Space Communications

NASA currently operates several independent networks that provide communications and tracking services for earth observation, human exploration, and planetary exploration. These networks are comprised of a constellation of relay satellites in geosynchronous orbit (the Space Network - SN) and a geographically distributed ground stations (the Near Earth Network and the Deep Space Network). These three networks have been historically operated and upgraded independently, and are in some cases up to 200% more expensive than their commercial counterparts.

In preparation for the exploration challenges of 2020 and beyond, NASA is seeking to redefine these networks into a single system that maximizes commonality and reduces costs called the Space Communications and Navigration (SCaN) Network.

Space Network constellation
Constellation of Tracking and Data Relay Satellites (TDRS) and their supporting ground stations

In this context, our work has focused on applying computational tools to architect the next generation of space communications by identifying the architectural decisions that characterize the network and building models that provide rapid assessments of their performance and cost. While many previous efforts have simulated sections of the architecture, such as link budgets or orbit location, we believe this is the first tool that can evaluate multiple communications architectures systemically.

[Sanchez Net et al., 2013] presented a model that is able to enumerate and evaluate network architectures using a rule-based expert system. We are able to enumerate thousands of possible architectures, including potential communications bands and payloads, hosted payloads on commercial satellites, and a variety of orbital locations. The system performance is assessed through a heuristic scheduler that simulates one day of network operations, while parametric models are used for pricing both the space segment and ground segment.

Notional space of alternative network architectures.
Notional space of alternative network architectures

Our current work is currently focused on two areas: first, explore the space of alternative architectures for the SN and provide recommendations on how to upgrade its capabilities in 2020-2030. For example, we quantify the potential cost savings of using hosted payloads to fly optical terminals, and are able to evaluate hosted payload business models under a variety of scenarios [Sanchez Net et al., 2014]. Second, we are also working on condensing the tradespace into deployment strategies for the space segment of the network given the limited lifetime of the relay satellites.