THOR System: Cloud THickness from Offbeam lidar Returns Co-Investigators:Robert Cahalan/913 & Matthew McGill/912 Chief Engineer:John Kolasinski/565 Optical Engineer:Luis Ramos-Izquierdo/924, SSAI  Source: 523 nm, 300 uJ, 1 kHz  Detector: 6° FoV, 25.4 mm focal plane  Annular concentric bundles  Photon Counter Detectors (10)  Data System from Cloud Lidar Conventional lidars “see” only thin cloud,  < 2 For  > 2, most reflection diffuse    Space laser spotsize > 100 meters Why study diffuse signal? THOR System

THOR Proof of Concept  Initial obs with Spinhirne Lidar   Signal detected in daytime out to 12° !  No angular averaging, only time-average  Realistic thicknesses “Cloud” properties  r eff, H) known Realistic sizes, mfp ÷ 1000 ≈ 10 cm Scale ~ Sqrt ( mfp*  ) Laboratory “Clouds”  Real Clouds 

THOR Fiber Bundle Array 1. Micropulse lidar: 523 nm, 300 uJ, 1 kHz 2. GSFC-designed Telescope: 6° FoV, 25.4 mm f.p. 3. Annular bundles O.D.  2 n  constant signal 4. Hamamatsu Photon-counting PMT Detectors 25.4 mm OD, roughly 250,000 fibers ea. 50  m OD (200  m center) Eight concentric rings, doubling in radius Outer in 3 sectors, 50,000 fibers each. Rings 3 - 7: OD = 0.8, 1.6, 3.2, 6.4, 12.7 mm Improved version: >> concentricity >> homogeneity

THOR System Telescope designed at Goddard, built by Model Optics, MA Bundle designed at Goddard, built by FiberOptic Systems, CA Hamamatsu Detectors  Data System - Cloud Lidar heritage 2. Telescope 3. Fiber Bundle 4. PMT’s nm Lidar Expander Steerer, 5. Data System Optics aligned on collimator First Msmts planned for March

Fiber Imaging on Collimator 39 fibers in Ring 2, but ~150,000 in Ring 8 Improvements planned under DDF Goal : errors < 1% concentric, < 5% uniform

Data Acquisition DAQ cards dev under contract for Cloud Lidar Data system upgradeable for ER-2 Timing goal: 15 m range gates

THOR “First Light” - March 8,

THOR Road Map TimeActivityResources Summer ‘01Ground-based 1 GSFC, Wallops Spring ‘02THOR Val on P3 2 Wallops  ARM site –P3 at 30 K ft, cloud top below 5 K ft. –ARM MPL cloud base, 30 m resolution Fall ‘03THOR ER-2 Certification Spring ‘03THOR ER-2 Mission radar, A-band Summer ‘03co-fly AMSR on P3 3 Antarctic night 1.Possible MPL overflights with THOR on ground 2.Engineering model on P3, upgrade for ER2, or WB57, etc 3.Co-fly w/ Aqua val, Antarctica:’03 (J. Comiso)

THOR-Val Experiment at ARM/SGP ItemResources THOR Aircraft 1 NASA-P3 –Mounting and laborWallops –Dedicated P3 is $3.6 K per flight hour –20 hours at DoE/ARM/SGP  $72 KMcConnell AFB, Wichita P3 over ARM SGP 2 MPL, Radar –Thickness accuracydz ~ 30 m, dx ~ 500 m –Time on site10 days –Suggested TimeframeSpring 2002 Later: ER-2 Validation Activities Onboard: Cl.Radar, Cloud Lidar, A-band Testing & Certification 4 1.Initial engineering flights on P3, upgrade 4 ER-2 2.THOR  Wallops may enable overflights 3.Co-fly w/ Aqua val, Antarctica: ‘02,’03 (Comiso) 4.ER-2 Cert requirements

THOR Challenge: Wide-angle Solar Filter Source TypeIV, Nd:YALO, 540 nm Repetition Rate1 kHz Pulse Energy170  J Pulse Width 8 ns Beam Waist4 mm Beam Divergence215  rad Detectors Telescope8” f/1.25, 6° FoV, f.p. Channel 1d1 = 200  m Channels 2 –7dn = 2 X dn-1 Channels 8–10120° sectors, d8 = 25.6 mm PMTsHamamatsu, single photon Data System215  rad Problem: How to filter Sun = 10 8 *signal? Need ±0.01 nm for 6° FoV. Dispersion filter selects wavelength by selecting angle. –Requires collimated beam. Faraday cell rotates polarization plane to select wavelength. –Faraday cell successfully used on ground. –Air/satellite use of magnetic fields problematic due to shielding and power. In space FoV ~ 1 milli radian. Wide angle solar filters might use other polarization effects, e.g. birefringence. Wideangle filters have other applications, e.g. filter out Earth in communications.