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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1992

A formal model of asynchronous communication and its use in mechanically verifying a biphase mark protocol

In this paper we present a formal model of asynchronous communication as a function in the Boyer-Moore logic. The function transforms the signal stream generated by one processor into the signal stream consumed by an independently clocked processor. This transformation 'blurs' edges and 'dilates' time due to differences in the phases and rates of the two clocks and the communications delay. The model can be used quantitatively to derive concrete performance bounds on asynchronous communications at ISO protocol level 1 (physical level). We develop part of the reusable formal theory that permits the convenient application of the model. We use the theory to show that a biphase mark protocol can be used to send messages of arbitrary length between two asynchronous processors. We study two versions of the protocol, a conventional one which uses cells of size 32 cycles and an unconventional one which uses cells of size 18. We conjecture that the protocol can be proved to work under our model for smaller cell sizes and more divergent clock rates but the proofs would be harder.

Moore, J. Strother↗
NASA NTRS1994

Refinement for fault-tolerance: An aircraft hand-off protocol

Part of the Advanced Automation System (AAS) for air-traffic control is a protocol to permit flight hand-off from one air-traffic controller to another. The protocol must be fault-tolerant and, therefore, is subtle -- an ideal candidate for the application of formal methods. This paper describes a formal method for deriving fault-tolerant protocols that is based on refinement and proof outlines. The AAS hand-off protocol was actually derived using this method; that derivation is given.

Marzullo, Keith↗
NASA NTRS1992

CAPTIONALS: A computer aided testing environment for the verification and validation of communication protocols

This paper covers the verification and protocol validation for distributed computer and communication systems using a computer aided testing approach. Validation and verification make up the so-called process of conformance testing. Protocol applications which pass conformance testing are then checked to see whether they can operate together. This is referred to as interoperability testing. A new comprehensive approach to protocol testing is presented which address: (1) modeling for inter-layer representation for compatibility between conformance and interoperability testing; (2) computational improvement to current testing methods by using the proposed model inclusive of formulation of new qualitative and quantitative measures and time-dependent behavior; (3) analysis and evaluation of protocol behavior for interactive testing without extensive simulation.

Feng, C.↗
NASA NTRS1996

Use of CCSDS and OSI Protocols on the Advanced Communications Technology Satellite

Although ACTS (Advanced Communications Technology Satellite) provides an almost error-free channel during much of the day and under most conditions, there are times when it is not suitable for reliably error-free data communications when operating in the uncoded mode. Because coded operation is not always available to every earth station, measures must be taken in the end system to maintain adequate throughput when transferring data under adverse conditions. The most effective approach that we tested to improve performance was the addition of an 'outer' Reed-Solomon code through use of CCSDS (Consultative Committee for Space Data Systems) GOS 2 (a forward error correcting code). This addition can benefit all users of an ACTS channel including those applications that do not require totally reliable transport, but it is somewhat expensive because additional hardware is needed. Although we could not characterize the link noise statistically (it appeared to resemble uncorrelated white noise, the type that block codes are least effective in correcting), we did find that CCSDS GOS 2 gave an essentially error-free link at BER's (bit error rate) as high as 6x10(exp -4). For users that demand reliable transport, an ARQ (Automatic Repeat Queuing) protocol such as TCP (Transmission Control Protocol) or TP4 (Transport Protocol, Class 4) will probably be used. In this category, it comes as no surprise that the best choice of the protocol suites tested over ACTS was TP4 using CCSDS GOS 2. TP4 behaves very well over an error-free link which GOS 2 provides up to a point. Without forward error correction, however, TP4 service begins to degrade in the 10(exp -7)-10(exp -6) range and by 4x10(exp -6), it barely gives any throughput at all. If Congestion Avoidance is used in TP4, the degradation is even more pronounced. Fortunately, as demonstrated here, this effect can be more than compensated for by choosing the Selective Acknowledgment option. In fact, this option can enable TP4 to deliver some throughput at error rates as high as 10(exp -5).

