• 117.6 Kilobit Telemetry from Mercury-A Major Deep Space Telecommunication Advance

      Clarke, Victor C.; California Institute of Technology (International Foundation for Telemetering, 1974-10)
      For nearly eight hours on March 29, 1974, Mariner 10 transmitted imaging telemetry in real time at 117.6 Kbps from Mercury. During this time, 562 very high quality frames were received, even though the bit error rate was only about 1 in 40. The transmission of 117.6 Kbps from Mercury is a magnificent telecommunications achievement, which permitted an order of magnitude increase in imaging science data return. The Mariner 10 imaging scientists' requirements, simply stated, were to obtain maximum area coverage at highest spatial resolution. More precisely, they desired photomosaics which were equivalent to the best earth-based pictures on the Moon, i.e., about 1 km resolution. The purpose of this paper is principally to relate the methods by which these "desirements" were translated into measurable telecommunication system requirements and some of the attendant tradeoffs. Additionally, same of the steps taken to achieve their goal are recited.
    • 117.6-Kilobit Telemetry from Mercury In-Flight System Analysis

      Evanchuk, V. L.; California Institute of Technology (International Foundation for Telemetering, 1974-10)
      This paper discusses very specifically the mode of the Mariner Venus/ Mercury 1973 (MVM'73) telecommunications system in the interplexed dual channel 117.6 kilobits per second (kbps) and 2.45 kbps telemetry. This mode, originally designed for only Venus encounter, was also used at Mercury despite significantly less performance margin. Detailed analysis and careful measurement of system performance before and during flight operations allowed critical operational decisions, which made maximum use of the system capabilities.
    • Adaptive Bit Synchronizer

      Halpern, Peter H. (International Foundation for Telemetering, 1974-10)
      The motivation for adapting loop bandwidth is reviewed. The ideal loopwidth is shown to be a monotonic function of the ratio of two statistical measurements, namely the input SNR and the present uncertainty of proper phase. This is seen from a relatively simple viewpoint of how to combine independent measurements of the same quantity. Means for measuring the statistical quantities are described. Simple means for varying loop widths are described. Experimental results of the adaptive bit synchronizer are compared with a classical bit synchronizer.
    • Aeroflight Communications and RF Navaids

      Lilly, Douglas S.; Lyndon B. Johnson Space Center (International Foundation for Telemetering, 1974-10)
      The Space Shuttle Program concept of a low cost, reliable and reusable orbital vehicle has proven to be a driving function in systems design and integration. Extensive use of existing designs to satisfy these requirements has been effectively employed in the aeroflight systems. Appropriate planning and a careful appraisal of maturity, cost, performance, vehicle burdens, and operational flexibility were completed prior to a system choice. The aerial navigation and landing systems selected for the orbital vehicle are described and their interfaces with the control and navigation system discussed.
    • Ambient and Industrial In-Situ Emissions Monitoring

      Lord, H. C.; Environmental Data Corporation (International Foundation for Telemetering, 1974-10)
      Most of the papers presented here deal with remote measurements of pollutants either from an emission source, or in the ambient air. This paper deals with an alternative route: The utilization of rugged, reliable instrumentation located in-situ. This instrumentation, based upon absorption spectroscopy, gives a specific and instantaneous analysis of multiple parameters (typically up to five) without sample handling or conditioning.
    • Analysis and Test Results of a Hybrid PCM/FM-subcarrier Baseband Multiplex on an FM Carrier

      Nichols, M. H.; The Aerospace Corporation (International Foundation for Telemetering, 1974-10)
      Engineering formulae have been developed for estimating the performance of a telemetry system utilizing an NRZ PCM multiplex plus an FM/FM multiplex frequency modulating a carrier. These formulae have been checked against a laboratory simulation and the agreement is within 1 dB for the PCM and 1.8 dB for the FM/FM. About 1 dB of the 1.8 dB is tentatively accounted for on the basis of lack of symmetry of the carrier predetection (IF) filter used.
    • The Antenna System of the Helios Solar Probe

