47 lines
2.7 KiB
Plaintext
47 lines
2.7 KiB
Plaintext
|
A text box entitled Astronomical Data provides information needed for
|
||
|
|
tracking the sun or moon, compensating for EME Doppler shift, and
|
||
|
|
estimating EME Doppler spread and path degradation. Toggle the
|
||
|
|
*Astronomical data* on the *View* menu to display or hide this window.
|
||
|
|
|
||
|
|
image::AstroData_2.png[align="center",alt="Astronomical Data"]
|
||
|
|
|
||
|
|
Available information includes the current UTC *Date* and time; *Az*
|
||
|
|
and *El*, azimuth and elevation of the moon at your own location, in
|
||
|
|
degrees; *SelfDop*, *Width*, and *Delay*, the Doppler shift, full
|
||
|
|
limb-to-limb Doppler spread in Hz, and delay of your own EME echoes in
|
||
|
|
seconds; and *DxAz* and *DxEl*, *DxDop*, and *DxWid*, corresponding
|
||
|
|
parameters for a station located at the *DX Grid* entered on the main
|
||
|
|
window. These numbers are followed by *Dec*, the declination of the
|
||
|
|
moon; *SunAz* and *SunEl*, the azimuth and elevation of the Sun;
|
||
|
|
*Freq*, your stated operating frequency in MHz; *Tsky*, the estimated
|
||
|
|
sky background temperature in the direction of the moon, scaled to the
|
||
|
|
operating frequency; *Dpol*, the spatial polarization offset in
|
||
|
|
degrees; *MNR*, the maximum non-reciprocity of the EME path in dB,
|
||
|
|
owing to a combination of Faraday rotation and spatial polarization;
|
||
|
|
and finally *Dgrd*, an estimate of the signal degradation in dB,
|
||
|
|
relative to the best possible time with the moon at perigee in a cold
|
||
|
|
part of the sky.
|
||
|
|
|
||
|
|
The state of the art for establishing three-dimensional locations of
|
||
|
|
the sun, moon, and planets at a specified time is embodied in a
|
||
|
|
numerical model of the solar system maintained at the Jet Propulsion
|
||
|
|
Laboratory. The model has been numerically integrated to produce
|
||
|
|
tabular data that can be interpolated with very high accuracy. For
|
||
|
|
example, the celestial coordinates of the moon or a planet can be
|
||
|
|
determined at a specified time to within about 0.0000003 degrees. The
|
||
|
|
JPL ephemeris tables and interpolation routines have been incorporated
|
||
|
|
into _WSJT-X_. Further details on accuracy, especially concerning
|
||
|
|
calculated EME Doppler shifts, are described in {lunarEchoes} for
|
||
|
|
November-December, 2016.
|
||
|
|
|
||
|
|
The sky background temperatures reported by _WSJT-X_ are derived from
|
||
|
|
the all-sky 408 MHz map of Haslam et al. (Astronomy and Astrophysics
|
||
|
|
Supplement Series, 47, 1, 1982), scaled by frequency to the -2.6
|
||
|
|
power. This map has angular resolution of about 1 degree, and of
|
||
|
|
course most amateur EME antennas have much broader beamwidths than
|
||
|
|
this. Your antenna will therefore smooth out the hot spots
|
||
|
|
considerably, and the observed extremes of sky temperature will be
|
||
|
|
less. Unless you understand your sidelobes and ground reflections
|
||
|
|
extremely well, it is unlikely that more accurate sky temperatures
|
||
|
|
would be of much practical use.
|