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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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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Some characteristics of low-frequency oscillations observed at ATS 1.

Analysis of low-frequency oscillations of the magnetic field at ATS 1 for the 25-month data interval from December 1966 to December 1968. Irregular oscillations and oscillations associated with magnetic storms were excluded from the analysis. Of the 222 events identified, 170 events were oscillating predominantly transverse to the background magnetic field. The oscillations were observed to occur most frequently in the early afternoon hours. They also seemed to occur more frequently during December, January, and February than at other times of the year. During a given individual event the frequency was fairly constant and it varied between .0015 and .02 Hz with a broad peak near .01 Hz. The event duration varied between a minimum of 10 min and a maximum of 14 hours and 26 min. During a given event the amplitude varied. The average maximum amplitude of an event was about 3 gamma.

Cummings, W. D.↗
NASA NTRS1972

A north-south stationkeeping ion thruster system for ATS-F.

An ion thruster system is being developed for the ATS-F satellite to demonstrate the application of ion thruster technology to the synchronous satellite north-south stationkeeping mission. The cesium bombardment ion thruster develops one millipound thrust at 2600 seconds specific impulse and provides thrust vectoring by accelerator electrode displacement. The propellant system is sized for two years operation at 25 percent duty cycle. Power conditioning circuitry is based on transistor inverters switching at 10 kHz. Thirteen command channels allow flexibility in operation; 12 telemetry channels provide information on system performance. Input power is less than 150 watts.

Worlock, R.↗
NASA NTRS1972

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.↗
NASA NTRS1972

Space science experiments aboard ATS-F.

The Environmental Measurements Experiment (EME) package is mounted on the ATS-F spacecraft to a structure that is located on top of the 30-foot parabolic reflector hub. The eight experiments of the EME package are designed to study the environment in space at synchronous altitude and to obtain information on electromagnetic-ionospheric interactions. Six of these experiments will obtain data on charged particles of several different types. A seventh experiment is to provide magnetic field data. The eighth experiment is concerned with solar cell degradation studies.

Wales, R.↗
NASA NTRS1972

Dual transponder time synchronization at C band using ATS-3.

The use of artificial satellites for time synchronization of geographically distant clocks is hindered by problems due to satellite motion or equipment delay measurements. The ATS-3 satellite with its two C-band transponder channels helps solve these problems through techniques for synchronization to accuracies of tenths of microseconds. Portable cesium clocks were used to verify the accuracy of the described system.

Mazur, W. E., Jr.↗
NASA NTRS1972

Telemetry and command, ATS-F's vital link with earth.

The susceptibility of a synchronous satellite to interference as compared with a low orbiting satellite poses a problem for command operations. The Applications Technology Satellites F and G (ATS F & G) are unique in that they will place the first high gain antenna in space that will reduce the need for high powered ground stations. The telemetry and command subsystem provides the necessary versatility required for the conduct of the many sophisticated experiments that will be conducted by the spacecraft. The subsystem provides continuous 24-hr operation of telemetry and command functions with complete redundancy to minimize problems due to RF interference.

Trudell, B. J.↗
NASA NTRS1972

A 15.3 GHz satellite-to-ground diversity experiment utilizing the ATS-5 satellite

During 1970 and 1971 the characteristics of a diversity satellite-to-ground communication link were measured using the ATS-5 15.3 GHz downlink. These data were gathered at two ground receiving terminals spaced 4 km apart during 1970 and 8 km apart during 1971 in the vicinity of Columbus, Ohio. These data have been subsequently analyzed to determine the improvement in link performance resulting from the use of space diversity. The results of this analysis have shown that substantial improvements in link performance may be gained through the use of space diversity on satellite-to-ground paths. For example, the durations of fades having depths exceeding 10 dB were reduced by more than two orders of magnitude for both the 4 and 8 km site separation distances.

Hodge, D. B.↗
NASA NTRS1972

Tornado occurrences related to overshooting cloud-top heights as determined from ATS pictures

A sequence of ATS 3 pictures including the development history of large anvil clouds near Salina, Kansas was enlarged by NASA into 8X negatives which were used to obtain the best quality prints by mixing scan lines in 8 steps to minimize checker-board patterns. These images resulted in the best possible resolution, permitting use to compute the heights of overshooting tops above environmental anvil levels based on cloud shadow relationships along with the techniques of lunar topographic mapping. Of 39 heights computed, 6 were within 15 miles of reported positions of 3 tornadoes. It was found that the tornado proximity tops were mostly less than 5000 ft, with one exception of 7000 ft, suggesting that tornadoes are most likely to occur when overshooting height decreases. In order to simulate surface vortices induced by cloud-scale rotation and updraft fields, a laboratory model was constructed. The model experiment has shown that the rotation or updraft field induces a surface vortex but their combination does prevent the formation of the surface vortex. This research leads to a conclusion that the determination of the cloud-top topography and its time variation is of extreme importance in predicting severe local storms for a period of 0 to 6 hours.

Fujita, T. T.↗
NASA NTRS1972

ATS ranging and position fixing experiment, phase 3

The experiments to test the concept of position location by range measurements from pairs of satellites in the L-band using ATS-5 are reported. Results of the ranging experiments confirmed that ranging resolution measured in tens or hundreds of feet may be achieved at VHF and L-band within the radio frequency bandwidths used for communications with simple, inexpensive, automatic equipment.

