Searching for cosmic Ray radar echoes in Tara Data

The TARA (Telescope Array Radar) cosmic ray detector has been in operation for over two years. This bistatic CW radar detector was designed with the goal of detecting the radar echoes of cosmic rays in coincidence with Telescope Array (TA). Thus far, TARA1.5 has operated with a 1.5 kW transmitter broadcasting through a single Yagi antenna into the air above the TA surface detector array. Potential radar echoes are detected in a receiver station 50 km away utilizing a 12.5 MHz USRP2 PC-controlled radio triggered by both the TA fluorescence detector and an independent threshold trigger. In spring 2013 a 40 kW transmitter with high-gain phased Yagi array was commissioned, increasing the power available for radar scattering by a factor of over 300 (TARA40). Additionally we have deployed a 250 MHz sample rate detector employing intelligent self-triggering algorithms that can detect radar echo signals below the level of sky noise, thus increasing sensitivity by another two orders of magnitude in power. Together these advances make TARA40 the most ambitious effort by far to test the hypothesis that cosmic ray air showers can scatter RF waves. The focus of this paper is to describe the analysis used in comparing TARA radar triggers with TA data, including both a synopsis of TARA1.5 findings and preliminary results from the TARA40 configuration.