Conceptual design of an orbital debris collector

The current Lower Earth Orbit (LEO) environment has become overly crowded with space debris. An evaluation of types of debris is presented in order to determine which debris poses the greatest threat to operation in space, and would therefore provide a feasible target for removal. A target meeting these functional requirements was found in the Cosmos C-1B Rocket Body. These launchers are spent space transporters which constitute a very grave risk of collision and fragmentation in LEO. The motion and physical characteristics of these rocket bodies have determined the most feasible method of removal. The proposed Orbital Debris Collector (ODC) device is designed to attach to the Orbital Maneuvering Vehicle (OMV), which provides all propulsion, tracking, and power systems. The OMV/ODC combination, the Rocket Body Retrieval Vehicle (RBRV), will match orbits with the rocket body, use a spin table to match the rotational motion of the debris, capture it, despin it, and remove it from orbit by allowing it to fall into the Earth's atmosphere. A disposal analysis is presented to show how the debris will be deorbited into the Earth's atmosphere. The conceptual means of operation of a sample mission is described

Validation of a new atmospheric correction Software using AERONET reference data

Atmospheric correction of satellite images based on radiative transfer calculations is a prerequisite for many applications. The program ATCOR, developed at the German Aerospace Center (DLR), is a rather versatile atmospheric correction software, capable of processing data acquired by different optical satellite sensors. A Python-based version of this code is currently being developed to process L2A products of Sentinel-2, Landsat-8 and of new space-based hyper-spectral sensors such as DESIS and EnMAP. In this contribution we will present the first validation results of this software, comparing L2A products generated from Sentinel-2 L1C images with in-situ (AERONET) data

Soil Reflectance Composites - Improved Thresholding and Performance Evaluation

Reflectance composites that capture bare soil pixels from multispectral image data are increasingly being analysed to model soil constituents such as soil organic carbon. These temporal composites are used instead of single-date multispectral images to account for the frequent vegetation cover of soils and, thus, to get broader spatial coverage of bare soil pixels. Most soil compositing techniques require thresholds derived from spectral indices such as the Normalised Difference Vegetation Index (NDVI) and the Normalised Burn Ratio 2 (NBR2) to separate bare soils from all other land cover types. However, the threshold derivation is handled based on expert knowledge of a specific area, statistical percentile definitions or in situ data. For operational processors, such site-specific and partly manual strategies are not applicable. There is a need for a more generic solution to derive thresholds for large-scale processing without manual intervention. This study presents a novel HIstogram SEparation Threshold (HISET) methodology deriving spectral index thresholds and testing them for a Sentinel-2 temporal data stack. The technique is spectral indexindependent, data-driven and can be evaluated based on a quality score. We tested HISET for building six soil reflectance composites (SRC) using NDVI, NBR2 and a new index combining the NDVI and a short-wave infrared (SWIR) band (PV+IR2). A comprehensive analysis of the spectral and spatial performance and accuracy of the resulting SRCs proves the flexibility and validity of HISET. Disturbance effects such as spectral confusion of bare soils with non-photosynthetic-active vegetation (NPV) could be reduced by choosing grassland and crops as input LC for HISET. The NBR2-based SRC spectra showed the highest similarity with LUCAS spectra, the broadest spatial coverage of bare soil pixels and the least number of valid observations per pixel. The spatial coverage of bare soil pixels is validated against the database of the Integrated Administration and Control System (IACS) of the European Commission. Validation results show that PV+IR2-based SRCs outperform the other two indices, especially in spectrally mixed areas of bare soil, photosynthetic-active vegetation and NPV. The NDVI-based SRCs showed the lowest confidence values (95%) in all bands. In the future, HISET shall be tested in other areas with different environmental conditions and LC characteristics to evaluate if the findings of this study are also valid

Remote sensing for cropland soils at the regional scale

Uta Heiden, German Aerospace Center (DLR), addresses the challenges of observing soils from optical satellite platforms. She introduces the technique of soil composite mapping (SCMaP) that creates a reflectance signal for each bare soil pixel based on a time series of images. The advantage of such system is that the coverage of cropland area is much larger than for single images and that the signal is more stable for each pixel as a result of averaging. She addresses the challenges of defining thresholds for spectral indices allowing to create an optimal bare soil mask and demonstrates the SCMaP product suite. These products can be used for soil property algorithms but also for indicators of management practices such as bare soil frequency and seasonality

Spectral aerosol optical depth from SI-traceable spectral solar irradiance measurements

Spectroradiometric measurements of direct solar irradiance traceable to the SI were performed by three spectroradiometer systems during a 3-week campaign in September 2022 at the Izaña Atmospheric Observatory (IZO) located on the island of Tenerife, Canary Islands, Spain. The spectroradiometers provided direct spectral irradiance measurements in the spectral ranges 300 to 550 nm (QASUME), 550 to 1700 nm (QASUME-IR), 300 to 2150 nm (BiTec Sensor, BTS), and 316 to 1030 nm (Precision Solar Spectroradiometer, PSR), with relative standard uncertainties of 0.7 %, 0.9 %, and 1 % for QASUME/QASUME-IR, the PSR, and the BTS respectively. The calibration of QASUME and QASUME-IR was validated prior to this campaign at Physikalisch-Technische Bundesanstalt (PTB) by measuring the spectral irradiance from two spectral irradiance sources, the high-temperature blackbody BB3200pg as a national primary standard and the tuneable laser facility TULIP

