Radio frequency noise during reentry

In flight, measurements of the effective noise temperature of a reentry plasma are compared with computed data. The vehicle utilized for the experiment was the Trailblazer II. The measurements were made at a frequency of 2235 MHz and transmitted to the ground in real time byX-band telemetry. Noise temperatures in excess of5000 were recorded. The flight data also demonstrate the importance of antenna location and angle of attack in determining the performance of an RF system. Another result of the flight has been to point out the power of temperature measurements as a diagnostic tool for flow field studies.