Description: GEROS-ISS stands for GNSS REflectometry, radio occultation, and scatterometry onboard the International Space Station (ISS). It is a scientific experiment, successfully proposed to the European Space Agency in 2011. The experiment as the name indicates will be conducted on the ISS. The main focus of GEROS-ISS is the dedicated use of signals from the currently available Global Navigation Satellite Systems (GNSS) in L-band for remote sensing of the Earth with a focus to study climate change. Prime mission objectives are the determination of the altimetric sea surface height of the oceans and of the ocean surface mean square slope, which is related to sea roughness and wind speed. These geophysical parameters are derived using reflected GNSS signals (GNSS reflectometry, GNSS-R). Secondary mission goals include atmosphere/ionosphere sounding using refracted GNSS signals (radio occultation, GNSS-RO) and remote sensing of land surfaces using GNSS-R. The GEROS-ISS mission objectives and its design, the current status, and ongoing activities are reviewed and selected scientific and technical results of the GEROS-ISS preparation phase are described.

Description: In February 2019 a Project Authorization Request was approved by the Institute of Electrical and Electronics Engineers (IEEE) Standards Association with the title “Standard for Global Navigation Satellite System Reflectometry (GNSS-R) Data and Metadata Content”. A Working Group has been assembled to draft this standard with the purpose of unifying and documenting GNSS-R measurements, calibration procedures, and product level definitions. The Working Group (http://www.grss-ieee.org/community/technical-committees/standards-or-earth-observations/) includes members, collaborators, and contributors from academia, international space agencies, and private industry. In a recent face-to-face meeting held during the ARSI+KEO 2019 Conference, the need was recognized to develop a standard with a wide range of operations, providing procedure guidelines independently of constraints imposed by current limitations on geophysical parameters retrieval algorithms. As such, this effort aims to establish the fundamentals of a potential virtual network of satellites providing inter-comparable data to the scientific community.

Description: 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.

Description: The Institute of Electrical and Electronics Engineers (IEEE) Geoscience and Remote Sensing Society (GRSS) created the GRSS “Standards for Earth Observation Technical Committee” to advance the usability of remote sensing products by experts from academia, industry, and government through the creation and promotion of standards and best practices. In February 2019, a Project Authorization Request was approved by the IEEE Standards Association (IEEE-SA) with the title “Standard for Spaceborne Global Navigation Satellite Systems Reflectometry (GNSS-R) Data and Metadata Content.” At present, 4 GNSS constellations cover the Earth with their navigation signals: The United States of America (USA) Global Positioning System GPS with 31 Medium Earth Orbit (MEO) operational satellites, the Russian GLObal’naya NAvigatsionnaya Sputnikovaya Sistema GLONASS with 24 MEO operational satellites, the European Galileo with 24 MEO operational satellites, and the Chinese BeiDou-3 with 3 Inclined GeoSynchronous Orbit (IGSO), 24 MEO, and 2 Geosynchronous Equatorial Orbit (GEO) operational satellites. Additionally, several regional navigation constellations increase the number of available signals for remote sensing purposes: the Japanese Quasi-Zenith Satellite System QZSS with 1 GSO and 3 Tundra-type orbit operational satellites, and the Indian Regional Navigation Satellite System IRNSS with 3 GEO and 4 IGSO operational satellites. On the other hand, there are different GNSS-R processing techniques, instruments and spaceborne missions, and a wide variety of retrieval algorithms have been used. The heterogeneous nature of these signals of opportunity as well as the numerous working methodologies justify the need of a standard to further advance in the development of GNSS-R towards an operational Earth Observation technique. In particular, the scope of this working group is to develop a standard for data and metadata content arising from past, present, and future spaceborne missions such as the United Kingdom (UK) TechDemoSat-1 TDS-1, and the National Aeronautics and Space Administration (NASA) CYclone Global Navigation Satellite System CYGNSS constellation coordinated by the University of Michigan (UM). In this article we describe the scene study, including fundamental aspects, scientific applications, and historical milestones. The spaceborne standard is under development and it will be published in IEEE-SA.

Description: Remote sensing radar instruments rely typically on active transmitters that have a power demand, which is difficult to cope with on CubeSats due to their size limitations. A passive reflectometer overcomes this problem by receiving the reflected beam from a known precise signal source in space. Due to the used frequency band, the signal modulation and the availability of their transmitter's ephemerides, GNSS signals are perfectly usable for this purpose. The PRETTY (Passive REflecTometry and dosimeTrY) satellite is currently developed by TU Graz, RUAG Space and Seibersdorf Laboratories under a contract with ESA. PRETTY hosts two payloads: The first payload is a passive GNSS based reflectometer. The main scientific goal is the precise altimetric determination of ocean and sea-ice surfaces using the interferometric phase-delay altimetry approach. The interferometric approach avoids the local generation of the original signal by additionally receiving of the direct (not reflected) signal from the signal source, which subsequently is correlated with the reflected beam. This methodology will be applied for the first time in space. The second payload is a dosimeter for analysis of the space radiation environment in the PRETTY orbit by collecting data from different sensors. The dosimeter is capable of providing information on the total ionizing dose (TID) as well as on the linear energy transfer (LET) of the space radiation environment. The satellite mission has entered the detailed design phase and a launch is scheduled for early 2021, with a nominal operational lifetime of one year. In the present publication, we introduce the mission and observation concept, as well as the current status of the project. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.