The EnMAP Observation Planning and Data Access for Scientific Users

EnMAP (Environmental Mapping and Analysis Program; www.enmap.org) is the first German imaging spectroscopy mission, to be launched in April 2022. After its Launch, Early Orbit and Commissioning Phase (6 months), the EnMAP mission will be available to the international user community for the data access and ordering process. EnMAP will be operated by the German Aerospace Center (DLR) covering all aspects relevant to assure successful mission operations. This comprises controlling and commanding the satellite using multi-mission infrastructures as well as observation planning, data reception, hyperspectral data processing including calibration, data archiving, data access and delivery, and providing web-interfaces to the international user community. This presentation will give an overview of EnMAP observation planning and data access concepts and outlines the data ordering workflow in particular for scientific users. The user can get access to EnMAP data using two different order options: On the one hand the user can submit future order requests through the EnMAP Data Access Portal (EDAP). The EDAP links to a set of functions for registered users that will support the international user community. This portal includes amongst others the proposal portal allowing submission of proposal for all scientific users responding to a Data Announcement of Opportunity (AO) and the Observation Request Portal providing planning support of observation requests and allowing submission of future orders. On the other hand, the already recorded data can be searched, processed and delivered based on catalogue from the archive through the EOWEB® GeoPortal. Although EnMAP is based on an open data policy and every type of user is in principle entitled to download data and request acquisitions, there will be different user categories to set acquisition priorities. The scientific (Cat-1) orders has higher priority and is requested to submit a proposal, which will undergo a scientific evaluation. The associated results will be presented by an interactive map supporting the establishment of a worldwide user network and guarantee the highest transparency of the proposal process. In the Observation Portal the user is able to submit future order requests by specifying following order parameters, such as the geographic area of interest (AOI) (between 74° North and 74° South), length of the AOI as a multiple of 30 km and up to 1000 km, the specification of the maximum allowable tilt angle of the satellite across the orbit (5° to 30°), the time span in which the acquisition should be performed and the option for time series and the number of data takes per months. To ensure acceptable illumination conditions, only images with sun zenith angle lower 60° will be considered. As for data acquisition EnMAP will be able to collect 5000 km along track and 30 km across track per day. The probability that the order will be included in the mission planning depends on the requirements for the observation as well as the specified priority and quota. Whether a specific data take is scheduled at the end depends on factors such as e.g. available data storage, cloud probabilities (e.g. historical and predicted cloud coverage) and, if requested by the user, sunglint probability (this is relevant for water products only). Users should make a request at least 25 hours before the scheduled recording to ensure the uplink. All data are available no later than 24 hours after collection for further processing into data products. The EnMAP ground segment will provide a range of standardized data products with different levels of processing of Level 1B, Level 1C and Level 2A based on archived Level 0 comprising extensive quicklooks and metadata. Due to required multiple processing options, each product is generated specifically for the order and delivered using FTPS (FTP with SSL) provided by multi-mission facilities

The Neurocognitive Assessment in the Metabolic and Aging Cohort (NAMACO) study: baseline participant profile.

The aim of the study was to examine baseline neurocognitive impairment (NCI) prevalence and factors associated with NCI among patients enrolled in the Neurocognitive Assessment in the Metabolic and Aging Cohort (NAMACO) study. The NAMACO study is an ongoing, prospective, longitudinal, multicentre and multilingual (German, French and Italian) study within the Swiss HIV Cohort Study. Between 1 May 2013 and 30 November 2016, 981 patients ≥ 45 years old were enrolled in the study. All underwent standardized neuropsychological (NP) assessment by neuropsychologists. NCI was diagnosed using Frascati criteria and classified as HIV-associated or as related to other factors. Dichotomized analysis (NCI versus no NCI) and continuous analyses (based on NP test z-score means) were performed. Most patients (942; 96.2%) had viral loads < 50 HIV-1 RNA copies/mL. NCI was identified in 390 patients (39.8%): 263 patients (26.8%) had HIV-associated NCI [249 patients (25.4%) had asymptomatic neurocognitive impairment (ANI)] and 127 patients (13%) had NCI attributable to other factors, mainly psychiatric disorders. There was good correlation between dichotomized and continuous analyses, with NCI associated with older age, non-Caucasian ethnicity, shorter duration of education, unemployment and longer antiretroviral therapy duration. In this large sample of aging people living with HIV with well-controlled infection in Switzerland, baseline HIV-associated NCI prevalence, as diagnosed after formal NP assessment, was 26.8%, with most cases being ANI. The NAMACO study data will enable longitudinal analyses within this population to examine factors affecting NCI development and course

EnMap In-flight Calibration Status

The Environmental Mapping and Analysis Program (EnMAP) hyperspectral satellite mission was successfully launched on 1st April 2022. The mission aims to monitor and characterise Earth’s environment in the spectral range from 420 - 2450 nm. The VNIR sensor provides 91 science channels ranging from 420 - 1000 nm with an average Spectral Sampling Distance (SSD) of 6.5 nm. While the SWIR sensor covers the range from 900 - 2450 nm with 131 channels and 10nm SSD. - The off-nadir pointing capability (up to 30 degrees) enables 5000 km to be monitored per day, with a swath width of 30 km and a spatial resolution of 30 m. The EnMAP satellite is equipped with several subsystems which allow periodic in-flight monitoring and calibration. The Full Aperture solar Diffuser Assembly (FADA) is used for absolute radiometric calibration. The On-Board Calibration Assembly (OBCA) is composed of 2 integrating spheres: one is coated with a doped diffuser material and is used for the spectral calibration; the second sphere, coated with a white spectralon, is used for Radiometric stability monitoring. Linearity LEDs are placed in front of the detector to monitor their linearity by measuring the response at constant illumination with increasing integration times. The Shutter Calibration Mechanism (SCM) allows for measurements with no light input to be performed in order to compute Dark Signal values and, in combination with Deep Space measurements, to compute any existing shutter emission in the SWIR range. This contribution will present a summary of the calibration activities performed during the EnMAP Commissioning Phase