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NASA NTRS1975

ATS-6 - Millimeter Wave Propagation and Communications Experiments at 20 and 30 GHz

The Applications Technology Satellite (ATS-6) Millimeter Wave Experiment, developed and implemented by the NASA Goddard Space Flight Center, has provided the first direct measurements of 20- and 30-GHz earth-space links from an orbiting satellite. Studies at eleven locations in the continental United States were directed at an evaluation of rain attenuation effects, scintillations, depolarization, site diversity, coherence bandwidth, and analog and digital communications techniques. In addition to direct measurements on the 20- and 30-GHz links, methods of attenuation prediction with radars, rain gauges, and radiometers were developed and compared with the directly measured attenuation. This paper presents a review of the major results of the first year of measurements with ATS-6, with emphasis on the impact of the measurements on millimeter wave space systems design.

Ippolito, L. J.↗
NASA NTRS1975

ATS-6 - Radio Beacon Experiment: The first years

The Radio Beacon Experiment aboard Applications Technology Satellite-6 (ATS-6) is designed to measure the total electron content and the ionospheric electron content between the satellite and ground. The spaceborne beacon transmits signals on frequencies of 40, 140, and 360 MHz with amplitude modulations of 1 MHz and/or 0.1 MHz for the measurement of modulation phase, Faraday rotation, and amplitude. The modulation phase delays are calibrated in the satellite and in the ground equipment, and the polarization of the emitted signals are predetermined by standard antenna range techniques. The design of the ATS-6 receiver in Boulder, Colorado, is discussed. The antennae are of the short backfire type described by Ehrenspeck (1967), with nominal gains of 13, 19, and 22 dB at 40, 140, and 360 MHz, respectively. Data recording and overall supervision of the receiver is carried out by a 16-bit minicomputer with 8 k of memory. Overall performance of the system is satisfactory. Sample data on the monthly median hourly values of the total electron content, plasmospheric content, and shape factor show distinct seasonal and diurnal variations.

Davies, K.↗
NASA NTRS1975

ATS-6 description

Basic design features of Applications Technology Satellite-6 (ATS-6) are discussed, and a variety of experiments carried out with the satellite is described. The 9.1 m reflector is a furlable 48-rib design. The earth viewing module housing most of the electronics is connected to the reflector by an A-frame truss made of graphic fiber reinforced plastic with excellent dimensional stability over a wide temperature range. The solar arrays, extended beyond the diameter of the reflector, are fixed hemi-cylinders consisting of 16 flat panels each. The communications system is an integrated multifrequency RF repeater capable of receiving up to 3 signals in any of 4 frequency bands (C, S, L, VHF) and retransmitting them on any desired frequency in 4 frequency bands (C, S, L, UHF). Results of the Tracking and Data Relay Experiment with GEOS-3 are summarized. Accuracies of 0.1 to 0.2 deg have been maintained in the programmed mode of tracking using the ATS-6 Digital Operational Controller, and communications links for the relay of 1.56 kilobit telemetry data from GEOS and for acquisition of range and range rate data performed as predicted or better.

Redisch, W. N.↗
NASA NTRS1975

ATS-6 description

The major design features of the sixth Applications Technology Satellite (ATS-6) are discussed. The three-axis stabilized, geostationary satellite, launched in May 1974, features a 9.1 meter parabolic antenna permitting the use of low cost 3 meter ground terminals for the reception of direct broadcast high quality color television programming. The communication subsystem is an integrated multifrequency RF repeater capable of receiving up to three signals in C, S, L, and VHF bands and retransmitting them at any commanded frequency in C, S, L, and UHF bands. A summary of the experiments carried aboard ATS-6 is provided, and early results from the GEOS Tracking and Data Relay Experiment are presented.

