Our latest development on USRP-based beacon satellite receiver has been accepted for publication in Radio Science. An early access version is available here. The project website is at Juha's personal page.
The reference is:
J. Vierinen, J. Norberg, M. S. Lehtinen, O. Amm, L. Roininen, A. Väänänen, P. J. Erickson and D. McKay-Bukowski, Beacon satellite receiver for ionospheric tomography, Radio Science, doi: 10.1002/2014RS005434.
... and here is the abstract:
Beacon satellite receiver for ionospheric tomography
We introduce a new coherent dual channel beacon satellite receiver intended for ionospheric tomography. The measurement equation includes neutral atmosphere and ionosphere propagation effects, relative errors in satellite and receiver clocks, and residual Doppler shifts caused by errors in the satellite ephemeris. We also investigate the distribution of errors for phase curve measurements and the use of phase curve measurements for limited angle tomography using the framework of statistical linear inverse problems. We describe the design of our beacon satellite receiver software, and present one possible hardware configuration. Finally, we present results obtained using a network of four newly developed receivers and compare the results with those of an existing ionospheric tomography network at Sodankylä Geophysical Observatory.