TCP/IP Communications over Iridium Satellite Modems Nick Spera Faculty Mentor: Dr. Gary Gear NASA Mentor: Larry Freudinger Saturday, April 19, 2008 Embry-Riddle Aeronautical University Electrical Engineering NASA Dryden

Motivation Long-range science missions Retrieve data from polar sensors Artic ice flows, climate change, etc.

Problem Line-of-sight is not a possibility No access to military satellites Must work with Linux

Solution Iridium network works globally and is readily available However, Iridium is limited to 2400bps Multiple channels are aggregated to increase data rate - MultiLink

Diagram Physical Iridium Physical Satellites Logical Linux Linux MultiLink Linux PC Linux PC Logical MultiLink Base Station Sensor Data

MultiLink Viable solution, readily available and cost-effective Complications: TEQL Dropped links TCP/IP issues unique to our environment MPPP Robustness of the configuration

Success and Conclusion After months of research and vigorous trial and error, a workable solution was still out of reach Embry-Riddle students suggested an alternate approach using different software (MPPP instead of TEQL) This shift in direction brought immediate results and allowed NASA to begin finalizing and polishing the system