10 research outputs found
Supporting research studies to booster flight control problems Final report
Get PDFAsymptotic stability and response of nonlinear system
Modelling and numerical simulation of microwave pulse propagation in an air-breakdown environment
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Lunar Radar Cross Section at Low Frequency
No full textRecent bistatic measurements of the lunar radar cross-section have extended the spectrum to long radio wavelength. We have utilized the HF Active Auroral Research Program (HAARP) radar facility near Gakona, Alaska to transmit high power pulses at 8.075 MHz to the Moon; the echo pulses were received onboard the NASA/WIND spacecraft by the WAVES HF receiver. This lunar radar experiment follows our previous use of earth-based HF radar with satellites to conduct space experiments. The spacecraft was approaching the Moon for a scheduled orbit perturbation when our experiment of 13 September 2001 was conducted. During the two-hour experiment, the radial distance of the satellite from the Moon varied from 28 to 24 Rm, where Rm is in lunar radii
Effects of Absorption On High-latitude Meteor Scatter Communication-systems
No full textData acquired with the Geophysics Laboratory's high-latitude meteor scatter test-bed between Sondrestrom Air Base (AB) and Thule AB, Greenland, during the solar disturbances of March and August 1989 are presented. These disturbances provided a unique opportunity to observe a number of naturally occurring disturbance effects on meteor scatter links operated in the frequency range (35 to 147 MHz) covered by the test-bed. The disturbances range from signal absorption to system noise variations. The properties of ionospheric absorption in general are discussed and illustrated with computations using electron density profiles from the September 1978 solar proton event (SPE). It has been found that accurate measurements of high levels of ionospheric absorption with riometers pose special problems. These problems are identified and discussed. The data acquired during the March and August 1989 solar disturbances are then related to the zenith absorption measured at Thule, and the influence of absorption as well as system noise variations are discussed. The two events presented are very different. The August event was dominated by ionospheric absorption which affected meteor arrival rates and duty cycles primarily at the lower frequencies (35 and 45 MHz), although some effects could also be seen at the higher frequencies (65 to 147 MHz). The March event combined weak ionospheric absorption with large solar noise bursts. The effects of this event on the test-bed were dominated by increased solar noise at all frequencies. The relative influence of solar noise and ionospheric absorption during SPE events is discussed along with speculation as to the validity of frequency dependence conclusions based on testing of the JANET system