Redisch, W. N.↗
NASA NTRS1977

ATS-3 ranging support

The purpose of this effort was to provide NASA-Goddard Space Flight Center with ATS-3 ranging data from ground stations of the VHF network and from an additional ground station installed at the NASA-Goddard Space Flight Center. Ranging measurements to the NASA transponder enabled calculation of the transponder's line-of-position. Installation of an S-band transponder at the same site and the conduct of ranging experiments to this transponder and others via ATS-6 provided a second line-of-position. The NASA S-band transponder was specifically designed for installation aboard spacecraft. Consequently, this program provided NASA an opportunity to compare two different techniques using geostationary satellites in the tracking low orbit satellites.

Brisken, A. F.↗
NASA NTRS1977

Significant initial results from the environmental measurements experiment on ATS-6

The Applications Technology Satellite (ATS-6), launched into synchronous orbit on 30 May 1974, carried a set of six particle detectors and a triaxial fluxgate magnetometer. The particle detectors were able to determine the ion and electron distribution functions from 1 to greater than 10 to the 8th power eV. It was found that the magnetic field is weaker and more tilted than predicted by models which neglect internal plasma and that there is a seasonal dependence to the magnitude and tilt. ATS-6 magnetic field measurements showed the effects of field-aligned currents associated with substorms, and large fluxes of field-aligned particles were observed with the particle detectors. Encounters with the plasmasphere revealed the existence of warm plasma with temperatures up to 30 eV. A variety of correlated waves in both the particles and fields were observed: pulsation continuous oscillations, seen predominantly in the plasmasphere bulge; ultralow frequency (ULF) standing waves; ring current proton ULF waves; and low frequency waves that modulate the energetic electrons. In additon, large scale waves on the energetic-ion-trapping boundary were observed, and the intensity of energetic electrons was modulated in association with the passage of sector boundaries of the interplanetary magnetic field.

Fritz, T. A.↗
NASA NTRS1979

Summary of the two year NASA program for active control of ATS-5/6 environmental charging

Experiments conducted on the ATS 5 and ATS 6 which have demonstrated the feasibility of modifying or clamping the environmentally induced potential of these spacecraft are described. The results of these experiments indicate that a thermionic electron source is capable of replacing photo-emitted electrons during eclipse. However, the utility of this type of device is limited if its emission is suppressed by local electric fields. On the other hand, it is shown that a plasma source will not only serve as a substitute for photo-emitted electrons but will also suppress differential charging of isolated elements of the spacecraft which would tend to suppress electron emission. This later device is therefore capable of clamping the potential of a spacecraft without special considerations of its coupling to the ambient plasma.

Bartlett, R. O.↗
NASA NTRS1979

Characteristics of differential charging of ATS-6

Thirteen days of data collected by the Auroral Particle Experiment onboard the ATS 6 were analyzed emphasizing peculiarities in the electron data attributed to differential charging. On one of these days the satellite was eclipsed by the earth at local midnight. Spectrograms were used to examine the data. It is concluded that differential charging is responsible for returning photoelectrons to the spacecraft up to a couple hundred eV, depending on the spacecraft charge. It is believed that the Minnesota experiment on ATS 6 is largely responsible for producing a potential barrier that returns particles and produces intense spon spots in the count rates.

Johnson, B.↗
NASA NTRS1979

ATS-6 satellite radio beacon measurements at Ootacamund, India

ATS-6 radio beacon measurements of modulation phase and Faraday rotation made at Ootacamund, India in 1975-1976 are discussed with emphasis on the measurement and analysis errors. The modulation-phase errors are insensitive to the geomagnetic field and provide an accurate determination of the total columnar electron content. Comparison of modulation-phase measurements at different frequencies shows a minor sensitivity to the ATS-6 pitch angle. For the low geomagnetic latitude and nearly transverse propagation conditions of Ootacamund, the use of a fixed conversion coefficient gives an unreliable Faraday content. However, the Faraday rotation measurements may be used to determine the shape factor F, which provides information about the electron density height profile.

