• Analysis of the Modified Integrate and Dump Decision Device

      Quinn, Mathew J., Jr.; Hayre, H. S.; NASA Manned Spacecraft Center; University of Houston (International Foundation for Telemetering, 1970-10)
      The purpose of this paper is to describe a system which exhibits better bit error rates for Frequency Shift Keying (FSK) signals than those now used to make the bit decision The system is similar to the popular Integrat6 and Dump device., but it is modified to take advantage of the information contained in the FM "clicks" resulting from the demodulation process to aid in making the proper bit decision. The paper is divided into four parts: First, a brief review of the Integrate and Dump Detector is presented. Then the "click" mechanism is described and such properties of this mechanism as the number of "clicks" in a channel are reviewed. Third, a method of using the information in the "clicks" to one's advantage is discussed. Fourth, and finally, the hardware needed to implement such a system is described in general and certain suggestions are made to improve the over-all decision making capabilities of the system.
    • Apollo Lunar Communications

      Sawyer, Ralph S.; NASA Manned Spacecraft Center (International Foundation for Telemetering, 1970-10)
      The Apollo unified S-band system was developed to handle ranging, telemetry, and voice data using one carrier. Television is transmitted in another mode with the same system. Frequent references are made to the unified S-band system in this report because other systems must work in conjunction with it; however, no description is provided because the S-band system is discussed thoroughly in numerous other reports. The astronauts must coordinate their activities on the lunar surface, and communications are required between them as well as between them and Mission Control Center. A VHF system that has performed excellently in providing voice and telemetry information for lunar-surface use is described in this report. Interest in television has progressed from casual to intense as the Apollo Program has matured; technology has evolved to provide color presentations using the same RF system that was once limited to black-and-white transmissions. The cameras that were developed for both black-and-white and color transmissions are described. Future lunar-surface operations will require traverses too long to be accomplished easily on foot. A system that permits long-range communications from a motorized vehicle on the lunar surface is described. Finally, brief descriptions of several communications-related lunar-environment experiments that have been proposed for the Apollo Program are discussed.
    • Appendix A: Telemetering Standards Coordination Committee Report

      Gardenhire, Lawrence W. (International Foundation for Telemetering, 1970-10)
    • A Burst-Trapping Code for Feedback Communication Systems

      Weinstein, S. B.; Bell Telephone Laboratories, Inc. (International Foundation for Telemetering, 1970-10)
      Many data communication channels are perturbed by "bursts" of noise separated by long intervals of comparatively low noise level. The block code described in this paper, a modification of the forward-acting scheme of S. Y. Tong, retransmits information which has been damaged by a noise burst in place of the parity-check digits of future blocks. The responsibility for error detection and correction is divided between the receiver and (via the feedback channel) the transmitter in such a way as to maximize the defense against both noise bursts and the occasional random errors between bursts. There is a fixed delay for decoding, in contrast to the variable buffering delay of ordinary retransmission-request systems. As a result, storage requirements are minimized and there is a constant throughput rate. The feedback channel can incorporate as much delay and be as noisy as the forward channel without significantly impairing performance. Simulation results are provided to illustrate the performance.
    • Computer Augmented Telecommunications Performance Analysis

      Gault, R. C.; Overall, G. D.; Moody, R.; TRW Systems (International Foundation for Telemetering, 1970-10)
      The increased range, greater accuracy, and complex trajectory of modern ICBM's create a telemetry data acquisition problem which cannot be adequately analyzed by classical manual techniques. To ensure that flight test data requirements are satisfied, systems personnel must order and quantify (model) the elements of a very complex system, i.e., communications system, acquisition stations, flight trajectory, data processor, etc. To satisfy this need, MINUTEMAN Instrumentation Systems personnel developed ISMAP (Instrumentation System Margin Analysis Program); a computer augmented technique for accurately evaluating the performance of ICBM data acquisition systems.
    • A Computerized Data Management Methodology for the Minuteman Instrumentation System

      Foust, L. D.; TRW Systems (International Foundation for Telemetering, 1970-10)
      The tasks associated with Development Management of complex instrumentation systems, from initial concept to production, involves the utilization of very large quantities of data. It is impossible to acquire, process, and analyze this data entirely by manual means, therefore, automated data management systems have been conceived to solve this type of problem. The computerized data system developed by SAMSO MINUTEMAN Instrumentation System Engineering Management is described and is further illustrated by presenting some of the specific applications of the system.
    • Data Tranmission Over Channels with Noisy Feedback

      Tong, S. Y.; Bell Laboratories (International Foundation for Telemetering, 1970-10)
      A low-cost error control technique is proposed for bulk data transmission with noisy feedback link. The scheme is ideally suited for tape-to-tape bulk data transmission as well as the store-and-forward type of data transmission system. By partition data into superblocks, the technique can be used for any feedback retransmission system. We also show that the scheme can be modified to correct synchronization errors and that noise in the feedback link can be made extremely unlikely to contribute to decoding errors.
    • Digital FM Discriminator System

