Update on Dependable Multiprocessor CubeSat Technology ...

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Technology Development. John R. Samson, Jr. Honeywell Aerospace., Defense & Space Systems. 13350 U.S. Highway 19 North. Clearwater, FL. (727) 539 - ...
Update on Dependable Multiprocessor CubeSat Technology Development John R. Samson, Jr. Honeywell Aerospace., Defense & Space Systems 13350 U.S. Highway 19 North Clearwater, FL (727) 539 - 2449 [email protected] Abstract—Since September 2010, when the Army SERB (Space Experiments Review Board) recommended the Dependable Multiprocessor (DM) CubeSat SERB project be merged with SMDC High Power Nano-Satellite SERB project to proceed as the SMDC TechSat project, the ongoing Honeywell DM project has supported the integrated SMDC TechSat effort. This effort included participation in the successful PDR in May 2011, participation in the successful Flat-Sat Demo in September 2011, and key risk and potential cost reduction efforts including refining the DM payload design to fit the space available in the SMDC TechSat, defining the DM/SMDC TechSat spacecraft interfaces, supporting 3D modeling of the SMDC CubeSat, and the development of the DM CubeSat Testbed, which was the basis for the DM portion of the SMDC TechSat Flat-Sat Demo. The paper includes a brief overview of DM technology and focuses on the DM CubeSat Testbed and its application in the SMDC TechSat Flat-Sat Demo. 1, 2, 3

Funded by the NASA New Millennium Program (NMP) Space Technology 8 (ST8) project since 2004, the development of Dependable Multiprocessor (DM) technology is a major step toward flying high performance COTS processing in space. The objective of the ST8 DM technology advance was to demonstrate that a highperformance, COTS-based processing cluster can operate in a natural space environment. The goals were to provide a high-throughput, scalable, and fully-programmable processing solution capable of achieving high throughout density, high system availability (> 0.995), and high system computational correctness (> 0.995) in terms of the probability of delivering undetected erroneous or untimely data to the user, with platform-, technology-, and application-independent system software that manages the cluster of COTS processing elements and enhances radiation upset tolerance. Flying high performance embedded computing in CubeSat applications presents particularly unique problems which require unique solutions. Fortunately, there are three technologies that make flying high performance embedded computing on CubeSats feasible: 1) the availability of highpower CubeSats, 2) the availability of small, light-weight, low-power, Commercial-Off-The-Shelf (COTS) Computeron-Module (COM), e.g., Gumstix™, technologies which are potential solutions to the size, weight, and power problems, and 3) platform-, technology-, and application-independent Dependable Multiprocessor Middleware (DMM), which allows COTS COM technologies to be used in space applications. The SMDC TechSat provides the high power CubeSat technology and the DM payload processor provides the two processing-related technologies. The combination of a High Power CubeSat technology with High Performance Payload Processing technology is considered to be major advancement in the development of small satellite capability.

TABLE OF CONTENTS 1. 2. 3. 4. 5. 6. 7.

INTRODUCTION – DM BACKGROUND SMDC TECHSAT DM PROCESSOR BASELINE DM CUBESAT TESTBED SMDC TECHSAT PDR SMDC TECHSAT FLAT-SAT DEMO SUMMARY AND CONCLUSION FUTURE WORK

1. INTRODUCTION – DM BACKGROUND Flying high performance Commercial-Off-The-Shelf (COTS) technology in space to take advantage of the higher performance and lower cost of COTS-based onboard processing solutions is a long-held desire of NASA and the DoD. Currently, there is increased interest in high performance COTS computing for a wide variety of small space and airborne platforms. This includes CubeSats, High Altitude Airships (HAAs), Unattended Airborne Systems (UASs), and micro Unattended Airborne Vehicles (UAVs).

As indicated in Figure 1, a DM system is a cluster of high performance COTS processors connected with a high speed interconnect and operating under the control of a reliable, possibly radiation-hardened, system controller and platform, technology, and application-independent fault tolerant middleware. The system controller provides a highly-

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978-1-4577-0557-1/12/$26.00 ©2012 IEEE. This paper has not been published elsewhere and is offered for exclusive publication except that Honeywell reserves the right to reproduce the material in whole or in part for its own use and, where Honeywell is obligated by contract. 2 IEEEAC paper #1581, Version 5, January 20, 2012. 3 The project formerly was known as the Environmentally-Adaptive FaultTolerant Computing (EAFTC) project.

