The Radar Echo Telescope for Cosmic Rays (RET-CR) is an experiment to verify the feasibility of the detection of
dense particle cascades in ice using radar. A successful detection at RET-CR would provide crucial insights and guide the subsequent development of the Radar Echo Telescope for Neutrinos (RET-N). RET-CR observes the high-energy cosmic ray air shower core that propagates into the high-altitude ice sheet near the Summit Station in Greenland. A dense secondary cascade is produced in ice, and the plasma left behind is theoretically predicted to be detectable via an in-ice radar system. To understand the in-ice cascade using radar, inputs from cosmic ray air shower reconstructions are also necessary, which will be discussed in this article.