WE PROPOSE TO DEVELOP PHOTON-COUNTING KINETIC INDUCTANCE DETECTORS (KIDS) FOR THE ORIGINS SPACE TELESCOPE (OST) AND ANY PREDECESSOR MISSIONS WITH THE GOAL OF PRODUCING BACKGROUND-LIMITED PHOTON-COUNTING SENSITIVITY AND WITH A PRELIMINARY TECHNOLOGY DEMONSTRATION IN TIME TO INFORM THE DECADAL SURVEY PLANNING PROCESS. THE OST A MID- TO FAR- INFRARED OBSERVATORY CONCEPT IS BEING DEVELOPED AS A MAJOR NASA MISSION TO BE CONSIDERED BY THE NEXT DECADAL SURVEY WITH SUPPORT FROM NASA HEADQUARTERS. THE OBJECTIVE OF SUCH A FACILITY IS TO ALLOW RAPID SPECTROSCOPIC SURVEYS OF THE HIGH REDSHIFT UNIVERSE AT 420-800 M USING ARRAYS OF INTEGRATED SPECTROMETERS WITH MODERATE RESOLUTIONS (R= ~1000) TO CREATE A POWERFUL NEW DATA SET FOR EXPLORING GALAXY EVOLUTION AND THE GROWTH OF STRUCTURE IN THE UNIVERSE. A SECOND OBJECTIVE OF OST IS TO PERFORM HIGHER RESOLUTION (R~10 000-100 000) SPECTROSCOPIC SURVEYS AT 20-300 M A UNIQUELY POWERFUL TOOL FOR EXPLORING THE EVOLUTION OF PROTOPLANETARY DISKS INTO FLEDGLING SOLAR SYSTEMS. FINALLY THE OST AIMS TO OBTAIN SENSITIVE MID-INFRARED (5-40 M) SPECTROSCOPY OF THERMAL EMISSION FROM ROCKY PLANETS IN THE HABITABLE ZONE USING THE TRANSIT METHOD. THESE OST SCIENCE OBJECTIVES ARE VERY EXCITING AND REPRESENT A WELL-ORGANIZED COMMUNITY AGREEMENT. HOWEVER THEY ARE ALL IMPOSSIBLE TO REACH WITHOUT NEW DETECTOR TECHNOLOGY AND THE OST CAN T BE RECOMMENDED OR APPROVED IF SUITABLE DETECTORS DO NOT EXIST. IN ALL OF THE ABOVE INSTRUMENT CONCEPTS PHOTON-COUNTING DIRECT DETECTORS ARE MISSIONENABLING AND ESSENTIAL FOR REACHING THE SENSITIVITY PERMITTED BY THE CRYOGENIC ORIGINS SPACE TELESCOPE AND THE PERFORMANCE REQUIRED FOR ITS IMPORTANT SCIENCE PROGRAMS. OUR GROUP HAS DEVELOPED AN INNOVATIVE DESIGN FOR AN OPTICALLY-COUPLED KID THAT CAN REACH THE PHOTON-COUNTING SENSITIVITY REQUIRED BY THE AMBITIOUS SCIENCE GOALS OF THE OST MISSION. A KID IS A PLANAR MICROWAVE RESONATOR PATTERNED FROM A SUPERCONDUCTING THIN FILM WHICH RESPONDS TO INCIDENT PHOTONS WITH A CHANGE IN ITS RESONANCE FREQUENCY AND DISSIPATION. THIS DETECTOR RESPONSE IS INTRINSICALLY FREQUENCY MULTIPLEXED AND CONSEQUENTLY KIDS AT DIFFERENT RESONANCE FREQUENCIES CAN BE READ OUT USING STANDARD DIGITAL RADIO TECHNIQUES WHICH ENABLES MULTIPLEXING OF ~10 000S OF DETECTORS. IN OUR PHOTON-COUNTING KID DESIGN WE EMPLOY A SMALL-VOLUME (AND THIN) SUPERCONDUCTING AL INDUCTOR TO ENHANCE THE PER-PHOTON RESPONSIVITY AND LARGE PARALLEL-PLATE NBTIN CAPACITORS ON SINGLE-CRYSTAL SILICON-ON-INSULATOR (SOI) SUBSTRATES TO ELIMINATE FREQUENCY NOISE. WE HAVE DEVELOPED A COMPREHENSIVE DESIGN DEMONSTRATING THAT PHOTON-COUNTING SENSITIVITY IS POSSIBLE IN A SMALL-VOLUME AL KID. IN ADDITION WE HAVE ALREADY DEMONSTRATED ULTRA-HIGH QUALITY FACTORS IN RESONATORS MADE OF VERY THIN (~10 NM) AL FILMS WITH LONG ELECTRON LIFETIMES. THESE ARE THE CRITICAL MATERIAL PARAMETERS FOR REACHING PHOTON-COUNTING SENSITIVITY LEVELS. IN OUR PROPOSED WORK PLAN OUR OBJECTIVE IS TO IMPLEMENT THESE HIGH QUALITY FILMS INTO OUR OPTICALLYCOUPLED SMALL-VOLUME KID DESIGN AND DEMONSTRATE PHOTON-COUNTING SENSITIVITY. THE SUCCESSFUL DEVELOPMENT OF OUR PHOTON-COUNTING TECHNOLOGY WILL SIGNIFICANTLY INCREASE THE SENSITIVITY OF THE OST MISSION MAKING IT MORE SCIENTIFICALLY COMPETITIVE THAN ONE BASED ON POWER DETECTORS. PHOTON-COUNTING AT THE BACKGROUND LIMIT PROVIDES A X4 INCREASE IN OBSERVATION SPEED OVER THAT OF BACKGROUND-LIMITED POWER DETECTION SINCE THERE IS NO NEED TO MEASURE AND SUBTRACT A ZERO POINT. PHOTON-COUNTING DETECTORS WILL ENABLE AN INSTRUMENT ON THE OST TO OBSERVE THE FINE STRUCTURE LINES OF GALAXIES WHICH ARE CURRENTLY ONLY OBSERVABLE AT REDSHIFTS OF Z~1 OUT TO REDSHIFTS OF Z=6 PROBING THE EARLY STAGES OF GALAXY STAR AND PLANET FORMATION. OUR PHOTONCOUNTING DETECTORS WILL ALSO ENABLE ENTIRELY NEW SCIENCE INCLUDING THE MAPPING OF THE COMPOSITION AND EVOLUTION OF WATER AND OTHER KEY VOLATILES IN PLANET-FORMING MATERIALS AROUND LARGE SAMPLES OF NEARBY YOUNG STARS.