      Breikss, Ivars P.; Honeywell, Inc. (International Foundation for Telemetering, 1970-10)
      The Digital FM Discriminator described in this paper is used to demodulate FM signals with a high percentage (±40%) deviations. When contrasted to the conventional constant pulse width or the phase locked loop discriminators, the digital system has advantages of improved linearity and distortion performance. Additionally, because of the digital nature of the circuit, it requires no adjustment during setup or manufacture. The digital discriminator can be operated at any center frequency within the range of the integrated circuits used, provided that the proper ratio of the FM carrier center frequency and the clock frequency of the discriminator is maintained. In other words, the center frequency of the discriminator can be altered by altering the clock frequency. The digital discriminator provides an analog output which is a step-by-step reconstruction of the original modulating signal. In addition a digital word for each cycle of the FM carrier is generated corresponding to the amplitude of the modulating signal at that instant. The digital output is available in parallel as well as serial format.
    • Disc Recording: Signal Acquisition and Reduction

      Calfee, R. W.; Data Disc, Incorporated (International Foundation for Telemetering, 1970-10)
      During the last several years, magnetic recording on plated discs has been developed and now can be applied to instrumentation recording. The disc recorder is available in a fixed head configuration for multichannel parallel recording and in a moving head configuration for one or two event parallel recording with extended time. The disc recorder can capture transient analog signals with bandwidth from DC to 6MHz or more for periods of time from microseconds to 20 seconds or more. The analog signal is stored on the disc after being processed through a proprietary period modulator. The disc recorder allows the user a natural base from which to reduce the analog data to computer understood words. Data reduction equivalent to 100 megabit conversion is possible at data rates compatible with the data device. Thus the disc recorder can capture transient analog signals and will allow simple data reduction.
    • Effects of Instrumentation Recorder time Base Error on Spectral Purity

      Leeke, P. D.; Minnesota Mining and Manufacturing Company (International Foundation for Telemetering, 1970-10)
      Experimental data is presented to show how carrier amplitude of a recorded signal is affected by Time Base Error. Time Base Error effects on the sideband structure of a recorded signal are also shown for different amounts of Time Base Error and at several frequencies. The effect of capstan servo adjustment on spectral purity demonstrates the need for new methods of performance evaluation to achieve optimum performance when recording spectrum information. The data presented shows that skew (ITDE) has little effect on spectral purity for analysis bandwidths of 50 Hz or greater.
    • Effects of Multipath on Telemetry Data Transmission

      Chen, C. H.; Southeastern Massachusetts University (International Foundation for Telemetering, 1970-10)
      Spurious amplitude and phase modulation effects occur in the received telemetry signal when both the direct waves and the indirect waves enter the receiving antenna. In this paper, a simple multipath model is used which has a single direct wave and a single indirect wave. The indirect wave differs from the direct wave by a time delay and a constant amplitude. With such a simple model, the effects of multipath on telemetry data transmission can be fully examined because of the mathematical simplicity. First an FM system operating above the threshold is considered. The intermodulation distortion and the degradation in the data signal-to-noise ratio due to multipath are both examined. Next we consider two digital systems, namely the noncoherent FSK and the PCM/FM with the discriminator detection. Both systems utilize a split-phase baseband signal. And the error rates depend on the multipath time delay. Comparison is made between the split-phase and the NRZ (non-return-to zero) baseband signals. Available performance improvement from using the predetection diversity combining and the synchronization problem are then discussed. Finally several methods to improve the telemetry data are suggested.
    • The Effects of Using a Finite Number of Bits and Approximate Division in a Data Compressor

      Bjorn, T., Jr.; Harshman Associates, Inc. (International Foundation for Telemetering, 1970-10)
      In the design of a data compressor one of the basic problems is error due to the use of a finite number of bits in calculating various parameters. This is error due to truncation (or round off) after a set number of bits to the right of the binary point. Another error that could be introduced to the system is that error caused by the use of an approximate divide instead of a full divide. It is the purpose of this study to find the effect of these two errors so that (1) a judgment may be made as to how many bits to the right of the binary point are necessary, and (2) find if a double shift approximate divide may be used instead of the slower full divide. The study is divided into three basic parts (1) the effect of truncation (or round off), (2) the effect of the double shift approximate divide, an (3) the combined effect of truncation (or round off) and the double shift approximate divide. Each one of these error-causing phenomenon has two variations; i.e., an error caused while compressing data and an additional error caused while reconstructing. The error during compression distorts the tolerance limits, and the error in reconstruction causes distortion of the reconstructed line segment. Each of the errors leads to an overall error in data magnitude over and above the normal allowable error of one tolerance level. For all of the analysis the maximum run length of the compressed data is assumed to be 128. A summary of the study is found in Table 6.
    • Feedback in Data Transmission

