Rocket measurement of a daytime electron-density profile up to 620 kilometers

On April 27, 1961, a four-stage research rocket was fired from Wallops Island, Virginia, to measure the ionospheric electron-density distribution by means of Seddon's [1953] CW propagation technique. This experimental technique is based upon the measurement of the dispersive Doppler effect at two harmonically related frequencies—in this instance, f = 12.267 Mc/s and 6 f = 73.6 Mc/s. The actually measured quantities in the CW propagation experiment are the beat frequencies due to the difference between the received high- and low-frequency signals, the latter multiplied by the factor 6 at the ground, for the two magnetoionic components. These beat frequencies can be expressed by where c is the velocity of light in vacuo, n(h) is the refractive index at the high frequency (73.6 Mc/s), n(l) that at the low frequency (12.267 Mc/s), and the subscripts o and x refer to the ordinary and extraordinary modes, respectively, and ṙ is the rocket velocity in the ray direction.