Test Report on the November 2005 

NATO RTG-40 Active Imager Land Field Trials 

by David Tofsted, David Quintis, Sean O‘Brien, Jimmy Yarbrough, 

Manuel Bustillos, and Gail Tirrell Vaucher 

ARL-TR-4010 December 2006 

Approved for public release; distribution is unlimited. 
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Army Research Laboratory 

White Sands Missile Range, NM 88002-5501 

ARL-TR-4010 December 2006 

Test Report on the November 2005 

NATO RTG-40 Active Imager Land Field Trials 

David Tofsted, David Quintis, Sean O‘Brien, Jimmy Yarbrough, 

Manuel Bustillos, and Gail Tirrell Vaucher 

Computational Information Sciences Directorate, ARL 

Approved for public release; distribution is unlimited. 
ii 

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4. TITLE AND SUBTITLE 

Test Report on the November 2005 NATO RTG-40 Active Imager Land Field Trials 

5c. PROGRAM ELEMENT NUMBER 

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6. AUTHOR(S) 

David Tofsted, David Quintis, Sean O‘Brien, Jimmy Yarbrough, Manuel Bustillos, and Gail 

Tirrell Vaucher 

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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

U.S. Army Research Laboratory 

Computational and Information Sciences Directorate 

Battlefield Environment Division (ATTN: AMSRD-ARL-CI-EE) 

White Sands Missile Range, NM 88002-5501

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U.S. Army Research Laboratory 

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ARL-TR-4010 

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Approved for public release; distribution is unlimited. 

13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

The NATO Research Technology Group 40 (RTG-40) was established in 2003 to develop improved models of active imaging system 

performance to include the effects of atmospheric optical turbulence. Supporting the development of these models is the performance of naval 

and land field trials to provide data bases of system performance under varying turbulence conditions. In support of the land trials, the U.S. 

Army Research Laboratory’s (ARL) Computational and Informational Sciences Directorate’s Battlefield Environment Division (CISD/BED) 

provided extensive instrumentation as well as range sponsorship and coordination of the measurement program. This report documents the 

major accomplishments by the ARL group in preparation for and during the trials. The experiment was conducted at and sponsored by the 

High Energy Laser Systems Test Facility, located on White Sands Missile Range, NM. The test occurred 7–18 November, 2005. Weather 

conditions were typical for a southern NM in November; with temperatures ranging between 0-30 °C, variable winds, and clear to moderate 

cloud cover. Data were collected during four lasing periods spanning morning or evening neutral events, with additional passive data 

collected whenever possible. Data collected by the ARL team included 20 Hz U-V-W wind speed and temperature data from 4 RM Young 

sonic anemometers mounted at 2.5, 4.5, 6.5, and 8.5 m heights on a mid-range met tower, and 2/3 Hz turbulence (Cn

2

) data collected by 4 sets 

of Lockheed scintillometers set up in pairs (one at 2 m AGL, the other at 4 m) two pairs measuring between 0 and 1 km and another pair 

between 1 and 2 km. In this report we describe the instrumentation, the test, the data collected, and discuss the initial analysis performed on 

the meteorological data collected. 

15. SUBJECT TERMS

Turbulence, scintillometer, active imagers, surface layer, characterization 

16. SECURITY CLASSIFICATION OF:

19a. NAME OF RESPONSIBLE PERSON

David H. Tofsted 

a. REPORT 

U 

b. ABSTRACT 

 U 

c. THIS PAGE 

U 

17. LIMITATION 

OF 

 ABSTRACT 

SAR 

18. NUMBER 

 OF 

 PAGES 

75 19b. TELEPHONE NUMBER (Include area code) 

(505) 678-3039 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18 
iii 

Contents 

List of Figures v

List of Tables vii

Preface viii

Acknowledgments ix

Executive Summary xi

1. Introduction 1

2. The Field Trials 10

2.1 Test Documentation ......................................................................................................10 

2.2 NATO Participants and Their Equipment.....................................................................11 

2.3 HELSTF Access............................................................................................................13 

2.4 Test Logistics ................................................................................................................13 

2.5 Site Layout, Maps, and Tables ......................................................................................14 

2.6 Test Day Planning .........................................................................................................23 

2.7 Post-Test Activities .......................................................................................................25 

3. Initial ARL Data Analysis 25

3.1 Data Acquisition............................................................................................................26 

3.2 Computing Mean and Second Order Statistics..............................................................27 

3.3 Temperature Corrections...............................................................................................30 

3.4 Turbulence.....................................................................................................................33 

3.5 Second Order Statistics .................................................................................................35 

4. Temperature and Wind Spectra and Turbulence Computations 42

5. Conclusion 51

References 52
iv 

Appendix: Scintillometer Calibrations 53

Acronyms and Abbreviations 55

Distribution List 58
v 

List of Figures 

Figure 1. Main test participants from ARL and RTG-40. Not shown are HELSTF and WSMR personnel. ...1

Figure 2. Main downrange test area including observation area, and backstopping target berm at 2 km. .......3

Figure 3. Targets used at 1 km (above) and 2 km, including 8’×8’ registration target (lower left), 3-D targets 

(right), resolution patterns (center), and “eye chart” (above left). ................................................................4

Figure 4. Line of tents sheltering main imagers. From left-to-right are the Canadian ELVISS, Canadian 

LASSIE, Canadian high speed imager, German high speed imager, Swedish Gated Imager, U.K. Burst 

Illumination Laser (BIL), Danish BIL, and U.S. NVESD Active Short Wavelength Infrared (SWIR) 

systems. ...............................................................................................................................................................5

Figure 5. 9 m ARL tower used during testing..........................................................................................................7

Figure 6. Two kilometer (2 km) scintillometers. ARL 2 m scintillometer is on scaffold at left. ARL 4 m 

scintillometer is at second level of scaffold at right. German scintillometer is on white tripod at left 

center...................................................................................................................................................................8

Figure 7. One-half kilometer (1⁄2 km) Sensors, including Canadian meteorological mast with Metek sonic 

anemometer, prop and vane anemometer, and hygrometer. HELSTF meteorological tower with twodimensional (2-D) sonic anemometers at 4 m and 8 m is shown in background. .........................................9

Figure 8. RTG-40 site map showing site area groupings. The north direction is upward and positive, and the 

eastward direction is to the right and positive...............................................................................................16

Figure 9. OA site group. System locations are surveyed as displacements along a line, anchored at the 

location of the Danish system (DASYS). ........................................................................................................17

Figure 10. 500 M site area map. Circles around locations depict approximate uncertainty in the GPS 

measurements (approximately 5 m). ..............................................................................................................18

Figure 11. 1 KM site area map. Rectilinear coordinates on this and all other maps in this section are 

referenced to the same origin, which is located near the DASYS location at the observation area..........19

Figure 12. 2 KM target area site map. The 2KSCAFFOLD point is located on the top of a berm that 

backstops this target area................................................................................................................................20

Figures 13 and 14. Fifteen-minute mean horizontal wind speeds during November 9th and 10th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................28

Figures 15 and 16. Fifteen-minute mean horizontal wind speeds during November 11th and 12th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................28

Figures 17 and 18. Fifteen-minute mean horizontal wind speeds during November 13th and 14th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................28

Figures 19 and 20. Fifteen-minute mean horizontal wind speeds during November 15th and 16th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................29

Figures 21 and 22. Fifteen-minute mean horizontal wind speeds during November 17th and 18th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................29

Figures 23 and 24. Fifteen-minute mean temperature plots for November 9th and 10th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. .................................................................................................................................31

Figures 25 and 26. Fifteen-minute mean temperature plots for November 11th and 12th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. .................................................................................................................................31

Figures 27 and 28. Fifteen-minute mean temperature plots for November 13th and 14th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. .................................................................................................................................32
vi 

Figures 29 and 30. Fifteen-minute mean temperature plots for November 15th and 16th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. .................................................................................................................................32

Figures 31 and 32. Fifteen-minute mean temperature plots for November 17th and 18th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. .................................................................................................................................32

Figures 33 and 34. Fifteen-minute mean turbulence plots for November 9th and 10th for 4 scintillometers.....33

Figures 35 and 36. Fifteen-minute mean turbulence plots for November 11th and 12th for 4 scintillometers.34

Figures 37 and 38. Fifteen-minute mean turbulence plots for November 13th and 14th for 4 scintillometers.34

Figures 39 and 40. Fifteen-minute mean turbulence plots for November 15th and 16th for 4 scintillometers.34

Figures 41 and 42. Fifteen-minute mean turbulence plots for November 17th and 18th for 4 scintillometers.35

Figures 43 and 44. Fifteen-minute mean parameter plots for November 9th and 10th for 2.5 m level...............36

Figures 45 and 46. Fifteen-minute mean parameter plots for November 11th and 12th for 2.5 m level.............36

Figures 47 and 48. Fifteen-minute mean parameter plots for November 13th and 14th for 2.5 m level.............36

Figures 49 and 50. Fifteen-minute mean parameter plots for November 15th and 16th for 2.5 m level.............37

Figures 51 and 52. Fifteen-minute mean parameter plots for November 17th and 18th for 2.5 m level.............37

Figures 53 and 54. Fifteen-minute mean vertical momentum fluxes for November 9th and 10th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. .......................................................................................................................38

Figures 55 and 56. Fifteen-minute mean vertical momentum fluxes for November 11th and 12th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................38

Figures 57 and 58. Fifteen-minute mean vertical momentum fluxes for November 13th and 14th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................38

Figures 59 and 60. Fifteen-minute mean vertical momentum fluxes for November 15th and 16th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................39

Figures 61 and 62. Fifteen-minute mean vertical momentum fluxes for November 17th and 18th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. ................................................................................................................39

Figures 63 and 64. Fifteen-minute averaged sensible heat fluxes for November 9th and 10th for 2.5, 4.5, 6.5, 8.5 

m sonic anemometer levels. .............................................................................................................................40

Figures 65 and 66. Fifteen-minute averaged sensible heat fluxes for November 11th and 12th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. .......................................................................................................................40

Figures 67 and 68. Fifteen-minute averaged sensible heat fluxes for November 13th and 14th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. .......................................................................................................................41

Figures 69 and 70. Fifteen-minute averaged sensible heat fluxes for November 15th and 16th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. .......................................................................................................................41

Figures 71 and 72. Fifteen-minute averaged sensible heat fluxes for November 17th and 18th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. .......................................................................................................................41

Figures 73 through 96. Hourly 15-minute-integration spectra of horizontal (u, red) and vertical (w, orange) 

wind, and temperature (blue) fluctuations of 9 November...........................................................................50
vii 

List of Tables 

Table 1. GPS (WGS 84) coordinates and derived local rectilinear (X-Y) coordinates for the observation area 

relative to a fixed origin of latitude X0=32° 38' N and longitude Y0=106° 20' W. .....................................21

Table 2. GPS and derived rectilinear coordinates for the 500 M target and control area relative to a fixed 

origin of latitude X0=32° 38' N and longitude Y0=106° 20' W. ...................................................................21

Table 3. GPS and rectilinear coordinates for location points at the 1 KM target area relative to a fixed origin 

of latitude X0=32° 38' N and longitude Y0=106° 20' W................................................................................21

Table 4. GPS and rectilinear coordinates for locations within the 2 KM target area relative to a fixed origin 

of latitude X0=32° 38' N and longitude Y0=106° 20' W................................................................................22

Table 5. Description key for site location labels.....................................................................................................22

Table A-1. Alignment drift for each sensor............................................................................................................54
viii 

Preface 

In the spring of 2004 Army Research Laboratory (ARL) personnel were contacted by 

representatives of NATO Research Technology Group 40 (RTG-40) to discuss involvement in 

their mission to develop models to characterize the performance of active imaging systems. 

These systems represent a next generation of capability for military field sensors, including the 

capability of defeating camouflage systems through the use of active range-gated imaging. 

Swedish researchers spearheaded the use of this technology, where targets may be discriminated 

from backgrounds by range stepping an imager “through” the target to generate a threedimensional concept of the battlefield. 

