HOLOGRAPHIC SCANNING LIDAR TELESCOPES Geary K. Schwemmer Laboratory For Atmospheres NASA Goddard Space Flight Center

OUTLINEOUTLINE m Objectives m Applications & ESE Science m Current State-of-the-Art m Current and Future Directions

OBJECTIVEOBJECTIVE m Decrease weight, volume, and cost of scanning lidar receivers by factor of 3 – 10 (and more) using Holographic Optical Elements (HOEs) m Combine with composite materials, membrane optical flats, or aerogels for featherweight optics

TARGET APPLICATIONS m DIRECT DETECTION WIND LIDAR m TOPOGRAPHIC MAPPERS (ALTIMETERS) m 3-D ATMOSPHERIC STRUCTURE AND DYNAMICS (CLOUD AND AEROSOLS, TRACE SPECIES)

ESE Science Themes n Global Change –atmospheric water vapor, topographic mapping: –How are global precipitation, evaporation, and the cycling of water changing? –What changes are occurring in the mass of the earth's ice cover? n Variability Forcings – atmospheric aerosols & greenhouse gases, topographic mapping : –What trends in atmospheric constituents and solar radiation are driving global climate? – What changes are occurring in global land cover and land use, and what are their causes? –How is the earth's surface being transformed and how can such information be used to predict future changes? n Responses – cloud heights and fractions, topographic mapping, atmospheric pollution –What are the effects of clouds and surface hydrologic processes on earth's climate? –How is global sea level affected by climate change? –What are the effects of regional pollution on the global atmosphere, and the effects of global chemical and climate changes on regional air quality? n Consequences –topographic mapping : –What are the consequences of climate and sea level changes and increased human activities on coastal regions? n Prediction – better weather and climate data –How can weather forecast duration and reliability be improved by new space-based observations, data assimilation, and modeling?

Prototype Holographic Atmospheric Scanner for Environmental Remote Sensing (PHASERS) pic_diagram.htm Holographic Airborne Rotating Lidar Instrument Experiment (HARLIE) HOE LIDAR INSTRUMENTS

 HOE Fields of view Foci SHared Aperture Diffractive Optical Elements (SHADOE)

5-HOE Pushbroom Lidar Imager Footprint

Technology Development Milestones m 355 nm laboratory prototype for wind lidar applications. m 1 meter diameter HOE for space m SHADOE - several optically addressable, fixed look angles in one film. No moving parts. m Holograms applied to featherweight composite or stretched membrane substrates.

Backup slides follow

HOE LIDAR TRANSCEIVER Transmission HOE used as a scannable laser collimating lens and receiver collecting lens

SummarySummary m Rotating HOE Cuts size and weight of scanning lidar receivers in 1/2 - 1/3. m Targeted Lidar Missions m Demonstrated HOE performance for nm wavelength systems m Two operating HOE lidars green and near-IR (TRL 6) m Further reductions in weight, size, and complexity using SHADOE (TRL 2)

HOE PERFORMANCE m 80-85% diffraction efficiency in 1st order   rad focal spots (87% of total energy in diffracted order) m 1064, 1047, 905, 770, 532, 523, 355 nm wavelengths m up to 40 cm diameter, f/2.5

HOLOGRAPHIC OPTICAL ELEMENT (HOE) Reflection HOE Construction / reconstruction Reference beam Object beam