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This article suggests that in order to be able to exercise control over a particular program, the program itself must be controllable. A controllable program therefore, according to the author, is one that has been properly scoped technically, realistically scheduled, and adequately budgeted. The article delves indepth into each of the above aspects of a controllable program and discusses both the pros and cons of each.
The authors regret the inaccuracy in the vertical axis title of Fig. 4 and the distortion in the legend of Fig. 13. Corrections have been made to the vertical axis title and legend of Figs. 4 and 13, respectively. These changes do not affect the analysis, calculations, or results in any way. The authors apologize for any inconvenience caused. The corrected figures are as follows:
The author has identified the following signficant results. An experiment was conducted to evaluate the feasibility of using ERTS-1 MSS imagery for spot transmission measurements on selected sites. Using the 15-unit gray scale on the 70 mm positive imagery as the base of comparison, a correlation was made between the transmittance measured at each site on the imagery and the radiance values (counts) recorded on CCT tape by the spacecraft over the same sites. The imagery was enlarged by a 750-watt projector and focused on a white cardboard screen 6 meters from the screen. Observations were made on 30 sub-sites which were pre-selected for their differing image brightness and total area; all are dried pond beds. Observations were also made on average gray backgrounds and a small lake. There was a very good correlation between the density values obtained from projected imagery and radiance values received by the detector on the spacecraft. A shorter experiment time and closer integration of gray scale and site readings would avoid the variation in lamp intensities that occurred.
The author has identified the following significant results. This project is to identify and map cotton fields in the southern deserts of California. Cotton in the Imperial, Coachella, and Palo Verde Valleys is heavily infested by the pink bollworm which affects both the quantity and quality of cotton produced. In California the growing season of cotton is regulated by establishing planting and plowdown dates. These procedures ensure that the larvae, whose diapause or resting period occurs during the winter months, will have no plant material on which to feed, thus inhibiting spring moth emergence. the underflight data from the U-2 aircraft has shound that it is possible to detect the differences between a growing, a defoliated, and plowed down field providing the locations of the fields are known. The ERTS-1 MSS data are being analyzed using an I2S optical color combiner to determine which combinations of dates and colors will identify cotton fields and thus provide the data needed to produce maps of the fields for the forthcoming season.
The author has identified the following significant results. Principal effort has been on the development of a PDP-10 software package to read the CCT tapes more cheaply and rapidly. This is 90% completed and debugged. A shade print example of Treasure Island is provided. Stanford area was overflown with the U-2 as an add-on photographic mission to help fill in record-gaps in ERTS-1 overpass which was clouded out.
The author has identified the following significant results. In a cooperative study with USGS personnel, it has been possible to detect a 1.5 by 1 mile anomaly on ERTS CCT data, in the pine-covered mountains of western Nevada. This anomalous area is about 3-5 times larger than that of the known geobotanical anomaly which lies centrally within the area. The site has been studied on the ground and bi-directional reflectances, relative to BaS04 obtained for 40 trees, using both in-vivo techniques (similar to cherry picker operations) and field determinations of cut branches. The anomaly can be seen best by color transparencies made from 5/4, 6/4, 7/4 ratioed digital data, the 3 ratios each being coded by one of 3 colors (blue, green, and red).
The author has identified the following significant results. LANDSAT digital data and ground truth measurements for Saginaw Bay (Lake Huron), Michigan, for 3 June 1974 can be correlated by stepwise linear regression technique and the resulting equations used to estimate invisible water quality parameters in nonsampled areas. Correlation of these parameters with each other indicates that the transport of Saginaw River water can now be traced by a number of water quality features, one or more of which are directly detected by LANDSAT. Five of the 12 water quality parameters are best correlated with LANDSAT band 6 measurements alone. One parameter (temperature) relates to band 5 alone and the remaining six may be predicted with varying degrees of accuracy from a combination of two bands (first band 6 and generally band 4 second).
There are no author-identified significant results in this report.
The Congressional committees that authorize the activities of NASA requested that the National Research Council (NRC) review the testing and quality assurance programs for the Advanced Solid Rocket Motor (ASRM) program. The proposed ASRM design incorporates numerous features that are significant departures from the Redesigned Solid Rocket Motor (RSRM). The NRC review concentrated mainly on these features. Primary among these are the steel case material, welding rather than pinning of case factory joints, a bolted field joint designed to close upon firing the rocket, continuous mixing and casting of the solid propellant in place of the current batch processes, use of asbestos-free insulation, and a lightweight nozzle. The committee's assessment of these and other features of the ASRM are presented in terms of their potential impact on flight safety.
The authors present an extension to the impulse shaping technique for commanding machines to move with reduced residual vibration. The extension, called frequency sampling, is a method for generating constraints that are used to obtain shaping sequences which minimize residual vibration in systems such as robots whose resonant frequencies change during motion. The authors present a review of impulse shaping methods, a development of the proposed extension, and a comparison of results of tests conducted on a simple model of the space shuttle robot arm. Frequency shaping provides a method for minimizing the impulse sequence duration required to give the desired insensitivity.