Anderson, R. E.↗
NASA NTRS1973

ATS-F radiant cooler contamination test in a hydrazine thruster exhaust

A test was conducted under simulated space conditions to determine the potential thermal degradation of the ATS-F radiant cooler from any contaminants generated by a 0.44-N(0.1-lbf) hydrazine thruster. The radiant cooler, a 0.44-N(0.1-lbf)hydrazine engine, and an aluminum plate simulating the satellite interface were assembled to simulate their flight configuration. The cooler was provided with platinum sensors for measuring temperature, and its surfaces were instrumented with six quartz crystal microbalance units (QCM) to measure contaminant mass deposits. The complete assembly was tested in the molecular sink vacuum facility (Molsink) at the Jet Propulsion Laboratory. This was the first time that a radiant cooler and a hydrazine engine were tested together in a very-high-vacuum space simulator, and this test was the first successful measurement of detectable deposits from hydrazine rocket engine plumes in a high vacuum. The engine was subjected to an accelerated duty cycle of 1 pulse/min, and after 2-hr of operation, the QCMs began to shift in frequency. The tests continued for several days and, although there was considerable activity in the QCMs, the cooler never experienced thermal degradation.

Chirivella, J. E.↗
NASA NTRS1973

ATS-5 millimeter wave propagation measurements

Long term experimental measurements to determine the propagation characteristics of 15 and 32 GHz earth-space links and to evaluate performance characteristics of operational millimeter wave systems are reported. The ATS 5 millimeter wave experimental link experienced attenuation and fading characteristics as a function of rainfall rate and other meteorological parameters. A method of site selection for the lowest attenuation rainfall rate improved reception tremendously.

Ippolito, L. J.↗
NASA NTRS1972

ATS-5 solar cell experiment after 699 days in synchronous orbit.

The data from the ATS-5 solar cell experiment for the first 699 days in synchronous orbit is presented. Comparison of the performance of several different types of solar cell/coverslide configurations is made. This behavior is in turn compared with the calculated performance for such cell/coverslide configurations in synchronous orbit and with the results of accelerator irradiations designed to simulate the omnidirectional electron environment. It is generally found that the cells on the flight experiment perform like the cells irradiated with the accelerator, but they degraded more than predicted by the calculation. Solar cells mounted on a thin kapton panel are degrading about the same as are their counterparts mounted on a rigid panel.

Anspaugh, B. E.↗
NASA NTRS1972

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.↗
NASA NTRS1972

System design of the ATS-F RFI measurement experiment.

Description of the system design of an RFI measurement experiment regarding optimal sharing of the 5.925- to 6.425-GHz frequency band between the ATS-F synchronous satellite and terrestrial telecommunication systems. The parametric measurements made will include transmitted and received power levels, propagation-path loss and variations as a function of range, elevation angle, RF polarization, and geographical location of interference sources. The technical objectives of the C-band RFI experiment are outlined, a functional diagram of the total system for the RFI measurement experiment is presented, and the design features of the receiver RF and IF circuits, the filters and detectors, and the computer control are summarized. A basic RFI measurement plan is presented which defines and briefly states the measurement procedure, which involves a number of different measurement modes, each of which is described in detail.

Henry, V. F.↗
NASA NTRS1973

The 3 DLE instrument on ATS-5

The performance and operation of the DLE plasma electron counter on board the ATS 5 are described. Two methods of data presentation, microfilm line plots and spectrograms, are discussed along with plasma dynamics, plasma flow velocity, electrostatic charging, and wave-particle interactions.

Deforest, S. E.↗
NASA NTRS1974

Radiation environment for ATS-F

The ambient trapped particle fluxes incident on the ATS-F satellite were determined. Several synchronous circular flight paths were evaluated and the effect of parking longitude on vehicle encountered intensities was investigated. Temporal variations in the electron environment were considered and partially accounted for. Magnetic field calculations were performed with a current field model extrapolated to a later epoch with linear time terms. Orbital flux integrations were performed with the latest proton and electron environment models using new improved computational methods. The results are presented in graphical and tabular form; they are analyzed, explained, and discussed. Estimates of energetic solar proton fluxes are given for a one year mission at selected integral energies ranging from 10 to 100 Mev, calculated for a year of maximum solar activity during the next solar cycle.

Stassinopoulos, E. G.↗
NASA NTRS1974

Average daily variations in the magnetic field as observed by ATS-5

Hourly averages of the magnetic field components are determined and analyzed using the measurements of the magnetic field monitor aboard the ATS-5. The data covering the time period of September 1969 through September 1971 are sorted and analyzed for various Kp values, geomagnetic latitude of the subsolar point, and local time. Local time variations are harmonically analyzed, and amplitudes and phases are given up to the fourth harmonic.

Skillman, T. L.↗
NASA NTRS1974

ATS-F launch planning document

Launch operations of the ATS 6 satellite and the Titan 3 C launch vehicle are analyzed. The subjects discussed are: (1) launch vehicle trajectory, (2) launch vehicle mark events, (3) standard orbital parameter messages, (4) STADAN ground station visibility, (5) launch window, (6) separation attitude, and (7) separation events. The VHF Omni earth coverage antenna is described. Graphs of visibility from various ground stations are developed.

Walsh, R.↗