prepared by j. rothermel* and s.c. johnson (nasa msfc) p.a. kromis (computer science corporation)
DESCRIPTION
Non-Contact Velocity Measurements on Simulated River Surfaces Using Coherent Doppler Lidar Preliminary Results. Prepared by J. Rothermel* and S.C. Johnson (NASA MSFC) P.A. Kromis (Computer Science Corporation) Earth Science Department NASA Marshall Space Flight Center - PowerPoint PPT PresentationTRANSCRIPT
MSFC/GHCC
12 micron pulsed ground based lidar
Non-Contact Velocity Measurementson Simulated River Surfaces
Using Coherent Doppler LidarPreliminary Results
Prepared by J. Rothermel* and S.C. Johnson (NASA MSFC)P.A. Kromis (Computer Science Corporation)
Earth Science DepartmentNASA Marshall Space Flight Center
Updated by D. Bowdle** (University of Alabama in Huntsville)
MSFC/GHCC
22 micron pulsed ground based lidar
MSFC Coherent Doppler Wind Lidar Initiated April 1999 Purpose:
CDWL technology validationAtmospheric properties researchSpace CDWL concepts investigationCDWL targets researchStudent Instruction
Location:MSFC Building 4467GSFC van (proposed)Van or trailer (future)Aircraft (future)
Initial components:Transceiver, 50 mJ, 6.6 Hz, 2.017 microns, FL pumped10 cm telescope from Schwartz Electro-Optics, Inc.Full hemispheric scanner (Bldg. 4467)Data acquisition & processing
MSFC/GHCC
32 micron pulsed ground based lidar
Long-term Objective
Streamflow Measurement with Doppler Lidar Complement proposed microwave radar measurements Relationship among surface velocity profile, bottom topography, and discharge Based on phased approach Controlled experimental conditions (initial phase) Collaborations with USGS, U. Washington (later phases)
Doppler lidar is only technique that can directlymeasure the influence of near-surface winds
MSFC/GHCC
42 micron pulsed ground based lidar
Background
Water surface velocity measurements depend on: Lidar wavelength Surface roughness Incidence (or nadir) angle Turbidity Surface contaminants (e.g., foam) Depth of penetration (of order millimeters at 2 micron) Near-surface wind velocity
MSFC/GHCC
52 micron pulsed ground based lidar
Target
TargetTarget
Lidar LidarLidar~3
50 m
rang
e
(Very) Preliminary Experiment at MSFC
MSFC/GHCC
62 micron pulsed ground based lidar
Water Slide Geometry
Water slide Nadir Angle
SlitWater Flow
Lidar Beam
MSFC/GHCC
72 micron pulsed ground based lidar
Experiment Parameters MSFC Doppler lidar, 6.6 Hz, 2.017 m Velocities toward lidar are negative (-) Water discharge nozzles: weirgate on new waterslide Water slide surface composition: plexiglass Lidar beam footprint: ~10 cm Discharge depth: several mm (variable) Nadir angles at target: 30, 60 deg Integration: 20 pulses Range gate, velocity plots: 210 m, centered on target Range gate, range plots: 38.4 meters Range to target: ~350 meters Minimum range: ~150 meters Number of good range gates in air near target: ~5
MSFC/GHCC
82 micron pulsed ground based lidar
LEGENDSide rails 2x43/4” p.t. plywd sheetPlate 2x4 Pipe (1-1/4” hvy ga. lined)Suspension tower 2x4Angle iron 1-?”Polycarbonate ?”Aircraft cableBolt
Plan ViewSide View NOTES:
1. Screws--No nails!2. HVHC plywood3. Pres. treated wood4. Zinc coated or
stainless h/w
Guides (polycarb)
Gate (polycarb)
Stick handle
Graduated adjustable stop (wing nut)
Turnbuckle (4)
Water
Capture plate (2)
16” width2’ 3” CL
Water
BeamApproximate
beam footprintduring operation
Open topWaterinlet
Carpet runner
MSFC Water Slide - Version 1.0J. Rothermel/NASA and D.A. Bowdle/UAH
Failsafe line
MSFC/GHCC
92 micron pulsed ground based lidar
NOTES:1. No nails!2. Clear p.t. pine3. Level with blocks4. Level at 4 corners
LEGENDExternal frameMending platePlate 2x4; block 4x4 Pipe (1-1/4” hvy ga. lined)Brace 2x4Capture plateAircraft cableBolts
Plan View
Side View
Winchw/ lock Pulley
RetainerSlide outline
(horizontal position)
To slide
CL
Setscrew
BeamFailsafe line
Failsafe line
Carabiner
MSFC/GHCC
102 micron pulsed ground based lidar
0 20 40 60 80 100 120 140 160 180 200
-4
-3
-2
-1
0
1
2
shot
m
e
t
e
r
s
/
s
e
c
o
n
d
Velocity vs. Shot
Figure 1 – Run 2, 210 Meter Range Gate Centered on Water Target, 30Degree Target Angle, Raw Target PSD Amplitude Threshold – 500,
Raw Target PSD Frequency Window – 750:850
MSFC/GHCC
112 micron pulsed ground based lidar
0 20 40 60 80 100 120 140 160
-2.8
-2.6
-2.4
-2.2
-2
-1.8
-1.6
-1.4
-1.2
-1
shot
m
e
t
e
r
s
/
s
e
c
o
n
d
Velocity vs. Shot
Figure 2 - Run 3, 210 Meter Range Gate Centered on Water Target, 60Degree Target Angle, Raw Target PSD Amplitude Threshold – 500,
Raw Target PSD Frequency Window – 750:850
MSFC/GHCC
122 micron pulsed ground based lidar
0 20 40 60 80 100 120 140 160 180 200
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
shot
m
e
t
e
r
s
/
s
e
c
o
n
d
Velocity vs. Shot
Figure 1 - Run 5, 210 Meter Range Gate Centered on Dry Target, 60Degree Target Angle, Raw Target PSD Amplitude Threshold – 500,
Raw Target PSD Frequency Window – 750:850
MSFC/GHCC
132 micron pulsed ground based lidar
-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.80
10
20
30
40
50
60
70
80
meters/second
shots
Shots vs. Velocity
Figure 1 - Run 5, 210 Meter Range Gate Centered on Dry Target, 60 Degree Target Angle, Raw Target PSD Amplitude Threshold – 500,
Raw Target PSD Frequency Window – 750:850
MSFC/GHCC
142 micron pulsed ground based lidar
Conclusions and Plans Conclusions
Velocity standard deviation for hard target is ~0.1 m/s. Velocity decreases slowly as reservoir empties, allows integrationSurface tension effects from untreated plexiglass slide surface create
flow channeling, with variable water layer thickness non-riverine water surface microstructure
Sanding the plexiglass surface reduces surface tension effectsvirtually eliminates flow channelingnearly mirror smooth water surfaces
PlansResume lidar operations (after minor repairs)Test runs with variable flow velocity and layer thicknessTest runs with controlled surface condition