Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Sentinel-2: ESA's Optical High-Resolution Mission for GMES Operational Services

Deep learning (DL) is a powerful state-of-the-art technique for image processing including remote sensing (RS) images. This letter describes a multilevel DL architecture that targets land cover and crop type classification from multitemporal multisource satellite imagery. The pillars of the architecture are unsupervised neural network (NN) that is used for optical imagery segmentation and missing data restoration due to clouds and shadows, and an ensemble of supervised NNs. As basic supervised NN architecture, we use a traditional fully connected multilayer perceptron (MLP) and the most commonly used approach in RS community random forest, and compare them with convolutional NNs (CNNs). Experiments are carried out for the joint experiment of crop assessment and monitoring test site in Ukraine for classification of crops in a heterogeneous environment using nineteen multitemporal scenes acquired by Landsat-8 and Sentinel-1A RS satellites. The architecture with an ensemble of CNNs outperforms the one with MLPs allowing us to better discriminate certain summer crop types, in particular maize and soybeans, and yielding the target accuracies more than 85% for all major crops (wheat, maize, sunflower, soybeans, and sugar beet).

Deep Learning Classification of Land Cover and Crop Types Using Remote Sensing Data

Persistent Scatterer Interferometry (PSI) is a powerful remote sensing technique able to measure and monitor displacements of the Earth’s surface over time. Specifically, PSI is a radar-based technique that belongs to the group of differential interferometric Synthetic Aperture Radar (SAR). This paper provides a review of such PSI technique. It firstly recalls the basic principles of SAR interferometry, differential SAR interferometry and PSI. Then, a review of the main PSI algorithms proposed in the literature is provided, describing the main approaches and the most important works devoted to single aspects of PSI. A central part of this paper is devoted to the discussion of different characteristics and technical aspects of PSI, e.g. SAR data availability, maximum deformation rates, deformation time series, thermal expansion component of PSI observations, etc. The paper then goes through the most important PSI validation activities, which have provided valuable inputs for the PSI development and its acceptability at scientific, technical and commercial level. This is followed by a description of the main PSI applications developed in the last fifteen years. The paper concludes with a discussion of the main open PSI problems and the associated future research lines.

https://zenodo.org/record/45568/files/Persistent_Scatterer_Interferometry.pdf

Persistent Scatterer Interferometry: A review

Obtaining accurate and widespread measurements of the vertical structure of the Earth’s forests has been a long-sought goal for the ecological community. Such observations are critical for accurately assessing the existing biomass of forests, and how changes in this biomass caused by human activities or variations in climate may impact atmospheric CO2 concentrations. Additionally, the three-dimensional structure of forests is a key component of habitat quality and biodiversity at local to regional scales. The Global Ecosystem Dynamics Investigation (GEDI) was launched to the International Space Station in late 2018 to provide high-quality measurements of forest vertical structure in temperate and tropical forests between 51.6° N & S latitude. The GEDI instrument is a geodetic-class laser altimeter/waveform lidar comprised of 3 lasers that produce 8 transects of structural information. Over its two-year nominal lifetime GEDI is anticipated to provide over 10 billion waveforms at a footprint resolution of 25 ​m. These data will be used to derive a variety of footprint and gridded products, including canopy height, canopy foliar profiles, Leaf Area Index (LAI), sub-canopy topography and biomass. Additionally, data from GEDI are used to demonstrate the efficacy of its measurements for prognostic ecosystem modeling, habit and biodiversity studies, and for fusion using radar and other remote sensing instruments. GEDI science and technology are unique: no other space-based mission has been created that is specifically optimized for retrieving vegetation vertical structure. As such, GEDI promises to advance our understanding of the importance of canopy vertical variations within an ecological paradigm based on structure, composition and function.