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Figure 1 - ST8 and Initial Reduced-Size Dependable Multiprocessor Implementations flexible, efficient, and cost-effective integration of userselectable cluster management and SEU tolerance enhancement software to achieve high reliability and high availability in a wide variety of missions and environments is one of the key benefits of DM technology.

reliable and SEE-immune host to support recovery from radiation-induced events in the COTS hardware. The DM Middleware (DMM) manages jobs and missions executed on the cluster and, most importantly, enhances the fault tolerance of the system. The DMM controls applications, monitors the health and status of DM hardware and software components, enhances SEU tolerance, and manages the system and application recovery strategies. The features that distinguish DM from other COTS-based solutions are flexibility, scalability, and ease of use which are supported through user-friendly DM mission and job configuration files. Scalability comes in the form of a modular implementation and is limited by the scalability of the high speed interconnect and the skill of the application developer. DM offers user-configurable fault tolerance with options spanning the mission level to the application level. Fault tolerant execution includes replication, i.e., temporal and spatial self-checking (SC) and triple modular redundancy (TMR), combined with more computationally-efficient Algorithm-Based Fault Tolerance (ABFT). DM can execute multiple missions sequentially or concurrently based on resource availability.

The DM project did its TRL6 technology validation in 2008 and 2009. The DM TRL6 technology validation demonstration included system-level radiation beam testing in which one (1) COTS DP board was exposed to a proton beam while executing the TRL6 application suite and operating in the context of a DM flight system including all DMM, experiment interface, and experiment data collection software. The system-level radiation testing validated DM design and operation in a radiation environment. DM met the objectives and the intent of the NMP TRL6 development effort and brought the goal of flying COTS in space closer to reality. DM CubeSat technology was sponsored by SMDC as an Army SERB experiment in 2010. The capability and the low size, weight, power and cost of DM CubeSat technology made it an ideal partner for SMDC TechSat. In return, the SMDC TechSat flight experiment afforded DM an opportunity to achieve that, all important, TRL7 technology validation. More information about DM and DM CubeSat Technology can be found in [1] - [7].

To support enhanced SEU-tolerant performance in the DM, the traditional resource management services have been augmented with SEU-tolerant modes of operation including hardware (spatial) and software (temporal) redundancy, rapid detection and recovery from soft errors, rapid detection and recovery from hard faults, and fault/error management services including fault/error logging, fault/error handling diagnostics, management of resource health status, management of application/process status, and management of redundancy and spare elements. The

2. SMDC TECHSAT DM PAYLOAD PROCESSOR BASELINE Prior to the 2010 Army SERB meeting, the Honeywell DM project had already taken significant steps to get DM CubeSat technology closer to flight and to reduce the risk of a DM CubeSat flight experiment. These steps included 2

As shown in Figure 2, the objectives of the DM portion of the SMDC TechSat flight experiment are twofold: 1) to achieve the DM TRL7 validation in a space environment, and 2) to demonstrate onboard processing capability of significant interest to the Army. Relative to the latter, ground-commanded programmable image/data compression to the disadvantaged, dismounted war fighter, was selected as the Army application. A six (6) Data Processing (DP) node Gumstix-based DM cluster was identified as the baseline for the flight experiment. The use of Gumstix technology offers wide variety of implementation options. These options included the use of a Gumstix Stage Coach board, which contains an integrated Ethernet switch and can host up to seven (7) Gumstix modules, and the use of multiple Gumstix Tobi Duo boards. The use of Tobi-Duo boards offers much more flexibility in terms of mechanical configuration. Electrically, the Tobi-Duo boards are connected with Ethernet cables. Physically, the Tobi-Duo boards can be mounted anywhere they fit in the CubeSat volume to meet spacecraft volume, mechanical, and/or thermal requirements. The Tobi-Duo boards can be stacked vertically or horizontally, they can be mounted around the periphery of the CubeSat, or they can be staggered and mounted in various combinations. The originally-proposed DM processor baseline assumed the Stage Coach-based solution, but the baseline was changed to the Tobi Duo periphery-mounted solution to meet the physical constraints of the SMDC TechSat. [1] The functionally-equivalent Stage Coach configuration was used as a low cost, low risk DM payload implementation for the Flat-Sat Demo.

