Olga Sykioti

National Observatory of Athens | NOA · Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS)

This article presents a comparative study of three different types of estimators used for supervised linear unmixing of two MEx/OMEGA hyperspectral cubes. The algorithms take into account the constraints of the abundance fractions, in order to get physically interpretable results. Abundance maps show that the Bayesian maximum a posteriori probabili...

The aim of this study was to propose a methodology that provides a detailed description of the argillic zone of a hydrothermal field, based on satellite multispectral data. More specifically, we developed a method based on spectral unmixing where hydroxyl-bearing alteration is represented by a single endmember (representing clays) and the three (ne...

Cesium-137, as the main fission product, is of special interest in the marine environment because of its solubility, which results to very low sinking time. Nevertheless, the conservative form of the main percentage of ¹³⁷Cs introduced in the marine environment (70%) makes ¹³⁷Cs to be included in the salinity of sea water. Based on this property, i...

Field geological mapping is the initial step of preliminary research in mining. However, in the last decades, the rapid progress of remote sensing data processing and its use for reconnaissance of geological outcrops for the purpose of locating possible mining sites gained increasing attention due to the significant time and cost savings. In this s...

Currently, the global shift towards green energy is at the forefront of efforts introducing a new era, thus rendering exploration for critical raw materials essential. To this purpose, the utilization of advanced machine learning methods in remote sensing has emerged as a rapid and cost-effective approach. This study proposes a new methodology, uti...

As space exploration is breaking through new frontiers, making the most of cutting-edge technologies such as Artificial Intelligence (AI), the legal regime that should apply to innovations and discoveries using AI in this context is gaining importance. A thorough examination of said AI output reveals that it can be roughly divided into two broad ca...

The mineralogical composition of airborne dust particles is an important but often neglected parameter for several physiochemical processes, such as atmospheric radiative transfer and ocean biochemistry. We present the development of the METAL-WRF module for the simulation of the composition of desert dust minerals in atmospheric aerosols. The new...

A new satellite-enabled interoperable service has been developed to provide high spatio-temporal and continuous time series of Growing Degree Days (GDDs) at the field. The GDDs are calculated from MSG-SEVIRI data acquired by the EUMETCast station operated by IAASARS/NOA and downscaled on-the-fly to increase the initial coarse spatial resolution fro...

The invention of the laser has pushed the boundaries of technological advancements with its variety of uses. This use case chapter analyses the implementation of an Autonomous Laser-Induced Breakdown Spectroscopy System for Chemical and Mineralogical Designation of Interplanetary Materials. In more detail, it highlights all the major components of...

During the last decades, the rapid progress of remote sensing data processing for their utilization in detecting locations of possible sites linked to hydrothermal alteration and ores has gained increasing attention due to significant time and cost savings. In this study, we present the findings of a joint remote sensing and laboratory examination...

Introduction and Objectives The Lavreotiki area (Attica, Greece) has been famous for mining since the 5th century BC producing silver and lead contributing to the economic development of ancient Athens during the classic era (Voudouris et al., 2021). The geology and metallogeny of the Lavreotiki area (Attica, Greece) were studied by Marinos and Pet...

Earth Observation satellites and environmental models are able to monitor changes of ecological parameters in the marine environment. Radionuclides cannot be directly measured using satellite remote sensing, because they are not currently detectable by the satellite instruments. Nevertheless, the levels of radionuclides, in the marine environment a...

Ni-laterites constitute a significant proportion of world nickel reserves. LARCO GMMSA exploits the domestic laterite deposits in Greece during the last 50 years, operating in Locris and Euboea island (Central Greece) as well as in Kastoria area (Northern Greece). Since the late 70’s, the use of remote sensing technology in geological mapping has g...

This paper aims to investigate the capability of Sentinel-1 Synthetic Aperture Radar (SAR) data to detect hydrothermal alteration zones within the caldera of the Nisyros volcano in Greece through a multitemporal interferometric coherence analysis. For that purpose, seven ascending pass Sentinel-1B SAR Single Look Complex images were collected spann...

The aim of the present study is the estimation of FeO και TiO2 content in the SW border of Mare Tranquillitatis. For this purpose, we used L2-level reflectance data of the global pattern with a spatial resolution of 140m of the Moon Mineralogy Mapper (M3) hyperspectral imager of the Indian mission Chandrayaan-1. The dimensions of the used hyperspec...

