Ionosphere electron-density measurements with the Navy Aerobee-Hi rocket

Electron densities in the ionosphere above White Sands, New Mexico, were measured continuously from the E region up to the lower F2 region with the Aerobee-Hi NRL No. 50, a rocket instrumented by the U.S. Naval Research Laboratory. This rocket was fired at 12:09 p.m. MST on 29 June 1956 and reached an altitude of 263.7 km. The method1 used consists in refractive index measurements based on propagation phenomena. Two harmonically related c-w signals, at 7.75 Mc and 46.5 Mc, respectively, are transmitted from the moving rocket to two receiving stations on the ground. The rocket motion causes each signal to experience a Doppler shift, which is related to the refractive index of the medium near the rocket. The high frequency is used as a reference, since its index is essentially unity. Comparison techniques used on the ground plus a knowledge of the rocket trajectory yield, as a function of altitude, the 7.75-Mc refractive indices for both ordinary and extraordinary rays. Since the electron density can be computed from either index, a check of the internal consistency of the data is possible.