Radio doppler experiment (astro)

[hangainlover]

Ive been going through some landers of Venus and Mars and I found they were equipped with radio doppler experiment(http://en.wikipedia.org/wiki/Venera_9 )

I was wondering what this does.
I mean there is radio signal transmitted through space everywhere and i suppose the device would measure this transmitted radio.
But is there doppler shift because the planet the lander is on is orbitting the Sun?
If the planet orbitting the Sun is the reason for doppler shift, is the doppler shift experiment simply to measure how fast the planet is going?

 

[Janus]

If I had to guess, I'd say that it had to do with wind speed measurements. Something akin to the Doppler radar we use for weather forecasting.

 

[Bobbywhy]

This is not a guess.

Planetary Radio Interferometry and Doppler Experiment (PRIDE) for the Europa
Jupiter System Mission
Major components of the initiative scientific study and R&D activity:
1. VLBI tracking of the planetary probes
2. Doppler tracking in the One-Way or Multi-Way signal reception mode
3. Propagation media effects study
4. Direct-to Earth telemetry data reception from planetary probes, landers, penetrators, etc
5. Passive radio spectroscopy of the natural molecular lines from planetary environments

www.planetaryprobe.eu/IPPW7/proceedings/.../Session3/pr525.pdf

There is a specific experiment for measuring the wind speed on Jupiter during the descent of a spacecraft . Google is your friend here.

 

[Chronos]

In the Venera 9 mission, radar doppler instruments were primarily intended for bistatic mapping of the surface of Venus, which would permit extraction of surface profiles. For further details see http://www.mentallandscape.com/V_RadarMapping.htm

 

[pmacias]

The radio doppler experiment on the Venera 9 lander was used to study the atmosphere and ionosphere of Venus. It works by transmitting a radio signal from the lander and then receiving the reflected signal back. The frequency of the reflected signal is then compared to the original transmitted signal, and any differences in frequency indicate the presence of atmospheric or ionospheric disturbances.

The Doppler shift in this case is caused by the relative motion between the lander and the reflected signal. As the lander moves through the atmosphere, the reflected signal will have a slightly different frequency due to the Doppler effect. This allows scientists to study the composition and dynamics of the atmosphere and ionosphere of Venus.

The Doppler shift experiment is not simply to measure the speed of the planet, but rather to gather information about the planet's atmosphere and ionosphere. By analyzing the Doppler shift, scientists can determine the speed and direction of winds, the presence of atmospheric layers, and other important data about the planet's atmosphere. This information is crucial for understanding the climate and composition of Venus and Mars, and can also provide insights into the formation and evolution of these planets.