Chirieleison, Don↗
NASA NTRS2000

Human Trials of a 2-Hour Prebreathe Protocol

We evaluate 2-hour prebreathe protocols combining simulated microgravity and exercise during prebreathe with the objective of validating a protocol for use on International Space Station (ISS). The protocol was tested with four different exercise doses during prebreathe in a multi-center trial involving three laboratories. Subject selection, Doppler monitoring techniques for venous gas emboli (VGE), test termination criteria, and definitions of decompression sickness (DCS) were standardized in all laboratories. The Phase II protocol met the accept criteria for a prebreathe procedure for use by astronauts during assembly and maintenance of the ISS Dual-cycle ergometry or light exercise individually was not sufficient to protect against DCS at acceptable levels. The combination of both was successful.

Butler, Bruce D.↗
NASA NTRS2002

Ocean Optics Protocols for Satellite Ocean Color Sensor Validation

This document stipulates protocols for measuring bio-optical and radiometric data for the SIMBIOS Project. It supersedes the earlier version, and is organized into four parts: Introductory Background, Instrument Characteristics, Field Measurements and Data Analysis, Data Reporting and Archival. Changes in this revision include the addition of three new chapters: (1) Fundamental Definitions, Relationships and Conventions; (2) MOBY, A Radiometric Buoy for Performance Monitoring and Vicarious Calibration of Satellite Ocean Color Sensors: Measurement and Data Analysis Protocols; and (3) Normalized Water-Leaving Radiance and Remote Sensing Reflectance: Bidirectional Reflectance and Other Factors. Although the present document represents another significant, incremental improvement in the ocean optics protocols, there are several protocols that have either been overtaken by recent technological progress, or have been otherwise identified as inadequate. Revision 4 is scheduled for completion sometime in 2003. This technical report is not meant as a substitute for scientific literature. Instead, it will provide a ready and responsive vehicle for the multitude of technical reports issued by an operational Project. The contributions are published as submitted, after only minor editing to correct obvious grammatical or clerical errors.

Mueller, James L.↗
NASA NTRS2002

Ocean Optics Protocols for Satellite Ocean Color Sensor Validation

This document stipulates protocols for measuring bio-optical and radiometric data for the SIMBIOS Project. It supersedes the earlier version, and is organized into four parts: Introductory Background, Instrument Characteristics, Field Measurements and Data Analysis, Data Reporting and Archival. Changes in this revision include the addition of three new chapters: (1) Fundamental Definitions, Relationships and Conventions; (2) MOBY, A Radiometric Buoy for Performance Monitoring and Vicarious Calibration of Satellite Ocean Color Sensors: Measurement and Data Analysis Protocols; and (3) Normalized Water-Leaving Radiance and Remote Sensing Reflectance: Bidirectional Reflectance and Other Factors. Although the present document represents another significant, incremental improvement in the ocean optics protocols, there are several protocols that have either been overtaken by recent technological progress, or have been otherwise identified as inadequate. Revision 4 is scheduled for completion sometime in 2003. This technical report is not meant as a substitute for scientific literature. Instead, it will provide a ready and responsive vehicle for the multitude of technical reports issued by an operational Project. The contributions are published as submitted, after only minor editing to correct obvious grammatical or clerical errors.

Mueller, James L.↗
NASA NTRS2002

A Draft Protocol for Detecting Possible Biohazards in Martian Samples Returned to Earth

