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The Communications, Navigation, and Networking reConfigurable Testbed (CoNNeCT) Project (CoNNeCT) Project will provide an on-orbit, adaptable, Software Defined Radio (SDR) facility located on the International Space Station (ISS) along with the corresponding ground and operational systems. These facilities will enable experiments and technology development to conduct a suite of communications experiments.

Internal to NASA, the “CoNNeCT” Project is funded to develop the Flight (space-based) and Ground (terrestrial-based) Systems, and to conduct mission operations.

External to NASA and for ISS operations, CoNNeCT is known as "SCAN Testbed" since the astronauts and ground operators needed a more specific name to avoid confusion. SCAN stands for Space Communications and Navigation.

The SCAN Testbed will be launched from Japan and is designed to operate for a minimum of two years.

The SCaN Testbed was recently turned over to the Japanese Aerospace Exploration Agency (JAXA) in anticipation of a Summer 2012 launch on an HII-B Transfer Vehicle (HTV-3). Members of the SCaN Testbed team traveled to Tanegashima, Japan for the turnover, conducted post-ship functional testing, and witnessed the integration of the testbed onto the EP-MP (Multi-Purpose Exposed Pallet).

	The SCaN Testbed is shown above in its launch configuration, fully integrated onto the EP-MP.

	In addition to other team members responsible for testing (not shown), the turnover team included: Front (L to R): Dwayne Kiefer, Kurt Horanic (KSC), Ross Miller, Rene Fernandez Back row (L to R): Andrew Sexton, Diane Malarik, Liz Gray

The growth of Software Defined Radios (SDRs) offers NASA the opportunity to improve the way space missions develop and operate space transceivers for communications, networking, and navigation. Reconfigurable SDRs with communications and navigation functions implemented in software provide the capability to change the functionality of the radio during a mission and optimize the data capabilities (e.g. video, telemetry, voice, etc.). The ability to change the operating characteristics of a radio through software once deployed to space offers the flexibility to adapt to new science opportunities, recover from anomalies within the science payload or communication system, and potentially reduce development cost and risk through reuse of common space platforms to meet specific mission requirements. SDRs can be used on space-based missions to almost any destination.

The CoNNeCT Project will provide NASA, industry, other Government agencies, and academic partners the opportunity to develop and field communications, navigation, and networking technologies in the laboratory and space environment based on reconfigurable, software defined radio platforms and the STRS Architecture. The CoNNeCT Project Experiments Program will devise, solicit, and conduct on-orbit experiments to validate and advance the open architecture standard for SDRs; advance communication, navigation, and network technologies to mitigate specific NASA mission risks and to enable future mission capabilities.
Identified below are several research and technology areas the SCAN Testbed was designed to support.

Software Defined Radios operating at S, L, and Ka-band.
On-board data management function and payload networking.
Radio Science experiments using the unique capabilities of the SDRs
Precise Navigation and Timing

At the core of the SCAN Testbed are three unique software defined radios (SDRs) provided by government and industry partners. All of the radios are compliant with the NASA Space Telecommunications Radio System (STRS) Architecture Standard. The SCaN Testbed also includes an Avionics Subsystem, RF switching, and a variety of antennas, two of which are on a gimbal. The General Dynamics (GD) SDR is S-Band only, while the Jet Propulsion Laboratory (JPL) SDR has both S-Band and L-Band (GPS) capability. The Harris Corporation (HC) SDR is Ka-Band. The operating systems and waveforms within these radios are reconfigurable and will be changed (modified or replaced) during on-orbit operations. The Avionics Subsystem provides general control and data handling, as well as supporting network routing. Just like the radios, the software loaded in the Avionics Subsystem will be changed for experiments. The radios are mounted to the Flight Enclosure and functionally interface with the Avionics and Radio Frequency (RF) subsystems.

