Another example I recently came across was the early measurements of the AU using radar. The first two experiments tried to bounce radar off of Venus had very

Another example I recently came across was the early measurements of the AU using radar. The first two experiments tried to bounce radar off of Venus had very noisy data, but they seemed to have a detection that implied a distance that was pretty close to the earlier measurements that had been done using parallax. But after the equipment was upgraded, the detections went away and it turned out that they had just been noise. Later on an even more powerful radar system was able to successfully bounce a radar signal off of Venus and it turned out that the AU was quite a bit different from its earlier value.