The promise of such systems is to some extent compromised by the presence of atmospheric 

optical turbulence in the near surface atmosphere. Turbulence causes the illumination pulses of 

these systems to experience various deleterious effects: wave front distortion, time of arrival 

fluctuations, and scintillation. On the return path, the reflected energy is subject to further 

atmospheric distortion. While various system parameters may be varied to determine the optimal 

means of mitigating these effects, without actually building multiple systems with varying 

system parameters (a very expensive process), the alternative is the development of physics and 

engineering models to simulate atmospheric impacts on system performance. To validate such 

models databases of measurements under various turbulence conditions are required. The 

NATO RTG-40 objective of land and sea trials addressed this requirement by providing 

databases of conditions and propagation results for comparison with models. The White Sands 

Missile Range, New Mexico, situated in the Chihuahuan desert, provided a useful setting for 

such measurements. Turbulence levels measured during testing varied over two decades in 

magnitude during the course of the measurements program. 
ix 

Acknowledgments 

Appreciation is extended to the many people who facilitated this test, including both local 

support, outside ARL staff, Strategic Missile Defense Command’s High Energy Laser Systems 

Test Facility (SMDC/HELSTF), and the North Atlantic Treaty Organization (NATO) nation 

staffs and the Night Vision and Electronic Sensors Directorate (NVESD) who supplied the active 

imagers needed to perform the imaging component of the testing. From the White Sands Missile 

Range (WSMR) staff, we wish to particularly acknowledge Mike Hart, the radiation safety 

officer, Robert Floyd, range coordination, and Marc Chavez, flight safety officer. From the 

HELSTF there were many seen and unseen people who supported us, but we especially wish to 

thank first Mr. Thomas Hodge, HELSTF manager, and Mr. William Sutton, MOA liaison, 

without whose assistance the measurements would not have taken place. Additionally, we wish 

to particularly thank Mr. Stan East, whose tireless assistance aided immensely in smoothing the 

way to crossing a number of administrative hurdles. We also thank the HELSTF meteorological 

team (Tim Chavez and Frank Robitaille), whose instrumentation aided greatly in the 

characterization work. The safety crew were highly professional as well, including Rob Ognan 

and Bob Street on the measurement line as well as Mike Blondell in the control booth, Scott 

McKay in safety training, and Gary Wilson, who solidified our ground safety plan. There was 

also the electrical crew who restored power to the downrange area after a lightning strike a few 

weeks prior to the test. Their assistance, though in obscurity, was vital to a successful test. 

We were also assisted significantly by the people at the ARL Survivability/Lethality Analysis 

Directorate (SLAD) Electro-Optical Vulnerability Analysis Facility (EOVAF): Norm Comer, 

chief, and Dave Bromley. They provided critical supplies for the operation of the optics and 

scintillometers. 

Aside from the authors named, we also need to thank many ARL staff who contributed 

significantly to the success of this experiment. We thank the following from ARL for 

participating as foreign escorts Sean D’Arcy, Terry Jameson, Doyle “Scott” Elliott, SFC Robert 

Brice, John Raby, and Dr. David Marlin. Finally, we were ably assisted in various administrative 

details by our program analyst Linda Duchow, purchasing agent Felipe Chavez, supply officers 

Mike Mason and Rick Hanson, safety officer Felicia Chamberlain, and security chief Joseph 

Trammel. Lastly, we wish to thank the support of Drs. Don Hoock, Rick Shirkey, and Ed 

Measure, who helped us clear key administrative hurdles, and Saba (Lou) Luces who provided a 

valuable review of the (near-final) document. 
x 

INTENTIONALLY LEFT BLANK. 
xi 

Executive Summary 

The North Atlantic Treaty Organization (NATO) Research Technology Group 40 (RTG-40) was 

established in 2003 with the mandate to improve models of active imaging systems currently 

being developed by several NATO nations. The operation of these systems involves essentially 

three components: a pulsing laser, a range gating imager, and associated computer control 

equipment to integrate the laser and imager responses. The laser source pulses are switched so 

that they are only a few feet long. These pulses travel downrange to a target, reflect, and travel 

back to a range-gating receiver. This receiver, depending on the accuracy, can determine the 

range to each pixel in the image by varying the range gate (delay timing) electronically. With a 

complete three-dimensional (3-D) picture of the target region, even camouflaged targets can be 

discriminated from background by studying their 3-D structure. Such systems would be 

relatively simple to model, except for the ubiquitous optical turbulence in the surface boundary 

layer atmosphere. 

Due to turbulence, the propagated downrange pulse becomes scintillated (varying illumination 

pattern) when it arrives at the target surface. The scintillated pattern is then reflected back 

through the atmosphere that can further blur the image. To model the effects of this scintillation, 

one must consider the vertical and temporal structures of the turbulent atmosphere. These 

scintillation effects are primarily due to localized temperature fluctuations. The greater the 

degree of diurnal variations in temperature, the greater will be the effects of the turbulence. 

Hence, White Sands Missile Range (WSMR), NM, located in the heart of the southwestern U.S. 

Chihuahuan desert, featuring daily diurnal temperature variations of as high as 40 degrees 

Fahrenheit, was viewed as a prime location for study of turbulence effects on active imaging 

systems. 

The RTG-40 Active Imager Land Field Trials were performed in November 2005 at the High 

Energy Laser Systems Test Facility (HELSTF) located on the WSMR range. HELSTF was 

chosen because it provides a well-instrumented range specifically tailored to measure optical 

turbulence effects. Data collected by HELSTF during the experiments was included in the 

database of conditions developed by RTG-40. HELSTF’s downrange test area also provided an 

area with existing instrumentation and hard power suitable for performing the trials both from 

safety and security viewpoints. 

The data collected by Army Research Laboratory (ARL) during the experiments will be useful in 

a number of applications. First, it will be used in conjunction with the imagery data collected 

during the experiments. Second, this database consists of correlated tower and scintillometer 

data. The scintillometer data includes four pairs of scintillometers set up at 2 meters (m) and 4 m 

above ground level (AGL) over the first and second kilometers (0–1 and 1–2) of the path. These 

sensors completely characterize the propagation path. The objective was to permit 
xii 

intercomparison of turbulence strength (Cn

2

) measured simultaneously as a function of height. 

The mean turbulence strength can then be intercompared, as well as the correlation of closely 

spaced paths. Meteorological wind and temperature data collected from the “met” tower set up 

mid-range can then be intercompared with the Cn

2

 data to determine the ability to predict 

turbulence strength based on micrometeorological variations. In this report the test is described 

and a preliminary data analysis is discussed. 
1 

1. Introduction 

The North Atlantic Treaty Organization (NATO) Research Technology Group 40 (RTG-40) was 

established in 2003 to develop improved models of active imaging systems. A key objective of 

this group was to perform field trials of both land and naval systems. The key U.S. participants 

in this group were initially with the Communications Electronics Research Development and 

Engineering Command (CERDEC) Night Vision and Electronic Sensors Directorate (NVESD) 

from Fort Belvoir, VA. However, in the spring of 2004 David Tofsted of the U.S. Army 

Research Laboratory (ARL) was invited to participate in a meeting of RTG-40 held in Panama 

City, FL. The purpose of this meeting was to discuss the substance of the land field trials and 

develop a plan for their conduct. The plan was to include both the optics measurements to be 

performed during the trials and the placement and approach to site characterization of the 

strength and structure of turbulence during the measurement periods. The final list of 

participants included researchers from ARL, NVESD, the Air Force Research Laboratory 

(AFRL), researchers from the NATO countries Canada, the United Kingdom (U.K.), Denmark, 

Germany, and France, as well as the NATO Partnership for Peace nation Sweden. Over 75 

personnel were involved, including direct participants (figure 1) and High Energy Laser Systems 

Test Facility (HELSTF) and White Sands Missile Range (WSMR) supporting staff. 

Figure 1. Main test participants from ARL and RTG-40. Not shown are HELSTF and WSMR personnel. 

An open question, initially, was where to locate the trials. Three potential sites for the land trials 

were proposed: WSMR, NM, Eglin Air Force Base, FL, and Fort Hunter Liggett, CA. Surveys 

of these three sites were made in the fall of 2004, the WSMR site survey was organized by David 

Tofsted. There were several beneficial features about HELSTF as the best choice. ARL and 

HELSTF have an existing memorandum of agreement (MOA) that was developed and has been 

supported for the past five years by ARL liaison Gail Vaucher and HELSTF liaison William 
2 

Sutton. The required agencies are in place and easily accessible for range coordination, safety 

and security. HELSTF has a high degree of safety and security control infrastructure built-in due 

to the sensitive nature of their site operations. The downrange area of HELSTF is well 

instrumented with in-situ meteorological sensors and is well-characterized by a good collection 

of historical measurement data. There is also considerable micro-turbulence measurement 

expertise available. Hard power is available at several downrange locations. There are fewer 

and shorter roadblocks to contend with than other choices considered and the terrain is flatter and 

drier. The HELSTF site and its support facilities are easily accessible from Highway (Hwy.) 70. 

ARL personnel were instrumental in providing most of the logistical aspects of the RTG-40 test, 

including shipping and receiving of equipment from the various test participants, visitor support 

requirements, range coordination with both HELSTF, where the test occurred, and WSMR 

operations staff. As events unfolded, it became apparent that ARL had undertaken what 

appeared to be an ever-growing set of responsibilities in sponsoring the RTG-40 land field trials. 

A presentation of logistical aspects of the RTG-40 test is provided in section 2 and discussion of 

their progression in severity is provided in section 4 of this report. 

The land field trials were performed in mid-November, 2005, at HELSTF. The week of 7–11 

November was the setup week, with Monday morning devoted to badging and site orientation. 

Monday afternoon and Tuesday morning were spent setting up active imagers, Canadian 

meteorological sensors, and German scintillometers. U.S. ARL meteorological equipment had 

been set up in the three weeks prior to the testing period. The trials were performed in the region 

of HELSTF known as the downrange area. It consists of a 2-kilometer (km) fenced area 

northwest of the primary HELSTF cantonment area containing the Laser System Test Center 

(LSTC). The active imagers and supporting equipment were located along a line ‘front line’ just 

northwest of the LSTC fence noted as the 0-km site and commonly referred to as the 

‘Observation Area’ (OA). The foreign visitors under ARL escort were restricted to the OA, the 

downrange area and the HELSTF cafeteria for security reasons. A schematic of the test area is 

shown in figure 2. 
3 

Figure 2. Main downrange test area including observation area, 

and backstopping target berm at 2 km. 

By Tuesday afternoon nearly all the equipment was ready for registration testing. The primary 

issues were to ensure that the beams directed downrange would not leave the HELSTF range. 

To determine this, a downrange registration target had been constructed. The target consisted of 

an 8’×8’ white-painted plywood panel, with registration markings at the target center consisting 

of 1 centimeter (cm) × 5 cm black stripes every 10 cm in both horizontal and vertical directions 

(refer to figure 3). At the 50 meter (m) downrange location, each 10 cm stripe separation would 

represent 2 millirad (mrad). Using this target each system was tested to determine the extent of 

its illumination beam. In particular, the Swedish gated imager system was a concern because its 

beam was a bright green. This beam was adjusted to lower the beam centroid so that it would 

fall below the level of the berm at 2 km for the full path testing. Similar adjustments were made 

for the other beams as well, though the other beams were all eye-safe after the first hundred 

meters. For convenience and safety purposes a series of three 10 by 20 foot (ft) tents were 

erected over the lasers so that if any should fall, the beam would be contained within the tent 

area. Also, use of the tents permitted test participants to stay behind and outside of the lasing 

enclosure; thus, not requiring protective eyewear whenever they were not operating their 

particular laser. 
4 

Figure 3. Targets used at 1 km (above) and 2 km, including 8’×8’ registration target (lower left), 3-D targets 

(right), resolution patterns (center), and “eye chart” (above left). 

