Search

The report discusses the organization, station network, optical tracking capabilities, and current observation programs of Soviet-bloc, primarily USSR, satellite observation stations. Emphasis is on the optical and radio facilities employed in near-space rather than deep-space tracking. The difficulties encountered by the Soviet Union in developing advanced tracking instrumentation and the methods elected to overcome them are outlined.

Three air-defense radar surveillance systems are described, each consisting of active radar satellites capable of operating at earth-synchronous orbit altitude with associated ground control stations. Systems 1 (three satellites) provides a detection fence around the North American continent and does target tracking within the fence. System 2 (three satellites) provides detection fences around the USSR and China. System 3 (seven Satellites) provides worldwide coverage for aircraft detection and tracking. The satellite carries a space-fed phased-array radar and the other necessary sub-systems for attitude control, station-keeping, and solar electrical power. Each ground station is capable of controlling three satellites. The ground station generates the transmitter pulse-burst chirp waveform, processes received signals, detects and tracks aircraft targets, and provides the communication interface with ADC and other users of the radar data. The satellites can be launched on Titan 3-Centaur launch vehicles into earth-synchronous orbit. The phased-array antenna deploys in orbit to a 300-m diameter. It provides 15,700 mi of fence with .999 probability of detection of 1-sq m targets, tracks 50 threat aircraft simultaneously, and requires an average radiated power of 2784 w.

An analytical solution is obtained to the problem of achieving continuous coverage of latitudinally bounded zones of the globe by systems of common-altitude satellites equally distributed among and evenly spaced within identically inclined orbits that are symmetrically arranged about the polar axis.

Timation (Time Navigation) is a technological development program designed to study, identify and develop the critical components and make measurements necessary to describe a navigation system which meets JCS requirements. The purpose of the navigation system development plan is to describe the technical parameters, tradeoffs, experiments, and costs encompassing the implementation of a satellite position fixing and navigation system that meets the requirements promulgated by the Joint Chiefs of Staff (JCS) Navigation Study Panel in 1968. This navigation system provides continuous all weather instantaneous readout to an unlimited number and variety of users on a worldwide basis. (Author), See also Supplement, AD-519 834L.

The description of the Augmented Satellite Control Facility (SCF) is approached from two points of view: first, the equipment subsystems are described in terms of their capabilities, functions, and primary usages; second, the principal activities performed by the SCF; i.e., telemetry, tracking, commanding, and scheduling are explained in such a way that the previously described equipments are tied together into systems, with emphasis on the functional aspects of SCF operations. The SCF is composed of a central control station called the Satellite Test Center (STC) and six remote tracking stations, three of have limited dual capability. The STC is equipped to support six satellites simultaneously. Its data processing subsystems are divided into two main functional groupings: one, the 'Bird Buffer complex,' is vehicle oriented, and has eight CDC 160A computers, each of which can be individually as signed to an active satellite as a buffer; the other grouping is the off-line-computer complex, which uses four CDC 1604 computers to do the main computational chores for the system. (Author)

The equations of motion of a satellite have been derived in a local vertical coordinate system. The method of derivation and the form of the equations provide a simplified means of visualizing and planning the maneuvering within multiple satellite constellations. The equations are also useful in station keeping, rendezvous, and collision avoidance considerations. (Author)

This U/A report describes the status of UH/ALOHA participation in the ATS-1 Computer Communications Experiment through January, 1974. This experment was initiated in January, 1972, by the Spacecraft Data Systems Branch of the NASA Ames Research Center, to demonstrate the feasibility of utilizing satellite communication links to rpovide computer-computer and terminal-computer communications between remotely located sites. In order that the experiment be conducted under realistic conditions, computing facilities at the University of Hawaii and the University of Alaska were connected ot the Advanced Research Projects Agency computer network, via an ATS-1 VHF link, through the Terminal Interface Message Processor located at the Ames Research Center. The ATS-1 VHF transponder was utilized as a broadcast repeater for the three nodes mentioned above, with the satellite network operating in the ALOHA random-access burst mode., Report on the Aloha System.

