• Central Data System Concepts for Spacecraft Data Management

      Fimmel, Richard O.; Egger, Alexander; Bello, Louis M.; Ames Research Center, NASA; TRW Systems (International Foundation for Telemetering, 1967-10)
      This paper discusses the design concepts of a central data system (CDS) for more efficient" flexible data management and its application in an advanced deep space solar probe. The design features high data sampling rates, programmable data processing, bulk data storage capability (for data sampled during periods of noncommunication), and standard experiment package/CDS interfaces. The basic system concept is based upon sampling each data point at a high rate in a fixed sequence and allowing a central processor to select, process, and format sampled data into a highly efficient format for transmission. The CDS is programmable so that data formatting and processing may be reprogrammed via the command link to optimize data transmission for unexpected conditions. Preliminary design efforts have indicated that a CDS to process data from seven particle and fields experiments can be designed, using present state-of-the-art components, to weigh 16.5 lb and consume 5.4 watts (not including bulk data storage unit) from the DC/DC converter.
    • Performance Standards for Eastern Test Range Telemetry Stations

      Harton, Paul L.; McRary, John W.; Pan American World Airways (International Foundation for Telemetering, 1967-10)
      An extensive engineering effort has been directed toward the rehabilitation of Eastern Test Range telemetry stations during the past five years. Initial planning began, at an earlier date) with studies of range user program plans. These studies have continued throughout the development period to assure a close agreement between range user needs for telemetry data and station capabilities. The plan to rehabilitate telemetry stations on the range has included airborne and shipborne systems, as well as the landbased stations. The stated needs of range users, and the projection of equipment trends formed the basis for specifying new telemetry systems for the Range. Design, production, initial tests, and installation followed in rapid sequence. An evaluation phase was then implemented to determine the operational readiness of the integrated systems and to establish the levels of performance at which each station should be assigned for support. Recent telemetry developments on the Eastern Test Range are briefly described, with emphasis on the launch area telemetry station, Tel 4. This general-purpose telemetry station must be operated in many different modes and configurations to accommodate the various signal structures that are used. Tests that have been used to estimate the station capabilities and limitations when it is configured to receive PAM/FM/FM and PCM/FM links are described as examples of the evaluation concept.
    • The Detection of PCM/FM

      Schilling, D. L.; Polytechnic Institute of Brooklyn (International Foundation for Telemetering, 1967-10)
      The calculation of the error rate resulting from the detection of PCM/FM is described. Emphasis is placed on characterizing the effect of the FM demodulator (FMD). The works of Schilling(l), Salz(2), and Klapper(3), are summarized and extended to yield error rate expressions when using an FM discriminator, Phase Locked Loop, or Frequency Demodulator Using Feedback (FCF). The "Integrate-and-Dump" and the Filter Detector are compared. The results indicate that in certain regions the error rate is due primarily to "smooth noise", and the FM demodulator followed by a PCM detector yields an error rate comparable to that obtained with a Matched-Filter (MF) detector. In other regions the error rate is shown to be due primarily to the spikes present at the FM demodulator output. The use of "Spike Detection and Correction" is discussed. It is shown that this technique results in reduced error rate in the "spike regions".
    • UHF Telemetry System Development at White Sands Missile Range

      Chin, Ball; White Sands Missile Range (International Foundation for Telemetering, 1967-10)
      This paper describes UHF telemetry system development at White Sands Missile Range (WSMR), New Mexico, to achieve the telemetry operation change from VHF to UBF. Component and subsystem development is discussed. Results of the S-band equipment testing using the L-20 light aircraft, the F-100F jet fighter, POGO missile, and ATHENA re-entry vehicles are presented. Comparative analysis of missileborne telemetry data transmitted through both the standard VHF and the developmental S-band links are made.
    • On-Line Computer Tuned S-Band Phase-Lock Receiver