The SCAN Testbed will exercise various components of the SDRs’ operating environments (OE), waveforms (WF), and performance characteristics. An OE is like the operating system on a computer (UNIX, Windows, etc) and provides a common infrastructure for waveforms and applications. A waveform or application is like a program running on the computer (Excel, AutoCAD, iTunes, etc). OEs and WFs have parameters that can be changed in the course of an experiment using a standardized method defined in the STRS standard. As well, new OEs and WFs will be loaded into the avionics or radios. Experiment Principal Investigators (PIs) will explore the efficacy and efficiency of different combinations of OEs and WFs.

The SCAN Testbed is a single hardware/software package that is shown in Figure 1.

NASA’s Space Communication and Navigation (SCaN) Office has developed an architecture standard for SDRs used in space and ground-based platforms to provide commonality among radio developments to provide enhanced capability and services while reducing mission and programmatic risk. The Space Telecommunications Radio System (STRS) architecture standard defines common waveform software interfaces, methods of instantiation, operation, and testing among different compliant hardware and software products. These common interfaces within the architecture abstract, or remove, the application software from the underlying hardware to enable technology insertion independently at either the software or hardware layer.

The SCAN Testbed will launch to the ISS on a Japanese H-II Transfer Vehicle (JAXA HTV-3), and be transferred and installed via Extravehicular Robotics (EVR) to the ExPRESS Logistics Carrier-3 (ELC3) in the inboard, Ram-facing, Zenith-facing payload location on an exterior truss of the ISS. Figure 2 illustrates the location of the SCAN Testbed on the ISS.

Figure 2. SCAN Testbed Location on ISS

The SCAN Testbed, radios and infrastructure components are shown in Figure 1.

Figure 1. SCAN Testbed, Radios and Infrastructure Components (viewed from Ram/Zenith Angle)

Mass: 800 lb
Power: 500 W
Main Processor:
Speed: 733 MHz
Flash Memory: 64 GB
Software Lines of Code: >100,000
Radios:
GD/JPL S-Band: 10 Mbps data rate class
Harris Ka-Band: > 100 Mbps data rate class
JPL GPS: Tracking and navigation performance at GPS L1, L2, and future L5 frequencies.
Operating Frequencies: (see Figure 2 for other NASA missions)
GD/JPL S-Band: 2.0-2.3 GHz
Harris Ka-Band: 22-26 GHz
JPL GPS Receiver: L1, L2, and L5 frequencies, 0.4-16 GHz

Figure 2. Representative NASA Spectrum Use (300 MHz-30 GHz) (Source: NASA's Space Flight Enterprise Strategy; November, 2003.)

By comparison, here are some common items and their operating frequency:

AM Radio: 1 kHz or 0.000001 GHz
FM Radio, Television, and GPS: 0.05-1.6 GHz
Cell phones: 0.8-2 GHz
3G/4G Data Networks: 1.7-2.7 GHz
Microwave: 3-30 GHz (ovens at 2.5 GHz)

The SCAN Testbed provides infrastructure to support operations of the three software defined radios:

General Dynamics (GD) Corporation
Jet Propulsion Lab (JPL)
Harris Corporation
The infrastructure is comprised of:

Mechanical Subsystem, includes Structural and Thermal
Avionics Subsystem, includes Command & Data Handling (C&DH), Electrical and Analog
RF Subsystem,
Antenna Pointing Subsystem (APS)
Flight Software
These subsystems provide interface to the carriers and environments, structural support, environmental control, commanding, data transfer, data processing, data storage, data routing, power control/distribution, RF signal switching, amplification, transmission and reception, and satellite pointing and tracking.
The SCAN Testbed system consists of four primary subsystems:

Flight System: SCAN Testbed located on the Express Pallet on the ISS
Ground System
SCAN Testbed Support Equipment located at various ground stations,
CoNNeCT Control Center (CCC)
SCAN Testbed Ground Testbed both located at the Glenn Research Center.
The overall functional interfaces are shown in figure 3.

Figure 3. SCAN Testbed System Simplified Functional Diagram

Both the SCAN Testbed and Ground System:

send and receive commands and data ;
manipulate (stores, routes, and processes) data;
interface with external systems to send and receive RF signals to and from space as shown in Figure 4.

Figure 4. Simplified Functional Diagram of the SCAN Testbed System

The SCAN Testbed interacts with the carriers and radios as shown in Figure 5.

