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Scintillation study using spacecraft signals

Submitter: Sergei Pogrebenko
Description: The ESA’s Venus Express (VEX) spacecraft was observed by EVN stations at X-band in the framework of the PRIDE (Planetary Radio Interferomery and Doppler Experiments) project initiated by JIVE in 2009. Among other scientific topics, we studied phase scintillations of the spacecraft signal due to the interplanetary plasma (IP) density fluctuations.

It is demonstrated that the scintillation index as measured on time-scales of 300 seconds is proportional to the total electron content (TEC) of the IP, while at larger solar elongations, where the TEC is decreasing, the limiting factor for the phase variations is the stability of clocks at observing VLBI stations. Because the S/C transmitter is phase-locked to the H-maser of the ESA’s transmitting station Cebreros (Spain), which is supposed to be of the same quality as the H-maser devices used at EVN stations, we can estimate the overall frequency stability as about or slightly better than 10 to the power of -14.

The VEX carrier signal can be considered as a reference beacon (a kind of remote phase-cal generator) for checking the quality of the VLBI network data acquisition systems and apart from its scientific value is useful for different system tests.
Copyright: JIVE
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