Several additional target types are shown in figure 3. Each was designed to test a particular 

aspect of the active imaging system performance. During testing, each sensor would 

successively dwell on each target at 1 km and 2 km. This series could then be used to evaluate 

the performance of the sensor at different resolution tasks at different ranges and under different 

levels of optical turbulence. The line of laser imagers is shown in figure 4. 
5 

Figure 4. Line of tents sheltering main imagers. From left-to-right are the Canadian ELVISS, Canadian 

LASSIE, Canadian high speed imager, German high speed imager, Swedish Gated Imager, U.K. 

Burst Illumination Laser (BIL), Danish BIL, and U.S. NVESD Active Short Wavelength Infrared 

(SWIR) systems. 

The testing phase occurred during the second week, November 14–18. Four testing periods were 

available, as dictated by other range missions and a missile flight safety plan, which stated that 

the proposed laser systems would be required to operate within a ceiling of 10,000 ft. Though 

we questioned this requirement, we were consequently not permitted to lase under several 

occasions when aircraft were in the area, even though our systems could not have caused laser 

hazards due to their very short hazard ranges, the presence of backstopping berms, and the use of 

the tents. Lasing operations were thus confined to four periods during the week: Monday 

morning, the 14th, from 0600–1000, Wednesday morning, the 16th, from 0500–0900 and from 

1600–1900, and Thursday evening from 1700–2000. Measurements were also taken on Tuesday 

afternoon with the passive Canadian and German high speed cameras. Data were also taken on a 

regular basis by the Canadian and ARL meteorological sensors. 

The systems present included the U.S. CERDEC NVESD Active Imager system and the U.K. 

Burst Illumination Laser (BIL) systems operating at 1570 nanometer (nm) wavelength, the 

Danish BIL and Swedish Gated Imager systems operating at 532 nm (green), and two Canadian 

systems operating in the near infrared (NIR) waveband (810 and 860 nm, respectively): ELVISS. 

Enhanced Low light level and VIsible Surveillance System (ELVISS) and Land-based Active 

System & Surveillance Image Enhancement (LASSIE). ELVISS was the more sophisticated of 

the systems, operating from a mounted tracking ball, ELVISS could be slewed by an operator 

using a joystick from inside the Canadian control van. ELVISS could also be controlled in 

various ways, including operation in passive mode and active modulation of its range gate, to 

select out objects at different general ranges. ELVISS is primarily a search and rescue type 

system, so one of the key areas of study for the Canadians was testing of a variable polarization 

reflecting material added to one of the standard targets. LASSIE was a prototype of an advanced 

version of ELVISS, with nearly the same wavelength and propagation characteristics as ELVISS, 

but without the same tracking or ranging capabilities. ELVISS and LASSIE were only operated 
6 

either just before sunrise or just after sunset during the test period, because they could not be 

operated under full sunlight. 

The NVESD system experienced problems almost from the beginning of the test. It had 

apparently been damaged during an experiment in California the week before, because the laser 

never operated properly during the test period. The U.K. BIL also experienced problems during 

the setup week with its Intevac receiver. However, the U.K. staff took it “home” for the 

weekend and repaired it, using their hotel room as a working laboratory. The U.K. system was 

thus online for Monday morning. It also was available for the Wednesday morning data 

collections. On Wednesday evening, however, it experienced a problem with the cooling system 

in the laser. Coolant flooded the laser box and the system was disabled for the remainder of the 

test. We thus lost our remaining SWIR (Short-wave IR) band sensor midway through 

Wednesday night. 

The remaining two sensors, the two visible systems, operated throughout the testing period. 

Though experimental systems, they performed well throughout. The Danish system worked 

particularly well under very low turbulence conditions. Its range gating capabilities allowed it to 

determine the range to downrange targets within a few millimeters. The Swedish gated imager, 

likewise, had range-gating capabilities, though it was designed to collect wider-angle images 

with a lower range step resolution. 

Of the meteorological (“met”) equipment used to characterize the atmospheric turbulence 

conditions during the lasing events, ARL had a met tower at 1 km downrange. This tower had 

RM Young sonic anemometers set up at 2.5, 4.5, 6.5, and 8.5 m above ground level (AGL). 

Figure 5 shows a schematic of the tower (the tower was accidentally left out of the photographic 

records). These were set to sample U-V-W winds at 20 samples per second. Air temperature 

was also collected at these levels. 
7 

Figure 5. Nine meter (9 m) ARL tower used during testing. 

A net solar radiation sensor was set up at the 1 km range on one of the scintillometer receiver 

scaffolds. ARL had four scintillometers set up to characterize the turbulence refractive index 

structure parameter (Cn

2

, [m-2/3]) at 40 samples per minute. Two scintillometers were situated to 

characterize the 0–1 km portion of the optical path; the other two characterized the second 

kilometer of the 2 km path to the backstopping berm. For each scintillometer pair, one 

scintillometer was set up at 2 m AGL, the other at 4 m AGL. All four scintillometer receivers 

were located at the 1 km downrange area. To avoid interference between the different 

scintillometer signals, each pair (0–1 km and 1–2 km) was set up in a crossed beam pattern so 

that the centers of each beam pair would overlap the same terrain. Figure 6 shows the 2 km 

scintillometer setup. Because the scintillometer sine-squared path weighting function is maximal 

at the center of the path, this geometry permits the pair of beams to bear the greatest weight over 

the path segment. 
8 

Figure 6. Two kilometer (2 km) scintillometers. ARL 2 m scintillometer is on scaffold at left. ARL 4 m 

scintillometer is at second level of scaffold at right. German scintillometer is on white tripod at left 

center. 

In addition to the ARL met equipment, the HELSTF range organization provided 

characterization data from their scintillometer, temperature, and wind equipment on their 1⁄2 km 

and 1 km met towers. Data were available at 10-second intervals throughout the measurement 

period. Data included 8 m and 32 m scintillometers, and temperature/wind data at 4, 8, 16, and 

32 m. Canadian meteorological equipment included a 1.5 m mast located at 500 m downrange. 

Data collected from this mast included air temperature, wind, and humidity data. Figure 7 shows 

the Canadian mast and the lower portion of the 1⁄2 km HELSTF tower. During lasing periods, the 

Canadians also operated an SLS 20 type Scintec scintillometer. This scintillometer model is 

useful in obtaining inner scale measurements of the turbulence conditions. Their wind data were 

collected using a Metec sonic anemometer. 
9 

Figure 7. One-half kilometer (1⁄2 km) Sensors, including Canadian meteorological mast 

with Metek sonic anemometer, prop and vane anemometer, and hygrometer. 

HELSTF meteorological tower with two-dimensional (2-D) sonic anemometers 

at 4 m and 8 m is shown in background. 

The Germans also set up two Scintec BLS-900 scintillometers (see figure 6). Unfortunately, 

these experienced problems from the outset, with apparent malfunctions of one of the 

transmitters and one of the receivers. The setup period was extended through Thursday to 

attempt to bring these systems on line. Eventually, the German personnel were able to get a 

working scintillometer setup functioning between 0 and 1 km, virtually along the same line as 

the ARL 0–1 km sensors, but at a height of around 1.5 m AGL. 

It had been hoped that we could collect met data throughout the measurement period with the 

available ARL instrumentation. However, because the observation area was forced to run on 

generator power, which was only available during lasing periods (when the OA site was 

occupied), we could only take several hours of data from the scintillometers originating from the 

0 km point. Met data from the downrange towers, however, were available during nearly the 

complete period, except for short intervals where the sensors were taken offline to download 

data. Monitoring of the data collected also revealed difficulties with one of the 1–2 km 

scintillometers. When the turbulence passed through each neutral event, the scintillometer 

apparently could not properly track the low level turbulence present, though it seemed to operate 

appropriately during relatively high turbulence periods. Intermittent difficulties with the 6.5 m 

sonic sensor were also uncovered during post-test analysis, as will be shown below. 
10 

Overall, despite the few outages of equipment that normally occur during an effort of this scope, 

this is likely the best-instrumented field test of turbulence effects on both active and passive 

imaging systems in existence. Massive imagery data sets were collected and distributed to the 

various NATO partners in the experiment. The meteorological data sets were also distributed for 

correlation to the imagery data collected. The meteorological data sets themselves are being 

studied intently for their information regarding turbulence characterization. For years to come, 

these data sets will provide the means to examine properties of the nocturnal boundary layer and 

should prove useful in assessing the relative merits of various surface layer prediction and 

characterization methods. Many thanks are due to the persistence and perseverance of the many 

participants in this test whose dedication and contributions made this test possible. 

2. The Field Trials 

In this section we present various issues and challenges that unfurled through the planning, pretest, test and post-test phases of the land trials. In total, there were 23 foreign visitors, 4 USA 

visitors, 23 direct HELSTF participants, and 28 direct ARL participants for a total of 78 direct 

participants. There were many others indirectly involved, especially oversight agencies (road 

block, range engineering, range communication, Army sponsor, flight safety, frequency control) 

from WSMR. 

2.1 Test Documentation 

A cyclic process of communication, correspondence, and coordination were required among 

ARL planners and various agencies to compose intermediate and finalized documents prior to 

the actual start of the RTG-40 land trials. Some of the documents composed in the planning 

phase included: the Laser Ground Safety (LGS) plan, the Missile Flight Safety (MFS) plan and 

the Operational Requirements Document (ORD). 

The ‘Safety Operating Procedure (SOP) for the NATO RTG 40 Experiment’ was over 44 pages 

in length. This SOP included references to: existing Army Regulations (AR), training assertions, 

laser operator statement forms, location descriptions, map and location graphics, site layout 

descriptions, target descriptions and pictures, active imager descriptions with pictures, 

instrumentation and equipment layout descriptions, transmitter-receiver characteristics and 

safeguards, personal protective equipment (PPE), laser goggles, roadblock and barricade 

planning, emergency response plans and much more. Attached were appendices for: Test 

Schedule, List Of Participants (by sub groups), Test Participant Responsibilities (by sub groups) 

and Hazard Analysis Lists. To gain a sense of the complexity and extensive nature of this SOP a 

short (20% of the complete) list of topic phrases from the last SOP iteration follows: 
11 

1) verify check of entire line-of-sight (LOS) for potential reflective surfaces that could cause 

inadvertent specular reflections 

2) check personnel jewelry that might cause inadvertent reflections 

3) no reflective surfaces on targets (nail or screw heads) 

4) how to control laser aperture to prevent lasing above 0 degrees elevation 

5) how to control azimuth slew within backdrop berm area 

6) potential hazardous range for each device 

7) announcement procedure before each lase event 

8) double verify laser alignment each time lase and switch to a new target 

9) must cover not bury cable wiring 

10) mark trip hazard and barrier tape personnel obstacles 

Environmental impact issues and personnel hazard questions had to be addressed and some 

required documented solutions. The support vehicles, diesel generators and any equipment that 

contained fluids had to include double barrier drip containers on the ground. Fire extinguishers 

were located near the generators and personnel break tent near the OA. The entire downrange 

site had an abundance of cacti. The cactus plants at the OA site were delineated with bright 

yellow caution tape. The field of view immediately in front of the line of imagers, 50 ft 

downrange was outlined in bright yellow caution tape. All towers, tripods, guy wires, rope tiedowns and ground stakes included conspicuous indicator ribbons of yellow caution tape. 

Also during the planning phase, a field test operations master plan was composed and 

disseminated showing each day’s itinerary of test operations and escort-visitor schedules. 

During the test phase, these daily itineraries were updated to reflect necessary changes and 

briefed after the convoy arrival and group assembly at the OA.

