A limb-viewing spatial heterodyne interferometer is developed to observe temperature in the mesosphere and lower thermosphere. This can be used to measure atmospheric waves with small vertical wavelengths. The instrument measures the O2 atmospheric A-band airglow emission in the near-infrared. The emission is visible during day- and night-time, allowing for a continuous observation. The image is taken by a 2d detector. The optical system conserves the 2d spatial temperature information. The spectral information is superimposed in horizontal detector direction. The usual processing thus uses the horizontal detector dimension to resolve the spectral while averaging the underlying spatial information. The altitude coverage is given by the vertical detector direction, resulting in a finely resolved vertical temperature profile for one image. In light of this, we explore a novel processing approach that exploits the spatial information along the horizontal axis as well. We propose to split the interferogram into two halves, mirror it around the center and perform a retrieval on both sides separately, obtaining two spatial cross tracks of independent temperature data. Assuming that the instrument views backward, consecutive measurements give along track sampling. Combining this with the split interferogram method and the usual fine vertical resolution of the instrument, it provides 3d information on the atmospheric temperature field which allows to obtain some information on 3d propagation characteristics of atmospheric waves. In our research, we delve into the viability, advantages and constraints of the split interferogram approach. We will discuss the impact of horizontal temperature variation onto the retrieval result. We show the impact of background temperatures on the retrieval. Furthermore, we discuss the influence of apodization onto the retrieval of split interferograms.
Spatial heterodyne spectroscopy has become increasingly attractive for remote sensing of the atmosphere from microsatellites. Its outstanding light gathering power makes this technology particularly suitable for the detection of faint signals with minimal volume requirements. This paper is about an instrument, which was designed to measure the spectral shape of an atmospheric oxygen emission. The near infrared emission is observed in limb viewing geometry from space. The optical setup and specific characteristics of the design are presented. A focus is on the straylight behaviour of the system. In-field and out-of-field contributions are discussed. Straylight kernels are applied to expected background radiation fields with regard to performance-limiting factors of the system.
KEYWORDS: Signal to noise ratio, Sensors, Remote sensing, Image sensors, Field programmable gate arrays, Detection and tracking algorithms, Digital filtering, System on a chip, Imaging systems
Large commercial of the shelf pixel arrays in current remote sensing instruments used in CubeSats make on-board processing increasingly important and enables data improvement. Therefore, we first consider the individual steps of the adapted bad pixel detection algorithm - ISMFD. In particular, we consider pixel-to-pixel variations and temporal flickering of pixels in commercial of the shelf sCMOS imaging sensors. We were able to detect an increase of bad pixels from (2.05±0.01)% to (4.1±0.1)% using real measurement images of the flying remote sensing instrument AtmoSHINE. A preliminary implemented adaptive on-board binning method was able to achieve a constant signal-to-noise-ration on an image with a dynamic light intensity. The additional consideration of bad pixels in the binning method could demonstrate the achievement of data quality of the future remote sensing instrument AtmoLITE.
This article presents the characterization and analysis of a commercial off-the-shelf (COTS) CMOS detector utilized in a miniaturized satellite payload for atmospheric temperature measurements. To evaluate the performance of the selected CMOS detector, a series of tests were performed. The temperature dependent dark current, the readout noise and the system gain are determined, which are provided for the subsequent system performance evaluation and data processing. A case study is established to simulate the space radiation effect to determine the needed shielding thickness on the instrument. The effect of radiation damage on the CMOS image sensors is investigated using a Co-60 Gamma radiation source.
Tom Neubert, Heinz Rongen, Denis Froehlich, Georg Schardt, Markus Dick, Tobias Nysten, Egon Zimmermann, Martin Kaufmann, Friedhelm Olschewski, Stefan van Waasen
KEYWORDS: Electronics, Remote sensing, Sensors, Imaging systems, Satellites, Logic, Commercial off the shelf technology, Aluminum, Interfaces, System on a chip
CubeSats have become very popular science platforms in the past decades, leading to a continuously increasing number of developers in the academic field. For science missions, customized payload electronics have to be developed, depending on measurement tasks and requirements. Especially for the deployment of complex remote sensing payloads, state-of-the-art performance is needed to provide operational control and specific data processing, e.g., for image sensors. Highly integrated system-on-module (SoM) architectures offer low resource requirements regarding power and mass, but moderate to high processing power capabilities. However, a requirement to use a standard SoM in a satellite is to quantify its radiation tolerance. The radiation environment has been modeled, estimating the hazards at module level and reducing the risks to an acceptable level by applying appropriate mitigation techniques. This approach results in a sensor electronics design that combines hardware and software redundancies to assure system availability and reliability for long-life science missions in low earth orbits. Integrated in a miniaturized limb sounding instrument for atmospheric remote sensing imaging, the payload electronics will be deployed on a technology demonstration satellite for in-orbit verification.
The Institute for Atmospheric and Environmental Research at the University of Wuppertal and the Institute of Energy and Climate Research Stratosphere at Research Center Juelich developed a CubeSat payload for atmospheric research. The payload consists of a small interferometer for the observation of airglow near 762 nm. The line intensities of the oxygen A-band are used to derive temperatures in the mesosphere and lower thermosphere region. The temperature data will be used to analyze dynamical wave structures in the atmosphere. The interferometer technology chosen to measure the ro-vibrational structure of the O2 atmospheric band near 762 nm is a spatial heterodyne interferometer originally proposed by Connes in 1958. It can be designed to deliver extraordinary spectral resolution to resolve individual emission lines. The utilization of a two-dimensional imaging detector allows for recording interferograms at adjacent locations simultaneously. Integrated in a six-unit CubeSat, the instrument is designed for limb sounding of the atmosphere. The agility of a CubeSat will be used to sweep the line-of-sight through specific regions of interest to derive a three-dimensional image of an atmospheric volume using tomographic reconstruction techniques.
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