The Flexible Microwave Payload-2: A SDR-Based GNSS-Reflectometer and L-Band Radiometer for CubeSats

Abstract

This article presents the FMPL-2 on board the FSS-Cat mission, the 2017 ESA Small Sentinel Satellite Challenge and overall Copernicus Masters Competition winner. FMPL-2 is a passive microwave instrument based on a software-defined radio that implements a conventional global navigation satellite system-Reflectometer and an L-band radiometer, occupying 1 U of a 6 U CubeSat. The article describes the FSSC at mission context, the payload design and implementation phases, the tests results in a controlled environment, and finally the calibration algorithms applied to the downloaded data in order to extract the appropriate geophysical parameters: sea-ice coverage, sea-ice thickness (SIT), and low-resolution soil moisture. This article covers the overall payload design, from a high-level block diagram down to singlecomponent specifications from both hardware and software points of view. The main block of the instrument is based on the combination of an FPGA, which virtualizes a dual-core ARM processor, where most of the calculus are performed, and a software-defined radio module, in charge of I/Q data demodulation. The article also explains the design and implementation of a signal conditioning board required for the correct operation and calibration of both instruments.

Snow and Ice Thickness Retrievals Using GNSS-R: Preliminary Results of the MOSAiC Experiment

“…Both instruments share a common power and data interface, physical enclosure, and the Right Hand Circular Polarization (RHCP) antenna used for time and geo-reference the instrument. The primary objective of both GNSS-R instruments is to provide ground-truth data for reflection modeling and originally also to support the calibration/validation of the FMPL-2 [3] onboard the FSSCat mission [1,2]. This manuscript focuses only on the data retrieved by the IEEC/UPC PYCARO-2 instrument [13], which is equipped with an antenna working at the same polarization (LHCP) as the FMPL-2 instrument onboard FSSCat.…”

“…where E i is the incident electric field, E r is the reflected electric field, F n (θ) is the antenna voltage pattern (amplitude and phase) for the up-looking and down-looking signals arriving to either the up-looking or down-looking antennas, with different patterns for each one (see Figure 2a), θ dir , and θ re f are the off-boresight arriving angles of the direct and reflected signals, θ i is the incidence angle of the signal arriving from a particular GNSS spacecraft, E 0 i is the direct signal, the one that would be received if there were no interference, R( r , θ) is the reflection coefficient as defined in (3), and ∆φ is the phase associated to the geometry. ∆φ is given by…”

“…FSSCat was the winner of the "2017 ESA Sentinel Small Satellite (S^3) Challenge" and the overall winner of the 2017 "Copernicus Masters" competition [1]. The mission consists of two "federated" 6U (10 × 20 × 30 cm 3 ) CubeSats ( 3 Cat5/A and 3 Cat-5/B) in support of the Copernicus Land and Marine Environment services [2], which were successfully launched on 3 September 2020 onboard the Vega SSMS (Small Spacecraft Mission Service) maiden flight in a Sun Synchronous Orbit of 550 km height. The goal of the ESA S^3 Challenge was to develop, in a record time of one year, a novel small satellite mission to complement the Sentinel family missions.…”

“…The goal of the ESA S^3 Challenge was to develop, in a record time of one year, a novel small satellite mission to complement the Sentinel family missions. One of the instruments onboard FSSCat is the Flexible Microwave Payload-2 (FMPL-2) [3], a dual Global Navigation Satellite System reflectometer (GNSS-R) and microwave radiometer instrument implemented using a Software Defined Radio.…”

Implementation of a Testbed for GNSS-R Payload Performance Evaluation

“…1: Sample Doppler frequency of a GPS signal generated by a commercial GNSS signal generator, showing its granularity (50 Hz Doppler step every second) Fig. 2: Delay-Doppler Map over the ocean measured by the U.K. TechDemoSat-1 mission calculations in the FMPL-2 [3]. An example of spaceborne DDM is shown in Fig.…”