Davies, K.↗
NASA NTRS1980

Observations of ULF oscillations in the ion fluxes at small pitch angles with ATS 6

The ultra-low-frequency modulation of ion flux densities at small pitch angles observed by ATS 6 is examined, with particular attention given to a detailed analysis of a representative event. ULF modulation events with maximum modulation at small pitch angles were identified 14 times during the first eight months of operation of the NOAA low-energy particle detector on ATS 6. For the event of October 23, 1974, maximum flux modulation, with a maximum/minimum intensity ratio of 3.7, was observed in the 100 to 150 keV detector at an angle of 32 deg to the ambient field. Spectral analysis of magnetic field data reveals a right elliptically polarized magnetic perturbation with a 96-sec period and a 5-gamma rms amplitude, propagating in the dipole meridian at an angle of about 15 deg to the ambient field and the dipole axis. Proton flux modulation is found to lag the field by up to 180 deg for the lowest-energy channel. Observations are compared with the drift wave, MHD slow wave, and bounce resonant interaction associated with transverse wave models, and it is found that none of the wave models can adequately account for all of the correlated particle and field oscillations.

Su, S.-Y.↗
NASA NTRS1980

Coincident particle observations from AE-C and ATS 6 during the October 28, 1977, geomagnetic storm

Simultaneous measurements of ion and electron energy spectra recorded during the October 28, 1977 geomagnetic storm by the AE-C and ATS 6 spacecraft when both were nearly on the same L shell are evaluated and compared. The orbit of the AE-C generates wide longitudinal coverage of the auroral oval, whereas the ATS 6, which is located at geosynchronous orbit, samples the equatorial particle population. It is shown that the coincident electron energy spectra obtained by the two satellites agree well above 5 keV and the spectra of electrons peak near 1 keV at ionospheric altitudes, while no peaks in energy appear at synchronous altitude.

Zanetti, L. J.↗
NASA NTRS1981

Observations of differential charging effects on ATS 6

Differential charging effects observed in the electron data of the University of California, San Diego, auroral particles experiment on Applied Technology Satellite 6 are described and analyzed. An electrostatic barrier around the environmental measurements experiment (EME) package on ATS 6 is shown to be the natural result of dielectrics around the spacecraft which are more negatively charged than the mainframe of the spacecraft. In particular, the large dish antenna on ATS 6 causes the formation of a barrier which traps particles emitted from the EME package surface and returns them to the spacecraft. The insulating surface of the rotating University of Minnesota detector on the otherwise conducting EME package is shown to be the source of accelerated fluxes of electrons during charging events.

Olsen, R. C.↗
NASA NTRS1981

ATS-6 engineering performance report. Volume 5: Propagation experiments

Propagation experiments at 1550 MHz to 1650 MHz are reviewed, including the Integrated L-Band Experiments system and results, and the Mobile L-Band Terminals for Satellite Communication system. Experiments at 4 GHz to 6 GHz are reported, including the Radio Frequency Interferometer Measurements system and results, and Earth station antenna evaluations. Experiments above 10 GHz are discussed, including Comsat and ATS-6 millimeter wave propagation/experiments, and communication ATS-6 version at 20 and 30 GHz.

Wales, R. O.↗
NASA NTRS1981

Preserved signatures of ion flux modulations observed by ATS 6

The considered investigation is concerned with a detailed analysis of the event of August 13, 1974. The considered day was a geomagnetically quiet day, and ATS 6 was stationed at 94 deg W longitude. On the basis of the conducted analysis it is found that the observed flux oscillations may be a fossil signature of flux modulations which have occurred in ions at an earlier time and at a region away from the spot of observation. In conclusion, it is pointed out that the August 13, 1974, and the January 23, 1975, events of proton flux oscillations observed by ATS 6 are of great importance. They reveal another unique capability of the drifting particles for preserving small modulation signatures imposed upon them during earlier wave-particle interactions. At the present, no conclusions are drawn as to what kind of the wave-particle interaction process was responsible for the observation.

Su, S.-Y.↗
NASA NTRS1967

ATS-I camera experiment successful.

Cloud photographs obtained on board ATS-I SATELLITE with camera equipped with reflecting telescope show feasibility of short-lived weather systems from synchronous altitude

SATELLITE PHOTOGRAPHY↗