Satellite tracking accuracies were investigated for the Defense Navigation Satellite Development Program via covariance analyses. Assessments of tracking geometries, improved monitor station mechanizations (i. e., monitor vs master station configurations), and the effects of ground station survey statistics were performed. The study included a sensitivity analysis to identify critical parameters. In addition to the orbit determination performance evaluation, the study identified those parameters that are observable and, hence, should be included in the solution vector. Representative covariance matrices for epoch and terminal time points of a three-day data span are presented as an appendix.

Contents: Biological sciences, Earth sciences, Education, Material sciences, Mathematical sciences, Naval architecture, Physical sciences, Psychological sciences, and Human engineering., See also Volume 24, Number 1, AD-864 412.

This report covers the progress achieved during the third quarterly reporting period of the Tactical Satellite Navigation Systems Study. This effort involves the study, analysis and evaluation of selected satellite navigation techniques for the purpose of determining the most appropriate approach to be utilized as a tactical satellite navigation system for Army aircraft. The selected approach will be used to provide accurate and continuous position information to an unlimited number of aircraft; during all hours of the day or night; under adverse weather conditions; and will generally be applicable to all locations throughout the world. Specifically, this report discusses the progress and preliminary results obtained under Phase III, 'Final Analysis and Evaluation of Selected Systems.' Phase III is scheduled for completion during the fourth quarter. The report also presents information relating to the efforts planned during the balance of the investigation. Preliminary results are also included relating to the system design effort which forms a significant part of Phase IV of the program. (Author)

The report synthesizes a set of satellite communications systems configurations to provide services to aircraft flying oceanic routes. These configurations are combined with access control methods to form complete systems. These systems are analyzed using a simulation and their performance is presented in terms of avionics complexity and cost, queuing delays, pilot workload, and operational considerations. A preferred system is selected and recommendations are made. (Author)

The proposed Defense Navigation Satellite System (DNSS) (called TIMATION by the Naval Research Laboratory) was evaluated in terms of aspects relating directly to the navigation performance of the System. Three areas were examined: configuration stability; orbit determination and prediction accuracy; and navigation. The first two areas were evaluated in terms of their effects on navigation accuracy. The error sources considered included gravity field modeling, Earth tides modeling, radiation pressure modeling, and observation biases and precision. The major error sources for navigation using the TIMATION system are radiation pressure modeling and the degree of synchronization of the satellites' clocks. (Modified author abstract)

For several years the Naval Weapons Laboratory has computed precise satellite ephemerides. he ephemerides, computed for Navy navigation satellites which are accurate to about 5 meters, are widely used for radar calibration and in determining positions of observing stations. The report summarizes computational procedures, coordinate frames, output forms and output formats pertinent to the ephemerides which are produced. (Author)

In the paper the author analyzes a polling modification providing increased efficiency of a data communication channel employing the ALOHA burst random access method. The primary goal is to increase channel use of the random access mode by employing software control from the host computer without requiring any more hardware at the small terminal. The resulting improvement in channel use can be of benefit to THE ARPANET SATELLITE SYSTEM as well as THE ALOHA SYSTEM. (Author)

In the paper the author analyzes several modifications of the ALOHA random access channel by considering time synchronization among the users. The primary goal is to improve the random access channel use by using a simple clock in the host computer and in each remote terminal for synchronization. On an intititive basis, it is predicted that the synchronous random access mode as in the case of conventional communications. In the paper the author is interested in the mathematical analysis of different synchronous schemes rather than on the cost of operational mechanisms of the synchronization equipments.

Scaling factors for atmospheric density were computed from Doppler observations made on polar satellites at an altitude of 1000 km. The scaling factors, which were computed at 48 hours intervals, show that the atmospheric at 1000 km altitude is affected by increases in solar flux and magnetic index as has been previously noted for satellites at lower altitudes. The prediction errors for the satellites are about 25 meters after 24 hours and about 100 meters after 48 hours. (Author)

A circuit to control charge current entering nickel -cadmium cells with auxiliary electrodes ('three-terminal' cells) using a shunt method of control was developed for use in satellite power systems requiring minimum weight and space with optimum control and temperature compensation. Reduction in charge current is caused when the set limits of either the total battery terminal voltage, or the potential of any individual cell at this auxiliary electrode, is exceeded. (Author)