conducting a feasibility study which addressed size, weight, power, mechanical (structural & thermal), and radiation considerations of a Gumstix-based DM CubeSat implementation, the successful porting of the DMM to a Gumstix module, and the development of a DM CubeSat testbed. The results of the feasibility study were positive; a Gumstix-based DM CubeSat can be flown in space. Preliminary analysis showed it can survive the launch environment, it can operate in the space thermal environment, and it can operate in the radiation environment of a LEO orbit. DM is an architecture and software framework that enables COTS-based, high performance, scalable, cluster processing systems to operate in space by providing software-based SEE-tolerance enhancement. The platform-, technology-, and application-independent Dependable Multiprocessor Middleware (DMM) is DM technology. DM was developed not to be a point solution, but to be able to incorporate new technologies as they come on-line. The DMM (Dependable Multiprocessor Middleware) was successfully ported to a Gumstix module. The biggest issue addressed in the Gumstix port was the Big Endian/Little Endian conversion for the Gumstix ARM processor. With the Big Endian/Little Endian conversion, DM TRL6 applications ran on a Gumstix module under DMM control. DM software has been successfully ported to many platforms. Porting to the Gumstix COM module was just the latest porting target for the DM Middleware. As a result of the DM CubeSat effort, DMM application now includes ARMs.

Figure 2 - DM Payload Processing Experiment 3

compression experiments and demonstrations. With a laptop computer serving as the DM ground command and telemetry terminal and as the display for the raw and processed image, this DM CubeSat Testbed fixture is a portable DM demonstration system. This testbed leveraged $14M of NASA-funded DM technology development effort including the DMM (Dependable Multiprocessor Middleware), the ground command and telemetry processing and display software, and the spacecraft interface software. The spacecraft interface software included the generation of system time to time tag events and the generation of periodic polling messages to extract and downlink SOH (State-of-Health) and Experiment Data Telemetry information. The DM CubeSat Testbed was, in large part, the basis for the DM portion of the SMDC TechSat Flat-Sat Demo.

3. DM CUBESAT TESTBED A complete, end-to-end, ground-space, DM CubeSat Testbed including command and telemetry over RF links was built as shown in Figure 3. The lower portion of the photo shows the DM CubeSat Testbed payload demonstration system components including the space and ground Pumpkin Sat RF modules. A close-up view of the DM payload processor testbed fixture is shown in Figure 4. The DM CubeSat Testbed payload processor is a DM cluster with four (4) Data Processing (DP) nodes and a DM System Controller implemented on a Gumstix Stage Coach board. The DM CubeSat Testbed fixture also has a spacecraft bus emulator, a UART interface board to interface with the Pumpkin Sat RF modules, and a Gumstix mini-camera to support the snapshot image capture and ground-commanded, programmable image/data

Figure 3 - DM CubeSat Testbed Photo

Figure 4 - DM Flat-Sat Demo Hardware (DM CubeSat Testbed Version) 4

Power Control board in the DM payload design is to require the cycling of power to the entire cluster even if a high current SEFI condition is experienced in a single node and to accept the correspondingly longer DM system recovery time. This risk mitigation will be included in the plans for the SMDC TechSat Phase 2 effort.

4. SMDC TECHSAT PDR The successful SMDC TechSat PDR was held in May 2011. This included a description of the DM payload processor baseline. Figure 5 shows an early conceptual view of the SMDC TechSat showing the spacecraft bus components, the DM payload, and the pop-out mechanism for the articulated solar array. An updated flight configuration for the DM payload which has the DM components mounted around the periphery of the middle 1U section of the 3U-size SMDC TechSat is shown in Figure 6. This physical configuration has structural advantages, thermal advantages, and advantages for characterization of the radiation environment. With DM components located on the four major surfaces of the CubeSat, this configuration serves as a “poor man’s” radiation detector using the radiation crosssections of the semiconductor components and the DM flight experiment instrumentation to capture and record radiation induced events along with the DM system response to those radiation events. This layout was validated by the Morehead State University (MSU) 3D CAD modeling effort and the full-size 3D-printed mockup of the SMDC TechSat constructed for the SMDC TechSat Flat-Sat Demo.