Figure 5. SCAN Testbed Subsystems & Functional Interactions

The Mechanical Subsystem is comprised of:

Flight Enclosure
Antenna Mounting
Thermal Control
Traveling Wave Tube Amplifier (TWTA) Power Supply Unit (PSU) housing
The mechanical subsystem interfaces with the ExPA, Radios, Avionics Subsystem, Integrated Gimbal Assembly, and RF Subsystem as shown in Figure 6.

Figure 6. Mechanical Subsystem

The SCAN Testbed is passively cooled. Three of its five sides (Starboard, Zenith and Ram) are effective radiators coated with 10-mil Silver Teflon. All heat generated by the SCAN Testbed electronics is radiated to space through these 3 radiators. The Wake and Nadir sides (toward other ORUs on the ELC) are not radiating (through coatings and/or MLI). The sixth Enclosure side, the ExPA will be covered with Multi-Layer Insulation (MLI – i.e. Beta Cloth) to minimize heat transfer to it.

There are two sets of heaters which provide thermal control post-installation on ELC-3

Survival heaters are supplied by ELC contingency power, thermostat controlled
Operational heaters are supplied by ELC operational power, Avionics controlled

The Avionics Subsystem is responsible for:

Command and Control of the payload
Gathering health and status data from all subsystems for downlink via the primary data path.
Running experiment software to support networking and other experiments
Controlling the radios
Controlling the antenna pointing for MGA and HGA

It provides the electrical interface between ISS systems and the SCAN Testbed systems. More specifically, the Avionics subsystem provides the electrical interface to the EP-MP and ELC (through the ExPA), SCAN Testbed power distribution and control, grounding and isolation, communications (commanding and data) interfaces with the ELC, Flight System health and status, and the various subsystem communications and control as shown in Figure 7.

Figure 7. Avionics Subsystem

The Avionics system provides power distribution, grounding, and isolation. Power distribution for the 28VDC operational and 120VDC operational power is performed within the Avionics subsystem for the three software defined radios, RF subsystem, APS, and the SCAN Testbed heaters.

While installed onto the ELC, the SCAN Testbed has two sets of heaters. The first set of heaters is powered from the ELC 120VDC contingency power feed. These are resistance type with electro-mechanical thermostat control. The second set of heaters is operational heaters powered from the ELC 120VDC operational power feed and controlled by solid-state MOSFET switches internal to the avionics subsystem.

When operating on the ELC, power is distributed through the avionics unit. ELC 28VDC operational power is used to power the avionics unit. A digital power card internal to the avionics unit is used to control (on/off) power to the SDRs. It also controls a latching relay internal to the TWTA to start power, inhibit lines to the TWTA PSU, and pulses power to the coax switches. The digital power card uses optically isolated high side power mosfets to control power. The avionics monitors power to “primary” power feeds used to power the major sub-systems. “Secondary” power feeds are not monitored. Each power line is also fused. Power for heaters is controlled with low side switches located on the input filter card.

The SCAN Testbed will consist of three reconfigurable and reprogrammable Software Defined Radio (SDR) transceivers/transponders:

JPL SDR: S-Band and L-Band (GPS)
GD SDR: S-Band
Harris SDR: Ka-Band
The SCAN Testbed will be in low earth orbit pointing to a series of NASA Space Network (SN) TDRSS satellites in geosynchronous orbits and NASA Near Earth Network (NEN) stations, as well as experimenter-provided facilities. The three SDRs will provide:

S-band (duplex) microwave Radio Frequency (RF) links directly with the ground, (also referred to as the Near Earth Network (NEN)),
S-band (duplex) microwave RF links with the Tracking and Data Relay Satellite System (TDRSS), (also referred to as the Space Network (SN)),
Ka-Band (duplex) with TDRSS,
L-Band (receive-only) with the Global Positioning Satellite System (GPSS).

Each SDR will have an Operating Environment (OE) which provides a software infrastructure (including an operating system), command processing, interact with hardware, and configure the SDR. All three OEs comply with the STRS Standard. SDR must run waveforms which implement the capability of the radio and generate the RF signal that will be transmitted. The OE does not actually generate or receive signals or perform communication functions. That is done by loadable waveforms which use the resources provided by the hardware platform and OE to communicate, network, or keep time (or anything else the experimenter wishes to do).

