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45 lines
2.6 KiB
Plaintext
45 lines
2.6 KiB
Plaintext
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A text box entitled Astronomical Data provides information needed for
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tracking the sun or moon, moon, compensating for EME Doppler shift,
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and estimating EME Doppler spread and path degradation. Toggle the
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*Astronomical data* on the *View* menu to display or remove this window.
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image::AstroData_2.png[align="center",alt="Astronomical Data"]
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Available information includes the current *Date* and *UTC* time; *Az*
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and *El*, azimuth and elevation of the moon at your own location, in
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degrees; *SelfDop*, *Width*, and *Delay*, the Doppler shift, full
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limb-to-limb Doppler spread, and delay of your own EME echoes; and
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*DxAz* and *DxEl*, *DxDop*, and *DxWid*, corresponding parameters for
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a station located at the DX Grid entered on the main window. These
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numbers are followed by *Dec*, the declination of the moon; *SunAz*
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and *SunEl*, the azimuth and elevation of the Sun; *Freq*, your stated
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operating frequency in MHz; *Tsky*, the estimated sky background
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temperature in the direction of the moon, scaled to the operating
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frequency; *Dpol*, the spatial polarization offset in degrees; *MNR*,
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the maximum non-reciprocity of the EME path in dB, owing to spatial
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polarization; and finally *Dgrd*, an estimate of the signal
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degradation in dB, relative to the best possible time with the moon
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at perigee in a cold part of the sky.
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The state of the art for establishing three-dimensional locations of
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the sun, moon, and planets at a specified time is embodied in a
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numerical model of the solar system maintained at the Jet Propulsion
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Laboratory. The model has been numerically integrated to produce
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tabular data that can be interpolated with very high accuracy. For
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example, the celestial coordinates of the moon or a planet can be
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determined at a specified time to within about 0.0000003 degrees. The
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JPL ephemeris tables and interpolation routines have been incorporated
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into _WSJT-X_. Further details on accuracy, especially concerning
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calculated EME Doppler shifts, are described in
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The sky background temperatures reported by _WSJT-X_ are derived from
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the all-sky 408 MHz map of Haslam et al. (Astronomy and Astrophysics
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Supplement Series, 47, 1, 1982), scaled by frequency to the (-2.6)
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power. This map has angular resolution of about 1 degree, and of
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course most amateur EME antennas have much broader beamwidths than
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this. Your antenna will therefore smooth out the hot spots
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considerably, and the observed extremes of sky temperature will be
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less. Unless you understand your sidelobes and ground reflections
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extremely well, it is unlikely that more accurate sky temperatures
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would be of much practical use.
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