Synchronous orbit models
The NASA guidelines for synchronous orbits are presented. Mathematical models are developed which encompass all test variables and systems engineering.
Maurer, D. W.↗
SEARCH · Search NASA
Results for “Synchronization”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Symbol synchronization in convolutionally coded systems
Alternate symbol inversion is sometimes applied to the output of convolutional encoders to guarantee sufficient richness of symbol transition for the receiver symbol synchronizer. A bound is given for the length of the transition-free symbol stream in such systems, and those convolutional codes are characterized in which arbitrarily long transition free runs occur.
Baumert, L. D.↗
Microprocessor-controlled data synchronizer
Versatile receiver processes data at variety of rates and code formats. Functions performed are: bit detection, NRZ-L conversion, frame synchronization (with programmable word length), bit-sync acquisition and tracking, error-curve normalization, lock detection, half-bit-ambiguity resolution, and data-rate tracking.
Houston, S. W.↗
Speed control for synchronous motors
Feedback circuit controls fluctuations in speed of synchronous ac motor. Voltage proportional to phase angle is developed by phase detector, rectified, amplified, compared to threshold, and reapplied positively or negatively to motor excitation circuit. Speed control reduces wow and flutter of audio turntables and tape recorders, and enhances hunting in gyroscope motors.
Packard, H.↗
Study for incorporating time-synchronized approach control into the CH-47/VALT digital navigation system
Techniques for obtaining time synchronized (4D) approach control in the VALT research helicopter is described. Various 4D concepts and their compatibility with the existing VALT digital computer navigation and guidance system hardware and software are examined. Modifications to various techniques were investigated in order to take advantage of the unique operating characteristics of the helicopter in the terminal area. A 4D system is proposed, combining the direct to maneuver with the existing VALT curved path generation capability.
Mcconnell, W. J., Jr.↗
A Study of Particle Acceleration Mechanisms and the Dynamics of the Outer Trapping Region by Observations at Synchronous Orbit: a Summary of Scientific Results
The research concerning the ATS-6 synchronous orbit satellite is reported. The completed research and results are discussed along with the research in progress. Abstracts of published papers are included.
Erickson, K. N.↗
Synchronization of Reed-Solomon codes
The synchronization capabilities of Reed-Solomon codes when an appropriate coset of the code is used instead of the code itself are examined. In this case an E-error correcting Reed-Solomon code is transformed into a code capable of determining that there are m symbols out of sync, if e symbol errors occurred, whenever m + e E. In the event that m = 0, i.e., the word is in sync, then decoder will correct any pattern of E - 1 on fewer symbol errors.
Miller, R. L.↗
Some implications of reciprocity for two-way clock synchronization
The difficulties related to propagation perturbances in one-way and two-way methods for the synchronization of remote clocks are defined, and a possible means of circumventing these problems in the two-way method is suggested. In the two-way method, if signals are launched from two sources, A and B, then the two signals arriving at A and B will be displaced in arrival time by an amount that is equal to the difference in launch times of the two signals. Thus, the only condition to comparing clocks is that the medium be isotropic. The practice implementation of this is explored theoretically, in some detail, with respect to the Loran-C navigation system.
Jespersen, J. L.↗
Comparison of different time synchronization techniques
The plans to set up an international TV synchronization network between four locations are discussed. A feasibility study was conducted between two of the locations and significant results are reported.
Kaarls, R.↗
Synchronous Energy Technology
The synchronous technology requirements for large space power systems are summarized. A variety of technology areas including photovoltaics, thermal management, and energy storage, and power management are addressed.
Source record↗
Synchronous energy technology program
The power program in NASA and DOD are discussed with emphasis on the technology for future large space power systems. The structure of the synchronous energy technology program is described and the technologies required for future geosynchronous power stations are defined. The output of the program is to be a series of design data documents to provide design information and to transfer the technology to the involved community.
