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Tag: HydroGNSS

  • ESA’s HydroGNSS satellites launched to scout for water

    ESA’s HydroGNSS satellites launched to scout for water

    The European Space Agency’s first Scout mission, HydroGNSS, was launched Nov. 28, marking a significant step in advancing global understanding of water availability and the effects of climate change on Earth’s water cycle.

    The two twin HydroGNSS satellites were carried into orbit at 19:44 CET aboard a SpaceX Falcon 9 rocket, as part of the Transporter-15 rideshare flight from the Vandenberg Space Force Base in California.

    Less than 90 minutes after liftoff, the two satellites separated from the rocket. Then, at 22:45 CET, Surrey Satellite Technology Ltd. (SSTL) in the UK confirmed that they had received signals, indicating that both satellites were safely in orbit around Earth.

    How GNSS reflectometry helps

    Both satellites use GNSS reflectometry to scout for water by capturing L-band signals from navigation systems such as GPS and Galileo. These navigation satellites transmit L-band microwave signals that change when they are reflected off Earth’s surface.

    The HydroGNSS satellites then compare these reflected signals with the signals the satellites receive directly from the GNSS satellites to reveal valuable information about the properties related to the water cycle, and more.

    To do this, each HydroGNSS satellite carries a delay doppler mapping receiver and two antennas. A zenith antenna tracks direct GNSS signals and a nadir antenna collects reflected signals and processes them into delay Doppler maps.

    Using this technique, the two small satellites, which orbit Earth 180 degrees apart, will measure soil moisture, freeze-thaw state, inundation and above-ground biomass.

    Understanding the water cycle

    The data will not only be vital for advancing our understanding of Earth’s water cycle, but also for supporting applications such as flood prediction and agricultural planning.

    Also, by observing the extent of inundation and areas of wetland, HydroGNSS will help reveal wetlands – important ecosystems that can act as significant sources of methane – often hidden beneath forest canopies.

    Information on freeze–thaw states will provide insight into the surface radiation balance, energy and carbon exchanges with the atmosphere, and the behaviour of subsurface permafrost in high latitudes.

    Meanwhile, data on above-ground biomass will contribute to estimates of forest carbon stocks and their role in the global carbon cycle.

    More Scouts to come

    The Scout satellite missions harness small, smart satellites to shrink proven technologies or test bold new ways of observing the planet. Each mission races from concept to launch in three years, on a lean budget of €35 million that covers everything from design and construction to in-orbit operations.

    “As the first of ESA’s Scout missions to launch, HydroGNSS marks an important milestone for this new family of rapid, low-cost Earth observation missions, and we extend our thanks to the mission’s prime contractor, SSTL,” said Simonetta Cheli, ESA’s director of Earth Observation Programmes. “The launch also represents a key step in the evolution of our FutureEO programme, where the Scouts embody a fast, agile, innovative and cost-efficient approach – complementing our larger Earth Explorer research missions.

    “We now look forward to seeing how HydroGNSS will employ GNSS reflectometry to deliver valuable insights into key hydrological variables that shape Earth’s water cycle,” Cheli said.

    ESA’s prime contractor for the HydroGNSS mission is SSTL in the UK. SSTL is also responsible for operating the satellites in orbit and for distributing the data. The mission is also thanks to partial funding from the UK Space Agency.

  • ESA’s HydroGNSS Scout satellites ready for launch

    ESA’s HydroGNSS Scout satellites ready for launch

    Two European Space Agency (ESA) microsatellites will soon be launched to study climate variables linked to water using GNSS reflectometry. The twin HydroGNSS satellites arrived at Vandenberg Space Force Base in California at the end of September, from where they will be launched later this month.

    The HydroGNSS twins are the European Space Agency’s first Scout venture, part of the agency’s Earth Observation FutureEO programme. Scout missions are designed to deliver cutting-edge science quickly and affordably, complementing ESA’s larger Earth Explorer missions.

    The identical microsatellites will launch from Vandenberg aboard a SpaceX Falcon 9 rocket, sharing their Transporter-15 ride into orbit with several other small satellites.

    Since their arrival, the HydroGNSS satellites have undergone a series of final checks — including testing, propellant loading, battery charging and integration with their launch adapter. Both satellites are now ready for closing of the rocket fairing.

    Once in orbit, the two satellites will travel 180 degrees apart around Earth to maximize coverage.

    The mission focuses on four crucial variables, all recognized as “essential climate variables” or closely related to them: soil moisture, freeze–thaw state over permafrost, inundation and above-ground biomass. These data are vital for improving our understanding of Earth’s water cycle, including wetlands, permafrost dynamics and forest carbon storage. The data will aid in agricultural planning, flood prediction, and others areas.

