In Space, GNSS receivers enable satellite navigation, precise timing, precise orbit determination and attitude determination. The EU-funded ENSPACE project has made quantum leaps in the development of a software GNSS solution that supports Galileo and is especially aimed at the small satellite market sector, one of the fastest growing in the ‘New Space’ age. Software-based GNSS receivers enable a new concept for Space. This is an activity that project coordinator Qascom initiated with NASA in 2016. The experiment was based on the use of NASA’s software-defined radio platform called SCaN, attached to the exterior of the International Space Station (ISS). A first, the SCaN Testbed provided an orbiting laboratory on the ISS for the development of software-defined radio technology for improved navigation and communication experimentations. “In ENSPACE, we evolved this concept and invested in a new software GNSS solution that has been installed in commercial off-the-shelf hardware and is also compatible with other system-on-chip components,” notes Samuele Fantinato, head of the Advanced Navigation Unit at Qascom. “Our goal is to provide a reference product for navigation, positioning and timing for Space missions that require a low-cost, secure and flexible software solution,” adds Fantinato. Compared to integrated circuits, the software version offers great design flexibility, fast adaptability to the needs of Space and the ability to customise the GNSS applications according to the mission requirements.
The key concerns in Space
In Space, GNSS receivers need to operate in quite different environments from those of ground-based receivers. “Precisely determining satellite position in Space is quite easy for those flying in low Earth orbits. At higher altitudes, such as in geostationary orbits or in interplanetary missions, signal variability becomes prominent. Adding new constellations could increase accuracy in these orbits,” explains Fantinato. Project members have proposed novel techniques for enhanced navigation, positioning and security in Space. Charged particles and gamma rays are another concern for GNSS receivers. The ENSPACE software GNSS solution integrates techniques and logic redundancy that offer a more robust positioning accuracy in case of radiation events. “ENSPACE experimentation has also shown the benefits of snapshot positioning on the ground – a technique for determining the GNSS receiver position using a very brief interval of the received satellite signal. In this case, the technology could be based on a satellite navigation payload with minimum hardware and software that collect the sampled signals transmitted to the ground,” notes Alessandro Pozzobon, director at Qascom. Researchers are currently planning evolutions in techniques to mitigate GNSS receiver vulnerability to jamming and spoofing. “Providing some level of authentication to tackle GNSS spoofing ensures accurate positioning and robust navigation that go beyond state-of-the-art GNSS services,” says Fantinato. The Galileo-enabled receiver is integrated into the CubeSat mission BOBCAT-1 that was recently deployed from the ISS. After validating its performance in Space, researchers will work to further evolve the solution and transform it into a full GNSS receiver product. Furthermore, they will investigate the possibility of adapting the receiver to launchers or satellites orbiting around the Moon.
ENSPACE, Space, satellite, navigation, Qascom, Galileo, GNSS, NASA, software-defined radio, BOBCAT-1, space economy