Since 2006 bistatic beampark experiments are conducted with FHR's TIRA L-band radar and MPIfR's Effelsberg radio telescope as a secondary highly-sensitive receiver. Due to its 100 m antenna and a cooled receiver objects down to one cm size should be detectable with the radio telescope, which was partly verified with data from the first bistatic campaign in 2006. But the subsequent campaigns 2007 - 2009 indicated an unexpectedly low detection performance which requires a comprehensive investigation of all relevant components of the processing chain, especially the newly developed estimation algorithms. Hence, the focus of this paper will be the revision and validation of the multi-beam estimation and calibration procedures. The results are demonstrated by comparisons based on data of the bistatic beampark campaigns of 2008 and 2009.