Analysis of Sky Profile Data (for low atmospheric attenuation)
Joachim Köppen Kiel April 2017

Some brief explanations

This utility allows to determine the system temperature of a radio telescope and the sky temperature from the measurements of the radio noise of the empty sky taken at several elevations. The analysis is accurate only for small attenuation by the Earth atmosphere, hence for frequencies below 10 GHz.
Since the thermal emission of the Earth atmosphere is proportional to the path length through the atmosphere, which is well approximated by a thin planar sheet, the measured signal increases linearly with the airmass, which is 1/sin(elevation). Ignoring any empty input fields, the tool fits any available valid data with a straight line. The sloping part is the sky emission component which is characterized by the zenith temperature. An elevation-independent component is due to the internal noise of the receiving system, which is described by the telescope's system temperature. The isotropic 2.7 K cosmic microwave background is subtracted.
To obtain these temperatures in absolute terms, it is necessary to measure also the radiation from the ground, a building, or a forest which serve as a flux calibrator with the physical temperature of 290 K.
The analysis and the plot are updated by clicking the Enter key after entering a datum (elevation or power).
Elevation power [dB]

System temperature
Zenith temperature
Mouse position:

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