Telescopes employing linear detector arrays in a push-broom configuration enable the reconstruction of two-dimensional images of the Earth by recombining successive one-dimensional captures. This configuration, which typically features a wide field of view in the across-track direction but a narrow one in the along-track direction, often suffers from stray light, which degrades optical quality by introducing artifacts into the images. With increasingly stringent performance requirements, there is a critical need to implement effective stray light (SL) correction algorithms in addition to control by design. We describe the development of such an algorithm, using the cloud imager (CLIM) linear detector array instrument as a case study. Our approach involves calibrating SL kernels obtained by illuminating the instrument with a point-like source from various angles. In the along-track direction, we interpolate the SL kernel for any field angle without initial assumptions about SL behavior. For the across-track direction, we employ a local shift variant assumption. When applied to images of a checkerboard scene, which includes transitions between bright and dark areas, our algorithm successfully reduces SL by two orders of magnitude, demonstrating its efficacy and potential for broader application in telescopes with linear detector array.
The European Space Agency (ESA), in collaboration with the European Commission (EC) and EUMETSAT, is developing as part of the EC’s Copernicus programme, a space-borne observing system for quantification of anthropogenic carbon dioxide (CO2) emissions. The anthropogenic CO2 monitoring (CO2M) mission will be implemented as a constellation of identical Low Earth Orbit satellites, to be operated over a nominal period of more than 7 years. Each satellite will continuously measure CO2 concentration in terms of column-averaged dry air mole fraction (denoted XCO2) along the satellite track on the sun-illuminated part of the orbit, with a swath width of 250 km. Observations will be provided at a spatial resolution < 2 x 2 km2, with high precision (< 0.7 ppm) and accuracy (bias < 0.5 ppm), which are required to resolve the small atmospheric gradients in XCO2 originating from anthropogenic activities. The demanding requirements necessitate a payload composed of three instruments, which simultaneously perform co-located measurements: a push-broom imaging spectrometer in the Near Infrared (NIR) and Short-Wave Infrared (SWIR) for retrieving XCO2 and in the Visible spectral range (VIS) for nitrogen dioxide (NO2), a Multi Angle Polarimeter (MAP) and a three-band Cloud Imager (CLIM). Following the kick-off Mid 2020, the industrial activities have now passed the Satellite PDR allowing to enter in phase C/D. The paper will provide an overview of the space segment development achieved during the phase B2, including the platform, the payload activities as well as the end-to-end simulator. The preliminary design of the instruments on board the CO2M mission, the progress of the critical technological activities and the first results of the development models will be highlighted.
The European Space Agency (ESA), in collaboration with the European Commission (EC) and EUMETSAT, is developing as part of the EC’s Copernicus programme, a space-borne observing system for quantification of anthropogenic carbon dioxide (CO2) emissions. The anthropogenic CO2 monitoring (CO2M) mission will be implemented as a constellation of identical Low Earth Orbit satellites, to be operated over a period of more than 7 years. Each satellite will continuously measure CO2 concentration in terms of column-averaged dry air mole fraction (denoted XCO2) along the satellite track on the sun-illuminated part of the orbit, with a swath width of 250 km. Observations will be provided at a spatial resolution < 4 km2 , with high precision (< 0.7 ppm) and accuracy (bias < 0.5 ppm), which are required to resolve the small atmospheric gradients in XCO2 originating from anthropogenic activities. The demanding requirements necessitate a payload composed of three instruments, which simultaneously perform co-located measurements: a push-broom imaging spectrometer in the Near Infrared (NIR) and Short-Wave Infrared (SWIR) for retrieving XCO2 and in the Visible spectral range (VIS) for nitrogen dioxide (NO2), a Multi Angle Polarimeter (MAP) and a three-band Cloud Imager (CLIM). Following the kick-off Mid 2020, the industrial activities have now passed the Satellite PDR allowing to enter the phase C/D. The paper summarises the payload activities performed during the phase B2 culminating with the PDR of the instruments and of the payload. The preliminary design of the CO2M mission’s instruments, the progress of the technological activities and the first results of the development models are presented.
The European Space Agency (ESA), in collaboration with the European Commission (EC) and
EUMETSAT, is developing as part of the EC’s Copernicus programme, a space-borne observing system for quantification of anthropogenic carbon dioxide (CO2) emissions. The anthropogenic CO2 monitoring (CO2M) mission will be implemented as a constellation of identical LEO satellites, to be operated over a period > 7 years and measuring CO2 concentration in terms of column-averaged dry air mole fraction (denoted as XCO2). Industrial activities for the phase B2CD have been kicked-off Mid 2020.
The demanding requirements necessitate a payload composed of a suite of instruments,
which simultaneously perform co-located measurements. A push-broom imaging spectrometer will perform co-located measurements of top-of-atmosphere radiances in the Near Infrared (NIR) and Short-Wave Infrared (SWIR) at high to moderate spectral resolution (NIR: 747- 773nm @0.1nm, SWIR-1: 1595-1675nm @0.3nm, SWIR-2: 1990-2095nm @0.35nm) for retrieving XCO2. These observations are complemented in the same spectrometer by measurements in the visible spectral range (405-490 nm @0.6nm), providing vertical column measurements of nitrogen dioxide (NO2) that serve as a tracer to high temperature combustion of fossil-fuel and related emission plumes (e.g. from coal-fired power plants and cities). High quality retrievals of XCO2 will be ensured even in situations of large aerosol loading, thanks to co-located measurements of aerosol resulting from a Multiple- Angle Polarimeter (MAP). Polarimetric measurements are performed over 40 angular views and in six spectral channels between 410 and 865 nm. Finally, due to the strong sensitivity of the XCO2 retrieval to cloud contamination, a three-band Cloud Imager (CLIM) will provide the required capacity to detect small tropospheric clouds and cirrus cover with an accuracy of 1% to 5% and a sampling better than 400 m.
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