The results of a TDMA equipment development applicable to military systems
TDMA applicability to military satellites, describing synchronization process
Dunn, J. G.↗
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Serrodyne frequency converter re-entrant amplifier system Patent
Serrodyne traveling wave tube reentrant amplifier for synchronous communication satellites operating at microwave frequencies
Allen, W. K.↗
Longitude repositioning of high power communication satellites
Analysis of requirements for longitude repositioning of high power communication satellites in synchronous equatorial orbit
Omalley, T. A.↗
Error control for the SMS data collection system
Synchronous meteorological satellite data collection and transmission system error control, considering design tradeoffs for radio sets and coding techniques
Wiggert, D.↗
Communications for future man-machine remote operations
Nationwide man machine remote employment/personal services system including synchronous communication satellite, information and control network and remote terminals
Lynch, T. J.↗
Aircraft altitude determination using multipath information in an angle-measuring navigation satellite system
In an angle-measuring navigation satellite system using a pair of crossed interferometers located on a satellite in synchronous orbit, three parameters are needed to determine a user's position unambiguously. These are the phase differences between received signals which were transmitted by the two antennas on each of the two interferometers, and the user's altitude. The two phase difference measurements yield a line of possible user locations, and the addition of the altitude measurement reduces this line to a single point. A method is proposed which makes use of the navigation signals received after reflection off the earth's surface. The iterative procedure employs the arrival time difference between direct and reflected signals. Based on previous calculations of errors in measuring the electrical parameters it is concluded that, for North Atlantic coverage and specular reflection, altitude measurements can be made with a 1-sigma error of 65 meters.
Kurjan, D.↗
The geopotential at synchronous-orbit altitudes
The earth's gravity potential at synchronous orbit satellite altitudes is studied by analyzing the small effects of the resonant harmonic of gravity in tracking data from eight satellites during 21 distinct drift-free arcs. Results show: (1) absolute accuracy of second degree resonant geopotential coefficients better than three percent and coefficients through fourth degree better than 15 percent; (2) positions of equilibrium points for geostationary satellites better than 1/2 degree; and (3) accuracy in predicting orbits for 24-hour satellites better than 1 degree for periods greater than 2 years.
Wagner, C. A.↗
ATS F&G pioneer application of space technology.
The Applications Technology Satellites will introduce an era of high-powered spacecraft without the limitations of the earlier small, low-powered satellites. To provide this high power, the two satellites will be equipped with high-gain, 30-foot diameter parabolic antennas. Another major innovation is the achievement of a tenth of a degree tracking accuracy. These new ATS spacecraft will eliminate the need for the immense ground stations required to communicate with satellites in synchronous orbits. The high-gain antenna will allow communication with simple inexpensive ground terminals, thereby permitting many advanced experiments not feasible in the past.
Gerwin, H.↗
Investigation of interaction between Pc 1 and 2 and Pc 5 micropulsations at the synchronous orbit during magnetic storms.
Coincident Pc 5 and Pc 1 and 2 micropulsations were observed at the synchronous equatorial satellite ATS 1 during the main phase of 11 geomagnetic storms that occurred in 1967. The Pc 1 and 2 oscillations were quasi sinusoidal, with periods of 5-20 sec and amplitudes of 1-2 gammas. Their average polarization was transverse to the ambient magnetic field. The oscillations were elliptical and rotation was to the left in relation to the main field. The observed characteristics suggest that the Pc 1 and 2 activity was due to ion cyclotron resonance of Alfven waves with energetic protons.
Barfield, J. N.↗
Multipath propagation study for L-band, over-ocean, satellite-aircraft communication link
The results are presented of a study of multipath propagation between an aeronautical relay satellite in synchronous earth orbit and an aircraft flying over the ocean. An analytical model for the reflected power is developed and the results of a computer solution are compared with an approximate solution obtained through integration by the method of steepest descent. The computer solution is shown to differ considerably from the approximate solution. Both methods are compared with the limited experimental results available.
Deal, J. H.↗
Visible infrared spin-scan radiometer
The visible infrared spin-scal radiometer (VISSR) may be considered as a camera system capable of simultaneously providing both visible and infrared earth and cloud cover pictures every 20 minutes from the geostationary synchronous meteorological satellite (SMS). With a 0.9-kilometer resolution in the visible spectrum and a 9-kilometer resolution in the IR spectrum, the VISSR/SMS SYSTEM makes its possible to study atmospheric dynamics through 24-hour continuous observation of cloud altitudes, patterns, motion, and temperature distributions.
Phenix, J. E.↗
SERT D spacecraft study
The SERT D (Space Electric Rocket Test - D) study defines a possible spacecraft project that would demonstrate the use of electric ion thrusters for long-term (5 yr) station keeping and attitude control of a synchronous orbit satellite. Other mission objectives included in the study were: station walking to satellite rendezvous and inspection, use of low cost attitude sensing system, use of an advanced solar array orientation and slip ring system, and an ion thruster integrated directly with a solar array power source. The SERT D spacecraft, if launched, will become SERT 3 the third space electric thruster test.
