摘要:

AbstractThe Skylab Experiment T002 Manual Space Navigation Sightings was successfully completed on Skylab missions II and III. Performing the experiment inflight were Major Jack R. Lousma, pilot SL‐II, and Lt Colonel William Poage, pilot SL‐III. The purpose of T002 was to investigate the feasibility of a manual navigation system for use in back‐up navigation applications and to investigate the capability of man to make the necessary celestial observations in terms of accuracy and precision under the conditions of long term space flight. The experiment, co‐sponsored by NASA Ames Research Center and the United States Air Force, involves the use of a handheld space stadimeter for measuring altitude as a function of earth horizon curvature and a handheld space sextant for measuring space observable angles such as star to earth horizon and star to moon.This study provides an analysis of the Air Force functional objectives—the sextant starhorizon measurements and stadimeter altitude measurements. Included are the preliminary accuracy and precision data, horizon characteristics, and instrument performance. During Skylab II, 378 sextant sightings and 88 stadimeter sightings were made. These data resulted in definitive horizon altitude determinations as well as an evaluation of the ranging performance of the space stadimeter.Star to earth horizon sextant sightings yielded mean observable horizons heights at 9.63 km for the apparent earth 33.34 km for the dark to light transition layer at the base of the airglow horizon, and 95.13 km for the top of the air‐glow horizon. Standard deviation for these horizons ranged from approximately 8.5 to 2.2 km during the sighting periods. The mean spacecraft height error for stadimeter sightings was 6.77 nm with standard deviations in the range of 2.28

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01227.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe world‐wide Omega navigation system, used in conjunction with locally‐derived differential Omega updates, promises to provide the position‐fixing accuracy and reliability required 1.) by commercial aircraft for area navigation in even heavily‐trafficked terminal locales, 2.) by military aircraft for the successful execution of the vast majority of tactical missions, and 3.) by space shuttle and similar vehicles for re‐entry navigation during the post‐blackout portion of flight. A mechanization of the differential Omega concept is presented which provides maximum flexibility, allowing users to determine their positions with circular (rho‐rho), hyperbolic, or pure differential mechanizations and yet does not require the differential ground subsystem to contain an expensive, highly‐accurate oscillator which is normally associated with rho‐rho capabilities. The hardware and software implementations are outlined and a rationale for the particular navigation and updating mechanization selected is presented. It is shown that while skywave propagation variations and local oscillator off‐sets are not separated by the ground subsystem, this ambiguity need not introduce errors to user aircraft. In fact, users operating in the circular mode can generally achieve greater accuracy than for a purely hyperbolic mechanization in which all clock errors were eliminated. The implementation described is incorporated as a selectable mode of operation in the Omega subsystems to be delivered by Bendix Navigation and Control to the FAA for its differential Omega

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01228.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractA Scanning Laser Radar that can acquire and track single or multiple targets has recently been developed. Scan patterns have been designed for acquisition and tracking of one or more targets using a narrow laser beam. A synchronously scanned transmitter‐receiver is used to acquire and track targets anywhere in a 376 × 376 element raster covering a 30° × 30° field. All scan patterns are electronically programmed and the system automatically acquires and tracks the target or targets without the aid of an operator. The maximum tracking rate is 1.0 deg/sec (10.0 deg/sec) when used with a 1 kHz (10 kHz) scan rate. The estimated free space range against passive cooperative targets (corner cube reflectors) is 30 nautical miles. The laser radar has an accuracy of 10 centimeters (range) and 0.05 degrees (angle). The developmental system is relatively small (1.5 cu. ft.), lightweight (60 pounds) and low‐power‐consuming (60 watts).The developmental Scanning Laser Radar was designed primarily for future rendezvous and docking applications. The multiple target capability is uniquely used here to determine the relative attitude of a passive cooperative target vehicle so that the docking axes of the two spacecraft can be properly oriented. For docking maneuvers, the laser radar measures the line‐of‐sight range and angles to four separate reflectors located on the target vehicle. This range and angle information is then used to calculate the relative pitch, yaw, and roll angles between the docking axes of the respective vehicles. Using this measurement technique, the attitude can be determined to better than one degree. The results of an example calculation are included here to illustrate

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01229.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstracta unique aspect of the San Francisco Experimental Vessel Traffic System has been its extensive use of real time automatic processing technology. Automatic detection and tracking of vessels in radar coverage areas has successfully been accomplished even in the presence of clutter. Vessel movement information has been extracted, presented to operators on computer‐animated displays, and traffic analyzed both automatically and at the request of operators. But these demonstrated capabilities should be employed only as a guide to the design of future systems and not interpreted as a literal prototype configuration.Future system designs should assume traffic will be controlled, rather than advised. Risk analysis based upon port geometry, traffic levels, and minimum turning radius can contribute to assessing deployment priorities. Vessel routing should be constrained to follow narrow tracks rather than broad lanes. A minimum configuration would be based upon a computerized Vessel Movement Reporting (VMR) system. Data entry and retrieval terminals could be available within the maritime community. Information, including guidance, could be selectively distributed to active ships via a novel multiplexed television transmission. All radar configurations would include automatic detection and tracking equipment. Finally, area navigation systems could be integrated with VTS.The opinions expressed in this document are those of the author, presented in the interest of stimulating discussion, and they do not necessarily reflect the views of either the Applied Physics Laboratory or the United States Coast Guar