In preparation for missions to Mars that will involve the return of samples, it is necessary to prepare for the safe receiving, handling, testing, distributing, and archiving of martian materials here on Earth. Previous groups and committees have studied selected aspects of sample return activities, but a specific protocol for handling and testing of returned -=1 samples from Mars remained to be developed. To refine the requirements for Mars sample hazard testing and to develop criteria for the subsequent release of sample materials from precautionary containment, NASA Planetary Protection Officer, working in collaboration with CNES, convened a series of workshops to produce a Protocol by which returned martian sample materials could be assessed for biological hazards and examined for evidence of life (extant or extinct), while safeguarding the samples from possible terrestrial contamination. The Draft Protocol was then reviewed by an Oversight and Review Committee formed specifically for that purpose and composed of senior scientists. In order to preserve the scientific value of returned martian samples under safe conditions, while avoiding false indications of life within the samples, the Sample Receiving Facility (SRF) is required to allow handling and processing of the Mars samples to prevent their terrestrial contamination while maintaining strict biological containment. It is anticipated that samples will be able to be shipped among appropriate containment facilities wherever necessary, under procedures developed in cooperation with international appropriate institutions. The SRF will need to provide different types of laboratory environments for carrying out, beyond sample description and curation, the various aspects of the protocol: Physical/Chemical analysis, Life Detection testing, and Biohazard testing. The main principle of these tests will be described and the criteria for release will be discussed, as well as the requirements for the SRF and its personnel.

Viso, M.↗
NASA NTRS2003

Refinement of Protocols for Measuring the Apparent Optical Properties of Seawater

Ocean color satellite missions, like the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) or the Moderate Resolution Imaging Spectroradiometer (MODIS) projects, are tasked with acquiring a global ocean color data set, validating and monitoring the accuracy and quality of the data, processing the radiometric data into geophysical units using a set of atmospheric and bio-optical algorithms, and distributing the final products to the scientific community. The long-standing requirement of the SeaWiFS Project, for example, is to produce spectral water-leaving radiances, LW(lambda), to within 5% absolute (lambda denotes wavelength) and chlorophyll a concentrations to within 35% (Hooker and Esaias 1993), and most ocean color sensors have the same or similar requirements. Although a diverse set of activities are required to ensure the accuracy requirements are met (Hooker and McClain 2000), the perspective here is with field observations. The accurate determination of upper ocean apparent optical properties (AOPs) is essential for the vicarious calibration of ocean color data and the validation of the derived data products, because the sea-truth measurements are used to evaluate the satellite observations (Hooker and McClain 2000). The uncertainties with in situ AOP measurements have various sources: a) the sampling procedures used in the field, including the environmental conditions encountered; b) the absolute characterization of the radiometers in the laboratory; c) the conversion of the light signals to geophysical units in a processing scheme, and d) the stability of the radiometers in the harsh environment they are subjected to during transport and use. Assuming ideal environmental conditions, so this aspect can be neglected, the SeaWiFS ground-truth uncertainty budget can only be satisfied if each uncertainty is on the order of 1-2%, or what is generally referred to as 1% radiometry. In recent years, progress has been made in estimating the magnitude of some of these uncertainties and in defining procedures for minimizing them. For the SeaWiFS Project, the first step was to convene a workshop to draft the SeaWiFS Ocean Optics Protocols (hereafter referred to as the Protocols). The Protocols initially adhered to the Joint Global Ocean Flux Study (JGOFS) sampling procedures (JGOFS 1991) and defined the standards for optical measurements to be used in SeaWiFS calibration and validation activities (Mueller and Austin 1992). Over time, the Protocols were revised (Mueller and Austin 1995), and then recurringly updated on essentially an annual basis (Mueller 2000, 2002, and 2003) as part of the Sensor Inter-comparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) project. 98

Hooker, Stanford B.↗
NASA NTRS2006

Comments on the "Byzantine Self-Stabilizing Pulse Synchronization" Protocol: Counter-examples

Embedded distributed systems have become an integral part of many safety-critical applications. There have been many attempts to solve the self-stabilization problem of clocks across a distributed system. An analysis of one such protocol called the Byzantine Self-Stabilizing Pulse Synchronization (BSS-Pulse-Synch) protocol from a paper entitled "Linear Time Byzantine Self-Stabilizing Clock Synchronization" by Daliot, et al., is presented in this report. This report also includes a discussion of the complexity and pitfalls of designing self-stabilizing protocols and provides counter-examples for the claims of the above protocol.