Connected and automated vehicles (CAVs) offer a huge potential to improve the operations and safety of transportation systems. However, the use of smart devices and communications in CAVs introduce new risks. CAVs would leverage vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communication, thus providing additional system access points compared to traditional systems. Automation makes these systems more vulnerable and increases the consequences of cyberattacks. This study utilizes an infrastructure-based communication platform consisting of cooperative adaptive cruise control and lane control advisories developed by the authors to perform cyber risk assessment of CAVs. The study emulates three types of cyberattacks (message falsification, dedicated denial of service, and spoofing attacks) in a representative traffic environment consisting of multiple CAV platoons and lane change events to analyze the safety and stability impacts of the cyberattacks. Simulation experiments using VISSIM reveals that traffic stream and CAV string is unstable under all three types of cyberattacks. The worst case is represented by the message falsification attack. Increases in volatility are observed over a no attack case, with variations increasing by an average of 43%–51% along with an increase of over 3000 crash conflicts. Similarly, lane change crash conflicts are observed to be more severe compared to rear end crash conflicts, showing a higher probability of severe injuries. Further, the case of slight cyberattack on a single CAV also creates significant disruption in the traffic stream. Analysis of variance (ANOVA) reveals the statistical significance of the results. Furthermore, these results pave the way for future design of secure systems from a monitoring perspective.
Flight research experiments have demonstrated that adaptive flight controls can be an effective technology for improving aircraft safety in the event of failures or damage. However, the nonlinear, timevarying nature of adaptive algorithms continues to challenge traditional methods for the verification and validation testing of safety-critical flight control systems. Increasingly complex adaptive control theories and designs are emerging, but only make testing challenges more difficult. A potential first step toward the acceptance of adaptive flight controllers by aircraft manufacturers, operators, and certification authorities is a very simple design that operates as an augmentation to a non-adaptive baseline controller. Three such controllers were developed as part of a National Aeronautics and Space Administration flight research experiment to determine the appropriate level of complexity required to restore acceptable handling qualities to an aircraft that has suffered failures or damage. The controllers consist of the same basic design, but incorporate incrementally-increasing levels of complexity. Derivations of the controllers and their adaptive parameter update laws are presented along with details of the controllers implementations.
Human teams collaborate by establishing roles, changing functional authorities, maintaining team cognition, coordinating, and mutually helping one another close control loops. These complex inter-actions are inspiring novel concepts to improve human-machine and multi-machine collaboration. However, these new systems face engineering gaps in modeling, analysis, design, and assurance. As such, few have been fielded in safety-critical domains like aerospace. To analyze safety, this paper introduces a system-theoretic framework to describe interactions that are—or are planned to be—used in multi-controller systems. It outlines a taxonomy of seven structural dimensions that influence controller interactions and nine dynamics observed in collaborative control that are defined using Systems Theory. An analyzed set of 101 controller interactions in aerospace systems demonstrates how to apply the framework and that designers are trying to create more sophisticated systems. This framework provides the foundation to extend system-theoretic hazard analysis techniques to systematically find collabora-tive-control causal factors.
A new digital redesign technique is developed for determining the digital version of an optimal momentum management controller previously designed by the authors for the Space Station Freedom. The technique matches all the states at all sampling instants to find a pseudo-continuous time quadratic regulator. It is shown that the redesigned digital states closely match the continuous time optimal states. It is also shown how the redesign technique can be applied to a state estimator.
In the practice of vortex flow controls, the most important factor is that the persistency and obstinacy of a concentrated vortex depend on its stability and dissipation. In this paper, the modern nonlinear stability theory for circulation-preserving flows is summarized, and the dissipation for general viscous flows is analyzed in terms of the evolution of total enstrophy. These analyses provide a theoretical base for understanding relevant physics of vortex flows, and lead to some guiding principles and methods for their controls. Case studies taken from various theoretical and/or experimental works of vortex controls, due to the present authors as well as others, confirm the feasibility of the recommended principles and methods.
The authors consider the design of controllers for the recovery of target loop transfer function or sensitivity and complementary sensitivity functions for general nonminimum phase discrete time systems. The necessary design constraints and the available design freedom are reviewed. In view of the available freedom, possible specifications on the eigenstructure of the observer dynamic matrix are formulated. Three different types of controllers which are respectively based on prediction, current, and reduced-order estimators are considered. For each one of those controllers, three different design techniques are developed. The first one is an eigenstructure assignment scheme, while the other two are optimization-based designs. The eigenstructure assignment method yields a controller design which achieves any chosen recovery error matrix among a set of admissible recovery error matrices. On the other hand, one of the optimization-based design methods leads to a controller that achieves a recovery error matrix having the infimum H-infinity norm, while the other does the same except it achieves a recovery error matrix having the infimum H2 norm.
This handbook sets forth the disposition of official records of the National Aeronautics and Space Administration. Its provisions are applicable to NASA Headquarters and all field installations. This revised edition has been enlarged in scope and re-titled to provide guidance in all aspects of records retirements, transfers, destruction, and retrievals from Federal Records Centers. New records control schedules have been added and others revised. Also included are procedures for making recommendations for improved coverage of records categories by additions or revisions. The NASA Records Control Schedules are issued under authority of the NASA Records Management Officer in accordance with Section 101-11.406, Federal Property Management Regulations. They were approved for NASA use by the National Archives and Records Service, the General Accounting Office, and by the Joint Committee on the Disposition of Executive Papers, U.S. Congress.
Software that enables authorized users to monitor and control scientific payloads aboard the International Space Station (ISS) from diverse terrestrial locations equipped with Internet connections is undergoing development. This software reflects a data-driven approach to distributed operations. A Web-based software framework leverages prior developments in Java and Extensible Markup Language (XML) to create portable code and portable data, to which one can gain access via Web-browser software on almost any common computer. Open-source software is used extensively to minimize cost; the framework also accommodates enterprise-class server software to satisfy needs for high performance and security. To accommodate the diversity of ISS experiments and users, the framework emphasizes openness and extensibility. Users can take advantage of available viewer software to create their own client programs according to their particular preferences, and can upload these programs for custom processing of data, generation of views, and planning of experiments. The same software system, possibly augmented with a subset of data and additional software tools, could be used for public outreach by enabling public users to replay telescience experiments, conduct their experiments with simulated payloads, and create their own client programs and other custom software.