    HydroGNSS satellites will use GNSS reflectometry to measure key hydrological climate variables, including soil moisture, freeze–thaw state over permafrost, inundation and wetlands, and above-ground biomass. (Image: ESA)
    HydroGNSS satellites will use GNSS reflectometry to measure key hydrological climate variables, including soil moisture, freeze–thaw state over permafrost, inundation and wetlands, and above-ground biomass. (Image: ESA)

    Navigation satellites such as GPS and Galileo transmit L-band microwave signals that change when reflected off Earth’s surface. HydroGNSS will compare these reflected signals with the direct GNSS signals to extract valuable information about geophysical parameters related to the water cycle.

    New Space missions. Inspired by the principles of New Space, the Scout programme emphasises agility and innovation — using small satellites to miniaturise proven technologies or demonstrate entirely new ways of observing Earth.

    Each Scout mission must move from kick-off to launch within just three years and under a budget of €35 million, covering everything from satellite development to in-orbit commissioning. The resulting data are provided as a service to the scientific community and ESA, helping accelerate our understanding of the planet.

  • SSTL’s HydroGNSS satellite gets green light for climate mission

    SSTL’s HydroGNSS satellite gets green light for climate mission

    The small satellite will measure climate variables using GNSS Reflectometry

    The European Space Agency (ESA) has selected HydroGNSS from Surrey Satellite Technology Ltd. (SSTL) for its second Scout Earth Observation small satellite mission. HydroGNSS is a 40-kg satellite that will be built and operated by SSTL.

    ESA selected the first ESA Scout satellite, ESP-MACCS, in December 2020. ESP-MACCS focuses on understanding and quantifying processes in the upper atmosphere over the tropics — processes that play an important role in the overall evolution of the atmosphere.

    HydroGNSS will take measurements of key hydrological climate variables, including soil moisture, freeze thaw state over permafrost, inundation and wetlands, and aboveground biomass, using GNSS reflectometry. It will complement missions such as ESA’s SMOS and Biomass, Copernicus Sentinel-1 and NASA’s SMAP.

    Both small satellites are expected to be the first in a series of ESA Scout missions demonstrating how small satellites on a budget of less than €30 million and a three-year schedule can play an important role in Earth observation, and be scaled up for future missions.

    Knowledge of these variables helps scientists understand climate change and contributes towards weather modelling, ecology mapping, agricultural planning and flood preparedness.

    “SSTL pioneered GNSS reflectometry, providing the payloads on TechDemoSat-1 and the NASA CYGNSS mission for measuring ocean wind speeds, and I am delighted that we will now launch the first satellite mission specifically addressing hydrological measurements using this innovative technique,” said Phil Brownnett, SSTL managing director.

    Previously, addressing hydrological variables such as these has required sizable and higher cost satellites with large aperture antennas, but GNSS reflectometry uses existing signals from GNSS as radar signal sources. These signals are reflected off the land, ice and ocean and can be collected by a low power receiver on a small satellite in low Earth orbit, and used to yield important geophysical measurements.

    Image: SSTL
    Image: SSTL

    SSTL is working closely with partners to tackle the scientific and technological challenges involved. Partners include Sapienza, Tor Vergata and IFAC-CNR in Italy; FMI in Finland; IEC/IEEC in Spain; and NOC and the University of Nottingham in the United Kingdom (UK),

    “The decision to implement HydroGNSS after ESP-MACCS demonstrates that the Earth observation community is very interested in the concept of Scout missions. We are confident that this interest will further flourish when we see the first data in 2024,” said Toni Tolker-Nielsen, ESA’s acting director of Earth Observation Programmes.

    As well as the already established GNSS-Reflectometry measurements, new techniques will be explored on HydroGNSS, including use of Galileo signals, dual polarization, dual frequency and recovery of coherently reflected components. These new measurements are expected to improve the separation, resolution and quality of the climate variables under observation.

    The HydroGNSS mission exemplifies the UK’s innovation in climate change research, according to SSTL. The 26th United Nations Climate Change Conference takes place in the UK Nov. 1-12.

    Image: SSTL
    Image: SSTL

    “The UK is leading the way in using space to tackle climate change, with Earth Observation satellites providing some of the most important data to monitor our environment as we build back greener,” said Science Minister Amanda Solloway. “Using a UK satellite just the size of a microwave oven, this pioneering mission will build on the UK’s expertise in space research by measuring changes in the Earth’s water, providing crucial information to address climate change, improve farming and support wider disaster management.”

