Satellite measurements of the HF radio environment in the topside ionosphere

Abstract

Measurements made on board the orbiting Air Force meteorological satellite equipped with a high‐frequency (HF) receiver have been studied in order to describe the HF radio environment at the satellite height. The satellite is in a sun‐synchronous dawn‐dusk orbit at a height of nearly 500 nmi (860 km) above the surface on the earth. The receiver sweeps repeatedly through the band 1.2–13.9 MHz in 100‐kHz steps once every 32 s, providing observations at each frequency approximately every 200 km along the satellite orbit. Measurements from a 3‐month period early in the satellite lifetime—September, October, and November, 1977—have been grouped and analyzed by frequency to yield results that are consistent with the hypothesis that the primary source of the observations is emissions from terrestrial transmitters. The relative differences in the received signals vary with frequency in a manner that agrees with the allocation of the HF spectrum.

Lunar Reflections of Terrestrial Radio Leakage

“…These parameters were based on the best engineering and industry data available, but one nevertheless should, whenever possible, check any model against the real world. Very little data exists relevant to the appearance of the radio earth from "outside"; see Herman (1978) for a summary and also Rush et al (1980) and Skomal (1983). The task then was to make actual measurements of our civilizations radio signature as it appears from deep space.…”

A predictive model of the HF noise environment at satellite heights

“…Figure 3-1 Change in noise levels with immersion and emersion 44 for lunar-orbiting RAE-2 (from Alexander, et al, 1975) Figure 3-2 RAE-1 antenna temperature variations 47 (from Herman, et al, 1973) Figure Worldwide noise contours at 9.18 MHz for 00 to 08 LT 49 (from Herman, et al, 1973) Figure 3-4 DMSP HF noise contours (from Rush, et al, 1980) 53 Figure 3-5 AMPTE/IRM Plasma Wave HF multichannel data 56 (January 3,1986) (from LaBelle, et al, 1989) Table 4-1 Important RAD2 performance parameters Table 4-2 Interference characteristics Table 4-3 Alternate observing frequencies for an orbiting interferometer Table 5-1 "Clear" frequency bands: interference simulation Table 5-2 Ionospheric transfer function longitudinal ranges 119 Table 6-1 Simulated spectra compared with WIND data 159 INTRODUCTION…”

“…This has limited the observations to qualitative assessments of the spatial and temporal dependencies of the HF noise. Rush, et al (1980) presented their analysis of the DMSP measurements for 4.0 -13.9…”

“…The AMPTE/IRM Plasma Wave Receiver Until November, 1994, the AMPTE/IRM noise observations were the only archived data on terrestrial HF noise. Rush, et al, 1980) (LaBelle, et al, 1989, but its Plasma Wave receiver did detect some interesting signals which could only be terrestrial in origin. This satellite, designed to study the dynamics of the ionosphere and magnetosphere, was placed in a highly elliptical orbit: the apogee was 18 Rg (120,000 km) and perigee was 550 km.…”

“…This can be attributed to the influence of ionospheric shielding; at times away from local noon, the ionosphere will be less dense, allowing more interference to penetrate. Figure 3-5 AMPTE/IRM Plasma Wave HF multichannel data (January 3,1986) (from LaBelle, et al, 1989) operational constraints prohibited obtaining the DMSP antenna performance, so noise temperature or field strength calculations can not be performed on the data (Rush, et al, 1980). The AMPTE/IRM data is in rms spectral density (V/VMHZ).…”