Study of spectrum usage and potential interference to passive remote sensing activities in the 4.5 cm and 21 cm bands

The increasing usage of radio spectrum in both frequency and power, coupled with the vulnerability of passive remote sensing systems to interference, necessitates a better understanding of the existing and predicted usage of the spectral environment. A Radio Spectrum Evaluation System (RSES) has been developed which provides coverage from 400 MHz to 7.2 GHz and offers the capability to observe and analyze spectral usage in multiple dimensions: frequency, power, location space, azimuth, polarization and time. Since passive radiometry can suffer interference at extremely low power levels, this system´s sensitivity has been enhanced by reducing intermodulation distortion and thermal noise. A study of the radio frequency usage in and adjacent to the remote sensing bands at 4.5 cm and 21 cm was undertaken to determine current usage levels and characteristics. These bands are of interest to instruments such as NPOESS/CMIS and ESA/SMOS. While this study was performed in an urban area, additional studies are measuring spectrum usage in suburban and rural environments to assist in predicting future spectral usage and characteristics