    HydroGNSS paves the way for an affordable future constellation that can offer measurements with a temporal-spatial resolution not accessible to traditional remote-sensing satellites, thus offering new capacity to monitor very dynamic phenomena and helping to fill the gaps in our monitoring of the Earth’s vital signs for the future.

     

    Featured image: SSTL

  • SSTL demonstrates new GNSS-R capabilities

    The successful demo consolidates concept designs for a proposed land-sensing ESA Scout mission, HydroGNSS

    Surrey Satellite Technology Ltd. (SSTL) has successfully demonstrated GNSS reflectometry (GNSS-R) from its 18-kg DoT-1 satellite. SSTL has pioneered the new field of GNSS-R with successful payloads on board TechDemoSat-1 and the CYGNSS constellation, and is continuing to develop the technology and data analysis in pursuit of this new science.

    SSTL's DoT-1 satellite
    SSTL’s DoT-1 satellite was launched in 2019. (Photo: SSTL)

    The GNSS-R payload onboard the DoT-1 satellite is incorporated within a new small-form-factor Core Avionics module integral to all SSTL’s future satellite platforms. This innovation paves the way for any SSTL satellite that can accommodate a nadir pointing antenna to become part of a GNSS-R small-sat constellation.

    GNSS reflectometry is an Earth-observation technique that uses GNSS signals as L-band radar sources, allowing the satellite to take measurements of ocean wind speeds, polar ice and hydrological land parameters, at a higher spatial resolution and an order of magnitude lower cost than other methods.

    “GNSS-R is a powerful new science that can contribute valuable data to help monitor changes in our global climate, and I am really pleased with the success of our DoT-1 demonstration.,” said Phil Brownnett, managing director of SSTL. “We now have an advanced instrument design and deep expertise in this new field, and I am hopeful that SSTL’s HydroGNSS concept will progress to a full mission to support the global climate-control challenge.”

    HydroGNSS mission

    The GNSS-R technology demonstration from SSTL’s DoT-1 satellite is also an important stepping stone for a proposed European Space Agency (ESA) Scout Mission Concept called HydroGNSS, which comprises two 40-kg satellites that collect data continually in near-polar orbits, taking hydrological measurements over the whole globe.

    The HydroGNSS mission concept makes advanced use of new GNSS reflectometry techniques such as Galileo signals, dual polarization, and coherent signal acquisition to measure four Essential Climate Variables (ECVs) over land: soil moisture, inundation, permafrost freeze/thaw, and biomass. HydroGNSS has been down-selected by ESA for a concept study; the finally selected Scout mission will commence in 2021.

    The below animated video illustrates the HydroGNSS mission.

    SSTL’s GNSS-R instrument collects and processes measurements into a “delay Doppler map” (DDM) that can be corrected and inverted into Level 2 products such as ocean wind speed, as has already been successfully demonstrated by the SSTL GNSS-R instruments onboard the TechDemoSat-1 and CYGNSS missions.

    The plot below shows results from data gathered by the DoT-1 satellite on Aug. 12, and shows simultaneous DDMs from four separate GPS satellites. As this is a forward scattering technique, the stronger signals with redder peaks indicate a calmer ocean with lower wind speeds. Approximately 40 minutes of data were collected from the Pacific to the Antarctic to the Southern Ocean.

    DoT-1 sub-satellite track (white) and GPS reflection tracks (yellow) collected during 40 minute data operation. (Image: SSTL)
    DoT-1 sub-satellite track (white) and GPS reflection tracks (yellow) collected during 40 minute data operation. (Image: SSTL)

    Four Delay Doppler Maps (DDMs) collected by DoT-1 that show signal reflections from four GPS satellites. (Image: SSTL)
    Four Delay Doppler Maps (DDMs) collected by DoT-1 that show signal reflections from four GPS satellites. (Image: SSTL)

    Soil moisture measurements

    Data from the SSTL GNSS-R instruments onboard the CYGNSS mission have demonstrated the potential for soil moisture measurement by GNSS reflectometry, and preliminary work shows that GNSS-R also has good sensitivity for freeze/thaw sensing in the active zone of permafrost. Unseasonal changes in the permafrost cycles could potentially release larger quantities of methane, which risks exacerbating global climate change.

    GNSS-R can also be used to assess biomass, a measure of forest density which acts as a vital sink for removing carbon dioxide from the atmosphere. In addition to longer term climate observations, soil moisture and inundation measurements from GNSS reflectometry can provide important information for short-term operational purposes, for example, towards Numerical Weather Prediction and flood warnings following rainfall events.

    The development of SSTL’s new GNSS-R instrument was funded in part by the European Space Agency.