Malekpour, Mahyar R.↗
NASA NTRS2006

Taking the Politics Out of Satellite and Space-Based Communications Protocols

After many years of studies, experimentation, and deployment, large amounts of misinformation and misconceptions remain regarding applicability of various communications protocols for use in satellite and space-based networks. This paper attempts to remove much of the politics, misconceptions, and misinformation that have plagued spacebased communications protocol development and deployment. This paper provides a common vocabulary for communications; a general discussion of the requirements for various communication environments; an evaluation of tradeoffs between circuit and packet-switching technologies, and the pros and cons of various link, network, transport, application, and security protocols. Included is the applicability of protocol enhancing proxies to NASA, Department of Defense (DOD), and commercial space communication systems.

Ivancic, William D.↗
NASA NTRS2009

A Self-Stabilizing Byzantine-Fault-Tolerant Clock Synchronization Protocol

This report presents a rapid Byzantine-fault-tolerant self-stabilizing clock synchronization protocol that is independent of application-specific requirements. It is focused on clock synchronization of a system in the presence of Byzantine faults after the cause of any transient faults has dissipated. A model of this protocol is mechanically verified using the Symbolic Model Verifier (SMV) [SMV] where the entire state space is examined and proven to self-stabilize in the presence of one arbitrary faulty node. Instances of the protocol are proven to tolerate bursts of transient failures and deterministically converge with a linear convergence time with respect to the synchronization period. This protocol does not rely on assumptions about the initial state of the system other than the presence of sufficient number of good nodes. All timing measures of variables are based on the node s local clock, and no central clock or externally generated pulse is used. The Byzantine faulty behavior modeled here is a node with arbitrarily malicious behavior that is allowed to influence other nodes at every clock tick. The only constraint is that the interactions are restricted to defined interfaces.

Malekpour, Mahyar R.↗
NASA NTRS2010

Rationale, Scenarios, and Profiles for the Application of the Internet Protocol Suite (IPS) in Space Operations

This greenbook captures some of the current, planned and possible future uses of the Internet Protocol (IP) as part of Space Operations. It attempts to describe how the Internet Protocol is used in specific scenarios. Of primary focus is low-earth-orbit space operations, which is referred to here as the design reference mission (DRM). This is because most of the program experience drawn upon derives from this type of mission. Application profiles are provided. This includes parameter settings programs have proposed for sending IP datagrams over CCSDS links, the minimal subsets and features of the IP protocol suite and applications expected for interoperability between projects, and the configuration, operations and maintenance of these IP functions. Of special interest is capturing the lessons learned from the Constellation Program in this area, since that program included a fairly ambitious use of the Internet Protocol.

Benbenek, Daniel B.↗
NASA NTRS2004

Data Relay Board with Protocol for High-Speed, Free-Space Optical Communications

In a free-space optical communication system, the mitigation of transient outages through the incorporation of error-control methods is of particular concern, the outages being caused by scintillation fades and obscurants. The focus of this innovative technology is the development of a data relay system for a reliable high-data-rate free-spacebased optical-transport network. The data relay boards will establish the link, maintain synchronous connection, group the data into frames, and provide for automatic retransmission (ARQ) of lost or erred frames. A certain Quality of Service (QoS) can then be ensured, compatible with the required data rate. The protocol to be used by the data relay system is based on the draft CCSDS standard data-link protocol Proximity-1, selected by orbiters to multiple lander assets in the Mars network, for example. In addition to providing data-link protocol capabilities for the free-space optical link and buffering the data, the data relay system will interface directly with user applications over Gigabit Ethernet and/or with highspeed storage resources via Fibre Channel. The hardware implementation is built on a network-processor-based architecture. This technology combines the power of a hardware switch capable of data switching and packet routing at Gbps rates, with the flexibility of a software- driven processor that can host highly adaptive and reconfigurable protocols used, for example, in wireless local-area networks (LANs). The system will be implemented in a modular multi-board fashion. The main hardware elements of the data relay system are the new data relay board developed by Rockwell Scientific, a COTS Gigabit Ethernet board for user interface, and a COTS Fibre Channel board that connects to local storage. The boards reside in a cPCI back plane, and can be housed in a VME-type enclosure.