2.2 NATO Participants and Their Equipment 

The amount of paperwork effort required to accommodate the participation by 23 foreign (and 4 

USA) visitors in RTG-40 was prodigious. NATO/Partnership-for-Peace nations were required to 

obtain visas and complete the requisite paperwork to verify security credentials. There was 

continuing communication among ARL planning personnel and ARL, SMDC (HELSTF’s 

headquarters element), and HELSTF security offices and visitors to complete visit request 

information and to ensure that all command organizations were in concurrence regarding the 

visitors’ requests. Lists of attendees, POCs, and security information were updated beginning in 

the planning phase until just prior to personnel arrivals. Visitors were provided information and 

pertinent printed material on hotel, restaurants, and local points of interest as well as maps and 

route information. 
12 

The test support requests appeared in a continuous and persistent stream. Many test participants 

had ventured over long distances, so they not unreasonably relied on ARL and HELSTF to 

provide for all their logistical support needs. At times during the planning phase the ARL test 

director had to reprioritize the list of support topics in which some requests were deemed to be 

unnecessary luxuries. An example of a curtailed effort was ongoing research of costs to 

rent/lease vans, truck, and portable buildings. ARL provided two diesel generators to supply all 

power required at the OA. Additionally ARL made the arrangements for a diesel tanker supply 

truck to make two deliveries over the course of the test. In retrospect, ARL provided more 

power generation capacity at the OA than was actually required. Several visitors incorrectly 

estimated their power requirement to be one 120-volt circuit per plug. One visiting group 

originally requested that ARL provide a power output in their country’s native standard rather 

than the differing 120/240-volt, 60 Hertz (Hz) American standard. 

The logistical task of tracking and coordinating shipments of equipment in and out of country 

and the transfer of that equipment between WSMR and HELSTF was coordinated by Manny 

Bustillos. The general procedure was to receive visitor’s equipment by commercial carrier at the 

ARL logistics location of building 1646 at WSMR. Each visiting group was required to plan and 

implement their equipment shipment procedures with the shipper of their choice. Some 

confusion resulted from shipments that were directed to the WSMR post receiving location 

rather than to ARL’s separate receiving location. Each shipment received was documented 

regarding the visual description, amount, and condition of equipment. In order to transfer 

equipment from ARL logistics at WSMR to HELSTF, Mr. Bustillos would coordinate with the 

ARL logistics personnel to load the equipment on a flatbed and meet him at the HELSTF site 

entrance. He would then escort the equipment load to the OA if the owners were ready to 

receive it or to a secured indoor holding facility until such time that the owners were ready to 

receive it at the OA. Problems were not restricted to the incoming leg of equipment shipments. 

One of the shipments out of the U.S. was delayed in customs for several months due to a 

discrepancy in paperwork. ARL personnel intervened by having a military shipper resolve the 

issue. 

The logistical task of providing food services was executed smoothly due to Mr. Bustillos’ 

coordination efforts with the HELSTF cafeteria personnel. The HELSTF cafeteria personnel 

were very flexible and adaptive to the needs of the RTG-40 participants. They not only stocked 

up with additional provisions to handle the increased volume of personnel but also purchased 

foods that were appropriate to the cultural preferences of the visiting participants. Menu 

selections were adjusted to accommodate medical issues such as diabetes. A general menu with 

always-available food and snack selections was composed and handed out to visitor groups for 

their convenience of planning. On several occasions the cafeteria personnel opened early, stayed 

open late and extended standard dining hours to suite the scheduling needs of the RTG-40 

personnel. ARL provided drinking water in insulated containers, bottled drinking water and, 

periodically, donuts at the OA. 
13 

There were several provisions made for restroom facilities. The HELSTF cafeteria had 

commercial grade restrooms. There were restroom facilities within the HELSTF facility 

compound by way of a valid escort at select times. Mr. Bustillos coordinated the efforts to set up 

portable units at the OA for the convenience of all field test participants. 

2.3 HELSTF Access 

As a secure facility, HELSTF required that all personnel receive training on safety and security 

aspects of the site. HELSTF has various protocols for specific types of emergencies, particularly 

those related to unexploded ordinance on range. All ARL escort personnel received foreign 

visitor escort training and specialized safety training regarding the HELSTF site. Foreign 

visitors received an abbreviated training session on procedures to follow when on range. During 

the pre-test phase a dry run safety drill was performed to test the escort-visitor groups’ 

knowledge of the appropriate cover areas, radio communications protocols, and evacuation 

timing issues. 

2.4 Test Logistics 

For safety purposes (that is, in order to account for all personnel in case of the need to evacuate 

the site), personnel communication, conduct and movement within the HELSTF was closely 

monitored. The personnel tracking system that was devised also provided for increased 

accountability of foreign visitors, and allowed test supervisors to know the whereabouts of every 

person at any given time, in case they needed to be contacted for a request. We constructed a 

scheme where each ARL, U.S. visitor, or foreign national test participant was identified by a 

unique card from a standard playing card deck. This scheme was used in radio and on-site 

communications to enhance both clarity and brevity. The system worked well for escort-visitor 

grouping and location accountability of personnel. We tried to implement this approach so that 

there would be enough escorts to comfortably oversee all visitors. There was typically a ratio of 

one ARL escort to no more than about five visitors. 

Prior to the start of each day’s operations, all personnel met at the guard gate entrance to the 

HELSTF facility on HWY 70. The ARL escort personnel would show up early to receive their 

visitor assignments. The group assembly area was parking areas near the guard gate and the 

adjacent cafeteria facility. The orderly movement of personnel from the HELSTF entrance area 

to the AO was accomplished in a convoy fashion with ARL personnel in the lead and rear 

vehicles. This convoy method was also used when the group traveled between the AO and the 

cafeteria facility for lunch breaks and for the group egress at the end of each day’s operations. 

The number of vehicles in the train was reduced by carpooling. Whenever one or more visitors 

required travel to a specific location in the downrange area in between lasing sessions, an ARL 

escort would accompany them. There were several key aspects to maintaining good 

communications. Communication among most groups in the field was accomplished using eight 

Family Radio Service (FRS) 1⁄2 watt walkie-talkies. Additionally, key HELSTF and ARL 

personnel had commercial grade radios for inter-communication between specific groups. These 
14 

groups included front-line safety and operations personnel, the HELSTF personnel in the 

command center, and ARL coordinators in a building at the 500 m site referred to as 

“Communications Central.” These ARL coordinators utilized a ‘playing field’ table representing 

a miniature mock-up of the downrange area. They updated (card suite and number) token 

positions to represent the site location of all personnel. So the communication announcement 

protocol for an operational status change or a personnel movement status change was to notify 

communications central with (1) identification (ID) of the caller, (2) status change message, and 

(3) ID of all other persons in immediate attendance. 

Any off-road excursions in the downrange area required that a person walk in front of the vehicle 

noting possible hazards and guiding the vehicle driver safely around the hazard. General hazards 

included endangered flora and fauna, cacti, pot-holes, and the possibility of unexploded 

ordinance (UXO). At one point during the test week, two objects suspected of being UXO were 

sighted and subsequently disposed of by the UXO team. During the pre-test and test phase 

during lasing periods, personnel within the three 10’×20’ tents end-to-end covering the front line 

of active imagers wore laser goggles of the proper optical density (OD) rating. The back flaps of 

these tents were unfurled providing a barrier to the common “break tent” area behind the front 

line. To the immediate west of this front line was the ARL high-speed equipment trailer and to 

the immediate east of this front line was the Canadians’ instrument trailer. 

2.5 Site Layout, Maps, and Tables 

During the course of the RTG-40 test, we used commercial grade Global Positioning System 

(GPS) personal receivers to mark the position of participating imager/camera systems, targets, 

meteorological sensors, support equipment, and shelter structures. We tried to get the best 

location accuracy possible by allowing sufficient time for individual GPS fixes to stabilize on the 

maximum number of available satellite signals and by averaging over multiple fixes. Generally 

speaking, we were able to obtain positional accuracies of the order of 16 ft (5 m) for the majority 

of our measurements. The 5 m error level is depicted (in approximation) as a circle around each 

GPS location point that is shown on the area detail maps below (figures 9–12). 

Unfortunately, both of the ARL personnel who collected GPS information also served as escorts 

for foreign national personnel during the test. The GPS measurements were thus collected while 

waiting for foreign investigators to attend to their test equipment, and were frequently interrupted 

when these personnel moved to different locations. Target boards and some site characterization 

equipment were also moved to different sites on the test range over the course of the test, 

sometimes before GPS measurements could be made for the earlier location. As a result, the 

catalogue of GPS fix points is not comprehensive, but it is felt that only a few, less significant 

points of interest have been omitted. 

One major problem was encountered with attempts to get accurate GPS fixes for sensor systems 

under the OA tent enclosure. Two sets of GPS location measurements were taken (on separate 

days) for these systems, and only the Danish visible band system (labeled as “DASYS” below) 
15 

showed any acceptable degree of repeatability. Most of the other system locations showed poor 

repeatability in absolute and relative (to other system) positioning. We are not certain about the 

source of this inconsistency, but we suspect that multipath reflections of the GPS signals of the 

thick metal tent skeleton or off of the sides of adjacent metal equipment trailers may have been at 

least partly responsible. As a work-around, we visited the site after the conclusion of the test and 

measured displacements of each system position along a baseline defined by the average GPS 

positions of the Danish system and the Canadian ELVISS system (which were on opposite ends 

of the line of systems at the OA). The GPS latitude-longitude coordinates were converted to a 

Cartesian (XY) system under a spherical earth assumption using the following relations: 

( ) α α λ π

cos

1.296 10

2

6 − × = D

RE X 

and 

( ), 1.296 10

2

6 D

RE Y λ λ π − × = 

where RE = 6372.8 km is the mean radius of the earth assumed here, 1.296×106

 = 360×3600 is 

the number of arc seconds in a circle, (λ, α) is the (latitude, longitude) of the given point, and (λD, 

αD) is the (latitude, longitude) of the first GPS fix that was taken for the location of the Danish 

system. Note that the longitude and latitude differences shown above are given in units of arc 

seconds. 

Figure 8 shows an overview of the four major site groupings or “areas” for the RTG-40 site. 

Note that we have omitted height details from the map because the GPS height measurements 

had errors that frequently exceeded actual terrain height differences (which can be appreciated 

by careful examination of heights given in tables 1–4). The main LOS ran from the OA to the 

northwest. The meteorological sensors and support equipment shelters were generally clustered 

to the west or southwest of target locations within each target area. 
16 

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

-1.6 -1.48 -1.36 -1.24 -1.12 -1.01 -0.89 -0.77 -0.65 -0.53 -0.41 -0.29 -0.17 -0.05 0.06 0.18

East-West Position (km, East +)

North-South Position (km, North +)

2 KM Site Area

1 KM Site Area

500 M Site Area

Observation Area

Figure 8. RTG-40 site map showing site area groupings. The north direction is upward and positive, and the 

eastward direction is to the right and positive. 

Figure 9 shows the layout of the systems and support equipment at the OA. As previously 

mentioned, an alternate approach for determining the systems locations had to be used to rectify 

inaccurate GPS positional data. 
17 

Observation Area Site Area Detail

-0.02

-0.01

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

-0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

East-West Position (km, East +)

North-South Position (km, North +)

GECAM

OASCIBLS

UKSYS

DASYS

OAPROTRLR

CANCAM

ELVISS

OAGEN1

OAGEN2

OASHORTSCI

OATALLSCI

LASSIE

SWESYS

USSYS

Figure 9. OA site group. System locations are surveyed as displacements along a line, anchored at the 

location of the Danish system (DASYS). 

Figure 10 shows the layout of the 500 m target area, which had the shortest LOS to the OA 

systems. Only a few targets were set up at this location, primarily by the Canadian group. 
18 

500 M Site Area Detail

0.08

0.09

0.1

0.11

0.12

0.13

0.14

0.15

0.16

0.17

0.18

0.19

0.2

0.21

0.22

0.23

0.24

0.25

0.26

-0.48 -0.47 -0.46 -0.45 -0.44 -0.43 -0.42 -0.41 -0.40 -0.39 -0.38 -0.37 -0.36 -0.35 -0.34 -0.33 -0.32 -0.31 -0.30 -0.29 -0.28 -0.27 -0.26 -0.25 -0.24 -0.23 -0.22 -0.21 -0.20 -0.19 -0.18

East-West Position (km, East +)

North-South Position (km, North +)

500MGASSVN

500MTABLE

500MSCRCVR

500MSCTRNS

500MTREE

500MRC

Figure 10. 500 M site area map. Circles around locations depict approximate uncertainty in the GPS 

measurements (approximately 5 m). 

