Temperatures at 85 km around Earth's poles in summer can be so cold that small ice particles form. These can become charged, and, combined with turbulence at these altitudes, they can influence the many electrons present. This can cause large radar echoes called polar mesospheric summer echoes. We use radio waves to heat these echoes on and off when the sun is close to or below the horizon. This allows us to gain some insight into these ice particles and how the sun influences the echoes.