Source record↗
Nutation control during precession of a spin-stabilized spacecraft
Precession maneuver control laws for single-spin spacecraft are investigated so that nutation is concurrently controlled. Analysis has led to the development of two types of control laws employing precession modulation for concurrent nutation control. Results were verified through digital simulation of a Synchronous Meteorological Satellite (SMS) configuration. An addition research effort was undertaken to investigate the cause and elimination of nutation anomalies in dual-spin spacecraft. A literature search was conducted and a dual-spin configuration was simulated to verify that nutational anomalies are not predicted by the existing nonlinear model. No conclusions were drawn as to the cause of the observed nutational anomalies in dual-spin spacecraft.
Source record↗
A comparison of acoustic and random vibration testing of spacecraft
Before selecting the most suitable testing technique in a particular case, it has to be considered which of the two methods duplicates better the distribution of vibration responses to be expected during the actual launch phase. An investigation is conducted of the case of a large, low density spacecraft launched by a vehicle which produces significant acoustic noise and transmits relatively little vibration through the mechanical path provided by the vehicle structure in the area of the spacecraft interface. Criteria for vibration-acoustic equivalence are discussed along with tests conducted with the Synchronous Meteorological Satellite, the Radio Astronomy Explorer, and the Orbiting Geophysical Spacecraft. The investigation indicates that the vibration test is generally a poor substitute for an acoustic study.-
Bangs, W. F.↗
A study of unmanned mission opportunities to comets and asteroids
Several unmanned multiple-target mission opportunities to comets and asteroids were studied. The targets investigated include Grigg-Skjellerup, Giacobini-Zinner, Tuttle-Giacobini-Kresak, Borrelly, Halley, Schaumasse, Geographos, Eros, Icarus, and Toro, and the trajectories consist of purely ballistic flight, except that powered swingbys and deep space burns are employed when necessary. Optimum solar electric rendezvous trajectories to the comets Giacobini-Zinner/85, Borrelly/87, and Temple (2)/83 and /88 employing the 8.67 kw Sert III spacecraft modified for interplanetary flight were also investigated. The problem of optimizing electric propulsion heliocentric trajectories, including the effects of geocentric launch asymptote declination on launch vehicle performance capability, was formulated, and a solution developed using variational calculus techniques. Improvements were made to the HILTOP trajectory optimization computer program. An error analysis of high-thrust maneuvers involving spin-stabilized spacecraft was developed and applied to a synchronous meteorological satellite mission.
Mann, F. I.↗
Man-Computer Interactive Data Access System (McIDAS). Continued development of McIDAS and operation in the GARP Atlantic tropical experiment
The complete output of the Synchronous Meteorological Satellite was recorded on one inch magnetic tape. A quality control subsystem tests cloud track vectors against four sets of criteria: (1) rejection if best match occurs on correlation boundary; (2) rejection if major correlation peak is not distinct and significantly greater than secondary peak; (3) rejection if correlation is not persistent; and (4) rejection if acceleration is too great. A cloud height program determines cloud optical thickness from visible data and computer infrared emissivity. From infrared data and temperature profile, cloud height is determined. A functional description and electronic schematics of equipment are given.
Suomi, V. E.↗
The cesium bombardment engine north-south stationkeeping experiment on ATS-6
Two one millipound-thrust cesium bombardment ion thrusters have been developed and integrated on the ATS-F spacecraft for the purpose of demonstrating compatible north-south stationkeeping of a synchronous communication satellite. Preliminary operation of the two thrusters on ATS-6 was completely successful on the first run of each. In addition to verifying operation, the principal accomplishments were the demonstration of a total absence of interference with the communications systems, verification of the predicted spacecraft operating potential, demonstration of compatibility with the star tracker, and demonstration of spacecraft attitude by thrust vectoring. Subsequent attempts to operate the thrusters have not been successful. Analysis indicates that the problem is associated with operation of the propellant reservoirs in zero-g.
Worlock, R. M.↗
The cesium bombardment engine north-south stationkeeping experiment on ATS-6
Two one-millipound-thrust cesium-bombardment ion thrusters have been developed and integrated on the ATS-F spacecraft for the purpose of demonstrating compatible north-south stationkeeping of a synchronous communication satellite. In addition to the two flight units, an identical system is undergoing extended testing on the ground to demonstrate operating lifetime. On July 17, 1974, approximately 50 days after launch, preliminary operation of one of the thrusters was begun. Completely successful operation was achieved on the first run. In addition to verifying operation, the principal accomplishments were the demonstration of a total absence of interference with the complete array of spacecraft-to-ground communication links and the verification of the predicted spacecraft operating potential of approximately -10 volts. Subsequent attempts to operate the same thruster have not been successful and an investigation of possible explanations is underway.
Hunter, R. E.↗