/pdf/the-global-ecosystem-dynamics-investigation-high-resolution-1i9f1upo3p.pdf

The Global Ecosystem Dynamics Investigation: High-resolution laser ranging of the Earth’s forests and topography

GMES Sentinel-1 mission

ERS-2 was piloted in yaw-steering mode using three gyroscopes since the beginning of the mission until February 2000, when a new yaw-steering mode using only one gyroscope was implemented. The ERS-2 gyroscopes have experienced several problems during the mission and the new mono-gyro mode (1GP) was intended to ensure the mission continuity even in case of additional failures. In January 2001 a new test piloting mode using no gyroscopes, the Extra- Backup Mode (EBM), was implemented as a first stage of a gyro-less piloting mode. The aim of this challenging mode was to maintain the remaining gyroscopes performance only for those activities absolutely requiring them, such as some orbit manoeuvres. A more accurate version of this yaw- steering zero-gyro mode (ZGM) was operationally used since June 2001 and the performance was further improved with the implementation of the Yaw Control Monitoring mode (YCM) at the beginning of 2002. The evolution from the nominal and extremely stable three-gyro piloting mode (3GP) to the YCM has allowed to successfully continuing the ERS-2 operations despite of the gyroscopes failures. Nevertheless, this evolution has significantly affected the stability of the satellite attitude and the SAR Doppler Centroid frequency. The scope of this paper is to provide an overview of the different ERS-2 piloting modes and to assess their impact on the platform attitude, the SAR Doppler stability, the product quality and the applications performance, particularly for interferometry.

https://earth.esa.int/fringe03/proceedings/papers/26_miranda.pdf

Review of the Impact of ERS-2 Piloting Modes on the SAR Doppler Stability

In line with the overall Sentinel operations strategy, Sentinel-1, the next European C-Band SAR mission following ERS and ENVISAT, will be operated based on a stable and predefined observation scenario. During the Full Operations Capacity of the mission, this observation scenario will make optimum use of the SAR duty cycle within the technical constraints of the overall system, with the main objective of satisfying the observation requirements from the GMES services and for use by ESA and EU Member States, as stipulated in the ESA GMES Space Component Programme Declaration. In addition, a secondary objective is to some extent ensure the continuity of ERS/ENVISAT SAR data exploitation. The process of collecting the Sentinel-1 observation needs (from GMES services, Member States, the scientific community, etc.) and deriving the baseline observation scenario is on-going at the time of writing this paper. The paper describes this process at high level. It provides an overview of the main types of services and applications to be supported by Sentinel-1 and their high level observation requirements, as well as the overall strategy which is followed to define the related observation scenario.

Sentinel-1 mission operations concept

ERS-2 was piloted in yaw-steering mode using three gyroscopes since the beginning of the mission until February 2000, when a new yaw-steering mode using only one gyroscope was implemented. The ERS-2 gyroscopes had experienced several problems during the mission and the new mono-gyro mode (1GP) was intended to ensure the mission continuity even in case of additional failures. In January 2001 a new test piloting mode using no gyroscopes, the Extra-Backup Mode (EBM), was implemented as a first stage of a gyro-less piloting mode. The aim of this challenging mode was to maintain the remaining gyroscopes performance only for those activities absolutely requiring them, such as some orbit manoeuvres. A more accurate version of this yaw-steering zero- gyro mode (ZGM) was operationally used since June 2001 and the performance was further improved with the implementation of the Yaw Control Monitoring mode (YCM) at the beginning of 2002. The evolution from the nominal and extremely stable three-gyro piloting mode (3GP) to the YCM has allowed to successfully continuing the ERS-2 operations despite of the gyroscopes failures. Nevertheless, this evolution has significantly affected the stability of the satellite attitude and the SAR Doppler Centroid frequency. The scope of this paper is to provide an overview of the different ERS-2 piloting modes and to assess their impact on the platform attitude, the SAR Doppler stability, the product quality and the applications performance, particularly for interferometry.

https://earth.esa.int/workshops/fringe03/proceedings/papers/26_miranda.pdf

Review of the impact of ers-2 piloting modes on the sar

The ESA Sentinels constitute the first series of operational satellites respondin g to the Earth Observation needs of the EU-ESA Global Monitor ing for Environment and Security (GMES) programme . The GMES space component relies on existing and planned space assets as well as on new complementary developments by ESA. This describes the Sentinel- 1 mission, as imaging synthetic aperture radar (SAR) satellite constellation at C-band . It provides an overview of mission requirements, its appl ications and the technical concepts for the system .

Betlem Rosich

Papers

GMES Sentinel-1 mission

Review of the Impact of ERS-2 Piloting Modes on the SAR Doppler Stability

Sentinel-1 mission operations concept

Review of the impact of ers-2 piloting modes on the sar

The Sentinel-1 radar mission: status and performance