Some conclusions are that the integration of command and telemetry with tracking provides a fundamental and substantial benefit in equipment costs, both at the ground sites and in the vehicle. The integration does compromise the performance of communications and tracking to some extent; however, the benefits derived from the use of a single antenna, receiver and transmitter on the ground and in space to accomplish all of these tasks will represent a simplification and significant economies over the conventional tracking arrangement, which involves a multiplicity of equipments. If duplication of equipment is desirable on the basis of system reliability, it is more efficient to duplicate part or all of an integrated system than it is to duplicate part or all of a non-integrated system. The development of an efficient system, able to perform all these functions within a single band of communications frequencies and having a large information bandwidth, both at the satellite and at the ground stations, will permit efficient planning with resulting developmental and operational cost saving. (Author)

At some twenty observing posts in the Netherlands satellites have been observed with a certain degree of regularity. At most posts the observations have been made visually, later some stations turned to the photographic technique. A description is given of the computer programs which were developed to predict the apparent path of a satellite from its orbital elements, and the program to compute the equatorial coordinates from the rectangular coordinates measured on a measuring machine. (Author)

A method is described which allows the identification of favored beam distributions for multiple beam aeronautical satellites. It is used to synthesize beam designs and compare the capacities of two satellite system configurations which cover the major Pacific routes. The first configuration has two satellites with eclipse capability adequate for housekeeping and independent aircraft surveillance; the second has additional battery capacity to provide 50% of the daylight communications capability in each satellite during eclipse. In this case, each satellite covers a limited portion of the full coverage area. (Author)

This paper presents a general procedure for timing all signals according to a single schedule in a communication satellite network consisting of several ground stations using a single satellite relay. The procedure gives promise of easy implementation and considerable accuracy. Design problems are indicated, and it is argued that a 'clock' should be put in the satellite and timing information broadcast on a beacon signal. The paper briefly discusses ways in which system performance is enhanced by network timing. (Author)

The TRANET satellite tracking network of radar receiving stations and other facilities acquires and processes doppler-frequency shift data from the signals of suitably equipped near-earth satellites. A small man-portable station, currently under development, will ultimately replace the van-mounted stations. The system is capable of handling 40 to 50 passes per station per day or between 480 and 600 passes per day for the basic network of earth stations. As many as ten satellites can be handled by full-time operation of the network and still maintain maximum accuracy. Data attrition from all causes is below 10 percent. The APL Time-and-Frequency Laboratory generates signals that are used by the TRANET stations to ensure the accuracy of their time and frequency standards. The TRANET Control Center serves as the hub of the TRANET network. It receives data from the stations and advises the stations on the status of the satellites and of their performance. Data from the Control Center are reduced by the APL Computing Center and by the Naval Weapons Laboratory. TRANET provides high-density high-accuracy data for a large number of satellites in a form ready for the computing process. Currently TRANET measures doppler frequency with an accuracy of one part in 10 to the 11th power and satellite position with an accuracy of 10 meters. (Author)

Contents: Multiple Access Modulation Techniques; Time-Division Multiple Access; Frequency-Division Multiple Access; Spread-Spectrum Multiple Access; Pulse-Address Multiple Access With Narrow-Band Pulses; Pulse-Address Multiple Access with Spread Spectrum Pulses; Network Timing; Signal Waveform Analysis; Probability Distributions.

The book discusses the basic science concerned with the motion of artificial celestial bodies -- earth satellites, automatic interplanetary stations and manned spaceships. From this work, the reader will learn how scientists intend to reach the stars and what considerations guide them in planning flights of space vehicles and expeditions to the moon and planets. The methods of types of flight trajectories of cosmonauts, both today and tomorrow, the methods of guiding and controlling the motions of space vehicles, and the different maneuvers in circumearth, circumlunar and interplanetary space are discussed. The reader will learn not only of the successes of stellar ballistics but also of the colossal difficulties which scientists and engineers must overcome and of the problems which have not yet been solved and which will be of real concern to tomorrow's scientists. (Author), Trans. of unidentified Russian language mono. Moscow, 1965.

The present study focuses on the possible system choices implied by United States policy to establish a commercial communications satellite system as promptly as possible and to extend it to provide global coverage at the earliest possible date.