Simulated JWST Data Sets for Multispectral and Hyperspectral Image Fusion

Abstract

The James Webb Space Telescope (JWST) will provide multispectral and hyperspectral infrared images of a large number of astrophysical scenes. Multispectral images will have the highest angular resolution, while hyperspectral images (e.g., with integral field unit spectrometers) will provide the best spectral resolution. This paper aims at providing a comprehensive framework to generate an astrophysical scene and to simulate realistic hyperspectral and multispectral data acquired by two JWST instruments, namely, NIRCam Imager and NIRSpec IFU. We want to show that this simulation framework can be resorted to assess the benefits of fusing these images to recover an image of high spatial and spectral resolutions. To do so, we make a synthetic scene associated with a canonical infrared source, the Orion Bar. We develop forward models including corresponding noises for the two JWST instruments based on their physical features. JWST observations are then simulated by applying the forward models to the aforementioned synthetic scene. We test a dedicated fusion algorithm we developed on these simulated observations. We show that the fusion process reconstructs the high spatio-spectral resolution scene with a good accuracy on most areas, and we identify some limitations of the method to be tackled in future works. The synthetic scene and observations presented in the paper can be used, for instance, to evaluate instrument models, pipelines, or more sophisticated algorithms dedicated to JWST data analysis. Besides, fusion methods such as the one presented in this paper are shown to be promising tools to fully exploit the unprecedented capabilities of the JWST.

Hyperspectral and Multispectral Image Fusion Under Spectrally Varying Spatial Blurs – Application to High Dimensional Infrared Astronomical Imaging

“…The simulated dataset considered in the experiments was specifically designed to assess multi-and hyperspectral data fusion in the particular context of high dimensional astronomical observations performed by the James Webb Space Telescope (JWST). The generation process is accurately described in [41] and more briefly recalled hereafter. This dataset is composed of a high spatial and high spectral resolution synthetic scene of a photodissociation region (PDR) located in the Orion Bar.…”

“…The synthetic scene has been generated under a low-rank assumption such that its constitutive spectra are linear mixtures of 4 synthetic elementary spectra spatially distributed according to 4 maps representing the spatial abundances of each elementary spectrum over the scene. To simulate the expected spatial and spectral content of the Orion bar, four real images acquired by different telescopes are combined to build the spatial maps and the spectral signatures of the elementary components were chosen to be those likely present in this region (see [41] for more details). This simulated scene will be denoted X in the following and will represent the reference (i.e., ground-truth) data-cube we aim to recover by fusing the HS and MS measurements.…”

Fusion of hyperspectral and multispectral infrared astronomical images

“…In this section, we study the performance of the proposed fast fusion method on a realistic simulated dataset of the Orion Bar. This dataset has been generated to assess data fusion performed on high dimensional astronomical observations [21]. It is composed of a simulated reference image of high spatial and high spectral resolution and corresponding HS and MS images that would be observed by two dedicated sensors.…”

“…Then we consider an additive spatially correlated Gaussian noise whose mean and covariance depend on the instruments, as specified in the JWST documentation. To evaluate the performance of our method on low SNR observations, we consider that the signal is 10 times less intense than the expected signal that would be observed in the Orion bar region presented in [21]. MS and HS observed images are shown in Fig.…”

Unmixing methods based on nonnegativity and weakly mixed pixels for astronomical hyperspectral datasets

“…The PACS, SPIRE, and HIFI instruments, on board Herschel all have a mode that allows for spectral mapping (e.g. Van Kempen et al 2010;Habart et al 2010;Joblin et al 2010) in atomic and molecular lines. Owing to its high spectral resolution, HIFI allows one to resolve the profiles of these lines, enabling one to study the kinematics of, for example, the immediate surroundings of protostars (Kristensen et al (2011)) or of star-forming regions (Pilleri et al (2012)) using radiative transfer models.…”