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01230.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstractastro‐fixes have the advantage of being extremely cheap. However, the tedious work, connected to the computation of altitudes and azimuths and the plotting of the position lines, has been a severe objection to this position fixing method. Moreover, the comparatively long time, needed to carry out these manipulations without the aid of a computer, is a severe potential disadvantage, especially for modern, fast going container carriers.Using a small, i.e. pocket size transistorized computer, the computing objections can be practically overruled.It is the object of this paper to present a uniform procedure to take over the plotting‐and‐position‐estimating‐part of the job.The procedure is fully explained, in order to prevent it from being seen by the navigating ship's officers as “another black magic box”. In addition to that, the observer's skill in estimating standard deviations can be used as a highly v

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01231.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstractthe design, fabrication and testing of an experimental Antenna Modification Kit providing an Interrogation Side Lobe Suppression (ISLS) capability to the beacon subsystem of Radar Set AN/TPS‐43 is described. It requires no modification of the radar antenna or pedestal.The experimental Antenna Modification Kit was installed at an AN/TPS‐43 radar site at Bergstrom AFB, Texas and flight tested. Flight test results demonstrated an overall suppression efficiency of 95.4%, with no adverse side effects on system performance.On the basis of the flight test results, a recommendation is made to consider the use of an operational Kit of similar design as a solution to existing problems in the field caused by excessive side lobe returns and the FAA requirement for ATCRBS beacon I

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01232.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe Inertial Reference Unit (IRU) used in NASA's Orbiting Astronomical Observatory (OAO‐C or Copernicus) uses three single degree of freedom, floated, rate‐integrating gyros operated in binary, pulse‐restrained torque loops to provide an inertial attitude reference for the spacecraft's altitude control system. Since 21 August 1972 when the spacecraft was launched, more than 15,000 hours of continuous and troublefree operation have been accumulated on the IRU. When prelaunch operation is included, the running times for the gyro wheels range between 17,000 and 22,000 hours.The drift rates observed on these inertial grade gyros during the 1½ year of in‐orbit operation have remained within a band of 16 arcsec per hour peak‐to‐peak When the effects of known disturbances are considered, the standard deviation of drift rate appears to approach one arcsec per hour (≤10−7degrees per second).Included in this paper are a brief description of the OAO and IRU, a summary of the data reduction programs used to calibrate the IRU in orbit, and some thoughts on how gyros with good long‐term drift stability could be applied to future spacecraft such as the Large Space Telescope and Earth Obs

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01233.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstractall lops, no matter how obtained, are subject to errors. Systematic errors can be predicted and accounted for, but random errors must be treated within the realm of Probable Error. Presuming a knowledge of the standard deviations of the random errors of a set of LOPs, the Probable Error Ellipse can be determined.An iterative method is developed whereby any number of LOPs can be combined to determine the Probable Error Ellipse, using two derived equations which have been put in graphical form for simplified determinations.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01234.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstractin a previous paper [1] the authors have shown that aircraft separations needed for safety are greatly reduced if good surveillance velocity measurements are available. Unfortunately, systems which derive speed estimates from smoothed position measurements are difficult to adapt to separation assurance. They suffer greatly from offset errors when accelerations are present and for most traffic organizations, dangerous situations arise only as the result of substantial accelerations.This paper derives the optimum compromise between noise and acceleration induced errors as a function of measurement accuracy, acceleration magnitude and sampling frequency. It is concluded that better accuracy and/or greater sampling frequency than presently being recommended are required for substantial separation gains.

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01235.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe benefits in reduced inertial navigation errors to be gained by implementating a gradiometer to measure and compensate for the gravitational vector is studied. A limit to this improvement is obtained through a parametric study that was made to compare the magnitude of the geodetic error, due to incorrect compensation, with error due to the instruments comprising the inertial system. This was done for three levels of system accuracy; “production” systems, characteristic of equipment used today; state‐of‐the‐art systems; and a future class of systems. It was found that geodetically induced position errors generally make up a rather small proportion of total system error, less than 30% even for the future class. However, its contribution to the velocity error is quite high, approximately 50% for production, 70% for state‐of‐the‐art, and 94% for future systems. The error behavior of a gradiometer compensated system was then investigated. When the gradiometer uncertainties are modelled as white noise, their level of accuracy must be within 1.7 and 0.93 Eotvos units to reduce, respectively, the geodetic induced velocity and position error below that value which a system with no gradiometer already exhibits. When gradiometer uncertainties are modeled as random biases, their level of accuracy must be within approximately 1.7 and .1 Eotvos units to reduce geodetic induced velocity and position err

ISSN:0028-1522    

DOI:10.1002/j.2161-4296.1974.tb01236.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY