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ESA promotes radio frequency monitoring as Spire becomes TPM

23 Nov 2023

Glaswegian-built nanosatellite
Glaswegian-built nanosatellite

The global company Spire, which specialises in using continuous global monitoring to track aircraft, ships and weather patterns using a large constellation of CubeSats, is now an ESA Third Party Mission.

As Earth’s population continues to grow, acquiring high quality data to help to predict the movement of the world’s resources is a priority. A specialist in this field, providing radio frequency datasets in near real-time, Spire Global today announced that it has officially joined ESA’s prestigious Earthnet Third Party Mission (TPM) programme.

Spire first began launching satellites in 2013, and since then has launched more than 160 satellites, maintaining a large, operational LEMUR (Low Earth orbit Multi-Use Receiver) constellation. The satellites were designed, built and operated by Spire’s UK office in Glasgow, and its European headquarters in Luxembourg.

Each of Spire’s shoe-box sized CubeSats contains powerful software defined radio payloads, which can be re-programmed in orbit and on demand to receive and process various radio signal types. The payloads can also collect short raw signal recordings for post-processing on ground. The flexibility of these payloads enables fast response to user demands, near real-time data, and service and constellation continuity, which is important for applications such as global shipping, aviation monitoring services and weather forecasting.

Refraction or reflection of GNSS signals from Earth

Spire’s LEMUR CubeSats can be equipped with either a space-based Radio Occultation (RO) payload – whereby instruments are used to measure how signals from the Global Navigation Satellite System (GNSS) are refracted by Earth’s atmosphere - or a GNSS-Reflectometry (GNSS-R) payload.

GNSS payloads for multiple applications
GNSS payloads for multiple applications

GNSS-R is a technique to measure Earth’s surface properties using reflections of GNSS signals from Earth, with bistatic scatterometry.

Extended RO measurements from Spire have the potential to serve a range of applications, such as weather forecasting. Very high-altitude measurements can help create space weather datasets including total electronic content and ionospheric density profiles, while grazing angle RO measurements for low-elevation reflections on Earth’s surface, can support sea ice detection. Additionally, polarimetric RO data can help detect heavy precipitation events in the lower atmosphere.

Spire’s GNSS-R capability provides information on Earth’s surface properties, such as sea surface wind speed and surface soil moisture. The data extend the global coverage and observation density of other sources of GNSS-R data, such as TDS-1, CYGNESS and ESA’s upcoming HydroGNSS, as well as complementing other missions, such as ESA’s Soil Moisture and Ocean Salinity (SMOS) mission, NASA’s SMAP and the future Copernicus Imaging Microwave Radiometer (CIMR) mission.

The Spire LEMUR satellites are also equipped with an Automatic Identification System (AIS) and Automatic Dependent Surveillance-Broadcast (ADS-B) payloads.

Good results from EDAP+ and Announcement of Opportunity

Data are downloaded from each spacecraft through Spire’s own global ground station network, consisting of 30 ground stations. Spire provides Level-0 raw instrument data and can also provide processed Level-1 and Level-2 products from Spire internal processing facilities.

In the period 2020 to 2023, Spire has been a so-called Third Party mission under evaluation. The data products were assessed with good results in the framework of the Earthnet Data Assessment Project (EDAP+), which aims to evaluate the quality and suitability of candidate non-ESA Earth observation (EO) missions for the TPM programme. An Announcement of Opportunity allowed scientists and researchers to access and evaluate Spire constellation data, for scientific research and application development.

Applications based on Spire data were assessed for their success in providing global weather intelligence and ship and plane movements. GNSS-RO data were used to evaluate the impact of Spire GNSS-RO on numerical weather prediction (NWP) systems, while Spire GNSS-R data were used in projects related to the monitoring of both soil moisture and ice.

Conventional (near-nadir) Spire GNSS-R measurements were applied to the detection and monitoring of flood inundations in Europe. Furthermore, both conventional and grazing angle GNSS-R data were used in the development of retrieval algorithms for monitoring lake ice phenology, as well as for the detection and characterisation of Antarctic Sea ice.

Collaboration with ESA InCubed programme

As part of the InCubed programme, a project was initiated to equip a Spire satellite with a Polarimetric Radio Occultation (PRO) demonstration sensor to detect and characterise precipitation, using L-band signals from GNSS satellites.

This ESA-sponsored LEMUR spacecraft with PRO payload launched on 3 January 2023, and collected several months of PRO measurements. Data assessment of the Spire PRO data was performed by the Institute of Space Studies of Catalonia (IEEC) in Barcelona, with promising results.

To foster further significant research and scientific development, the TPM data portfolio will be expanded foremost with Spire GNSS-R (both conventional nadir as well as grazing angle) and GNSS-RO polarimetric data (PRO).

Other Spire data products (GNSS-RO, AIS) can be offered to the science community on a case-by-case basis, according to research needs.

Spire data will be offered freely to scientists for research and application development projects. The data will be distributed via project proposal, whereby the user submits a proposal, which is then evaluated by a board with a scientific, cost and feasibility analysis. If the project is accepted, the user shall be entitled to order data from the data provider (specifically Spire).

For further information, see this step-by-step guide on submitting a project proposal.