Wright, Malcolm↗
NASA NTRS2013

Remote Memory Access Protocol Target Node Intellectual Property

The MagnetoSpheric Multiscale (MMS) mission had a requirement to use the Remote Memory Access Protocol (RMAP) over its SpaceWire network. At the time, no known intellectual property (IP) cores were available for purchase. Additionally, MMS preferred to implement the RMAP functionality with control over the low-level details of the design. For example, not all the RMAP standard functionality was needed, and it was desired to implement only the portions of the RMAP protocol that were needed. RMAP functionality had been previously implemented in commercial off-the-shelf (COTS) products, but the IP core was not available for purchase. The RMAP Target IP core is a VHDL (VHSIC Hardware Description Language description of a digital logic design suitable for implementation in an FPGA (field-programmable gate array) or ASIC (application-specific integrated circuit) that parses SpaceWire packets that conform to the RMAP standard. The RMAP packet protocol allows a network host to access and control a target device using address mapping. This capability allows SpaceWire devices to be managed in a standardized way that simplifies the hardware design of the device, as well as the development of the software that controls the device. The RMAP Target IP core has some features that are unique and not specified in the RMAP standard. One such feature is the ability to automatically abort transactions if the back-end logic does not respond to read/write requests within a predefined time. When a request times out, the RMAP Target IP core automatically retracts the request and returns a command response with an appropriate status in the response packet s header. Another such feature is the ability to control the SpaceWire node or router using RMAP transactions in the extended address range. This allows the SpaceWire network host to manage the SpaceWire network elements using RMAP packets, which reduces the number of protocols that the network host needs to support.

Haddad, Omar↗
NASA NTRS2013

Fifteen-minute Extravehicular Activity Prebreathe Protocol Using NASA's Exploration Atmosphere (8.2 psia/ 34% 02)

A TBDM DCS probability model based on an existing biophysical model of inert gas bubble growth provides significant prediction and goodness-of-fit with 84 cases of DCS in 668 human altitude exposures. 2. Model predictions suggest that 15-minute O2 prebreathe protocols used in conjunction with suit ports and an 8.2 psi, 34% O2, 66% N2 atmosphere may enable rapid EVA capability for future exploration missions with the risk of DCS ≤ 12%.  EVA could begin immediately at 6.0 psi, with crewmembers decreasing suit pressure to 4.3 psi after completing the 15-minute in-suit prebreathe. 3. Model predictions suggest that intermittent recompression during exploration EVA may reduce decompression stress by 1.8% to 2.3% for 6 hours of total EVA time. Savings in gas consumables and crew time may be accumulated by abbreviating the EVA suit N2 purge to 2 minutes (20% N2) compared with 8 minutes (5% N2) at the expense of an increase in estimated decompression risk of up to 2.4% for an 8-hour EVA.  Increased DCS risk could be offset by IR or by spending additional time at 6 psi at the beginning of the EVA.  Savings of 0.48 lb of gas and 6 minutes per person per EVA corresponds to more than 31 hours of crew time and 1800 lb of gas and tankage under the Constellation lunar architecture. 6. Further research is needed to characterize and optimize breathing mixtures and intermittent recompression across the range of environments and operational conditions in which astronauts will live and work during future exploration missions. 7. Development of exploration prebreathe protocols will begin with definition of acceptable risk, followed by development of protocols based on models such as ours, and, ultimately, validation of protocols through ground trials before operational implementation.

