Kythera Space Solutions provides software solutions to help manage satellite communications networks. In this age where both satellites and the ground are increasingly becoming software-defined, this work is important.

Constellations spoke with Jeff Freedman, CEO of Kythera Space Solutions, on the podcast episode Changing Demand, Software-Defined Satellites, and the Operating System for Space released on June 1st, 2021. In this follow-on interview, Constellations sat down with Freedman again to dive further into the complex topic of software-defined satellites, and how these will interact with ground systems.

Constellations: What is your definition of a software-defined satellite?

Jeffrey Freedman: We define software-defined satellites as having payloads that can be reconfigured using ground commands. Typically, these satellites have on-board processors that can be re-configured using datafiles that are uploaded from the ground. Examples of software defined systems on the satellite include:

• Channelizer and Router Processor. Signals received in the satellite are sampled and digitized. Typically, an ASIC or FPGA is used to digitally separate a large receive signal bandwidth into individual channels which are routed to the appropriate downlink channel and beam. This process is configurable, so typically, any channel from any uplink beam could be cut out and sent to a unique channel in a downlink beam based on a configuration file.
• Beamforming Antennas. There are many different types of beamforming satellites, but they typically have the ability to steer, and in many cases, shape uplink and downlink beams. This flexibility allows the satellite to change coverage areas dynamically in orbit.
• Demodulation/Remodulation and Routing Processors. These satellites have on-board processing that detects bits from individual signals from all users within a beam. Unlike the channelizer router processor which divides and routes bandwidth chunks, this processor actually turns bits that were sent from a terminal on the ground into bits that are received on the satellite. A common application for these types of processors is routing from satellite to satellite by digitally examining a header that includes information on the destination.

Software-defined satellites typically have one or more of these functions and all provide a level of flexibility that allows for re-definition in orbit.

Constellations: What’s the difference between a software-defined satellite and a software-defined payload?

Jeffrey Freedman: Software-defined satellites and software-defined payloads are synonymous. The payload of the satellite provides the service. The payloads on communication satellites include the radios, antennas, and all the equipment required to relay communication signals. The rest of the satellite, known as the bus, includes everything required to keep the satellite operating in its orbit like propulsion, power, and stability.

Constellations: In the podcast episode, you address how a satellite management system can help orchestrate satellites in both GEO and MEO. How does this differ in LEO?

Jeffrey Freedman: With the right design, Dynamic Satellite Management Systems like the Kythera Operating System (KOS) can orchestrate GEO, MEO and LEO satellites. Some LEO constellations have unique challenges because the number of satellites is typically much larger, and coverage is constantly changing. Generally, LEO satellites have to operate autonomously for extended periods of time because dynamic ground control is often not practical. They can either have on-board processing which can dynamically adapt to conditions, or they have an extended pre-programmed schedule of activities as they fly from region to region.

Constellations: You also mentioned that managing software-defined satellites will take more automation in the future. Could you expand on this?

Jeffrey Freedman: One day satellite-defined services will be as flexible as the service delivered by your telephone, creating service on-demand using whatever space resources are available. One day, terminals will be agnostic to a given satellite or even a space network. Some next generation terminals are being designed to use flexible, phased array antenna technologies that will be capable of dynamically switching between different satellite systems. Software-based Dynamic Satellite Management Systems like our KOS will orchestrate these changes, enabling customers to seamlessly switch between spacecraft with the available capacity to deliver the service when and where needed.

Constellations: It would make sense that a software-defined satellite would have an easier time integrating with a software-defined ground system. What are the advantages and challenges of virtualizing the ground, as it relates to operating a software-defined satellite?

Jeffrey Freedman: A virtualized system could be capable of providing a variety of applications and services on-demand from available space and ground assets. Dynamic pricing could allow for a competitive market providing customers with the best price for the service desired. Customers could have access to desired services by utilizing the unique capabilities of ground and space system elements to provide backhaul, internet access, multicasts, broadcasts, protected wave forms and secure reliable communications. Getting manufacturers of ground and space systems to work together in a single integrated system will be challenging, as these systems have unique capabilities and interfaces.

Constellations: What does the ground segment need to do to better support these new dynamic capabilities in space?

Jeffrey Freedman: Standardization is the key to allow flexible support of different ground components and satellites. This will ensure capability among various ground components and enable highly flexible dynamic services.

Constellations: What are the advantages and challenges for both the ground segment and satellite operators working to integrate software-defined components with legacy hardware?

Jeffrey Freedman: Support for legacy hardware is critical. It takes time and money to upgrade to the latest and greatest technologies. The key is management software that can support both legacy hardware and the next generation flexible hardware. The software needs to optimize resources considering their limitations. This incentivizes the customer to upgrade but does not require that they do so.

Constellations: Do you think software-defined satellites will be wildly adopted in the space industry, or will only be used for specific use cases?

Jeffrey Freedman: I think most future satellites will be software defined. Cost of production will drive the market. A satellite that can be reconfigured to support any market can be mass produced. This will dramatically lower costs. Spacecraft manufacturers who don’t follow this model will be pushed out of the business by less expensive more flexible competitors.