Optical investigations of CDOM-rich coastal waters in Pärnu Bay

Pärnu Bay in the Eastern Baltic Sea was chosen for studying the spatial-temporal variability of water parameters as an optically complex and semi-enclosed coastal area. The water properties of Pärnu Bay are influenced by the town of Pärnu with its 70 000 inhabitants and by the high inflow from the Pärnu River. The in situ database was collected during the ice-free period of 2006–2007 (11 sampling stations, 10 series of field trips). According to the results, the main factor influencing the light attenuation in the water was coloured dissolved organic matter (CDOM) which overshadows the relationships between the radiation characteristics and organic/inorganic particles. In April and May, when the freshwater discharge of the Pärnu River was highest, the values of aCDOM(380) were between 4.6 and 31.8 m–1, while in September they varied only within 2.52–10.2 m–1. The concentrations of chlorophyll a (including its metabolite phaeophytin a) generally ranged from 4 to 12 mg m–3 but during algal blooms they rapidly increased to 31.8 mg m–3. The temporal and spatial irregularity of suspended matter concentrations was caused by the loading of unpacked peat at the Pärnu River mouth as well as by undulation and ship traffic in Pärnu Bay. MODIS level 1 data with 250 m resolution were used for illustrative comparison of spatial and temporal variations in the water properties in Pärnu Bay and the Gulf of Riga. An attempt to perform the quantitative analysis with the purpose of estimating the concentrations of different optically significant substances separately gave statistically incorrect results

In situ determination of the remote sensing reflectance: an inter-comparison

Inter-comparison of data products from simultaneous measurements performed with independent systems and methods is a viable approach to assess the consistency of data and additionally to investigate uncertainties. Within such a context the inter-comparison called Assessment of In Situ Radiometric Capabilities for Coastal Water Remote Sensing Applications (ARC), was carried out at the Acqua Alta Oceanographic Tower in the northern Adriatic Sea to explore the accuracy of in situ data products from various in- and above-water optical systems and methods. Measurements were performed under almost ideal conditions including: a stable deployment platform, clear sky, relatively low sun zenith angles and moderately low sea state. Additionally, all optical sensors involved in the experiment were inter-calibrated through a post-field absolute radiometric calibration performed with the same standards and methods. Inter-compared data products include: spectral water-leaving radiance Lw,above-water downward irradiance Ed(0+) and remote sensing reflectance Rrs. Data products from the various measurement systems/methods were directly compared to those from a single reference system/method. Results for Rrs indicate spectrally averaged values of relative differences comprised between -1 and +6%, while spectrally averaged absolute values of relative differences vary from approximately 6% for the above-water systems/methods to 9% for buoy-based systems/methods. The good agreement between Rrs spectral relative differences and estimates of combined uncertainties of the inter-compared systems/methods is noteworthy.JRC.H.1-Water Resource

The European Butterfly Indicator for grassland species: 1990-2013

This report presents the fifth version of the European Grassland Butterfly Indicator, one of the EU biodiversity indicators of the European Environment Agency

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with -1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.Peer reviewe

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with - 1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.</p

Detecting cyanobacterial blooms in large North European lakes using the Maximum Chlorophyll Index

The Maximum Chlorophyll Index (MCI), developed for the MERIS sensor processing scheme, is used to investigate the seasonaldynamics, spatial distribution, and coverage of cyanobacterial blooms over Lake Peipsi (Estonia/Russia) and Lake Võrtsjärv(Estonia). In these optically complex waters, the amounts of suspended matter and dissolved organic matter vary greatly andindependently of the phytoplankton biomass. We demonstrate that MCI is a useful, new tool for detecting and estimating cyanobacterialbiomass (R2 = 0.73), phytoplankton biomass (R2 = 0.70) and chlorophyll a concentration (R2 = 0.64). The MCI-derivedresults are consistent with known patterns of phytoplankton dynamics in these lakes, whose optical properties are in the same range as in many coastalregions of the Baltic Sea