This paper focuses on the processing of experimental data collected with a small modular GPS bistatic radar software receiver on a balloon flight. The receiver is designed for remote sensing purposes and the design process will be covered in some detail. GPS bistatic radar focuses on the surfacereflected signal, which can be used to determine properties of the reflection surface, including roughness, ocean wave height and also ranging to the surface. In the past, a mixture of both ASIC-based and software receivers have been used, but these require desktop or laptop computers to operate them. Previous receiver configurations have been prohibitively large and could not be mounted on smaller platforms. This design features two analog front-ends with a common clock, a FPGA and USB bridge to move the digital samples to a Linux-based Single Board Computer. The system features a modular design and allows for easy integration with other analog frontends.Airborne data collected with this instrument near Boulder, Colorado during a balloon flight will be presented. The data from the balloon flight has been processed to extract the height above ground using GPS bistatic radar as an altimeter and the GPS position as a reference. GTOPO30 Digital Elevation Models have been used to estimate the surface elevation used for height estimates in the altimeter. This project opens up new opportunities to perform remote sensing with cheaper and smaller platforms.