Exploration of a free-space optical communications system for sounding rocket sub-payloads

The results of an exploration regarding the novel use of free-space optics (FSO) between sounding rockets and their sub-payloads are presented. This includes an evaluation of optoelectronic and optical devices against environmental and system level criteria. A preliminary test using available in-house components and bench-top equipment was also performed to determine potential distances and data rates of FSO in this environment. Using a light emitting diode with an optical power output of approximately six milliwatts, and a photomultiplier tube originally purposed for use on the Compton Gamma Ray Observatory, a pulse rate of ten kilohertz was transmitted over a distance of four-hundred meters in-atmosphere. Transmission distance was increased to five-hundred meters using an optical bandpass filter, and nine-hundred meters using a baffle. It is expected that even greater distances and data rates can be achieved in the final design by using more transmitters, each with greater optical power output.