5. SMDC TECHSAT FLAT-SAT DEMO The successful SMDC TechSat Flat-Sat Demo was held in September 2011. The primary purpose of the Flat-Sat Demo was to demonstrate the maturity of SMDC TechSat technology to high-level government customers and representatives. The Flat-Sat Demo, which integrated all of the components of the SMDC TechSat for the first time, was a major milestone for the SMDC TechSat project. Honeywell Space provided the Dependable Multiprocessor (DM) payload processor portion of the Flat-Sat Demo. This included the demonstration of autonomous startup, autonomous fault recovery, and real-time, groundcommanded, programmable image/data compression, all of which are of significant interest to the Army. The DM FlatSat demonstration capability encompassed demonstrating DM response to commands including the ability to turn the DM payload on and off via the Power Management & Distribution (PMAD) board, and the ability to command the DM payload to change application. The DM application suite demonstrable at the Flat-Sat Demo included SAR, HSI, LU Decomposition, Branch Test, Logic Test, and Image/Data Compression applications. The latter included the demonstration of ground-commanded programmable data compression ratio and the ability to observe snapshot data compression results in real time. Only the SAR and image compression applications were actually demonstrated during the Flat-Sat Demo.

Six (6) potential DM payload risk areas were identified at the PDR along with the corresponding mitigation approaches and consequences. In the intervening period between the PDR and the end of the Phase 1 effort, only one of the identified risks has been realized. That risk is the need to develop a separate DM Power Control board to sense a high current SEFI (Single Event Functional Interrupt) condition, to limit the current, and to cycle power to an individual node to remove the transient high current SEFI condition. The consequences of not including this DM

Figure 5 – Possible SMDC TechSat Configuration 5

Figure 6 - SMDC TechSat - DM Payload Integration & Mounting TechSat teammate Tethers Unlimited, Inc. is shown at the far right hand side of the photo. The DM payload processor subsystem provided by Honeywell is shown the upper left of the photo. This functional layout coupled with the fullsize 3D-printed mock-up made SMDC TechSat seem “real.”

A block diagram of the DM Flat-Sat Demo configuration showing the two DM electrical interfaces with the SMDC TechSat spacecraft, the Switched + 5VDC Power and the Command & Telemetry UART interfaces, is shown in Figure 7. These two DM interfaces were demonstrated as part of the Flat-Sat Demo.

Not shown in the figure, a large flat screen monitor was located to the right of the Flat-Sat Demo panel. The monitor was used to show the DM ground command and telemetry display. It also was used to show the SMDC TechSat STK orbit model integrated with a dynamic 3D model of the SMDC TechSat including the articulating solar array. The orbit model was running about 20 times faster than normal and, together with the 3D model of the spacecraft and the power management system, was used to demonstration battery charging and discharging during periods of solar exposure and solar eclipse operation. During the pre-demonstration presentations, SMDC TechSat teammate Tethers Unlimited Inc. showed videos of multiple-folded solar panels deploying during zero-G experiments on NASA’s Vomit Comet.

A photo of the SMDC TechSat Flat-Sat Demo is shown in Figure 8. This form factor for a Flat-Sat Demo with all components mounted on a large Aluminum plate has become a de facto “standard” for flat-sat demos. The vertically-oriented format was very beneficial because the components, and which teammate provided them, were clearly labeled and visible throughout the entire demonstration. The battery pack and PMAD (Power Management and Distribution) subsystem provided by SMDC TechSat teammate Radiance Technologies, Inc. is shown in the lower left corner of photo. The C&DH (Command and Data Handling) and communication subsystems provided by SMDC TechSat teammate Morehead State University are shown in the middle of the photo. The articulating mechanism provided by SMDC

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Figure 7 - DM Flat-Sat Demo Configuration

Figure 8 - SMDC TechSat Flat-Sat Demonstration Fixture (Photo Courtesy of Morehead State University) 7

DM Flat-Sat demonstration capability also encompassed the viewing of DM “on-orbit” telemetry on the DM ground system displays. These displays included reports of DM payload health status during system start-up and in response to injected fault events as shown in Figure 9 and reports of application execution status and performance as shown in Figure 10. The results of DM ground processing, which analyzed the data in downlink data telemetry streams and assessed DM flight experiment System Availability and Computational Correctness are also shown in Figure 9.

A Gumstix-compatible mini-camera was used to demonstrate real-time, ground-commanded, programmable image compression. Figure 11 shows examples of two compresses images, the top one lossless, and the bottom one with a compression 1000:1 compression ratio using a JPEG 2000 algorithm. For comparison, the raw images are shown on the left hand side of the figure, the compressed images are shown in the middle of the figure, and the “error,” i.e., the difference between the raw image and the compressed image for each of the three colors.

Figure 9 depicts the DM State-Of-Health (SOH) display. The SOH display presents the health status of the DM System Controller and Data Processor hardware and software components.