      Horwath, L.; Liesekötter, B.; Tymann, G.; Messerschmitt-Boelkow-Blohm GmbH. (International Foundation for Telemetering, 1974-10)
      For the Helios solar probe a complete antenna system was developed and manufactured which is suitable for the various mission requirements, as near earth phase varying aspect angles, close sun flyby and maximum distance of 3,0. 10⁸ km with spin axis orientation perpendicular to the ecliptic. The near earth phase requirements were covered by a low gain antenna system with an isotropic radiation pattern. After the rough orientation of the spin axis a medium gain antenna with an omnidirectional radiation pattern will be used. After final orientation of the spin axis perpendicular to the ecliptic plane a high gain antenna with a despun wire grid reflector will be used for the telemetry link. By switching devices and/or hardwire connections the antenna systems are partly redundant in order to get the required high reliability. The maximum operating temperature range of the antenna system is + 200° to - 200°C.
    • Appendix A: Thirteenth Annual Report of the Telemetering Standards Coordination Committee

      Muller, Ronald M. (International Foundation for Telemetering, 1974-10)
    • Atmospheric Monitoring Using Infrared Heterodyne Radiometry

      Peyton, Bernard J.; Cutler-Hammer (International Foundation for Telemetering, 1974-10)
      Atmospheric constituents have unique vibrational-rotational signature lines within the infrared spectrum and the signature intensities and line shapes vary with the constituent concentration and the atmospheric density. The recent development of stable, single frequency, single-mode laser local oscillators and nearly quantum-noise-limited heterodyne receivers have permitted the development of infrared heterodyne radiometers (IHR's) which provide good sensitivity and excellent specificity for the remote examination of individual atmospheric constituent signature lines. A 9 to 11 μm IHR employing a CO₂ laser local oscillator has been developed and can be used to resolve the spectral signature of atmospheric constituents such as SO₂, O₃ C₂H₄, and NH₃. The IHR has a bandwidth of 100 MHz (33 x 10⁻³ cm⁻¹) and a minimum detectable power spectral density of 5.4 x 10⁻²⁴ W/Hz for a 1-second integration time. For atmospheric monitoring applications the IHR telescope collects the thermal energy radiating from the earth at: (1) a clear spectral window, and (2) a spectral region in which the signature lines of the constituent gases at various layers of the atmosphere will be energized by the upwelling thermal radiation. When the vertical temperature distribution of the atmosphere is known, the concentration of the atmospheric constituent gas can be determined as a function of altitude from the radiance data collected at the IHR using an iterative mathematical technique.
    • Capacity of Noncoherent MFSK Channels

      Bar-David,I.; Butman, S. A.; Klass, M. J.; Levitt, B. K.; Lyon, R. F.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1974-10)
      This article computes the capacity of a noncoherent multifrequency-shift-keying channel as a function of the number of orthogonal signals, M, and the predetection signal-to-noise ratio, ST/N₀, for three basic receiver types; these are hard decision, unquantized (optimum), and quantized (soft decision). Computational cutoff rates for sequential decoding are also computed.
    • Carrier Tracking, Bit Synchronization, and Coding for S-Band Communications Links

      Odenwalder, J. P.; LINKBIT Corporation (International Foundation for Telemetering, 1974-10)
      This paper presents the results of a study of the performance of Viterbi-decoded convolutional codes in the presence of nonideal carrier tracking and bit synchronization. A constraint length 7, rate 1/3 convolutional code and parameters suitable for the Space Shuttle coded communications links are used. Mathematical models are developed and theoretical and simulation results are obtained to determine the tracking and acquisition performance of the system. It is shown that the combined E(b)/N(o) degradation due to nonideal carrier tracking and bit synchronization over that required for the ideal tracking case can be held to less than 1.5 dB and that combined carrier tracking and bit timing can be acquired in only a few seconds for the parameters and operating ranges of the Space Shuttle coded communications links.
    • A Central Controller/Display System with Real Time Processing for Remote Data Acquisition Units

