This paper presents the architecture and results achieved by the EO-ALERT H2020 project. EO-ALERT proposes the definition and development of the next-generation Earth Observation (EO) data processing chain, based on a novel flight segment architecture that moves optimised key EO data processing elements from the ground segment to onboard the satellite, with the aim of delivering the EO products to the end user with very low latency (in almost real-time). This paper presents the EO-ALERT architecture, its performance and hardware. Performances are presented for two reference user scenarios; ship detection and extreme weather nowcasting/monitoring. The hardware testing results show that, when implemented using Commercial Off-The-Shelf (COTS) components and available communication links, the proposed architecture can deliver EO products and alerts to the end user with a latency lower than one-point-five minutes, for both SAR and Optical Very High Resolution (VHR) missions, demonstrating the viability of the EO-ALERT concept and architecture.

PRETTY is a 3U Cubesat mission by a consortium of Technical University Graz, Seibersdorf Laboratories and RUAG Space GmbH with a planned launch in 2022. The satellite is based on the OPS-SAT platform [1] and will host two payloads, a radiation monitor and a passive reflectometer. Within the present publication we will discuss the current status of the reflectometer payload including the most relevant risks and also their mitigation by prototype developments and measurements. A first operational version of the instrument using commercial off the shelf (COTS) demonstration boards, hosting flight representative components for the RF front end as well as for the digital signal processing has been assembled and integrated with the corresponding hard- and software. While measurement results based on using the output of a global navigation satellite system (GNSS) simulator as input to the PRETTY instrument have been presented earlier, we focus within this publication on the result of field tests on representative hardware in order to evaluate the expected L1 band environment for the mission.

Passive remote sensing from space with signals of opportunity has been studied for a long time beginning in the early 90s [1]. The technique uses already existing signals, transmitted from satellites, which are reflected from ground in order to determine properties of earth surface. GNSS signals are the main interest here, due to their well-known signal properties. The Passive reflectometer acts as a bistatic radar, hence no expensive and power-consuming radar transmitter are needed. The received signal is correlated with a local code replica, where the resulting waveform shows properties of the reflected surface area. Instead of using a local code replica, the PRETTY mission will correlate the received reflected signal with the received direct signal. This technique is known as the interferometric approach. The main advantage for the interferometric approach is, that one is not bound to use known signals but can also exploit signals with unknown data modulation, opening up the possibility to use more generic signals for earth observation.The PRETTY satellite architecture will be based on the OPS-SAT architecture with modifications to accommodate the two payloads. RUAG Space GmbH as prime contractor will design the passive reflectometer payload, and Seibersdorf Laboratories is responsible for a novel dosimeter payload for measuring the space radiation environment during the PRETTY space mission. The dosimeter system will assess Total Ionizing Dose (TID) by the use of radiation integrating sensors, as well as LET spectral information, which is related to Single-Event Effects (SEE) in electronic components. Technical University Graz contributes the satellite platform based on the OPS-SAT architecture [2]. Furthermore TU Graz conducts the Manufacturing, Assembly, Integration and Test (MAIT) activities and will be in charge for the operation of the satellite. The scientific advisory group to be established will support the design of the payload and the evaluation of the raw data from the operation of the satellite. Within the present paper we will describe the architecture of the passive reflectometer payload within this 3U CubeSat mission and discuss operational routines and constraints.

In a recent paper, the modified Gardner detector has been proposed for advanced symbol-timing recovery of M-ary phase-shift keying signals. Compared with the original algorithm, the self-noise jitter can be considerably reduced for highly bandlimited systems and smaller values of M. In this letter, a completely different approach is investigated, which improves the self-noise performance for larger values of M, as well