      Van Wechel, Robert J.; Counter, James M.; Interstate Electronics Corporation (International Foundation for Telemetering, 1967-10)
      Long-loop phase-lock receivers utilize a voltage-controlled crystal oscillator (VCXO) as the first local oscillator (LO). Tuning across a band of frequencies with such an arrangement has been virtually impossible in many of the existing space and satellite tracking equipments; the characteristics of the long-loop configuration have necessitated the use of VCXO's. One particular advantage of the long-loop, the capability of maintaining coherent LO and reference frequencies for coherent demodulation of all IF outputs, is a constraint on the receiver system described here. One approach for multi-channel operation has been to employ one VCXO for each frequency; this has obvious economic limitations in applications requiring many channels. For stations used in multiple vehicle tracking, frequency-agile or frequency-hopping anti-jamming applications, or for nearly unlimited tuning capability in a data gathering station it is desirable to use a frequency synthesis technique to tune the receiver. Such a synthesizer should lend itself to on-line computer control. It is the intent of this paper to describe a technique of digital synthesizer tuning for a long-loop S-band phase-lock receiver. Hardware utilizing this technique is now in operation at Marshall Space Flight Center and Kennedy Space Center. The synthesizer provides both direct-reading pushbutton and computer tuning; frequency changing can be accomplished in microseconds. The frequency band 2200-2300 MHz is covered in 0.1 Hz steps. Although capable of providing on-line computer controlled operation, the system is presently being operated in the manual mode.
    • Description of Computer Program to Analyze Gain Distribution of an Antenna Pattern

      McQuaid, Bruce L.; Hughes Aircraft Company (International Foundation for Telemetering, 1967-10)
      The gain of a radiating antenna is generally a function of the direction in which the antenna is pointing relative to the direction of the received or transmitted signal. The gain distribution over an imaginary sphere surrounding the antenna is called the antenna gain pattern and can be measured experimentally. Under certain circumstances the tolerances associated with the pointing vector make it impossible to determine the antenna gain precisely but rather circumscribe an area on the spherical surface which include a number of different gain values. A computer program called INTGRT has been developed that will determine from measured antenna pattern data the gain distribution within the uncertainty region and will provide a measure of the probability of the gain being above a certain gain value. The boundary of the uncertainty region is described in terms of the coordinate system used in measuring the antenna patterns. Each gain value contained inside this boundary is compared to some reference gain level and a running total is made of the number of values found to be equal to or greater than the reference value and the total number of values inside the region. After weighting each total by an equal area function, the ratio of the number of values above a reference level to the total number of values in the region gives an estimate of the probability that the gain of the antenna will be equal to or above the reference gain. If the region is analyzed in this way for a number of reference levels, the distribution of gain values within the region is obtained. This information is extremely valuable in determining space communication system performance during periods in which the orientation of the spacecraft's antenna with respect to the earth cannot be determined precisely but is known to be within certain limits.
    • Graphical Determination of Third Order Intermodulation Frequencies in RF Systems

      Jeske, Harold O.; Sandia Corporation (International Foundation for Telemetering, 1967-10)
      A simple discussion is given on the origin of intermodulation distortion in nonlinear devices concluding with reasons for placing primary interest on third order products. Nearby third order products are located at 2f(x) – f(y) and f(x) + f(y) – f(z) where f(x), f(y), and f(z) represent all frequencies in a group. The number of nearby IM products of this type is equal to N(N - 1) (1 + (N - 2 / 2)) where N is the number of input frequencies to the nonlinear device. For eight input signals, for example, a total of 224 intermodulation products are produced that are located in a bandwidth that is three times the bandwidth between the highest and lowest input frequencies. The graphical method of locating intermodulation products is rapid and simple. Basically, interfering frequencies are found by the alignment of two pieces of paper. On each piece of paper, the spacings between all input frequencies are plotted on a linear scale. Frequencies which may cause interference are easily identified. A guide which will allow the selection of frequencies to avoid third order intermodulation interference is also given.
    • Analysis of Multiplex Systems Based on Orthonormal Function Groups

      Balas, Mark J.; Harry Diamond Laboratories (International Foundation for Telemetering, 1967-10)
      Linear multiplex systems may be represented as sequential, invertible transformations on a message set. Such transformations are based on orthonormal functions in the Hilbert space of square-integrable functions. Demultiplexing is accomplished with the inner product which results in high immunity to noise and bandlimiting. When the orthonormal functions form a multiplicative group, easily generated pulse functions arise. Methods are presented for determining these function groups and their corresponding algebras which yield simple and useful multiplex systems.
    • Summary and Discussion of Signal-to-Noise Ratio Improvement Formulae for FM and FM/FM Links

