RADAR echoes can provide information about the atmospheric constituents like water vapor,temperature, wind etc. Now, if we send a vhf/uhf signal from space and receive it on earth, will it be possible to extract any information of the atmosphere using that signal?
take a look a the attached link.
best regards
Article VHF radar observation of atmospheric winds, associated shear...
Hirakjyoti,
I guess this depends on the frequencies you include within the signal, and the way they are individually affected by atmospheric phenomena.
Depending on the beam frequency and the atmospheric environment, the frequencies could be attenuated, absorbed, reflected, refracted, diffracted, or simply passed unaffected !
So if the beam frequencies and the effects are carefully segregated and observed, I guess atmospheric phenomena can be selectively interpreted.
And Andrea has already provided one such example.
-Sanjay
Dear Goswami,
Initially, you need to have a huge data of various environment conditions when a signal is transmitted through it.
Then, in your experimentation after accumulation of the data, compare them and extract the information of the atmosphere. In fact, this is a ideal analogy.
you need to take care of frequencies, distances b/w transmitter and receiver (Stored data case and experimentation case, whether conditions).
Thanks for your valuable replies. Instrumentation and data collection is not a problem. The main doubt related to this work is , whether the VHF/UHF absorption spectra will carry information about the medium as optical signals do when passed through a gaseous medium. It is well known that optical absorption spectra gives information related to the gaseous medium through which light is passed. More over we all know about the attenuation of d2h signal by severe weather conditions. So is there any literature where i can get some information regarding the VHF/UHF absorption spectra.
If you know the precise position of the transmitter then by measuring the direction of arrival of the signal, again very precisely, you will be able to measure the atmospheric refraction. Furthermore if you use linear polarisation and you happen to know the orientation of the transmitting antenna then by measuring the polarisation angle on reception you will get knowledge of the total electron content of the upper atmosphere. The effect is known as Faraday Rotation and occurs due to the free electrons moving under the combined influence of the radio frequency field and the Earth's static magnetic field. To get the total electron content unambiguously you need to use several closely space VHF frequencies.
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