The Flat-Sat Demo included a full-size 3D-printed mock-up of the SMDC TechSat CubeSat which validated the physical configuration of the CubeSat including the peripherymounted DM payload components. The 3D-printed mockup was fabricated by SMDC TechSat teammate Morehead State University (MSU). Figure 12 shows top- and sideview photos of a real Tobi Duo board and the 3D-printed mock-up. Figure 13 shows the full-size 3D-printed mockup of SMDC TechSat (minus articulated solar array) with a Plexiglas window to allow viewing of the details of the DM payload, the camera, the camera mount, and the battery pack for pre-solar panel deployment start-up and solar eclipse

Figure 10 depicts the DM Experiment Data Telemetry display. This is a scrolling display which presents the most recent DM “event” at the top of the display. DM Experiment Data Telemetry data reported includes application start and completion events and times, and error detection and recovery events. The recorded SOH Experiment Data Telemetry data is archived for subsequent analysis.

Figure 9 - DM Payload - SOH Display – Key Areas of Interest 8

Figure 10 - DM Payload - Experiment Data Telemetry Display

Figure 11 – Example: Ground-Commanded Programmable Data Compression – JPEG 2000 Algorithm 9

Figure 12 - DM Tobi Duo Board & 3D-Printed Mockup (3D-Printed Mock-up Courtesy of Morehead State University)

Figure 13 – SMDC TechSat Mockup (Photos Courtesy of Morehead State University) 10

throughput performance and optimization, reduction of the DMM software footprint, and building and testing a flight prototype of the configuration shown in Figure 6. The Gumstix processing engine used in the current implementation of the DM CubeSat is one example of COM technology and represents just the latest port of the technologyand platform-independent Dependable Multiprocessor Middleware to a new platform. The Gumstix processor was selected as the initial target for DM CubeSat implementation because it met the requirements for size, weight, power, cost, and availability. It also represented a porting challenge because it was the first DMM port to an ARM processor and it required addressing the Big Endian/Little Endian issue. Fortunately, preliminary radiation testing showed the Gumstix processor did not exhibit catastrophic latch-up and exhibited modest SEE rates which allow DM middleware to be effective in achieving high availability and high computational correctness in a natural LEO radiation environment. Manifestation of a catastrophic latch-up would have been an automatic “no-fly” situation. Since the radiation testing did not manifest catastrophic latch-up, work with the Gumstix processors moved forward. Future work will include comprehensive component-level and system-level proton and heavy ion testing to validate the preliminary radiation performance conclusions. Future work will include development and testing of current-sensing, currentlimiting, voltage cut-off, and reset DM power control and switching circuitry. Future work will also look at extending the application of DM technology to other COM technologies including advanced Gumstix multi-core processing modules, Intel Atom™ and TRITON-TX51 processing engines, and tiled processing architectures such as the Tilera TILE64. There is also interest in combining control processing and payload processing in a single unified architecture. The later is possible with the DM architecture.

operation. The Gumstix Stage Coach version of the DM payload processing cluster was used for the Flat-Sat Demo to reduce risk and cost. Original plans were to build a mockup of the DM payload in the flight experiment form factor for the Flat-Sat Demo but, until MSU (Morehead State University) validated the physical layout of the DM payload processor with their 3D CAD and 3D-printed models of the SMDC TechSat including the DM payload processor, the DM flight form factor was TBD. There were two versions of the DM payload processor working at the SMDC Tech-Sat Flat-Sat Demo: one working as part of the integrated Flat-Sat Demo system, the other as a complete, end-to-end, stand-alone, DM CubeSat Testbed demonstration system including Pumpkin Sat RF modules.

6. SUMMARY AND CONCLUSION The SMDC TechSat Phase 1 effort culminated with the successful Flat-Sat Demo including the successful integration and demonstration of the DM payload processor as part of the SMDC TechSat Flat-Sat demonstration system. This demonstration included DM powered from the Radiance PMAD board, DM end-to-end ground & telemetry through the MSU C&DH board and SMDC TechSat ground station, and the use of existing ST8 DM software including DMM, spacecraft interface, and ground command and telemetry software. The successful Flat-Sat demonstration was the latest development in the effort to show the DM payload would be a low risk flight experiment. The lowered risk of a DM flight experiment is due in large part to the successful leveraging of both $14M of NASA NMP ST8 DM technology development through TRL6 technology validation and preparation for a TRL7 flight experiment and Honeywell-funded development of DM CubeSat technology. The latter included preliminary radiation testing of the COTS components, preliminary structural & thermal analysis, successful porting of DMM (Dependable Multiprocessor Middleware) to Gumstix processors, and construction of a DM CubeSat testbed which demonstrated complete DM end-to-end space-ground command and telemetry over an RF link. The combination of high power CubeSat technology and “self-healing” high performance onboard payload processing technology in the Flat-Sat Demo meets a critical need for the DoD. The DM CubeSat technology demonstrated is applicable to UAVs, HAAs, and larger satellites. In the context of larger satellites, smaller, lighter-weight, lower-power, and lower-cost onboard payload processors allow more payload for given size, weight, power, and cost constraints.