      Rechter, Robert J.; Hughes Aircraft Company (International Foundation for Telemetering, 1967-10)
      Frequently, a need exists to compute the postdetection (recovered data) signal-to-noise ratios (SNR) in a given frequency modulated (FM) or double frequency modulated (FM/FM) transmission link; alternately certain postdetection SNR requirements are established, and the link's parameters must be correspondingly specified. In either case, relationships that clearly relate postdetection SNR to link parameters, for either FM (or FM/PM) or FM/FM links, are useful to the telemetr system designer. Although such relationships have been stated in varying degrees of applicability, and rigor of derivation, it has been the author's experience that the sources are scattered, and often not sufficiently explicit. Further, the deviations from the mathematically ideal situation are often overlooked. It is the purpose of this paper to present useful SNR improvement formulae for the general FM and FM/FM case (both for IRIG and non-IRlG multiplexes), and also present data that takes nonideal postdetection filtering into account.
    • Anticipated Problems of Re-Entry Vehicle Telemetry at UHF

      Numrich, Fred H.; General Electric Company (International Foundation for Telemetering, 1967-10)
      Present information on missile range planning indicates that serious UHF telemetry coverage problems are likely to occur during reentry of ballistic vehicles. Flight test experience at VHF has demonstrated that receiving stations experience difficulty in tracking re-entry vehicles under conditions of rapid changes of signal strength caused by combinations of vehicle motion, vehicle antenna pattern, and plasma attenuation. Similar but greater variations at UHF coupled with narrow beamwidths and reduced sensitivity of re-entry stations portend greater problems at UHF. Conical scan systems may prove inadequate. Comparisons of similar telemetry systems at VHF and S-band are presented, demonstrating that received signal to noise ratios at re-entry stations will be 3 to 9 db below levels Presently obtained at VHF for reentry stations. The narrow antenna beamwidths (1° to 3.5°) will also cause problems in acquisition so that some form of acquisition aid will be required at each station. Omnidirectional antennas currently used in aircraft at VHF will be useless at UHF. Ships and aircraft will require stabilized or compensated antennas. Acquisition of hypersonic targets will be a particularly severe problem for aircraft receiving stations. In addition to defining the re-entry problem, system limitations, and expected effects, this paper also makes recommendations to range planners and users to minimize or correct the anticipated problems.
    • Detection of Orthogonal Sine and Cosine Pulses by Linear Active RC-Networks

      Schmid, P. E.; Nowak, D. J.; Harmuth, H. F.; Allen-Bradley Co. (International Foundation for Telemetering, 1967-10)
      An active RC matched filter, particularly useful for phase-coherent, coded or uncoded, binary or non-binary communication channels, is described. One detector circuit performs the equivalent of two simultaneous cross-correlations, avoiding the need for electronic multipliers, reference wave generation and phase synchronization. For example, only I circuits are needed in a receiver that is required to detect the polarity or presence of an orthogonal set of I sine and I cosine pulses. In view of the circuits realizability with linear IC technologies, the sensitivities with respect to circuit component variations are analyzed in detail. The results of the sensitivity analysis are presented in graphical form. Experimental results confirm the predicted performance; i.e. Q-factors in excess of 4000 were obtained with small, general-purpose operational amplifiers.
    • Multichannel, Free-Flight Base Pressure Telemetry in Wind Tunnels

