Investigations to characterize multijunction solar cells in the stratosphere using low-cost balloon and communication technologies

The use of current balloon, control and communication technologies to test multi-junction solar cells in the stratosphere to achieve near AMO conditions has been investigated. The design criteria for the technologies are that they be reliable, low cost and readily available. Progress is reported on a program to design, launch, fly and retrieve payloads dedicated to testing multi-junction solar cells. The system investigated includes a state-of-the-art multi-junction solar cell and two-axis suntracker that weighs less than one pound. Data acquisition is carried out with a module that employs programmable microprocessors, A/D converters, digital I/O lines, AX.25 encoding, GPS, and VHF, UHF and HF transmitters. One flight has been carried with a 1000 gram extensible helium balloon and payload that weighed under six pounds. During a flight that lasted about two hours, the balloon traveled to an altitude of 87,000 feet and data were downlinked. The payload was retrieved about 40 miles from the launch site.