Finke, R. C.↗
Ramp time synchronization
A new method of intercontinental clock synchronization has been developed and proposed for possible use by NASA's Deep Space Network (DSN), using a two-way/three-way radio link with a spacecraft. Analysis of preliminary data indicates that the real-time method has an uncertainty of 0.6 microsec, and it is very likely that further work will decrease the uncertainty. Also, the method is compatible with a variety of nonreal-time analysis techniques, which may reduce the uncertainty down to the tens of nanosecond range.
Hietzke, W.↗
Effects of the solar wind on magnetospheric dynamics - Energetic electrons at the synchronous orbit
Data on energetic electron fluxes at the synchronous orbit, covering the 1967-1978 time interval, obtained by experiments flown on the ATS-1, ATS-5 and ATS-6 spacecraft, have been analyzed. Long term (year) and short term (days) electron flux averages are found to correlate positively with corresponding averages of the solar wind velocity.
Paulikas, G. A.↗
Dynamics of plasma, energetic particles, and fields near synchronous orbit in the nighttime sector during magnetospheric substorms
Two phases of substorm-associated magnetospheric dynamics are discussed in terms of particles and fields at synchronous orbit. The first phase corresponds to the 'decreases' of energetic particle flux. The second phase is the conventional expansion phase that begins with the 'onset', characterized in the study by (1) a sudden decrease in the tail current and a return of the inflated magnetosphere to a dipolelike configuration, (2) a sudden shift of trapped high-energy particles toward the tail again following contours of constant B, and at the same time (3) a surge of tail plasma toward the earth as the induced electric field now increases the total convection field.
Sauvaud, J.-A.↗
Conical distributions of low-energy ion fluxes at synchronous orbit
Low-energy ion fluxes observed at synchronous orbit often display conical pitch angle distributions, that is, peak fluxes between 0 and 90 deg to the magnetic field direction. They are observed at all local times and are an especially common occurrence near dusk. The conic peaks normally occur in the 15-35 deg pitch angle range. Many of the low-energy ion conics in the late afternoon-dusk sector appear to be associated with low-energy plasma from the vicinity of the dusk plasmasphere bulge region. Several hypotheses for the production of these conics are advanced, and it is judged likely that cyclotron acceleration of ions at geocentric distances of 3.1 to 5.1 earth radii is operative in many cases. It is suggested that cyclotron acceleration in this altitude range may be an effective mechanism in trapping ionospheric ions within the magnetosphere.
Horwitz, J. L.↗
An accelerated test design for use with synchronous orbit
The Naval Weapons Support Center at Crane, Indiana has conducted a large scale accelerated test of 6.0 Ah Ni-Cd cells. Data from the Crane test have been used to develop an equation for the description of Ni-Cd cell behavior in geosynchronous orbit. This equation relates the anticipated time to failure for a cell in synchronous orbit to temperature and overcharge rate sustained by the cell during the light period. A test design is suggested which uses this equation for setting test parameters for future accelerated testing.
Mcdermott, P. P.↗
Accelerated testing for synchronous orbits
Degradation of batteries during synchronous orbits is analyzed. Discharge and recharge rates are evaluated. The functional relationship between charge rate and degradation is mathematically determined.
Mcdermott, P.↗
The statistical character of Pc 4 magnetic pulsations at synchronous orbit
A statistical study of 215 magnetic pulsation events identified on the basis of waveform and period as Pc 4 (45- to 150-s period) observed at synchronous orbit by ATS 6 is reported. The study was designed to be similar to that done with Pc 3 (10- to 45-s period) by Arthur et al. (1977). These Pc 4 are found to occur most often near 1800 local time but are observed at all local times. The dominant period is approximately 100 s, but a secondary peak in the distribution occurred at approximately 53 s. They tend to be nearly linearly polarized, principally transverse to the ambient magnetic field. The Pc 4 are found to divide naturally into two classes (radial and azimuthal) on the basis of the azimuth of the major axis of polarization. These classes divide further into low-frequency (less than or equal to 0.015 Hz) and high-frequency (greater than or equal to 0.015 Hz) classes. These four classes organize the remaining wave characteristics quite well. Division of the Pc 4 events into these classes does not lead to identification of a single source mechanism as it did with Pc 3. However, some correspondence between the classes and various proposed mechanisms does exist.
Arthur, C. W.↗