The RF subsystem enables the SDRs to transmit/receive RF signals from the SN and NEN, and receive GPS signals, through one of five antennas (3 fixed, 2 movable).

The Radio Frequency (RF) Subsystem is comprised of:

Traveling Wave Tube Amplifier (TWTA)
three Coaxial Transfer Switches
Antennas
Diplexers
RF Isolator
RF Attenuator
transmission lines to interconnect the RF Subsystem components with the SDRs.
The RF Subsystem radiates RF signals intended for the Tracking and Data Relay Satellite (TDRS) and the ground and receives RF signals from the TDRS, the ground, and the GPS system. The architecture of the SCAN Testbed permits, and there is a requirement for, the ability of sending RF signals from two separate SDRs to two antennas simultaneously. The ability to send RF signals from two separate SDRs to the same antenna is not supported by the architecture and cannot happen due to switch positions required.

The RF Subsystem interfaces with the Avionics Subsystem, the Flight Enclosure, the Antenna Pointing Subsystem, and the three SDRs. The Mission Operations tab further details RF communication paths.

The Antenna Pointing System (APS) allows the Ka-Band High Gain Antenna (HGA) and S-Band Medium Gain Antenna(MGA) to be moved to track TDRSS (or other experimenter selected targets). The antenna pointing may be done in either open loop or closed loop mode. In the former, the antennas are pointed according to a pre-computed track profile. In closed loop mode, the tracking algorithm uses signal strength information from the Ka-band radio to point the Ka-band HGA more accurately to the Ka-band source. The ISS is sufficiently large and flexible that open loop pointing of the Ka-band antenna may have pointing errors reducing the maximum data rate that can be carried. The gimbaled antennas are locked for launch and deployed on-orbit.

Figure 8. SCAN Testbed Antenna Pointing System (on ExPA)

As shown in Figure 8, the APS consists of:

The SCAN Testbed flight software resides in the Avionics subsystem and the three Software Defined Radios.

The avionics software runs on the single-board computer to:

process commands
provide thermal monitoring and control
communicate with the radios and ISS
command and configure the radios
control RF subsystem switching
command the APS
collect sensor data
send telemetry to the ground
perform data and file management
Software development for the Avionics subsystem is the responsibility of GRC.

Each of the three SDRs has an Operating Environment (OE), which includes an operating system and provides infrastructure services to applications and waveforms. In addition to the OE, each SDR must run Waveforms, which implement the unique capabilities of the radio to receive and transmit RF signals, provide networking capability, and do navigation and timing. Each radio will have an initial experimental waveform, in addition to test waveforms developed by the radio supplier.

The initial SCAN Testbed software is developed by five organizations:

Glenn Research Center (GRC)
Goddard Space Flight Center (GSFC)
Jet Propulsion Laboratory (JPL)
General Dynamics (GD)
Harris Corporation (HC)
All avionics software that interfaces with ISS is NASA Class C, in accordance with NPR 7150.2 NASA Software Engineering.

Software which will be loaded into the Avionics Subsystem, which directly interfaces with the ISS and which is responsible for safety critical functions, is and will be developed in accordance with NASA Class C. Any reconfigurations/updates to any individual or combination of the SDRs default version will be developed and implemented in accordance with Class E procedural requirements as stated in NPR 7150.2, NASA Software Engineering Requirements, as a minimum, plus selected augmented Class D requirements as supplied by NASA and negotiated between NASA and the Experimenter. Experimenter developed software in the radios will not be Class C, but will require some verification to insure that safety requirements are met.

During the operations phase, radios and the avionics package can be reconfigured from the ground with new software. Software, here, means both that which is running on a processor in the radio, and the configuration of in-flight reconfigurable Field Programmable Gate Arrays (FPGAs). There are no in-flight reconfigurable FPGAs in the Avionics Subsystem.