ACKNOWLEDGEMENTS The DM ST8 results presented in this paper were carried out under the auspices of the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The Dependable Multiprocessor effort was funded under NASA NMP ST-8 contract NMO-710209. The DM CubeSat effort to date was funded by Honeywell. The author would like to thank the following people for their contributions to the Dependable Multiprocessor CubeSat effort: Dr. Matthew Clark, Dr. Eric Grobelny, Dr. David Campagna, Susan Van Portfliet, Matt Smith, John Gourvellec, Lee Hoffmann, Andrew White, Jamal Haque, and Alvin Badillo of Honeywell Aerospace, Defense & Space, Dr. Ben Malphrus, Kevin Brown, Margaret Powell, Jeffrey Kruth, and Robert Krull of Morehead State University, and James Stafford of Radiance Technologies, Inc.

7. FUTURE WORK The DM CubeSat and Phase 2 SMDC TechSat efforts will continue. The DM CubeSat and Phase 1 SMDC TechSat work described in this paper focused on functionality. Future work will focus on performance, particularly 11

REFERENCES

BIOGRAPHY

[1] Samson, Jr., John R., “Implementation of a Dependable Multiprocessor CubeSat” Proceedings of the 2011 IEEE Aerospace Conference, Big Sky, MT, March 6-11, 2011.

John R. Samson, Jr. is a Principal Engineering Fellow with Honeywell Aerospace, Defense and Space in Clearwater, Florida. He received his Bachelor of Science Degree from the Illinois Institute of Technology, his Master of Science degree and the Degree of Electrical Engineer from the Massachusetts Institute of Technology, and his Ph.D. in Engineering Science with Specialization in Computer Science from the University of South Florida. During his 42-year career, John has worked at M.I.T. Lincoln Laboratory, Raytheon Company Equipment Division, and Honeywell Space Systems. His work has encompassed multiple facets of ground, airborne and space-based surveillance system applications. He has spent most of his career developing onboard processors, onboard processing architectures, and onboard processing systems for real-time and mission critical applications. He was Principal Investigator for a pioneering study investigating the feasibility of migrating high-performance COTS processing to space, a predecessor of the work described in this paper. Dr. Samson was the Principal Investigator for the Dependable Multiprocessor project and is currently the Principal Investigator for the DM CubeSat efforts. He is an Associate Fellow of the AIAA and a Senior Member of the IEEE.

[2] Samson, John, Jr., “Dependable Multiprocessor (DM) Implementation for Nano-satellite and CubeSat Applications (Challenging Packaging for High Performance Embedded Computing),” 14th High Performance Embedded Computing Workshop, M.I.T. Lincoln Laboratory, September 16, 2010. [3] Samson, John, Jr., et al., “Post-TRL6 Dependable Multiprocessor Technology Developments,” Proceedings of the 2010 IEEE Aerospace Conference, Big Sky, MT, March 7-11, 2010. [4] Samson, John, Jr., et al., “NMP ST8 Dependable Multiprocessor: Technology and Technology Validation Overview,” Proceedings of the 48th AIAA Aerospace Sciences Meeting Conference, Orlando FL, January 4-8, 2010. [4] Samson, John, Jr. and Eric Grobelny, “NMP ST8 Dependable Multiprocessor: TRL6 Validation – Preliminary Results,” Proceedings of the 2007 IEEE Aerospace Conference, Big Sky, MT, March 8-13, 2009. [6] Samson, John, Jr., et al., “High Performance Dependable Multiprocessor II,” Proceedings of the 2007 IEEE Aerospace Conference, Big Sky, MT, March 3-10, 2007. [7] Samson, John, Jr., et al., “Technology Validation: NMP ST8 Dependable Multiprocessor Project II,” Proceedings of the 2007 IEEE Aerospace Conference, Big Sky, MT, March 310, 2007.

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