Software defined radios (SDRs) have been used in ground and airborne applications for decades. Applications on the ground range from communications systems, test and measurement, electronic surveillance, and more. Space, however, has traditionally been focused on bespoke, application-specific payloads that optimize physical size, power consumption, and reliability — all of which are critical for geosynchronous (GEO) and deep space applications.
With accelerating deployment of low earth orbit (LEO) satellites, there is an emerging opportunity for SDRs to migrate to the space domain and provide configurable radio capability in a new frontier. LEO satellites operate both in a different environment and with a different concept of operations (CONOPS) compared to GEO and deep space satellites. The intersection of applications that would benefit from a LEO satellite — with the opportunities provided by the differences in space environment and CONOPS — are driving a rapid transition for moving SDRs from ground and airborne platforms into space.
A challenge in any satellite application is that electronics in the space environment are exposed to radiation, which can cause semiconductor devices (a key building block for SDRs) to degrade, upset, or even fail entirely. For satellites in GEO and deep space, this means that a rigorous design process must be followed to ensure that the payload is fully radiation hardened and as robust as possible. GEO and deep space satellites can have decades long missions, so sustained operational life in a difficult radiation environment is a key requirement. Often this design process would exclude many components critical to building modern SDRs, therefore GEO and deep space satellites typically have very bespoke radio solutions in their payload.
LEO satellites do not need to be as radiation tolerant for two reasons. First, the LEO environment is less harsh from a radiation perspective than GEO or deep space environments. As such, the required level of robustness and radiation tolerance is inherently lower in these orbits. This allows for the integration of more modern and capable SDR-related semiconductor devices into LEO satellites.
Second, unlike GEO and deep space satellites — which are typically launched in singular or small constellations and need to have very long life cycles — LEO constellations are launched in tens, hundreds, and potentially thousands of satellites. Additionally, the life cycle of LEO satellites may only be three to five years, not decades. This allows for constellation-level robustness. If one LEO satellite experiences a radiation-induced event, the other satellites in its constellation provide the redundancy to continue the mission. In addition, the lower launch costs to LEO allow for more regular replacement satellites to be added to the system, followed by decommissioning of end-of-life satellites. The resultant lower radiation tolerance requirements for these satellites allow the use of more capable SDR devices, providing orders of magnitude, more performance, and flexibility.
The applications driving SDR deployment in space cover a wide range. These include broadband communications, Internet of Things (IoT), RF sensing and signal intelligence (SIGINT), inter-satellite communications, and more. There are commercial constellations, like Amazon's Kuiper or SpaceX's Starlink, that provide broadband internet access via satellite communications instead of terrestrial fiber optics. These constellations are being rapidly deployed as the competition to be first to market is very strong. This means that the LEO satellite may be launched with only a fraction of its radio capability (bandwidth, throughput, frequency range, etc). The benefit of an SDR versus a bespoke radio is that these attributes can be modified and enhanced after deployment, enabling new features post-launch and providing more value to the constellation and user base. There are also new threats, such as hypersonic missiles, that are best detected by sensors in space rather than on the ground. For an emerging threat, an SDR provides significant value as it can be programmed into the radio's behavior as more information about the radio nature of the target is learned.
LEO satellites offer an exciting new frontier for SDRs. Epiq Solutions is excited to be involved in pushing the limits of SDR and processing technology in this space. With the combination of Epiq and Xiphos Systems, there is a unique opportunity to create uniquely low-power, high-performance platforms that are optimized for the LEO environment, CONOPS, and applications. Reach out to us at Epiq Solutions or Xiphos to learn more about our LEO space SDR capability.