The Ground System software is developed by GRC in accordance with NPR 7150.2 NASA Software Engineering Requirements and the procedural requirements it specifies for NASA Class C software. Primary path ground software utilizes the NASA Telescience Resource Kit (TReK), a suite of PC-based software applications used by scientists and engineers to monitor and control payloads on-board the International Space Station

Waveform software and firmware defines functionality for most of the SDRs. STRS defines standards for SDRs to maximize waveform firmware and software reuse and reduce porting effort between various radios. All three SCAN Testbed radios will be launched with baseline STRS-compliant waveforms.

Refer to the SCAN Testbed Flight and Ground System Description (in the Candidate Experimenter Info Tab) for more information about waveforms and waveform updates.

The SCAN Testbed software interfaces externally with the ELC via the 1553 interface and the Ethernet interface as shown in Figure 9. The Ground System interfaces with the Enhanced Huntsville Operations Center (EHOSC) through the GRC Telescience Support Center (TSC) and the NASA Integrated Services Network (NISN)/Internet Protocol Operations Network (IONet) as shown in Figure 10.

Figure 9. SCAN Testbed and Ground System Software External Interfaces

SCAN Testbed ground operations include the following components:

Ground System
GIU
GSE

The Ground System provides a portion of the terrestrial control of the SCAN Testbed through the CoNNeCT Control Center (CCC). SCAN Testbed provides a platform for the SDRs to experiment with software and firmware configurations, while communicating via RF links with the TDRSS and GPS satellite constellations and Near Earth Network. Operations are based at the CCC, which is inside the GRC Telescience Support Center (TSC).
The following sections expound upon the Ground System components that interface operationally or physically with the SCAN Testbed.
The SCAN Testbed Ground System consists of the following components:

CoNNeCT Control Center (CCC)
CoNNeCT Experiment Center (CEC)
Ground Verification Facility (GVF)
the external ground systems and their interfaces located at:
Huntsville Operations Support Center (HOSC)
White Sands Complex (WSC)
Wallops Ground Station (WGS)
Experimenter-provided facilities
Other entities, including the Network Integration Center and the Flight Dynamics Facility at Goddard Spaceflight Center, are also involved.
The NASA Integrated Services Network (NISN) is the network that connects these entities. Other ground stations beyond the baseline WGS may also be used during operations, including White Sands 1, APL, and JPL.

Figure 10. SCAN Testbed Ground System

The CoNNeCT Control Center (CCC) is located within the GRC TSC, which supports on-going operations with several ISS Payloads. The interfaces between the EHOSC and TSC are established and functional. SCAN Testbed will operate within the existing TSC infrastructure to command and control the SCAN Testbed via the primary path through the EHOSC to accomplish planned technology demonstrations. The TSC will interface with the Space and Near Earth Networks, allowing bidirectional data transfer and commanding through the experimental path as shown in Figure 11.

The CCC will provide command and telemetry processing, experiment demonstration/execution, experiment data archiving, and health and status data archiving. A subset of data will be provided to approved remote users. The CCC will also interface with the Ground Integration unit (GIU) for on-orbit anomaly resolution and waveform and Flight System software verification prior to on-orbit upload. The CCC functional diagram is shown in Figure 11.

Figure 11. CoNNeCT Control Center Functional Diagram

The Ground Integration Unit (GIU) is the ground-based version of the Flight System. This unit will be used for software check-out and/or simulated on-orbit operations for the duration of the project. It will include the flight spare avionics, engineering models of the SDRs, TDRSS simulators (TSIMs), the SCAN Tested-provided ELC Suitcase Simulator, and other test support equipment. The GIU is configuration managed and will be used to verify Flight Software Requirements, specifically the non-carrier interfacing software (i.e., SDRs).

The SCAN Testbed Ground Support Equipment (GSE) is the comprehensive set of non-flight equipment required to test, operate, transport, support/suspend, maintain, or store the SCAN Testbed. GSE is controlled and certified safe to operate/transport by appropriate NASA personnel, per the requirements of NASA Standard 5005. All hardware/software that interfaces with flight hardware/software, carrier hardware/software, or heritage hardware/software is configuration managed.