EXTENDED ABSTRACT Mare Tranquillitatis lays the Tranquillitatis basin of pro-Nectarian age 4.5-.4Ga) on the Moon [1]. The mare material within the basin consists of basalts formed in the intermediate to young age group of the Upper Imbrian epoch (3.53Ga). According to the analyses of the samples collected by Apollo 11 mission, the mare is composed...

Detection of potential alteration in the dacitic lavas of the geothermal system of Methana using spectral unmixing on multispectral Sentinel-2 data.

A program concept has been developed to utilize sea parameters like sea surface temperature (SST), ocean colour (OC) and sea surface salinity (SSS), in order to explore their potential relations with 137Cs activity concentrations in sea water. These relations are expected to lead to the creation of an innovative tool based on remote sensing data an...

This paper deals with (both supervised and unsupervised) classification of multispectral Sentinel-2 images, utilizing the abundance representation of the pixels of interest. The latter pixel representation uncovers the hidden structured regions that are not often available in the reference maps. Additionally, it encourages class distinctions and bo...

Considering that ground areas with intense compositional variability appear as mixed pixels in hyperspectral data, we focus on the mixing problem imposed by the various volcanic products found in the vicinity of Mt. Etna’s volcanic craters. Mt. Etna, which is one of the most active volcanoes globally, is a generator of diverse mineralogical environ...

Considering that ground areas, with intense compositional variability appear as mixed pixels on hyperspectral data, focus on the imposed mixing problem of various volcanic products found in the vicinity of Mt. Etna’s volcanic craters. Mt. Etna, as being one of the most active volcanoes globally, is itself a generator of diverse mineralogical enviro...

Considering that ground areas, with intense compositional variability appear as mixed pixels on hyperspectral data, focus on the imposed mixing problem of various volcanic products found in the vicinity of Mt. Etna’s volcanic craters. Mt. Etna, as being one of the most active volcanoes globally, is itself a generator of diverse mineralogical enviro...

During the last decade, hyperspectral imaging (HSI) has been extended to the field of planetary exploration. Investigating the geochemical composition and evolution of a planet is a challenging task of high scientific importance. Spectral unmixing (SU) is one of the most challenging problems in HSI processing. SU is the process of indentifying (a)...

In this study we use Landsat 8 OLI satellite imagery in order to identify and map alteration zones in Limnos island (N. Aegean, Greece). Pre-processing included sea and vegetation masking. In order to enhance spatial resolution, data fusion to 15m is performed. A lineament map is extracted from the panchromatic image that gives the general tectonic...

Mt. Etna (Italy) is a composite stratovolcano and one of the most active volcanoes in the world. Eruptions occur almost every year and there is a persistent degassing activity at the summit craters. The aim of this study is to investigate the capabilities of the spectral signatures and polarimetric backscatter coefficient values on the discriminati...

The advancing technology of hyperspectral remote sensing offers the opportunity of accurate land cover characterization of complex natural environments. In this study, a linear spectral unmixing algorithm that incorporates a novel hierarchical Bayesian approach (BI-ICE) was applied on two spatially and temporally adjacent CHRIS/PROBA images over a...

In this study we use Landsat 8 OLI satellite imagery in order to identify and map altera-tion zones in Limnos island (N. Aegean, Greece). Pre-processing included sea and vege-tation masking. In order to enhance spatial resolution, data fusion to 15m is performed. A lineament map is extracted from the panchromatic image that gives the general tec-to...

The aim of this study focuses in the investigation of vegetation’s responses to precipitation variations and water stress conditions in three Pinus sp. (pine) forests in Greece and in the assessment of NDWI and NDVI in terms of drought and water stress detection capacity for this type of ecosystems. For the purpose of this study, 11–year time serie...

In the present study an innovative tool is explored in terms of the radiological remote control. The levels of radionuclides in the marine environment, especially the soluble ones, are associated with other physical parameters. For this purpose, sea parameters such as sea surface temperature and ocean colour issued from satellite and field measurem...

Mt. Etna is a young composite strato-volcano and one of the most active volcanoes in the world. Eruptions occur almost every year with a persistent degassing activity at the summit craters. In the last 100 years it has produced in average 107m3 of new lava per year. The main goal of our work is to detect land cover changes, including different lava...