Figure 11 shows the layout of the 1 km target area, where many of the resolution targets used by 

the SWIR and visible band laser ranging systems were deployed. 
19 

Figure 11. 1 KM site area map. Rectilinear coordinates on this and all other 

maps in this section are referenced to the same origin, which is located 

near the DASYS location at the observation area. 

1 KM Site Area Detail

0.5

0.51

0.52

0.53

0.54

0.55

0.56

0.57

0.58

0.59

0.6

0.61

0.62

0.63

0.64

0.65

0.66

0.67

0.68

0.69

0.7

0.71

0.72

0.73

0.74

0.75

0.76

0.77

0.78

0.79

0.8

-0.73 -0.72 -0.71 -0.70 -0.69 -0.68 -0.67 -0.66 -0.65 -0.64 -0.63

East-West Position (km, East +)

1KPROPANEM

1K3D

1KVAN

1KTALLSCI

1KSHORTSCI

1KLETTR2

1KCHKRBRD2

1KTALLMET

1KGSCI01

1KTSONIC

North-South Position (km, North +)
20 

The longest LOS range target site was at 2 km, which is depicted in figure 12. At both this and 

the 1 km site, HELSTF has installed permanent tall meteorological towers, upon which laser 

scintillometers are situated. 

2 KM Site Area Detail

1.45

1.46

1.47

1.48

1.49

1.5

1.51

1.52

1.53

1.54

1.55

-1.37 -1.36 -1.35 -1.34 -1.33 -1.32 -1.31 -1.30 -1.29 -1.28 -1.27

East-West Position (km, East +)

North-South Position (km, North +)

2KLOWSCINT

2KSCAFFOLD

2KSHORTSCI

2KGSCIN02

2KVAN

2KGSCIN01

2KTALLSCI

2K50FTTBRD

2K3DTGT

2KCHKRBRD

2KLETTR

Figure 12. 2 KM target area site map. The 2KSCAFFOLD point is located on the top of a berm that backstops 

this target area. 

Tables 1 through 4 contain the basic positional data that were used to construct the layout maps 

of figures 8–12. An explanation of labels that are used in figures 9–12 and tables 1–4 is 

contained in table 5. 
21 

Table 1. GPS (WGS 84) coordinates and derived local rectilinear (X-Y) coordinates for the observation area relative to 

a fixed origin of latitude X0=32° 38' N and longitude Y0=106° 20' W. 

Point Lat (X0+X") Lon (Y0+Y") Elev (ft) Y-N (km) X-E (km) R (km) 

USSYS -0.00229 -0.00323 0.003965 

DASYS 1.2 2.4 3962 0 -0.0013 0.001301 

UKSYS 0.0028 0.001057 0.002992 

SWESYS 0.004895 0.002822 0.00565 

GECAM 0.00758 0.005083 0.009126 

CANCAM 0.008628 0.005965 0.010489 

ELVISS 0.009324 0.006551 0.011396 

LASSIE 0.010143 0.00724 0.012462 

OAGEN1 2.1 1.7 3962 0.027807 0.018213 0.03324 

OAGEN2 2.1 1.6 3945 0.027807 0.020815 0.034734 

OAPROTRLR 0.7 2.5 3983 -0.01545 -0.0026 0.015666 

OASHORTSCI 3 1.1 3938 0.055613 0.033824 0.065092 

OATALLSCI 3.6 0.6 3944 0.074151 0.046833 0.087703 

OASCIBLS 2.5 1.5 3947 0.040165 0.023417 0.046493 

Table 2. GPS and derived rectilinear coordinates for the 500 M target and control area relative to a fixed origin of 

latitude X0=32° 38' N and longitude Y0=106° 20' W. 

Point Lat (X0+X") Lon (Y0+Y") Elev (ft) Y-N (km) X-E (km) R (km) 

500MGASSVN 6.1 16.9 3955 0.151391 -0.37727 0.406509 

500MSCRCVR 6 15.9 3944 0.148302 -0.35125 0.381273 

500MSCTRNS 4.6 12.8 3942 0.105047 -0.27059 0.290268 

500MTABLE 9.2 9.6 3943 0.24717 -0.18733 0.310138 

500MTREE 6.5 15.9 3942 0.16375 -0.35125 0.387542 

500MRC 4.4 20.5 3967 0.098868 -0.47094 0.481202 

Table 3. GPS and rectilinear coordinates for location points at the 1 KM target area relative to a fixed origin of latitude 

X0=32° 38' N and longitude Y0=106° 20' W. 

Point Lat (X0+X") Lon (Y0+Y") Elev (ft) Y-N (km) X-E (km) R (km) 

1K3D 26 27.6 3959 0.766226 -0.65562 1.008436 

1KVAN 18.5 28.7 3959 0.534504 -0.68426 0.868276 

1KPROPANEM 19.9 29.8 3955 0.577759 -0.71287 0.917603 

1KSHORTSCI 19.3 27.2 3969 0.559221 -0.64523 0.853844 

1KTALLSCI 18.8 27.9 3953 0.543773 -0.66344 0.857815 

1KCHKRBRD2 25.9 27.8 3951 0.763136 -0.66083 1.009489 

1KLETTR2 25.8 27.8 3955 0.760047 -0.66083 1.007156 

1KGSCI01 21.2 27.3 3955 0.617924 -0.64783 0.895272 

1KTALLMET 18 29.3 3962 0.519056 -0.69987 0.871342 

1KTSONIC 19.5 28.2 3960 0.565401 -0.67125 0.877639 
22 

Table 4. GPS and rectilinear coordinates for locations within the 2 KM target area relative to a fixed origin of latitude 

X0=32° 38' N and longitude Y0=106° 20' W. 

Point Lat (X0+X") Lon (Y0+Y") Elev (ft) Y-N (km) X-E (km) R (km) 

2K3DTGT 49.9 51.9 3943 1.504645 -1.28774 1.98046 

2K50FTTBRD 49.8 52.2 3937 1.501556 -1.29554 1.983203 

2KCHKRBRD 49.8 51.6 3936 1.501556 -1.27993 1.973042 

2KGSCIN01 49 52.9 3968 1.476839 -1.31375 1.976614 

2KGSCIN02 48.5 53.6 3958 1.461391 -1.33197 1.977321 

2KLOWSCINT 49.1 54.8 3961 1.479928 -1.36318 2.012077 

2KSCAFFOLD 50.5 53.1 4025 1.523183 -1.31895 2.014874 

2KSHORTSCI 48.7 53.6 3959 1.46757 -1.33197 1.981892 

2KTALLSCI 49 52.9 3971 1.476839 -1.31375 1.976614 

2KLETTR2 50 51.5 3956 1.507735 -1.27733 1.976065 

2KVAN 48.6 53.7 3968 1.46448 -1.33457 1.981356 

Table 5. Description key for site location labels. 

Label Description 

USSYS SWIR system (U.S.-NVEOL) 

DASYS Visible band system (Denmark) 

UKSYS SWIR system (U.K.) 

SWESYS Visible band system (Sweden) 

GECAM CCD camera system (Germany) 

CANCAM CCD camera system (Canada) 

ELVISS ELVISS SAR system (Canada) 

LASSIE LASSIE imaging system (Canada) 

OAGEN1 Portable 120 VAC diesel power generator #1 

OAGEN2 Portable 120 VAC diesel power generator #2 

OAPROTRLR Propagation equipment trailer (hitch area) 

OASHORTSCI ARL optical scintillometer (2 m short scaffold) 

OATALLSCI ARL optical scintillometer (4 m tall scaffold) 

OASCIBLS Scintec optical scintillometer transmitter (Germany) 

500MGASSVN GASS van entry door 

500MSCRCVR Short path optical scintillometer receiver (Canada) 

500MSCTRNS Short path optical scintillometer transmitter (Canada) 

500MTABLE 500 m painted plate target table (Canada) 

500MTREE 500 m met instrument ensemble (Canada) 

500MRC Radio communication station (front entrance) 

1K3D 1 KM site position for 3-D target (U.S.) 

1KVAN 1 KM site location of ARL instrument van (U.S.) 

1KPROPANEM Propeller anemometer location (U.S.) 

1KSHORTSCI 1 KM site 2 m AGL ARL scintillometer (U.S.) 

1KTALLSCI 1 KM site 4 m AGL ARL scintillometer (U.S.) 

1KCHKRBRD2 1 KM site location for checkerboard target “eye chart” (U.S.) 

1KLETTR2 1 KM site location for billboard letter target (Canada) 

1KGSCI01 1 KM site Scintec optical scintillometer receiver (Germany) 

1KTALLMET 1 KM site 8 m ARL tall met tower (U.S.) 

1KTSONIC 1 KM site sonic anemometer location (U.S.) 

2K3DTGT 2 KM site position for 3-D target (U.S.) 

2K50FTTBRD 2 KM site position for 50 m system registration target (U.S.) 
23 

Table 5. Description key for site location labels (continued). 

Label Description 

2KCHKRBRD 2 KM site location for checkerboard target “eye chart” (U.S.) 

2KGSCIN01 2 KM site Scintec optical scintillometer receiver #1 (Germany) 

2KGSCIN02 2 KM site Scintec optical scintillometer receiver #2 (Germany) 

2KLOWSCINT HELSTF scintillometer location (2 m) (U.S.) 

2KSCAFFOLD Front of scaffold atop berm behind 2 KM target area 

2KSHORTSCI 2 KM site 2 m AGL ARL scintillometer (U.S.) 

2KTALLSCI 2 KM site 4 m AGL ARL scintillometer (U.S.) 

2KLETTR2 2 KM site location for billboard letter target (Canada) 

2KVAN 2 KM site location of HELSTF instrument van (U.S.) 

2.6 Test Day Planning 

Our test schedule was planned in advance based primarily on two issues. First, several other 

competing missions occurred during the time of the RTG-40 test. Second, the number of 

conflicting missions was increased by the Missile Flight Safety plan requirement that airspace be 

cleared up to 10,000 ft. Because of our low priority, this stricture effectively kept us from 

operating anytime there were aircraft between the surface and 10,000 ft. This left us with only 

four windows of operations during the test week and two short windows during the preparation 

week. 

Fortunately, the two short windows during the setup week did allow us to determine some 

critical information regarding system performance. First, we knew that a problem could likely 

exist for the Swedish system because of its power levels. To avoid the possibility that energy 

could exit the HELSTF range, the Swedish system was aligned so that the illumination beacon 

spot fell on a point below the centerline of the observation system. The illumination pulses 

would thus not overshoot the target berm at 2 km. Second, the U.K. system was found to have a 

faulty imager during one of the short window periods. Through some determined tinkering over 

the weekend, the U.K. team was able to repair their sensor and return from the weekend break 

with a fully functioning system. 

Supporting us in establishing lasing times was Mark Simmons of the HELSTF group. He and 

Gary Wilson of the HELSTF safety group coordinated with WSMR range scheduling to establish 

four lasing periods during the test week. These were 0600–1000 Monday 14 November, 0500–

0900 Wednesday 16 November, and 1600–1900 that evening, and 1700–2000 on Thursday 17 

November. Although these were the only lasing periods, additional passive measurements were 

made via the scintillometer and sonic anemometer devices, the Canadian met instrument mast, 

and the high speed cameras of Canada and Germany when lasing operations were not being 

conducted. 

The conduct of lasing operation days was fairly straightforward. The period usually began 

approximately an hour and a half prior to lasing with personnel arriving at the outer gate of 
24 

HELSTF as an assembly point. Once personnel had arrived, escorts were assigned to foreign 

visitors and a caravan of vehicles was formed up to travel inside the HELSTF gate to the 

downrange test area. Once at the area active systems crews would begin startup procedures on 

their systems. These procedures usually took no more than half an hour. Also, once on site the 

Canadian group would send a party to the 500 m area to activate their met data acquisition 

systems. 