      Ebert, P. M.; Bell Telephone Laboratories (International Foundation for Telemetering, 1970-10)
      A survey of the possible gains to be realized by the use of various feedback techniques is given. Noiseless information feedback is considered in detail, and a transmission system for this latter case is given and analyzed. This system is shown to achieve a transmission rate very close to the largest rate possible.
    • Field Testing of Telemetry Systems

      Pickett, R. B.; Vandenberg Air Force Base (International Foundation for Telemetering, 1970-10)
      Tests have been developed and implemented at the Western Test Range for calibration of telemetry receiving systems. The tests serve an additional function as diagnostic aids.
    • FM Distortion Caused by Head-to-Tape Spacing

      Hodder, W. K.; Monson, J. E.; Bell & Howell Research Labs; Harvey Mudd College (International Foundation for Telemetering, 1970-10)
      Although it is well-known that frequency-modulated waves are distorted by systems with non-uniform frequency response, this distortion is difficult to calculate for most systems. The nature of the head-to-tape spacing transfer function allows the development of a closed form solution for FM distortion. Three methods of processing the voltage off the playback head are considered. Integrating the voltage results in amplitude-frequency distortion, but no harmonic distortion. Taking the voltage either directly off the head or differentiating it give both amplitude-frequency distortion and harmonic distortion. Experiments have verified the theoretical results.
    • Format and Address Equation Generation by Computer

      Leighou, R. O.; Hill, K. H.; Martin Marietta Corporation (International Foundation for Telemetering, 1970-10)
      Addressable remote multiplexed time division telemetry systems are being used more and more. Most of these systems operate with serial addresses generated by a central unit where each data source has a unique address. Thus the address sequence determines the particular format. In one type of system, the address sequence is determined by transfer logic between a counter and an address shift register. It takes several man-weeks of effort to develop a format and the logic equations to implement the address sequence for that format. To avoid this effort, an algorithm and computer program that generates the formats and the logic equations has been developed and is described. The program data inputs are: the basic format configuration of addresses (channels or data sources) per frame and the frames per master frame; and the number and types of channels at each samples per master frame (S/MF) rate. The program outputs are: address assignments by program ID, telemetry formats sequences with program ID, and the set equations for the address output shift register. Several checks are made during the program and if program restrictions are violated or format generation is impossible, error messages are printed and the program may be halted.
    • The Implmentation and Utilization of DSB/FM Telemetry Systems

      Johnson, C. S.; Sandia Laboratories (International Foundation for Telemetering, 1970-10)
      Two different double sideband suppressed subcarrier telemetry systems have evolved in the past few years: the harmonic subcarrier method (HSM) and the independent subcarrier method (ISM). This paper provides information pertinent to the implementation and utilization of both systems. The important features of the two systems are discussed by comparing the circuits used in their implementation. Test data is used to illustrate some of the important points about the performance of a DSB/FM telemetry system.
    • Instrumentation Systems Engineering Management

      Warren, J. R.; Norton Air Force Base (International Foundation for Telemetering, 1970-10)
      Examples of practical, effective, tools for the management of systems engineering have been presented. The usage of those tools is further examined. Management, as used here, pertains to the technical management of the systems engineering Job. The techniques described are structured around a medium/large data transmission/ acquisition/processing system. The principles can be applied to other systems also. Fundamental to the discussion is the use of models, criteria, and selected data for evaluation which results in decisions and program direction for systems optimization.
    • International Telemetering Conference Proceedings, Volume 06 (1970)

      International Foundation for Telemetering, 1970-10
    • L- and S-Band Antenna Calibration Using Cass. A or Cyg. A

      Taylor, Ralph E.; NASA Goddard Space Flight Center (International Foundation for Telemetering, 1970-10)
      This paper describes a stellar calibration technique, using the absolute flux density from Cassiopeia A or Cygnus A, to determine effective antenna gain, or system noise temperature, at the IRIG L- and S-band frequencies. Paraboloidal dish antennas, ranging from 20 feet to 85 feet in diameter, can be calibrated using a total-power conventional RF receiver. Previous investigators utilized a Dicke radiometer to perform the same function. It is recommended that the Cass. A and Cyg. A flux densities, known within several tenths of a decibel, be utilized to calibrate IRIG antennas located on the North American Continent. It is demonstrated that Cass. A and Cyg. A provide sufficient signal power to calibrate a 20-foot diameter dish antenna; dish antennas up to 85-feet in diameter may be calibrated without applying a beam correction factor. Precision values of absolute flux density for Cass. A and Cyg. A are given for the 1700-1710 MHz space research, and IRIG 1435-1540 MHz and 2200-2300 MHz bands. An accurate radio sky map is also provided that may be scaled in frequency for the various bands.