GWOLF and VALIDAR Comparisons M. Kavaya & G. Koch NASA/LaRC D. Emmitt & S. Wood SWA Lidar Working Group Meeting Sedona, AZ January 2004

Outline NASA/LaRC’s Lidar Intercomparison Facility VALIDAR GWOLF –VALIDAR intercomparisons –Hard target experiments –Cloud returns –Vertical motion

Lidar Intercomparison Facility (LIF) at NASA Langley Research Center

Lidar Intercomparison Facility Features: Inside NASA grounds Paved parking lot for up to 4 lidar systems Row of surveyed marks on parking lot with 32-foot spacing Row of 4 target lights on tall structure with 32-foot spacing Surveyed positions of lidars and targets allows for parallel alignment among the lidars Target lights at 677-m range, and 6° elevation angle Target lights atop poles allowing atmospheric data collection while aimed at lights Utilities available including telephone, intercom, internet, and electrical power

VALIDAR & GWOLF at the Lidar Intercomparison Facility Location Of Target Lights Bldg 1297 R-B-Y-G

View Of Lidars From The Target Lights’ Location Location Of Lidars Bldg 1159

Lidar Intercomparison Facility Possible Enhancements: Lidar aim compensation for differing beam departure heights Calibrated flat targets mounted on flat structure or at ground level for horizontal path Calibrated velocity moving targets (> ? m/s) Detectors near the target lights to confirm lidar aiming Ancillary in situ and/or lidar sensors

Validar Objectives: Demonstrate advanced 2-  m lidar components in a complete lidar system. High-energy lasers, receiver optics, detectors, and electronics are being developed at LaRC from a variety of funding sources. Validar serves as a testbed for this development. Make field measurements as required for validation. FY ’04 Specifications are - laser pulse energy = 100 mJ (78 mJ) - pulse repetition rate = 5 Hz (10 Hz) - pulse width = 150 ns - wavelength = nm

Lidar Specifications FY 02 FY 03 FY 04 (water cooled) (cond. cooled) (cond. cooled) pulse energy 30 mJ 83 mJ (65 mJ) 100 mJ (78 mJ) pulse rep. freq. 5 Hz 5 Hz (10 Hz) 5 Hz (10 Hz) wavelength nm nm nm pulse length 180 ns 150 ns 150 ns spectrum single freq. single freq. single freq.

VALIDAR Trailer Lidar System Data Analysis & Visitors Rooms Validation Lidar Facility

Validation Lidar (VALIDAR) Facility: Well-instrumented 48 ft long Trailer  Hemispherical Scanner with 20 cm effective aperture  Elaborate Video System consisting of 2 sets of cameras, monitors, and recorders  Weather Station  GPS Receiver Powerful state-of-the-art Coherent Doppler Lidar  mJ, 5-10 Hz, Diode-pumped Transmitters  10 cm COTS and 25 cm SPARCLE Telescopes Real-time data processor and display Validation Lidar Facility

GWOLF (Groundbased Wind Observing Lidar Facility) Funded by IPO as part of NPOESS development of cal/val program for space based wind observing systems such as QuikScat, WindSat, CMV, WVMV and future DWLs Currently the TODWL system mounted in a trailer; plan to replace TODWL scanner with a roof mounted hemispherical scanner.

Validar/GWOLF Comparisons Performed at LaRC’s LIF Horizontal and vertical stares 200m resolution for Validar 1 minute averaging

GWOLF hard target and threading Performed at LaRC’s LIF Using corrugated metal enclosed elevator shaft at 677 meters from lidar as hard target 100 meter range gates 5 peak threading

Cloud returns Performed at LaRC’s LIF Objective is to understand how to process and interpret GWOLF returns from cloud boundaries (large ~ dB backscatter gradients)

Vertical velocity from VADs Performed at LaRC’s LIF Question is “ How accurate and reliable is the estimate of the vertical velocity using the offset in the sine fit of a partial VAD” Interweaved a 25 second vertical stare into a 7 point partial VAD.

Summary The LaRC’s Lidar Intercomparison Facility enables long term, iterative evaluation of specific lidar performance issues. –Cloud boundary returns, hard target (ground surrogate) returns, instrument stability and low SNR signal processing investigations Plan is to bring direct detection systems to LaRC for detailed investigations of both individual as well as hybrid wind sensing issues.

Clouds Backscatter values based upon backscatter data at wavelengths other than 2 microns Modeled to 2 microns (rather wavelength independent) Cirrus (0 to -37 C): 7.0 E-5 m -1 sr -1 Warm, opaque: 1.8 E-5 m -1 sr -1

Per hard target calibration Per current theory TODWL 03

Cirrus at 5800 m agl

Lidar Design