      Choate, R. H.; ARO, Inc. (International Foundation for Telemetering, 1967-10)
      Radio telemetry techniques permit the acquisition of aerodynamic data from free-flight models in wind tunnels, a method which ensures that the data are completely free from support interference effects. No serious difficulties were experienced in the development of a telemetry system to record simultaneously four channels of base pressure data from a free-flight model; however, precautions were necessary to prevent interactions between channels and to prevent interference between telemetered and extraneous signals. This telemetry system is based upon small, transistorized, transmitter units, placed aboard the model, which are directly modulated (FM) by capacitance-type pressure transducers. All units are powered from a single battery package. These units, one for each data channel, transmit to antennas located outside the tunnel. All units are interchangeable between models, and have built-in provisions for preselecting full-scale pressure range (0.0005-0.1 psid) to provide optimum data resolution under a variety of test conditions in three different wind tunnels (at nominal Mach numbers of 8, 10, and 20). Oscillograph traces resulting from tests of typical models, both in free flight and on a sting mount, are compared and discussed from an instrumentation point of view. Satisfactory system operation is demonstrated by comparing telemetered base pressure data to data obtained by conventional means during a test of a sting-mounted model.
    • Redundancy Removal Algorithms Applies to Gemini XII Data

      Jory, H. M.; McDonnell Douglas Corporation (International Foundation for Telemetering, 1967-10)
      This report presents the results of a company funded computer study to deter-mine the effectiveness of redundancy removal algorithms as applied to manned spacecraft data. The company familiarity with and access to manned space flight data provided an almost unique opportunity to study this method of data compression using data representative of that which will be required from a Manned Mars Mission. A total of 28,500 seconds of the Gemini XII flight is examined using seven algorithms and three different tolerance bands. Over eleven million samples have been examined using terminology and descriptions consistent with previously published literature to allow direct comparison of actual flight data with previous results using synthetic data. The outputs from the computer presented the following information: A. Compression ratios as a function of technique, channel number and type of data for each of the activity periods. B. Buffer input rates and accumulated queue lengths every 2.4 seconds for the ZFN technique. C. Error distribution, for each of the techniques for six different apertures. The results indicate that the zero order - variable corridor - adjusted preceding sample transmitted (ZVA) technique can provide data compression ratios of 187:1 using a 1.2% tolerance. Nominal buffer sizes of 20K bits are adequate to handle the data activity period involved. The error distribution evaluation indicates that the error distribution is primarily a function of the technique and the aperture.
    • Telemetry of Piston Parameters at Elevated Temperatures

      Slaffer, M.; Admiralty Engineering Laboratory (International Foundation for Telemetering, 1967-10)
      A system is described whereby piston information is continuously monitored using frequency modulation of carriers in the band 2 to 10 mc/s. The basic design of a miniaturised one channel transmit-ter for temperature measurement has been completed and practical details are given in the text. A thermistor was used as sensor. Trials with two operating channels have been carried out on a Lister engine over periods exceeding five hours without component replacement. The choice of high frequency band vras influenced by the desire to avoid the use of an iron cored sensor when the measurement of displacement was to be considered.
    • Transmission of Direct Blood Pressure from Dogs During Obedience Training

      Rader, R.; Sears, W. J.; Reid, D. H.; Meehan, J. P.; Henry, J. P.; University of Southern California, School of Medicine (International Foundation for Telemetering, 1967-10)
      A method for transmission of direct blood pressure from dogs during obedience training, treadmill exercise and sleep is described. Solid state transducers, 6.5 mm diameter, were implanted in the abdominal aorta of healthy young mongrel dogs. The design of the specialized circuitry required to detect and transmit blood pressure data is presented. Calibration was performed by comparing direct and transmitted data. An obedience training course provided emotional arousal, and for physiological stimuli the animals exercised on a treadmill at various grades and speeds up to exhaustion. Blood pressures taken during natural sleep were defined as basal for each animal. Representative observations are noted to emphasize the practical benefits of advanced biotelemetry in research.
    • A Quantitative Impedance Pneumograph

