Application of complementary optical and incoherent scatter radar techniques has detected the presence of Ca+ in lower thermospheric intermediate layers over Arecibo. The altitude distribution and density of the calcium ion is inferred from the variation of twilight resonant scattering with solar depression angle while the Arecibo 430 Mhz radar measured electron densities. Comparison between the Ca+ and electron column densities indicates that the composition of low-altitude intermediate layers was 2% Ca+. This value is consistent with both rocket mass spectrometer measurements and with the relative concentration of calcium expected for meteoric debris. These results have implications regarding both possible nighttime tropical E region ionization sources and metal ion circulation in the tropical thermosphere.