems. We apply this powerful new tool to enhance high-angular-resolution astronomical imaging. Self-calibrating observables such as the 'closure phase' or 'bispectrum' have been widely used in optical and radio astronomy to mitigate optical aberrations and achieve high-fidelity imagery. Kernel phases are a generalization of closure phases in the limit of small phase errors. Using automatic differentiation, we reproduce existing kernel phase theory within this framework and demonstrate an extension to the Lyot coronagraph, finding self-calibrating combinations of speckles which are resistant to phase noise, but only in the very high-wavefront-quality regime. As an illustrative example, we reanalyze Palomar adaptive optics observations of the binary alpha Ophiuchi, finding consistency between the new pipeline and the existing standard. We present a new Python package 'morphine' that incorporates these ideas, with an interface similar to the popular package poppy, for optical simulation with automatic differentiation. These methods may be useful for designing improved astronomical optical systems by gradient descent.
... This naive implementation shows a median-best performance degradation of 9% and median-worst degradation of 26% on compartments with a single processor core. Further information on the conducted tests is available in Section 4.10, as well as performance measurements for 6 different application scenarios modeled after the NASA/James Webb Space Telescope's Mid-Infrared Instrument (MIRI) [219]. ...
... We chose to utilize the background scenario of scientific computing, as devices for scientific instrumentation are usually better documented. The program flow of our demo application is based on the NASA/James Webb Space Telescope's Mid-Infrared Instrument (MIRI) described in [219]. This program continuously reads three 16-bit 1024x1024 false-color sensor arrays, stores, and processes the results. ...
... This program continuously reads three 16-bit 1024x1024 false-color sensor arrays, stores, and processes the results. It averages multiple captured frames to optimize the instruments exposure time and avoid pixel saturation, or to capture faint astronomical sources [219]. ...
Thesis
Full-text available
Miniaturized satellites enable a variety space missions which were in the past infeasible, impractical or uneconomical with traditionally-designed heavier spacecraft. Especially CubeSats can be launched and manufactured rapidly at low cost from commercial components, even in academic environments. However, due to their low reliability and brief lifetime, they are usually not considered suitable for life- and safety-critical services, complex multi-phased solar-system-exploration missions, and missions with a longer duration. Commercial electronics are key to satellite miniaturization, but also responsible for their low reliability: Until 2019, there existed no reliable or fault-tolerant computer architectures suitable for very small satellites. To overcome this deficit, a novel on-board-computer architecture is described in this thesis. Robustness is assured without resorting to radiation hardening, but through software measures implemented within a robust-by-design multiprocessor-system-on-chip. This fault-tolerant architecture is component-wise simple and can dynamically adapt to changing performance requirements throughout a mission. It can support graceful aging by exploiting FPGA-reconfiguration and mixed-criticality. Experimentally, we achieve 1.94W power consumption at 300Mhz with a Xilinx Kintex Ultrascale+ proof-of-concept, which is well within the powerbudget range of current 2U CubeSats. To our knowledge, this is the first COTS-based, reproducible on-board-computer architecture that can offer strong fault coverage even for small CubeSats.
... Note that the size of the illuminated area was limited by the bandpass filter holder; the diameter of the illuminated area was about 25 mm, corresponding to the clear aperture of the filter mount. The latter restricts the observing wavelength to a narrow band with a center wavelength of 8.6 μm and a bandwidth of 0.1 μm because the Si:As IBC detector is sensitive to the wavelength ranging from 2 to 30 μm (e.g., Rieke et al. 2015). ...
... We operated the mid-infrared Si:As IBC detector at the effective bias of 1 V because the basic parameters of the detector were measured at that voltage in a previous study (Ennico et al. 2003). However, because the IR-active layer in this type of detector is not fully depleted unless the effective bias is more than 1.5 V (Rieke et al. 2015), these detectors are normally operated at higher effective bias. The thick depletion layer leads to enhance the well capacity as well as the quantum efficiency (Rieke et al. 2015). ...
... However, because the IR-active layer in this type of detector is not fully depleted unless the effective bias is more than 1.5 V (Rieke et al. 2015), these detectors are normally operated at higher effective bias. The thick depletion layer leads to enhance the well capacity as well as the quantum efficiency (Rieke et al. 2015). For example, while the well capacity of our detector was approximately 50,000 e − at 1 V applied detector bias (Ennico et al. 2003), that for the focal plane arrays of the MIRI mounted on JWST is 250,000 e − at 2.2 V and the system gain is approximately 210,000 e − V −1 . ...