First HF radar measurements of summer mesopause echoes at SURA

HF sounding of the mesosphere was first carried out at SURA in summer 1994 at frequencies in the range 8–9 MHz using one of the sub-arrays of the SURA heating facility. The observations had a range resolution of 3 km. Almost all measurements indicated the presence of strong radar returns from altitudes between 83 and 90 km with features very similar to VHP measurements of mesopause summer echoes at mid-latitudes and polar mesopause summer echoes. In contrast to VHP observations, HF mesopause echoes are almost always present.