      Prichard, Guy D.; Teledyne Controls Company (International Foundation for Telemetering, 1974-10)
      A flexible Data Management and Display Unit (DMDU) has been developed as part of the On-Board Data System developed for the 40' x 80' Wind Tunnel at Ames Research Center. The DMDU can be operated as a slave to a Systems Engineering Laboratories Model SEL-840MP computer or as a standalone system receiving instructions from an operator via data terminal/keyboard inputs. It is capable of controlling the acquisition data from four data acquisition units at software selectable word rates of 250 to 125,000 words per second in increments of 50 words per second. The number of remote acquisition units can be expanded to twenty-nine units providing data point capacity in excess of 10,000 channels. Acquired data can be distributed in real time to the host computer (SEL-840MP), a bar graph CRT display (up to 128 data points), a strip chart recorder (up to 3Z data points), to one or both of two analog magnetic tape recorders (BI0/ -L or DM-M format) or to a PDP-11/05 minicomputer for data processing in real time. The DMDU can be utilized as a "quick-look" playback facility for the playback and display of data previously recorded on magnetic tapes in any of the standard IRIG PCM formats. It receives initialization information consisting of the remote acquisition units and data point address, amplifier gain, each data points required sampling rate and the data output destination entered locally via punched paper tape or from the SEL-840MP computer. Resident software generates a "master sampling format" with sub-commutation and super-commutation as required. Embedded within the master cycle are the minor cycle sampling formats for the individual recorder outputs, complete with software controllable fram ' e synchronization patterns. Conversion from the data acquisition mode to the data playback or data reduction mode can be performed dynamically under interrupt control.
    • A Coding Algorithm for Random Access Satellite Systems

      Wu, W. W. (International Foundation for Telemetering, 1974-10)
      In satellite communications systems, when a code-division scheme is desirable for random multiple access, specific codes must be constructed for the users in the system to share the same satellite channel. This paper develops a coding algorithm for such purposes by means of a binary matrix. Step-by-step procedures are separately described. An example demonstrates the usefulness of the algorithm, and its advantages and disadvantages are discussed. Finally, a problem for future work is suggested.
    • Comparison of Viterbi and Sequential Decoding with a Noisy Carrier Reference

      Hofman, L. B.; Lumb, D. R.; NASA Ames Research Center (International Foundation for Telemetering, 1974-10)
      Performance of convolutionally encoded telemetry systems with Viterbi decoding or sequential decoding is well understood for the additive white Gaussian noise channel with coherent detection of bi-phase-shift-keyed signals. Significant degradation from ideal performance can occur due to correlated noise resulting from low signal-to-noise ratios in the receiver carrier tracking phase-locked loop. Performance at the lower telemetry data rates on the two Pioneer Jupiter deep space probes provides examples of the effect of correlated noise on a sequential decoding system. Performance degradation needs to be quantified as a function of carrier signal-to-noise ratio (P(c)/N(o)2B(lo)) and carrier-tracking- loop-bandwidth-to-symbol-rate ratio (B(l)/R(s)) in order to provide design and analysis information on such effects. Analytical modeling is extremely difficult, particularly where B(l)/R(s) is neither very large nor very small.
    • Computer Controlled Radio Information System for Public Vehicle Operations

      Go, G. Bie; AEG-Telefunken (International Foundation for Telemetering, 1974-10)
      Radio control centers for Public vehicle operations has long been an essential instrument to control and monitor schedules and operations. However, due to the rapid development of city and urban traffic the capacity limit of the small amount of voice channels is already reached, especially during rush hours. Moreover the dispatchers are overburdened, so that adherence to schedule and safe operations cannot be guaranteed. Data communications is the means to increase the efficiency and the capacity of the existing system. AEG-TELEFUNKEN has conceived an advanced system TELETRANS utilizing computer control and radio monitoring. This system makes improved use of the existing channel capacity without infringing on current FCC regulations. Through the use of co-channel transmission, which is a special type of transmit diversity, large areas with diameters up to 40 km (25 mi.) can be covered. This system is flexible, so that requirements of small and large public transportation authorities can be fulfilled economically.
    • A Computer-Controlled, On-Board Data Acquisition System for Wind-Tunnel Testing