Usually the ARL met technician crew of Jimmy Yarbrough and Ed Vidal were onsite prior to the 

rest of the group to download data, restart the data acquisition system if necessary, and to check 

logistical items such as the condition of the diesel electrical generators. Approximately 40 

minutes prior to commencement of lasing operations the HELSTF safety crew would arrive to 

begin coordinating with WSMR range control. At 30 minutes prior to lasing the downrange area 

to the northwest of the laser line in the OA would be cleared, except for the ARL 

communications group of Gail Vaucher and Lou Luces at a trailer out of the propagation area 

behind the 500 m downrange building. From this location, their FRS radios could reach any 

point of the downrange area. 

Once the range had been cleared and clearance was received from WSMR range, the laser line 

became active. Only personnel properly goggled for the type of laser being fired at the time 

were permitted on the laser line. Since there were essentially three different wavebands of lasers 

(visible (532 nm), NIR (810 and 860 nm), and SWIR (1570 nm)), the typical procedure was to 

test similar wavelength devices in succession. Hence, the Danish and Swedish visible systems 

were typically tested back-to-back, as were the two Canadian NIR systems. At the SWIR 

waveband, unfortunately, because the NVESD system developed difficulties, the U.K. system 

was tested separately. Once each system had been tested against each target, the procedure was 

repeated with as many repetitions as possible. Typically the testing of a given system required 

8–10 minutes to sense all available targets. In a four hour time window, the result was 

approximately 4 to 5 complete sets for each sensor. Safety concerns regarding control of 

multiple lasers simultaneously prevented us from lasing with more than one device at a time. It 

would also have been impossible to goggle properly for two different wavelengths at once since 

the goggles available could only shield for one wavelength band at a time. 

Some experience was required to learn to use time wisely during the testing periods. Tuesday of 

the setup week was our first experience with laser operations and much time was lost organizing 

the activities involved. We managed to adjust the Swedish and Danish systems, but the 

Canadian systems could not operate during daylight due to low laser power. We also ran out of 

time to check on the NVESD system. 

On Wednesday (10 November) we had our second chance to test the systems and were 

somewhat more successful. It was during this testing that the U.K. staff recognized their 

instrument was malfunctioning. The NVESD system also appeared to come on line, but 
25 

apparently the laser overheated. It was believed at the time that it would operate on Monday 

morning once the unit had cooled. 

On Monday (14 November) we began the first set of measurements. As we were starting prior to 

dawn, the Canadians were permitted to gain extra time prior to dawn to test their systems. Then, 

after sunrise, the other systems were alternated: the Danish, Swedish, and U.K. systems. But 

because the NVESD system was not coming up, an attempt was made to block out extra time so 

that this system could be tested to see if it could come up. Even with the extra time, it became 

clear the unit’s imager was not working properly. Eventually the NVESD unit was shipped out 

on Tuesday afternoon. 

On Wednesday morning the NVESD group refocused their efforts on setting up their downrange 

camera. This instrument is designed to set up at approximately 30–80 m from a target in the 

LOS of an illuminating laser system so that a sensor on the back of the camera can detect a laser 

pulse arriving. The camera then triggers the system aperture to open briefly so that an image of 

the illumination pulse on the target can be imaged. Richard Espinola of NVESD was sent 

downrange along with Jimmy Yarbrough of ARL and Bob Street of HELSTF safety to operate 

this camera during the experiments. After some discussion regarding safety issues, it was agreed 

that these individuals could remain downrange as long as they were properly goggled for the 

laser system in operation. After some further adjustments, the downrange camera was brought 

on line and three 30-second sequences of illumination pulses were captured, as provided by the 

U.K. BIL system. Simultaneously the U.K. system was detecting the returned images of the 

same scenes. 

2.7 Post-Test Activities 

At the conclusion of the test, several matters of consequence still needed to be accomplished. 

First, the ARL crew cleared equipment from the site. Second, equipment needed to be shipped 

back to Europe, which caused some problems, depending on the shipper. Third, the data needed 

to be extracted from the Structured Query Language (SQL) database and hourly files produced 

for purposes of distribution to the NATO RTG-40 group. Fourth, the analysis discussed in the 

next section was begun. This involved both software development and access to the data. Fifth, 

the scintillometers were recalibrated. This last step is described in the appendix. 

3. Initial ARL Data Analysis 

The ARL met data has been analyzed to characterize the atmospheric conditions under which the 

optical measurements were collected, as well as the varying met conditions present during the 

entire experimental period. Several statistical and derived-parameter calculations of the data 

were made, focusing initially on the mean parameters, and using data taken by the sonic 
26 

anemometers and other sensors. Of primary interest in the initial analysis were the means of 

temperature, wind, Cn

2

, and solar radiation. Subsequently, the computed fluxes of sensible heat 

and momentum were considered. The calculation of Cn

2

 directly from the sonic anemometers 

data and the determination of the inner scale of turbulence from these data was then considered. 

An ancillary study was also performed after the RTG-40 test to determine means of extracting 

better relative temperatures from the temperature sensors on the sonic anemometers. 

3.1 Data Acquisition 

The data collection for the ARL met sensors was undertaken using a series of acquisition 

routines based on Java-spaces developed by Edward Vidal of ARL/WSMR. The 

software/hardware data acquisition architecture for the sonic anemometers was implemented 

differently than that which was used for the scintillometers and radiation sensor. The former 

devices generate ASCII signals and may be transmitted on either RS-232 or RS-485, serial data 

lines. These data were carried from the sensor on RS-485 lines to the Sensor Interface Module 

(SIM) converted to transistor-transistor logic (TTL) and fed to an RCM 3000 microprocessor. 

The data are then directly ingested via 802.3 Ethernet into one or more laptop personal 

computers (PCs). The data rate for the sonics was set to 20 Hz. The data from the Lockheed 

scintillometers and the Kipp and Zonen radiometer was first fed to a Rabbit RCM 3400 

Prototyping Board mounting a Rabbit RCM 3400 Rabbitcore microprocessor in order to first 

digitize the analog signals, then ingested via 802.3 Ethernet into a laptop PC. The data rates for 

the scintillometers were set at 40 samples per minute. The same data rate was chosen for the 

radiometer, since the incident sunlight was not expected to vary significantly on the order of a 

second. The sampling rate for the scintillometers is slow because the processing hardware 

internal to the devices is low pass filtered. The Rabbit then time stamped each record of the data 

and output it, via Ethernet 803.2 to the archiving PC. 

The software used to archive the data was developed over several years and included several 

phases. The primary storage for the data was within an SQL database. To merge data into that 

database, two archiving PCs were used. The initial ingest into the archival system was via input 

“workers” within the Java-based system. These workers would read the data input from the 

serial input lines and input the data into the Java “space.” Once in the space, the data would 

await a second worker that would send the data into the SQL database. The database was located 

on one of the computers. This machine ingested data from one of the sonics and all of the 

scintillometer and radiometer data. The other machine ingested data from the remaining sonics 

and transferred this data into the main archiving PC. 

Because of the volume of data being archived to the database, the data sets needed to be 

periodically dumped to other storage media. This process took the better part of an hour, during 

which the data acquisition process had to be temporarily halted. This created gaps in the data 

sets of roughly one hour intervals on the 10th and 15th of November. 
27 

3.2 Computing Mean and Second Order Statistics 

The first stage of the data analysis was to develop plots of mean temperatures and winds from 

the sonic anemometer data, as well as mean scintillometer output and radiation data. From these 

data a more comprehensive and accurate picture of the measurement period can be appreciated. 

For the most part, the period of measurement was not characterized by extremes of weather 

events. The only critical events occurred when high winds were briefly present. Otherwise, the 

skies were relatively clear (some high clouds), and the winds were fairly moderate. Mean plots 

of weather parameters derived from observations were thus somewhat representative of the state 

of the atmosphere over reasonably large spans of space and time. These longer-period norms 

were used as starting points for a second phase in the analysis where higher order statistics are 

described. 

A Hanning window weighting function was employed to evaluate mean effects. Under this 

weighting approach, a Full Width at Half Maximum (FWHM) of 15 minutes was used to 

generate 15 minute averaged effects. The results of these calculations were then output every 

5 minutes. These averages represented a compromise between the 30 minute averages 

recommended in personal communications with J. Churnside of NOAA’s Wave Propagation 

Laboratory, Boulder, CO, some years ago, and the variability of atmospheric conditions present. 

Of course, for conditions that are static or linearly trending, the distinction is irrelevant, since the 

same mean value will result regardless of the averaging period. For fluctuating atmospheric 

conditions, driven by such factors as variable cloud cover, nocturnal stability conditions, or 

rapidly evolving conditions at the neutral event, shorter time averages are recommended. A 

compromise between the 30 minute average and these shorter-term periods is required because 

very short averaging intervals will tend to reflect higher frequency (e.g., turbulent) fluctuations 

rather than the evolution of the mean. 

The Hanning window (cf. Ludemann, 1986) is expressed by 

WH (x) = [1− cos(2π x / X )]/ X , (1) 

where x ranges from 0 to X. Numerically, the weighting function is evaluated by computing the 

numerator of the weighting function at each time in the period, summing the coefficients over the 

complete integration interval, and subsequently dividing each weight element by the summation. 

The new sum of weight terms will then equal 1.0. Use of this approach yields an equivalent 15 

minute average, but has smoothly truncated ends. It thus is also directly comparable to a 

similarly weighted Fast Fourier Transform (FFT) analysis, where the apodizing window function 

is used to minimize aliasing. 

The window-weighted winds at each tower level for the sonic anemometer data at the ARL 1 km 

site tower are plotted for each day of the measurement period starting on November 9th through 

the 18th in figures 13 through 22. 
28 

Note the varying scale of the plots, depending on the maximum wind speed for the given day. 

(Figure 13-November 9th) (Figure 14-November 10th) 

Figures 13 and 14. Fifteen-minute mean horizontal wind speeds during November 9th and 10th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 

(Figure 15-November 11th) (Figure 16-November 12th) 

Figures 15 and 16. Fifteen-minute mean horizontal wind speeds during November 11th and 12th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 

 (Figure 17-November 13th) (Figure 18-November 14th) 

Figures 17 and 18. Fifteen-minute mean horizontal wind speeds during November 13th and 14th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 
29 

 (Figure 19-November 15th) (Figure 20-November 16th) 

Figures 19 and 20. Fifteen-minute mean horizontal wind speeds during November 15th and 16th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 

 (Figure 21-November 17th) (Figure 22-November 18th) 

Figures 21 and 22. Fifteen-minute mean horizontal wind speeds during November 17th and 18th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 

A qualitative assessment of these measurements revealed two anomalies in the 6.5 m (green line) 

sonic data. These effects appeared intermittently, later in the experimental period. The first of 

these phenomena is manifested when the wind speeds recorded by the 6.5 m sensor appear to fall 

below the 4.5 m wind values at times, particularly in the early morning hours of the 16th (figure 

20) and 17th (figure 21). Less obvious from the plots is the second anomaly, which is an 

apparent timing issue. Fluctuations in the 6.5 m data from the 13th and 14th seem to be 

temporally advanced by about 5 minutes ahead of locally similar variations at the other three 

sensor levels. The cause of this time advance is unknown, but calls into question the use of the 

6.5 m data on several days of the data collection period. The determination of which of the 

6.5 m sonic data to reject can better be determined at a later point by a momentum flux 

intercomparison among the different sensor levels. Good consistency exists for the remaining 

2.5 m, 4.5 m, and 8.5 m wind data throughout the measurement period. 
30 

3.3 Temperature Corrections 

A second parameter data set analyzed using the 15 minute averaged weighting scheme was the 

sonic temperature data. The RM Young sonic temperatures exhibit systematic biases between 

their reported temperatures and the actual temperature, an offset that is different from sensor to 

sensor. Measured values for this bias for a given sensor appear to be constant over the test 

period. Thus, the temperatures measured at the different levels of the tower can be adjusted 

relative to one another to produce a model of the relative vertical temperature structure, provided 

that the sensors all experience the same absolute temperature. This condition would correspond 

to one of the neutral events sensed during the experiment (as suggested by Cheryl Klipp, ARL, 

personal communication). In particular, the best neutral events would be accompanied by high 

winds. Such conditions occurred during the neutral events on the evenings of November 11th

and 15th. 