Abercromby, Andrew F. J.↗
NASA NTRS2015

Designing an Exploration Atmosphere Prebreathe Protocol

Extravehicular activities (EVAs) at remote locations must maximize limited resources such as oxygen (O2) and also minimize the risk of decompression sickness (DCS). A proposed remote denitrogenation (prebreathe) protocol requires astronauts to live in a mildly hypoxic atmosphere at 8.2 psia while periodically performing EVAs at 4.3 psia. Empirical data are required to confirm that the protocol meets the current accept requirements: less than or equal to 15% incidence of Type I DCS, less than or equal to 20% incidence of Grade IV venous gas emboli (VGE), both at 95% statistical confidence, with no Type II DCS symptom during the validation trial. METHODS: A repeated measures statistical design is proposed in which groups of 6 subjects with physical characteristics similar to active-duty astronauts would first become equilibrated to an 8.2 psia atmosphere in a hypobaric chamber containing 34% O2 and 66% N2, over 48 h, and then perform 4 simulated EVAs at 4.3 psia over the next 9 days. In the equilibration phase, subjects undergo a 3-h 100% O2 mask prebreathe prior to and during a 5-min ascent to 8.2 psia to prevent significant tissue N2 supersaturation on reaching 8.2 psia. Masks would be removed once 34% O2 is established at 8.2 psia, and subjects would then equilibrate to this atmosphere for 48 h. The hypoxia is equivalent to breathing air at 1,220 meters (4,000 ft) altitude, just as was experienced in the shuttle 10.2 psia - 26.5% O2 staged denitrogenation protocol and the current ISS campout denitrogenation protocol. For simulated EVAs, each subject dons a mask and breathes 85% O2 and 15% N2 during a 3-min depressurization to 6.0 psia, holds for 15 min, and then completes a 3-min depressurization to 4.3 psia. The simulated EVA period starts when 6.0 psia is reached and continues for a total of 240 min (222 min at 4.3 psia). During this time, subjects will follow a prescribed repetitive activity against loads in the upper and lower body with mean metabolic rate approaching 1500 BTU/hr [378 kcal/hr (O2 consumption about 1.3 l(sub STPD)/min)] in ambulatory subjects. Noninvasive Doppler ultrasound bubble monitoring for VGE in the pulmonary artery will be performed on subjects by 2 Doppler Technicians at about 15 min intervals while at 4.3 psia. At the end of this period, a 15-min repressurization returns all subjects back to 8.2 psia and the cycle is repeated 3 additional times with a day of rest between simulated EVAs. RESULTS: With an assumed 1.5% probability of DCS [P(DCS)] and accounting for within-subject correlation, running the proposed study with 20 subjects has a 95% probability of meeting the accept criterion for DCS. But if the true probability of DCS is 3.0%, then 30 subjects would be needed to achieve about the same probability to meet our accept criterion. These results assume a standard deviation of 1.4 for the between-subjects random component of P(DCS) on a logit scale, which was estimated from a previous study.

Conkin, Johnny↗
NASA NTRS2015

A Self-Stabilizing Hybrid Fault-Tolerant Synchronization Protocol

This paper presents a strategy for solving the Byzantine general problem for self-stabilizing a fully connected network from an arbitrary state and in the presence of any number of faults with various severities including any number of arbitrary (Byzantine) faulty nodes. The strategy consists of two parts: first, converting Byzantine faults into symmetric faults, and second, using a proven symmetric-fault tolerant algorithm to solve the general case of the problem. A protocol (algorithm) is also present that tolerates symmetric faults, provided that there are more good nodes than faulty ones. The solution applies to realizable systems, while allowing for differences in the network elements, provided that the number of arbitrary faults is not more than a third of the network size. The only constraint on the behavior of a node is that the interactions with other nodes are restricted to defined links and interfaces. The solution does not rely on assumptions about the initial state of the system and no central clock nor centrally generated signal, pulse, or message is used. Nodes are anonymous, i.e., they do not have unique identities. A mechanical verification of a proposed protocol is also present. A bounded model of the protocol is verified using the Symbolic Model Verifier (SMV). The model checking effort is focused on verifying correctness of the bounded model of the protocol as well as confirming claims of determinism and linear convergence with respect to the self-stabilization period.

Malekpour, Mahyar R.↗