Communications
There are two large driving factors in trying to communicate between Earth and Venus: distance and the Venusian atmosphere.
Alone, these are easily manageable. Taken together, they become a difficult combination to overcome.
Earth Side Communications
We are using NASA's Deep Space Network. There are three locations around the world, 120 degrees apart, that
offer round-the-clock coverage. Much of the probe design was built around interfacing with pre-existing
NASA equipment as outlined in [1].
Venus Side Communications
As demonstrated in [2], the Venusian atmosphere severely attenuates the typical high frequency bands used
for high data rate deep space communication. At the surface, X-band can lose more than 1dB of signal power
per km. The attenuation is even more severe at K and Ka-bands. The natural choice that has been
used since the Soviet Venera program and the US Pioneer-Venus is S-band. This reduces both path loss
due to distance and attenuation in the Venus atmosphere.
No matter the frequency band, there is still a large hurdle to overcome. Through the link budget calculations,
250Watts from three RTGs and a 3m steerable antenna must be combined with Turbo Codes to achieve a 5.11dB link margin
at a Bit Error Rate (BER) of 10^-6. All this to transmit 23.5kbps uncoded, equivalently 47kbps coded, of atmospheric and
seismographic data.
[1] Jet Propulsion Laboratory, Telecommunications and Mission Operations Directorate, "DSMS Telecommunications Link Design Handbook," Rev. E, 2000.
[2] J. M. Jenkins, "Variations in the 13 cm Opacity below the Main Cloud Layer
in the Atmosphere of Venus Inferred from Pioneer-Venus Radio Occultation Studies 1978-1987,"
Doctor of Philosophy in Electrical Engineering, Electrical Engineering, Georgia Institute of Technology, 1992.