The Gulf of Corinth (Greece) has been long identified as a site of major importance due to its intense and high variety of past geophysical activity. It has one of the highest seismicity rates in the Euro-Mediterranean region occurred from a variety of fault mechanisms. The rifting mechanism observed is crucial for the stability of the region as it...

Mt. Etna (Italy) is a composite strato-volcano and one of the most active volcanoes in the world. Eruptions occur almost every year and there is a persistent degassing activity at the summit craters. The main goal of our work is to discriminate different lava flows as well as detect land cover changes over the volcano that occurred between 2009 and...

This study presents the use of multi-temporal Synthetic Aperture Radar (SAR) images for detection of land cover changes in the eastern part of the Island of Crete (Greece). For this purpose, fourteen Envisat ASAR acquisitions from July 2004 to December 2006 were calibrated and registered. We applied a temporal filter and spatial averaging to the ba...

This study presents the use of multi-temporal Synthetic Aperture Radar (SAR) images for detection of land cover changes in the eastern part of the Island of Crete (Greece). For this purpose, fourteen Envisat ASAR acquisitions from July 2004 to December 2006 were calibrated and registered. We applied a temporal filter and spatial averaging to the ba...

Monitoring of lakeshore ecosystems requires fine-scale information to account for the high biodiversity typically encountered in the land-water ecotone. Sentinel-2 is a satellite with high spatial and spectral resolution and improved revisiting frequency and is expected to have significant potential for habitat mapping and classification of complex...

In this paper a joint spectral unmixing and clustering approach for the identification of homogeneous regions in hyperspectral images is proposed. The endmembers required in the unmixing stage are manually selected based on the most significant principal components of the image at hand. Each pixel is decomposed as a linear combination of the endmem...

sCASE is an automated continuous monitoring system that produces near real-time daily gross primary productivity (GPP) estimates of North Pindus National Park forests. The algorithm is based on the light use efficiency (ε) approach, incorporating species-specific maximum ε values (εo) and εo downscaling according to temperature, water scarcity and...

Abstract

The capability of ordinary Εarth observation satellites to record changes of ecological parameters in the environment is well documented. Nevertheless, radionuclide dispersion cannot be detected by the installed devices directly. However, the levels of radionuclides in the marine environment, especially for the soluble ones, are associated with oth...

Landslide phenomena constitute a major geological hazard in Greece and especially in the western part of the country as a result of anthropogenic activities, growing urbanization and uncontrolled land – use. More frequent triggering events and increased susceptibility of the ground surface to instabilities as consequence of climate change impacts (...

The NETSPACE Workshop was organized by the National Observatory of Athens in the framework of the “Space-Data Routers for Exploiting Space Data” project. The “Space-Data Routers” project received research funding from the Seventh Framework Programme of the European Union, through Grant Agreement No 263330. The project was implemented by a consortiu...

Magnetospheric processes play an important role in the Sun-Earth connection and space weather in general. The availability of multi-spacecraft observations can lead to the comprehensive characterization of magnetospheric processes and set the foundations for a deeper understanding and eventual forecasting of them. However, multi-spacecraft distribu...

The prospect of accurately tracking photosynthetic processes using satellite observations is very important for understanding and monitoring global carbon cycle and climate change. The present study investigates the efficiency of the Photochemical Reflectance Index (PRI) in detecting light use efficiency (ε) in different spatial scales. The study s...

Data distribution and access are major issues in space sciences as they influence the degree of data exploitation. The project "Space-Data Routers" (SDR) has the aim of allowing space agencies, academic institutes and research centres to share space data generated by single or multiple missions, in an efficient, secure and automated manner. The app...

Data sharing and access are major issues in space sciences, as they influence the degree of data exploitation. The project "Space-Data Routers", which was initiated recently, has the aim of allowing space agencies, academic institutes and research centres to share space-data generated by single or multiple missions, in an efficient, secure and auto...

The Gulf of Corinth study area has been long identified as a site of major importance due to its intense past geophysical activity. It is one of the world's most rapidly extending continental regions and it has one of the highest seismicity rates in the Euro-Mediterranean region, having produced a number of earthquakes with magnitude greater than 5...