Apollo unified S-band system.
Apollo unified S-band system covering station locations, uplink and downlink spectrums, spacecraft gross parameters, theory of operation, etc
SPACE COMMUNICATION↗
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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.
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Spectral studies of signals present in the command and communications system up-link transmitter
Spectral studies of signals present in command and communications system uplink transmitter of Saturn 5 radio frequency tracking and ranging systems
Walsh, J. R., Jr.↗
A guide to onboard checkout. Volume 5: Data management
The baseline data management subsystem for a space station is discussed. The subsystem consists of equipment necessary to transfer, store, and process data to and from users and subsystems. It acquires and conditions a wide variety of input data from experiments, vehicle subsystems sensors, uplinked ground communications, and astronaut-activated controls. Computer techniques for failure analysis, reliability, and maintenance checkout onboard the space station are considered.
Source record↗
Information transfer satellite concept study. Volume 4: computer manual
The Satellite Telecommunications Analysis and Modeling Program (STAMP) provides the user with a flexible and comprehensive tool for the analysis of ITS system requirements. While obtaining minimum cost design points, the program enables the user to perform studies over a wide range of user requirements and parametric demands. The program utilizes a total system approach wherein the ground uplink and downlink, the spacecraft, and the launch vehicle are simultaneously synthesized. A steepest descent algorithm is employed to determine the minimum total system cost design subject to the fixed user requirements and imposed constraints. In the process of converging to the solution, the pertinent subsystem tradeoffs are resolved. This report documents STAMP through a technical analysis and a description of the principal techniques employed in the program.
Bergin, P.↗
Millimeter wave propagation measurements using the ATS 5 satellite
The ATS 5 millimeter wave propagation experiment determines long- and short-term attenuation statistics of operational millimeter wavelength earthspace links as functions of defined meteorological conditions. A preliminary analysis of results with 15 GHz downlink and 32 GHz uplink frequency bands indicates that both frequency bands exhibit an excellent potential for utilization in reliable high data rate earth-space communications systems.
Ippolito, L. J.↗
Modifications of the wideband FM TDRS system
The wideband FM scheme for the Tracking and Data Relay Satellite (TDRS) system is discussed. The technique achieves a spread-spectrum advantage against multipath and interference through the inclusion of a large deviation FM subcarrier. The signal also permits co-channel spread-spectrum multipath access (SSMA) on the downlink from mission spacecraft to TDRS. Each user is assigned a unique combination of carrier and subcarrier which allows the ground receiver to separate user signals with overlapping spectra. The system was modified by the addition of a low-deviation fine range tone to both the uplink and the downlink, separate from the wide-deviation subcarrier. The magnitude of the interference components due to other SSMA signals are analyzed. A carrier and subcarrier frequency plan was worked out based on the modified signal format. A configuration to accommodate 42 and 60 users is described. The inclusion of ambiguity resolving ranging sidetones is also discussed.
Wachsman, R. H.↗
Multipath errors in range rate measurement by a TDRS/VHF - GRARR
Range rate errors due to multipath reflection are calculated for a tracking and data relay satellite system using the VHF Goddard range and range rate (GRARR) system. At VHF the reflection is primarily specular, and the strength of the multipath relative to the direct path can be modeled in terms of the geometry and the surface characteristics, specifically the root-mean-square (rms) ocean wave height. The uplink and downlink multipath introduces phase jitter on the GRARR carrier and subcarrier. The derivation of these effects is reviewed leading to an expression for the rms range rate error. The derivation assumed the worst-case orbital configurations in which there was very little relative specular Doppler. This means that the specular multipath interference was not attenuated by the carrier and subcarrier PLL transfer functions. Curves of range rate error are presented as a function of grazing angle with wave height 0.3 to 0.7 meters and spacecraft altitude 100 to 700 miles as parameters.
Sohn, S. J.↗
Guidance system operations plan for manned cm earth orbital and lunar missions using program Colossus 3. Section 2: Data links
The data links for use with the guidance system operations plan for manned command module earth orbital and lunar missions using program Colossus 3 are presented. The subjects discussed are: (1) digital uplink to CMC, (2) command module contiguous block update, (3) CMC retrofire external data update, (4) CMC digital downlink, and (5) CMC entry update.
Hamilton, M. H.↗
Guidance system operations plan for manned LM earth orbital and lunar missions using program luminary 1E. Section 2: Data links
Data links for the guidance system of manned lunar module orbital and lunar missions are presented. Subjects discussed are: (1) digital uplink to lunar module, (2) lunar module liftoff time increment, (3) lunar module contiguous block update, (4) lunar module scatter update, (5) lunar module digital downlink, and (6) absolute addresses for update program.
Hamilton, M. H.↗
Apollo 14 and 15 missions: Intermittent steerable antenna operation
An attempt was made to determine the cause of antenna tracking interruptions during Apollo 14 and Apollo 15 missions prior to powered descent, and after ascent from the lunar surface but before rendezvous. Probable causes examined include: (1) amplitude modulation on the uplink radio frequency carrier, (2) noise capacitively or inductively coupled into the track error line, and (3) hardware problems resulting in tracking loop instabilities. It was determined that amplitude modulation caused the antenna oscillations. The corrective procedures taken are given.