Based on analysis of these data sets, the 4.5 m, 6.5 m, and 8.5 m tower temperatures were 

adjusted to the same relative temperature as the 2.5 m sensor by subtracting amounts 1.70, 0.67, 

and 0.68 °C, respectively, from data from the 4.5 m, 6.5 m, and 8.5 m sensors. 

On November 11th, the evening neutral event occurred between minutes 970 (16:10) and 980. 

The offsets of the 4.5 m, 6.5 m, and 8.5 m sensors from the 2.5 m sensor were as follows: 

 4.5 m 6.5 m 8.5 m 

 970 1.823 0.652 0.668 

 975 1.827 0.678 0.682 

 980 1.833 0.685 0.697 

While the transition for the 2.5 m and 4.5 m sensors was approximately at the same time of 

970 minutes, the transition times for the 6.5 m and 8.5 m sensors were slightly delayed due to the 

upward progression of the neutral temperature profile after the surface heat flux crossover time. 

Thus, more than one time had to be considered at these higher levels. 

On November 15th, the neutral event occurred between minutes 990 (16:30) and 1000: 

 4.5 m 6.5 m 8.5 m 

 990 1.670 0.604 0.624 

 995 1.682 0.633 0.656 

 1000 1.697 0.665 0.692 

Two issues are of note here. First, the 6.5 m and 8.5 m temperature offsets appear consistent, 

while the 4.5 m offset is somewhat inconsistent. The selection of an offset of 1.70 °C was 

ultimately based more on art than science, a trial and error choice based on the data from the 

evening of the 15th after sunset. The “art” in this procedure was to place the 4.5 m data track 

between the 2.5 m and the 6.5 m temperature tracks. The offset selected produced this result. 

The choice also worked well on the other days. Plots of these temperature tracks are shown in 

figures 23 through 32. 
31 

Interestingly, the 6.5 m sensor displays marked deviations from the expected temperature vertical 

profile behavior at about the same times as the aforementioned wind speed anomalies (see, in 

particular, figures 30 and 31). Fortunately, periods where the 6.5 m sensor appears to be 

producing inappropriate results are not those associated with the imaging sensor data collection 

periods of the RTG-40 testing. 

 (Figure 23-November 9th) (Figure 24-November 10th) 

Figures 23 and 24. Fifteen-minute mean temperature plots for November 9th and 10th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. 

 (Figure 25-November 11th) (Figure 26-November 12th) 

Figures 25 and 26. Fifteen-minute mean temperature plots for November 11th and 12th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. 
32 

 (Figure 27-November 13th) (Figure 28-November 14th) 

Figures 27 and 28. Fifteen-minute mean temperature plots for November 13th and 14th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. 

 (Figure 29-November 15th) (Figure 30-November 16th) 

Figures 29 and 30. Fifteen-minute mean temperature plots for November 15th and 16th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. 

 (Figure 31-November 17th) (Figure 32-November 18th) 

Figures 31 and 32. Fifteen-minute mean temperature plots for November 17th and 18th for 2.5, 4.5, 6.5, 8.5 m 

sonic anemometer levels. 
33 

3.4 Turbulence 

To conclude our discussion of the first order data, we plot the diurnal turbulence strength in 

figures 33 through 42. Four scintillometers were used, but only two of these were operational 

most of the time, as is evident in the plots. The two southern lasers were only operational during 

a minority of the time, due to limited availability of both fuel for the diesel generators and 

support personnel at the OA. The scintillometers at the northern end of the test area were on 

hard (permanent) power, and thus only show downtimes due to data archival or system 

maintenance activities. The plots show all available data. 

One of the scintillometers apparently had difficulties. The blue line indicating the turbulence 

level at 4 m from 1 to 2 km does not appear to capture the full variation seen by the 2 m sensor 

(red line), particularly at times of low turbulence near neutral events. Unfortunately, this 

behavior was not detected during the experiment itself. The cause of this phenomenon is 

difficult to determine from the mean data, which only shows low frequency trends. Because the 

problem is especially evident at low turbulence periods, it is possible that system noise (either 

optical or electronic) could have been a factor. This and other possibilities may be examined at a 

later point with the high frequency (instantaneous) data. 

When they are available, the two southern scintillometers appear to capture the same neutral 

event features as the 2 m northern sensor. Further analysis of the scintillometer data is expected, 

but is limited to the mean trends in this document. The figures also include estimates of the Cn

2

based on the spectral analysis of the 2.5 m sonic anemometer data discussed further in section 

3.3. 

 (Figure 33-November 9th) (Figure 34-November 10th) 

Figures 33 and 34. Fifteen-minute mean turbulence plots for November 9th and 10th for 4 scintillometers. 
34 

 (Figure 35-November 11th) (Figure 36-November 12th) 

Figures 35 and 36. Fifteen-minute mean turbulence plots for November 11th and 12th for 4 scintillometers. 

 (Figure 37-November 13th) (Figure 38-November 14th) 

Figures 37 and 38. Fifteen-minute mean turbulence plots for November 13th and 14th for 4 scintillometers. 

 (Figure 39-November 15th) (Figure 40-November 16th) 

Figures 39 and 40. Fifteen-minute mean turbulence plots for November 15th and 16th for 4 scintillometers. 
35 

 (Figure 41-November 17th) (Figure 42-November 18th) 

Figures 41 and 42. Fifteen-minute mean turbulence plots for November 17th and 18th for 4 scintillometers. 

3.5 Second Order Statistics 

We next consider second order statistics related to the vertical fluxes of sensible heat and 

momentum. We compute flux values of <w’T’> and <u’w’> by removal of mean trends of the 

wind and temperature data and evaluating mean fluctuation products weighted according to a 

Hanning window weighting scheme similar to that used for the mean value calculations. The 

procedure for removing the local mean from the data was straightforward. First, the 5-minute 

averaged mean wind and temperature values were used to develop a spline of these averages 

over the 1⁄2 hour interval of the weighting period. The interpolated mean values were then 

removed from the sonic data. The bulk of influences due to varying winds, illumination 

conditions, and mesoscale type effects were thus removed, leaving only the fluctuations about 

the mean. The analysis method used here is essentially a fixed high-pass frequency filter 

approach, as opposed to a putatively more versatile dynamic high-pass filtering method such as 

the cospectral gap technique (Vickers and Mahrt, 2003). In most cases, the 5-minute running 

average should be adequate to eliminate most low frequency trends from the processed data. 

Results from these calculations are shown in figures 43 to 52. Plots include 15-minute averaged 

solar radiation data scaled at 1⁄3 collected value for comparison with the sensible heat computed 

from the sonic 2.5 m data. Also plotted is a scaled momentum flux. The significance of this 

intercomparison is seen during a few nights where the sensible heat flux is clearly proportional to 

the momentum flux. 
36 

 (Figure 43-November 9th) (Figure 44-November 10th) 

Figures 43 and 44. Fifteen-minute mean parameter plots for November 9th and 10th for 2.5 m level. 

 (Figure 45-November 11th) (Figure 46-November 12th) 

Figures 45 and 46. Fifteen-minute mean parameter plots for November 11th and 12th for 2.5 m level. 

 (Figure 47-November 13th) (Figure 48-November 14th) 

Figures 47 and 48. Fifteen-minute mean parameter plots for November 13th and 14th for 2.5 m level. 
37 

 (Figure 49-November 15th) (Figure 50-November 16th) 

Figures 49 and 50. Fifteen-minute mean parameter plots for November 15th and 16th for 2.5 m level. 

 (Figure 51-November 17th) (Figure 52-November 18th) 

Figures 51 and 52. Fifteen-minute mean parameter plots for November 17th and 18th for 2.5 m level. 

Similar intercomparisons of parameters obtained at 4.5 m, 6.5 m, and 8.5 m were also prepared, 

but showed essentially the same trends, and are not shown here. Of greater interest are the 

simultaneous intercomparisons of either the momentum or heat fluxes obtained from the four 

anemometers at the different levels at the same time. These are included in figures 53 through 

62 for the momentum flux intercomparisons and figures 63 through 72 for sensible heat flux. 
38 

 (Figure 53-November 9th) (Figure 54-November 10th) 

Figures 53 and 54. Fifteen-minute mean vertical momentum fluxes for November 9th and 10th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. 

 (Figure 55-November 11th) (Figure 56-November 12th) 

Figures 55 and 56. Fifteen-minute mean vertical momentum fluxes for November 11th and 12th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 

 (Figure 57-November 13th) (Figure 58-November 14th) 

Figures 57 and 58. Fifteen-minute mean vertical momentum fluxes for November 13th and 14th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 
39 

 (Figure 59-November 15th) (Figure 60-November 16th) 

Figures 59 and 60. Fifteen-minute mean vertical momentum fluxes for November 15th and 16th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 

 (Figure 61-November 17th) (Figure 62-November 18th) 

Figures 61 and 62. Fifteen-minute mean vertical momentum fluxes for November 17th and 18th for 2.5, 4.5, 

6.5, 8.5 m sonic anemometer levels. 

We note as a background for our results that a major wind event occurred on the evening of 

November 11th, and is reflected in the data plotted in figures 3 and 55. Precautions therefore 

were taken to insure that all the tents were secured and plastic was wrapped over the optical 

instrumentation and monitors as protection from blowing dust. A similar procedure was 

conducted on the evening of the 14th in anticipation of a wind event to occur later that night. As 

seen in figures 19 and 59, the event actually occurred on the morning of the 15th, but test 

personnel were not permitted on site due to White Sands road blocks and where even on-site 

HELSTF personnel had to remain underground during testing periods. 

Also of interest was the operational condition of the wind sensor at 6.5 m. It is apparent in 

figures 57, 58, 60, and 61, that the sensor was intermittently in error on the 13th, 14th, 16th, and 

17th. The occurrence of these errors appears to be in conjunction with cold weather conditions. 

On the morning of the 13th the temperature first reached approximately 3 °C for an extended 
40 

period. Thereafter, on the other days listed above, the temperature was at or below this 

temperature. The phenomenology indicates the possibility of a loose solder joint that shrinks and 

loses contact under cold weather conditions. Only second order data analysis unambiguously 

revealed this difficulty, arguing strongly for near real-time second order analysis of data in future 

tests. 

 (Figure 63-November 9th) (Figure 64-November 10th) 

Figures 63 and 64. Fifteen-minute averaged sensible heat fluxes for November 9th and 10th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. 

 (Figure 65-November 11th) (Figure 66-November 12th) 

Figures 65 and 66. Fifteen-minute averaged sensible heat fluxes for November 11th and 12th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. 
41 

 (Figure 67-November 13th) (Figure 68-November 14th) 

Figures 67 and 68. Fifteen-minute averaged sensible heat fluxes for November 13th and 14th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. 

 (Figure 69-November 15th) (Figure 70-November 16th) 

Figures 69 and 70. Fifteen-minute averaged sensible heat fluxes for November 15th and 16th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. 

 (Figure 71-November 17th) (Figure 72-November 18th) 

Figures 71 and 72. Fifteen-minute averaged sensible heat fluxes for November 17th and 18th for 2.5, 4.5, 6.5, 

8.5 m sonic anemometer levels. 
42 

The sensible heat flux data appears to show a similar behavior for the 6.5 m sensor as the 

momentum flux plots, deviating from the other sensors on the same nights during the same 

periods. Aside from these deviations, however, the heat flux data appear to indicate a significant 

amount of consistency between the sensors, even the 6.5 m sensor outside the cold intervals, 

particularly during the daytime. 

We observed several periods where the sensible heat flux at night was near zero, as well as 

several intervals of large heat flux, which are interesting from the standpoint of stable boundary 

layer (SBL) studies. We thus would expect to find considerable variations in the stability 

conditions present during the measurement period. 

