Space Communications and Navigation Testbed (SCAN Testbed (Facility)) - 02.25.14
ISS Science for Everyone
Science Objectives for Everyone
The Space Communications and Navigation Testbed (SCAN Testbed) consists of a set of reconfigurable software defined radios (SDRs), including newer Ka-band and Global Positioning System (GPS) L5 frequency bands, and uses software based communications and navigation functions capable of being functionally modified once on-orbit. Such reconfigurable software to an existing radio platform allows different radio vendors the ability to demonstrate multiple radio implementations based on the common Space Telecommunications Radio System architecture standard. The goal of providing this facility is to encourage the development and advancement of SDR technologies for common, open space based architectures, in hopes of reducing future developmental risks and costs.
Science Results for Everyone
Glenn Research Center, Cleveland, OH, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
September 2012 - September 2014
Previous ISS Missions
SCAN Testbed is comprised of three reconfigurable software defined radios (SDRs) developed by General Dynamics, Harris Corporation, NASA’s Jet Propulsion Laboratory (JPL), and integrated by Glenn Research Center. The SDRs communicate with the Space Network and Near Earth Network. SCAN Testbed is also comprised of the Antenna Pointing System, developed by Sierra Nevada Corporation, and integrated by Glenn, which tracks NASA’s Tracking and Data Relay Satellite System (TDRSS).
SCAN Testbed is the first NASA in-space, duplex user of Ka-band. SCAN Testbed is also comprised of low-, medium-, and high-gain antennas used to communicate, via S- and Ka-band frequencies, with NASA’s TDRSS satellites and ground stations located throughout the United States. SCAN Testbed uses a Global Positioning System (GPS) antenna to receive signals from GPS satellites at all civilian GPS frequencies. The GPS receiver can be used to study improved orbit determination capabilities using multiple GPS frequencies. SCAN Testbed is the first space-based user of the GPS L5 capability.
Current SDRs, being a relatively new technology for space missions, are uniquely designed and developed within individual companies. These unique designs only allow the developing company to provide waveform software for the radio. Traditional approaches to radio development have been exemplified by proprietary or custom implementations that only meet a specific set of mission requirements. Presently, most requirements can only be satisfied by functions implemented in the hardware (i.e., application-specific integrated circuits (ASIC's)) and thus fixed for a specific mission duration. Historically, this was often the only approach given the available ASIC technology suitable for space flight. Therefore, NASA is not able to benefit from lessons learned, or have the ability to reuse software, from one development program to another. These limitations have a tendency to increase NASA's cost and dependence on single vendor solutions.
As SDRs further infuse into deep space, near-Earth, and lunar space applications , a new approach must be considered to best apply the new reprogrammable field programmable gate array (FPGA) technologies for NASA. SCAN Testbed’s SDRs offers NASA the opportunity to separate the software from the underlying hardware technology by adopting an open architecture standard. Published, well-defined interfaces enable different groups to provide radios that conform to the interface standard, providing commonality among different implementations and enabling interoperability between providers of different hardware and software elements. Standard interfaces provide for software component reuse, and technology insertion through the hardware abstraction. Such a standard also promotes the growth of a large base of domain experts such as agency personnel, software and hardware providers, and the user and operations communities, which help reduce the risks of using unique custom architecture implementations.
This common architecture, entitled Space Telecommunications Radio System (STRS), provides the desired software abstraction and flexibility, while minimizing developmental and operational resources. NASA’s SCaN Program has developed the STRS architecture standard for SDR use in space and ground-based platforms. SCAN Testbed has the first three STRS standard compliant radios in space.
The SDRs will host software applications and waveforms developed by experimenters. With software-based communications and navigation functions, developers have the capability to change the functionality of the radio once on orbit. The ability to change the operating characteristics of the radio’s software after launch allows missions to change the way a radio communicates with ground controllers. It also offers the flexibility to adapt to new science opportunities and increased data return. Additionally, this flexibility allows teams to recover from anomalies within the science hardware or communication system. This potentially reduces development cost and risk by using the same hardware platform for different missions, while using software to meet specific mission requirements.
The SCAN Testbed provides a baseline capability that is designed to support experimentation in the following areas of research and technology:
- Demonstration of mission applicability of SDR, including aspects of reconfiguration and unique/efficient use of processor, Field Programmable Gate Array (FPGA), and Digital
- Signal Processor (DSP) resources.
- Spectrum efficient technologies
- Space internetworking, including Disruption Tolerant Networking (DTN)
- Position, navigation, and timing (PNT) technology
- Technologies/waveforms for formation flying
- High data rate communications
- Uplink antenna arraying technologies
- Cognitive applications
- Multi-access communication
- Radio frequency sensing applications (science emulation)
- Command and control of SCAN Testbed is performed from the Glenn Telescience Support Center, the hub of operations for Glenn’s ISS payloads
- The experiment plan specifies radio and antenna combinations required to complete a particular test.
- The flight system is powered on and prepared for the experiment by uploading files and adjusting parameters from the control center.
- Commands and data sent to the radio system include software files that configure and control the radio.
- When commanded from the ground, the radios establish a communication link with the White Sands Complex through TDRSS, and begin to flow data or receive GPS signals (depends on payload configuration).
- NASA will provide access to ground systems for development and testing and ultimately upload new software to the space flight system on ISS.
- Mission operations are planned to last 5 years or more
Ground Based Results Publications
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External image of ISS showing SCAN Testbed installed on ELC 4 nadir side (NASA)
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