WE WILL DEVELOP A SOFTWARE-DEFINED PULSE MODULATOR AND INTEGRATED SEED LASER SYSTEM FOR OPTICAL COMMUNICATIONS BETWEEN SMALL SPACECRAFT INCLUDING CUBESATS USING A PULSE POSITION MODULATION SCHEME. THIS TECHNOLOGY WHICH HAS BEEN DEVELOPED TO TRL 3 AT THE UNIVERSITY OF FLORIDA UNDER A PREVIOUS EARLY CAREER FACULTY GRANT CAN GENERATE<1 NANOSECOND-WIDE 1550 NM OPTICAL PULSES WITH<50 PICOSECOND TIMING ACCURACY. SINCE THE PULSE TIMING IS GENERATED USING SOFTWARE-DEFINED PRECISION DELAYS WITHIN AN FPGA IT DOES NOT REQUIRE A POWER HUNGRY ~20 GHZ SLOT CLOCK OR PROCESSOR. INSTEAD A 10 MHZ CHIP-SCALE ATOMIC CLOCK CONSUMING ONLY ~100 MW IS USED TO CONTINUOUSLY CALIBRATE THE TIMING DELAY CHAIN. THE MODULATOR IS PAIRED WITH AN AVALANCHE PHOTODETECTOR-BASED RECEIVER WITH A MEASURED ~50 PS TIMING ACCURACY. THE PROPOSED TECHNOLOGY ADDRESSES TOPIC 2: CROSS-LINKING COMMUNICATIONS SYSTEMS. THE PROPOSED MODULATOR AND RECEIVER ARE PARTICULARLY INTERESTING FOR CROSS-LINKS BETWEEN SMALL SATELLITES WHERE THE TRANSMITTED ELECTROMAGNETIC WAVE NEED NOT PROPAGATE THROUGH THE EARTHS IONOSPHERE WHICH TYPICALLY LIMITS TIMING PRECISION TO NO BETTER THAN ~100 PS. THE IMPROVED TIMING RESOLUTION OF THIS SYSTEM COMPARED WITH PREVIOUS TECHNOLOGIES MEANS THAT MORE BITS OF DATA ARE TRANSMITTED WITH EACH OPTICAL PULSE. IT IS ALSO IMPORTANT TO NOTE THAT SINCE THE PROPOSED TECHNOLOGY CAN BOTH GENERATE AND TIME-STAMP THE ARRIVAL OF SHORT OPTICAL PULSES WITH ~50 PS PRECISION IT SIMULTANEOUSLY PROVIDES POWER EFFICIENT COMMUNICATIONS AND RELATIVE RANGING BETWEEN SMALL SPACECRAFT AT THE CM-LEVEL. THIS PROJECT WILL BE A COLLABORATION WITH THE NASA AMES RESEARCH CENTER. IT WILL ALSO COMPLEMENT RELATED RESEARCH PERFORMED BY PROFESSOR KERRI CAHOY AT MIT. THE MODULATOR /SEED LASER AND THE PHOTORECEIVER WILL BE DEVELOPED AT THE UNIVERSITY OF FLORIDA AND EACH WILL BE INTEGRATED INTO A SINGLE CUBESAT-COMPATIBLE ELECTRONICS BOARD. COMMUNICATIONS PROTOCOLS WILL BE MADE COMPATIBLE WITH THE NASA AMES EDSN-DERIVED CUBESAT BUS ALLOWING FOR A SMOOTH TRANSITION TO A FUTURE FLIGHT DEMONSTRATION. THE MODULATOR AND RECEIVER WILL BE INTEGRATED WITH A COMMERCIAL FIBER LASER AMPLIFIER AND A FAST BEAM-STEERING MIRROR PROVIDED BY MIT. IN RETURN UF WILL PROVIDE A PHOTORECEIVER TO MIT FOR TESTING WITH THEIR OPTICAL COMMUNICATIONS SYSTEM. POINTING REQUIREMENTS WILL BE EVALUATED BASED ON THE SELECTED LASER PULSE ENERGY AND COMMUNICATIONS ACQUISITION STRATEGY AS WELL AS ON THE ATTITUDE ACTUATION AUTHORITY OF THE EDSN CUBESAT BUS WHICH RELIES ON A SET OF REACTION WHEELS FOR ATTITUDE CONTROL. THE COMPLETE CROSS-LINK OPTICAL COMMUNICATIONS SYSTEM WILL BE TESTED IN THE LABORATORY AND DRIVEN BY A CONTROLLER THAT IS EQUIVALENT TO THE EDSN COMMAND AND DATA HANDLING SYSTEM. AT THE CONCLUSION OF THIS WORK THE TECHNOLOGICAL READINESS OF THE MODULATOR AND RECEIVER WILL BE AT A POINT WHERE THEY WILL BE READY FOR A FLIGHT DEMONSTRATION.