      Bergey, George E.; U.S. Naval Air Development Center (International Foundation for Telemetering, 1967-10)
      An impedance pneumograph capable of quantitatively measuring respiratory volumes is described. Physically, the pneumograph is one of several 3/8 x 5/8 x 7/8 inches modules incorporated in a miniature biotelemetry system, with separate modules being utilized to process signals derived from a number of physiological parameters such as EEG and EKG in addition to respiration. Considerable experimentation was performed regarding optimization of the electrodes used in this impedance pneumograph as well as the frequency and amplitude of the excitation voltage applied between the electrodes. The result was a fairly simple and inexpensive device which uses a higher frequency (300 KHz) excitation voltage than is normally used in impedance pneumography. The two electrodes, constructed of silver coated nylon for flexibility, are insulated from the subject by a layer of polyethylene film, thus forming a capacitive coupling of the electrode to the subject. This technique effectively eliminates changes in skin-to-electrode resistance, largely responsible for baseline drift encountered with previous impedance systems, so that this pneumograph responds only to variations in the actual impedance between the two electrodes. Empirically, a nearly perfect linear correlation was found to exist between the transthoracic impedance measured by this impedance pneumograph and pulmonary volume. The two insulated electrodes are pasteless and therefore easily applicable and non-irritating. They are held in position by an elastic, quick-donning, vest-like garment.
    • Optimum Telemetry for a Meteorological Platform

      O'Bryant, Richard; Hoover, Wayne M.; Sharpe, John H.; Texas Instruments Incorporated (International Foundation for Telemetering, 1967-10)
      In order to predict the large-scale elements of the atmospheric circulation, measurements must be made on a global scale. One such method of measurement involves the telemetry of meteorological data from balloons floating at a constant level over the earth. The balloons are interrogated and their data relayed through a synchronous satellite to a central ground station. A study, funded by the Environmental Science Services Administration, has been made to determine the optimum electronics, in the sense of low cost, for the interrogation and telemetry systems within the constraints of minimum weight and power. This paper presents the problems of such a system, the approaches to the selection of an optimum system, the system selected, and a discussion of the implementation of the electronics of the selected system.
    • Data Collection Station for Automobile Safety Testing

      Goes, Ing F.; Hill, John J.; Volkswagen Works; Defense Electronics, Inc. (International Foundation for Telemetering, 1967-10)
      Increased emphasis on the incorporation of additional safety features in automobile designs has accelerated the adaptation of aerospace telemetry and datahandling techniques to the field of automotive performance testing. Described is a multiple link FM/FM telemetry ground station as used for acquisition of data from an automotive test track. System inputs adhere to aerospace telemetry standards, the output being a computer-compatible digital tape. Detailed attention is given to the high-speed sampling, data conversion, and digital tape formatting subsystem.
    • Single Side Band Translation Techniques for FM Data Acquisition Systems

      Roth, Allen R.; Lear Siegler, Inc. (International Foundation for Telemetering, 1967-10)
      A Single Side Band Data Translator has been developed and used successfully with any combination of reference and data frequencies from 100 Hz to 10 MHz. This translator, consisting of a computer calculated 90° phase difference network and field effect transistor multiplier circuits yielded undesired sideband signals which were at least 50 db below the desired sideband level over an input frequency range of ten to one. The translator was used to implement a system which recorded 75 time-correlated broadband data channels on a single track of a 5 MHz rotating head tape recorder. After de-translation, a signal to noise ratio of 60 db was measured with the recorder by-passed and a signal to noise ratio of 40 db was measured with all channels recorded. This paper presents the results of research carried out under Contract No. N123(60530)51701A sponsored by U. S. Navy.
    • A Multiple Format Stored Program Data Acquisition System

      Bauer, W. R.; Hodges, G. G., Jr.; Telemetry Systems Department (International Foundation for Telemetering, 1967-10)
      A multiple format telemetry system is described which is flexible enough to be adaptable to many applications. The system incorporates a flexible programmer that utilizes a non-destructive readout memory which operates in conjunction with an external index counter. Subcommutator addresses stored in memory are addressed partially by the index counter and partially by the format instruction. Multiple formats can be generated, limited only by the requirement that the sampling rates in a given format be binary multiples of the slowest sampling rate in that format. The advantage of this programmer lies in the flexibility accommodated, typically, with one or two read-only memory cycles. The remote acquisition units used in the system are flexible in that they can be configured to provide various combinations of low-level, high-level, and bi-level inputs. These units are designed primarily from two large scale integrated (LSI) metal-oxide-semiconductor (MOS) building blocks. One LSI circuit is a sequential multiplexer, which also functions as an analog-to-digital (A/D) converter; the other circuit is a 16- channel random access multiplexer.