Source record↗
Misalignment estimation software system
A system of computer software, spacecraft, and ground system activity is described that enables spacecraft startrackers and inertial assemblies to be aligned and calibrated from the ground after the spacecraft has achieved orbit. The system generates in the uplink flow an exercise designed to render misalignments visible, and sends the exercise to the spacecraft where the spacecraft inserts the misalignment into the information in the form of attitude sensor error. The information is downlinked for processing into misalignment estimates to be used for correcting spacecraft model at data base.
Desjardins, R. L.↗
ATS-F COMSAT millimeter wave propagation experiment.
Description of the transmitting and receiving system configurations to be used in an ATS-F propagation experiment designed to gather data on the attenuation of satellite uplink signals (at approximately 13.2 and 17.8 GHz) due to atmospheric hydrometeors (mostly rain). The data will be used for statistical determination of system power margins required for operational communications systems at frequencies above 10 GHz. A secondary analysis will study site diversity as a means of reducing the required system margins. A spacecraft transponder receives signals from 15 dual-frequency ground transmitter stations and retransmits these signals to a central ground receiving terminal at a frequency of 4 GHz.
Levatich, J. L.↗
Design of communication systems using short-constraint-length convolutional codes.
A method is presented for calculating the effect of carrier-phase reference error in a receiver phase-locked loop on bit error rates in convolutionally coded data, for the practical design of systems using short-constraint-length convolutional codes. A set of design curves shows the relation between design bit error rate, uplink carrier tracking loop SNR, downlink total SNR, and downlink modulation index. These curves make possible rapid and simple system optimization.
Merrill, H. M.↗
VHF command system study
Solutions are provided to specific problems arising in the GSFC VHF-PSK and VHF-FSK Command Systems in support of establishment and maintenance of Data Systems Standards. Signal structures which incorporate transmission on the uplink of a clock along with the PSK or FSK data are considered. Strategies are developed for allocating power between the clock and data, and spectral analyses are performed. Bit error probability and other probabilities pertinent to correct transmission of command messages are calculated. Biphase PCM/PM and PCM/FM are considered as candidate modulation techniques on the telemetry downlink, with application to command verification. Comparative performance of PCM/PM and PSK systems is given special attention, including implementation considerations. Gain in bit error performance due to coding is also considered.
Gee, T. H.↗
Dual frequency dichroic feed performance
The NASA Deep Space Net (DSN) in support of the Viking Mars Project in 1976, and for science and technology demonstrations during the Mariner-Venus-Mercury mission in 1974, has developed and implemented a dual (S- and X-band) feed for large ground microwave antennas. This feed provides for a multiplicity of functions; very low listening capability at each downlink (spacecraft-to-earth) band as well as simultaneous diplexed very high cw power uplink (earth-to-spacecraft) at the S-band frequency. Total 64-m antenna system performance, is considered in terms of gain, operating noise temperature and dual beam pointing or boresight coincidence. Because of the unique ability to fold or stow the dual band feed elements for single band operations, the performance definition between single and dual band operations will be reliable and accurate.
Bathker, D. A.↗
The ATS-F radio frequency interference measurement experiment
The technical objectives of the uplink interference tests and measurements to be performed during this experiment are set forth as the determination of the integrated interference power from all 6-GHz terrestrial sources sharing the common carrier band with the RF field of view of the ATS-F satellite; the establishment of practical limits of receiver antenna gain-to-noise temperature ratios for satellites sharing the common 6-GHz carrier band; and the determination of the geographical and frequency distribution of 6-GHz terrestrial sources sharing the common carrier band. A brief description of the RF interference measurement system with some details on its hardware and subsystems is included. The performance characteristics of the mission and a measurement program are discussed.
Henry, V. F.↗
A remotely augmented vehicle approach to flight testing RPV control systems
A remotely augmented vehicle concept for flight testing advanced control systems was developed as an outgrowth of a remotely piloted research vehicle (RPV) program in which control laws are implemented through telemetry uplink and downlink data channels using a general purpose ground based digital computer which provides the control law computations. Some advantages of this approach are that the cost of one control system facility is spread over a number of RPV programs, and control laws can be changed quickly as required, without changing the flight hardware. The remotely augmented vehicle concept is described, and flight test results from a subscale F-15 program are discussed. Suggestions of how the concept could lead to more effective testing of RPV control system concepts, and how it is applicable to a military RPV reconnaissance mission are given.
Deets, D. A.↗
Single- and dual-carrier microwave noise abatement in the deep space network
The NASA/JPL Deep Space Network (DSN) microwave ground antenna systems are presented which simultaneously uplink very high power S-band signals while receiving very low level S- and X-band downlinks. Tertiary mechanisms associated with elements give rise to self-interference in the forms of broadband noise burst and coherent intermodulation products. A long-term program to reduce or eliminate both forms of interference is described in detail. Two DSN antennas were subjected to extensive interference testing and practical cleanup program; the initial performance, modification details, and final performance achieved at several planned stages are discussed. Test equipment and field procedures found useful in locating interference sources are discussed. Practices deemed necessary for interference-free operations in the DSN are described. Much of the specific information given is expected to be easily generalized for application in a variety of similar installations. Recommendations for future investigations and individual element design are given.
Bathker, D. A.↗