      Finger, Herbert J.; Cambra, Joseph M.; NASA Ames Research Center (International Foundation for Telemetering, 1974-10)
      A computer-controlled data acquisition system has been developed for the 40x80-Foot Wind Tunnel at Ames Research Center. The system, consisting of several small "on-board" units installed in the model and a data-managing, data-displaying ground station, is capable of sampling up to 256 channels of raw data at a total sample rate of 128,000 samples/sec. Complete signal conditioning is contained within the on-board units. The sampling sequence and channel gain selection is completely random and under total control of the ground station. Outputs include a bar-graph displays digital-to-analog converters, and digital interface to the tunnel's central computer, an SEL 840MP. The system can be run stand-alone or under the control of the SEL 840MP.
    • The Data Handling System of the Helios Probes

      Pabst, Dietrich; Digital Space Applications (International Foundation for Telemetering, 1974-10)
      The Helios probes A and B will have a maximum distance of 2AU from Earth. The typical requirements which are applicable to all deep space missions, especially decreasing link capacity, need a flexible data handling system. Taking the Helios probe as an example, it will be shown how the specific problems of data handling in deep space probes were solved from the technical standpoint. The system processes 4 selectable scientific formats at 8 to 4096 bit/sec with 320 subcommutated housekeeping channels, also to be transmitted in a separate engineering format. Simultaneously, a special format is stored cyclically with up to 16kbit in a 0.5Mbit memory, which can also be used for the storage of all the other data in an automatic sequence mode. Telemetry data are convolutional coded. Due to its flexibility and its multiplicity, the data handling system is a useful instrument for deep space missions.
    • Deep Space Telecommunications-Pioneer Mission to Jupiter

      Heist, E. K.; TRW Inc. (International Foundation for Telemetering, 1974-10)
      The Telecommunication subsystem for the Pioneer 10 and 11 spacecraft is described in terms of the exacting design requirements which have been met and the operational performance which has been achieved. Those features which are unique or novel and which contribute substantially to our knowledge of advanced techniques for future interplanetary missions, are emphasized. The discussion includes earth-pointing of the spacecraft high gain antenna by an on-board conical scan system, tracking, telemetry, and command functions at multi-million kilometer distances complicated by round trip communication delays of 90 minutes, and the versatility of special data formats which cater to certain instrument high rate sampling requirements during selected phases of the mission. With the successful flyby of the planet Jupiter by Pioneer 10 in December 1973, the technology and experience for much more ambitious, challenging, and complex missions to the outer planets has been demonstrated.
    • Design of the Mariner Jupiter/Saturn 1977 Telemetry System

      Wood, Gordon E.; Risa, Thomas; California Institute of Technology (International Foundation for Telemetering, 1974-10)
      In 1977 NASA will launch two spacecraft to perform scientific investigations of the Jupiter and Saturn planetary systems. The science payload includes a total of 10 instruments to support both the interplanetary cruise and planetary encounter phases. These will be the first launches of a new generation of Mariner-class spacecraft designed for outer-planet missions. The telemetry system design for these missions was especially challenging because of extreme communication ranges (1.5 X 10⁹ km), high data rate requirements (up to 115.2 kb/s), and more stringent data quality requirements than previous Mariner missions. This paper discusses the evolution and design of the Mariner Jupiter/Saturn 1977 telemetry system and presents the performance anticipated therefrom.
    • Evolution of the Douglas Flight-Test Data System

      Crowley, L. D.; Douglas Aircraft Company (International Foundation for Telemetering, 1974-10)
      The process of developing new techniques and systems for the purpose of flight-test data acquisition, communication, and processing is, in fact, an evolutionary one. It is filled with potential mutations formed when an orderly or direct path is not taken in any of supporting disciplines or when the capabilities of one link greatly exceed those of another. The rigid design philosophy that made the Douglas system so successful in support of numerous test programs has had both a negative and positive effect of limiting, or at least slowing, the future growth in flexibility. Upgrading the system with new hardware and software must be accomplished in a manner that does not degrade the existing performance and throughput capabilities while making room for the new species to evolve. Problems have been minimized by placing the development of the acquisition and processing systems under common management and, in turn, having this group accountable to the project users of the system. Constant feedback between system developers and users has ensured a degree of adaptability to the hostile environment of test program costs and schedules.