4. Temperature and Wind Spectra and Turbulence Computations 

The spectral properties of temperature and wind provide additional information regarding the 

structure of atmospheric fluctuations. The primary region of interest in the spectrum is the 

inertial subrange, which is the cascade region between the outer scale source range and the inner 

scale dissipation region. Standard theories of atmospheric turbulent motions have the spatial 

spectra of atmospheric parameters typically exhibiting a 5 / 3

1

− κ spectral dependence characteristic 

of one-dimensional stationary tower measurements in this spectral subrange. Here, κ 1 is the 

one-dimensional stream wise spatial frequency. Assuming a mean horizontal wind speed U

during a set of measurements, the cyclic temporal frequency, n , produced by the collections can 

be converted to spatial frequency by means of the transformation κ1 = 2π n /U . 

Our main focus in this study has been on the fluctuations of horizontal wind speed (u’) about the 

mean U, vertical wind speed fluctuations (w’) about an assumed zero mean vertical wind speed, 

and temperature fluctuations (T’) about the mean T. From the spectral power density of u’, 

Suu(n), the kinetic energy dissipation rate can be determined. In the inertial subrange 

[ ] , 2 2 ( )

3 / 2 5 / 3

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

= α

π

ε

n S n

U

uu (2) 

whereε is the energy dissipation rate, α is the Kolmogorov constant equal to 0.53, U is the 

mean streamwise wind speed, and the numerator in angle brackets is the compensated spectral 

intensity that is to be averaged over the inertial subrange. The factor of 2 that appears in the 

bracketed factor of equation 2 above is not seen in some common developments (e.g., Kaimal et 

al., 1972), where spectra are defined over a single-sided domain. Our development below, which 

relies upon the double-sided domain of the FFT, requires that we add an additional factor of 2 to 

correctly calculate the spectral power density. Knowledge of the dissipation rate provides an 
43 

estimate of the inner scale of turbulence. An important intermediate scaling parameter is the 

Kolmogorov scale, 

/ , 4 3 η = ν ε k (3) 

with ν the kinematic viscosity, ν = μ / ρ , where μ is the dynamic viscosity (e.g., List, 1951) 

and ρ is the atmospheric density. Dynamic viscosity can be computed as, 

,

3 / 2

0

0

0

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

+

+ = T

T

T C

T C

μ

μ (4) 

with 16 291. T0 = K, C = 120 K, 4

0 1.827 10− μ = × g/cm/s. Given η k , the inner scale is computed 

as o 41η k l = 7. (Wyngaard, 1973). 

A similar statistically-based analysis can be applied to the temperature power spectrum. 

Ishimaru (1978) bases his analysis on fluctuations of the potential temperature, θ . Beland 

(1993) writes a general structure function as 

( ) [ ( ) ( )] 2 [1 ( )] 2 2 D r R x r R x r R R R

r r r r r = + − = σ − ρ , (5) 

where 2 σ R is the variance of parameter R , and (r) R

r ρ is the autocorrelation. The power spectrum 

for variable R is the Fourier transform of ) ( 2

r R R

r σ ρ . 

An atmospheric conservative passive additive scalar parameter R (e.g., temperature and 

refractive index fluctuations) has the structure function 

2 2 / 3 D (r) C r R ≈ R

r for o Lo l << r << , (6) 

where turbulence is assumed homogeneous and isotropic. The quantities 2 CR are termed 

structure parameters. Here, the parameters ol and Lo are the respective inner and outer scales of 

turbulence. Near the earth’s surface, the inner scale is generally on the order of several 

millimeters, while the outer scale is on the order of several meters. As noted previously, 

between these scales is the so-called inertial subrange. 

Variations of refractive index near the earth’s surface are primarily due to temperature 

fluctuations. Effectively, 

( ) 2 2 2 / n T CT C = ∂n ∂ , (7) 

2

6 78.2 10

T

P

T

n − = − ×

∂

∂ . (8) 

From this basis, we note that the Kolmogorov spectrum of turbulence, a spectral form assuming 

zero inner scale and infinite outer scale, is given by, 
44 

2 11/ 3 ( ) − Φn κ = β n Cn κ , (9) 

with 033 = 0. β n (Tofsted, 2000). This spectral form is the three-dimensional spectrum of 

refractive index fluctuations. A one-dimensional form of this spectrum is found by integration: 

5 / 3

1

2

0

2 2

1 1 5

6 ( ) ( ) 2 −

∞

= Φ + ≈ ∫ β κ

π Vn κ n κ κ r πκ r dκ r n Cn , (10) 

in the inertial subrange portion of the spectrum ( Lo o 1/ 1/ l << κ1 << ), and κ 1 is the onedimensional spectral variable. ) ( Vn κ1 can also be related to the 3-D spectrum ) Φn (κ through 

the relation (Tatarskii’s equation (1.27), 1961), 

π κ κ

κ

d

dVn

n 2

1 Φ ( ) = − . 

The governing frequency variable in the one-dimensional spectrum is envisioned by Tatarskii 

via: “If in a homogeneous and isotropic field we single out any straight line and consider the 

values of the field only along this line, then as a result we obtain a random function of one 

variable x, to which we can apply all the results pertaining to stationary random functions.” 

From our tower measurements we make the assumption that the wind speed is relatively uniform 

over the 15-minute averaging period. These considerations then lead to a frequency variable 

corresponding to the streamwise spatial frequency component κ1 = 2π n /U associated with 

tower data. 

Because of their close connection at visible and IR frequencies, the temperature and refractive 

index spectra will take roughly the same form as long as we confine our considerations to those 

portions of the electromagnetic spectrum. Therefore, the value of 2 Cn should theoretically be 

derivable from the tower temperature spectra. The only restriction is that when tower 

measurements are used, the spectra produced are averaged over the integration period of the 

tower measurements, as opposed to scintillometer measurements, which use spatial integration to 

obtain an average result. To find the appropriate connection we must use the auxiliary relation 

between the one-dimensional temperature spatial spectral density VT and the temperature 

temporal frequency spectral density STT : ( ) ( ) 1 1 V f S f κ T κ = TT , where f is the temporal 

frequency [Hz] of the tower sensed spectral power density. Because of numerical peculiarities of 

the tower data FFT procedure, S ( f ) T ( f ) ( f ) TT = Δ Θ + Θ − , where ΔT = N / R , the total 

integration time equal to the number of samples N in the FFT divided by the data acquisition rate 

R (20 Hz for these runs), and the FFT Θ itself defined as 

N

n

Tn W

N f l R N ln

1 ' Θ ( = / ) = ∑ , (11) 
45 

with “twiddle” factors N Wln , and the product ) Θ(+ f )Θ(− f identified as the transformed 

equivalent of the autocorrelation function (e.g., equation. (33) of Tofsted, 2001). The estimate of 

the 2 Cn is therefore given by, 

()() ( ) 2

6

5 / / 5 / 3

2 / 3

2 2 2 2 f S f U

C n T C n T TT

n

n T ⎟

⎠

⎞ ⎜

⎝

⎛ = ∂ ∂ = ∂ ∂ π

π β . (12) 

Note here that S ( f ) TT is a two-sided spectrum, again, as opposed to the single-sided spectra 

normally considered in some parts of the literature (e.g., Panofsky and Dutton, 1984; Kaimal et 

al., 1972). 

The temperature power spectrum may also be used to estimate the dissipation rate of fluctuations 

of virtual temperature, parameter Nθ . In the near surface atmosphere, the variables of 

temperature, T , and virtual temperature, θ , are essentially identical. From Ishimaru (1978) we 

can therefore write the adapted form 2 2 1/ 3 / ε CT ≈ Cθ = b Nθ , relating the temperature structure 

parameter to the dissipation rate and the temperature fluctuation dissipation rate, and where b is 

considered a universal constant. Nθ is also considered to vary linearly relative to the square of 

the vertical temperature gradient. 

Our primary limitation to exploiting these results is the nature of the observed spectra. As an 

example, hourly spectral plots from November 9th are shown in the next 24 figures (figures 73 

through 96 on the following pages). In each plot there are three spectra: in red is the streamwise 

horizontal wind speed fluctuation spectrum, in orange is the vertical wind spectrum, and in blue 

is temperature spectrum. Also plotted are three lines corresponding to -5/3rds, -4/3rds, and -

3/3rds power laws. As expected, the spectra of vertical wind begin at points depressed below the 

streamwise wind spectra at low frequency and eventually appear to nearly coincide with the 

streamwise spectra at high frequency. However, the behaviors of these two spectra are not 

consistent throughout the day. For example, in the 2:30, 3:30, 7:30–11:30, and 20:30–23:30 

hour plots, the vertical and horizontal wind spectra observed are consistent with a 4/3rds verticalto-horizontal ratio that would be expected from theory. However, the 16:30 and 17:30 plots 

show high frequency vertical wind spectra that are distinctly below the horizontal wind spectra. 

The optical turbulence values estimated from the 2.5 m sonic anemometer data that are coplotted 

on the half-hour with measured turbulence data in figures 33 through 42 may be used to assess 

the utility of this estimation technique. Several observations may be made about this 

comparison. First, the predicted 2.5 m Cn

2

 values from the sonic data appear to be consistently 

low compared to the 1–2 km scintillation measurements, for the 2 m level and often for the 4 m 

level. Part of this difference can be explained by the height and location differences of the sonic 

anemometer and scintillometer sensors, and part must be due to the point time averaging of the 

sonic versus the spatial and temporal averaging applied to the scintillometer data, but the factor 

of 2 seems large. Certainly this would not explain why the results are also often below the 4 m 
46 

scintillometer measurements as well. Further analysis of the terrain profiles may reveal a region 

where the LOS is closer to the surface near the center of the path, where the weighting function 

of the scintillometers reaches a maximum. 

We had expected that it would be the two southern scintillometers that would register higher 

levels than the two northern instruments. The reason was that a very low “ridgeline” extended 

out some distance from the 500 m tower area into the region between the 0–1 km scintillometer 

transmitters and receivers. Indeed, some difficulty was experienced selecting the proper point so 

that LOS could be established. No similar problem was experienced on the 1–2 km paths. 

Contrarily, the 1–2 km Cn

2

 values appeared to be a factor 2 stronger than the values along the 

0–1 km paths. 

 Figure 73 Figure 74 

 Figure 75 Figure 76 
47 

 Figure 77 Figure 78 

 Figure 79 Figure 80 

 Figure 81 Figure 82 
48 

 Figure 83 Figure 84 

 Figure 85 Figure 86 

 Figure 87 Figure 88 
49 

 Figure 89 Figure 90 

 Figure 91 Figure 92 

 Figure 93 Figure 94 
50 

 Figure 95 Figure 96 

Figures 73 through 96. Hourly 15-minute-integration spectra of horizontal (u, red) and vertical (w, orange) 

wind, and temperature (blue) fluctuations of 9 November. 

The vertical wind speed fluctuation spectrum had no observational data with which it might be 

directly compared in this experiment. However, the vertical fluctuation spectrum data can be put 

to use in comparisons with spectral behavior that is expected from theory. Of perhaps greatest 

interest are cases where the inertial subrange behavior does not appear to follow the -5/3rds 

power law rule for the horizontal and/or temperature spectra. These exceptional behaviors seem 

to follow several different patterns. In one pattern, the entire subrange spectrum may not exhibit 

the -5/3rds slope. This is seen, for example, in the vertical wind spectrum of the 17:30 graph. 

Another behavioral pattern is an inconsistency of aliasing effects. The 20 Hz sampling rate will 

yield a Nyquist frequency of 10 Hz, with the associated aliasing of higher frequency energy into 

spectral components below 10 Hz. In one instance, the aliasing effect appears relatively minor in 

the 18:30 spectrum, where the energies at the 10 Hz frequency are 10-4.3. In a contrasting 

example, aliasing is a major effect in the temperature spectrum of the 13:30 graph where the 

spectral energy is roughly 10-3.1. 

An analysis of the noise spectrum of the RM Young sonic anemometers must acknowledge the 

fact that these devices only report wind and temperature data to 2 digits of accuracy after the 

decimal point. Therefore, the reported values have a random +/-0.005 unit uniform distribution 

of error. The spectrum associated with this error has been analyzed and displays a magnitude of 

approximately 6 10− with a white noise characteristic shape. This is roughly equivalent to (within 

about a factor of 2) the variance of the error (0.012

/12) divided by the sampling rate (20 Hz). 

This value is well below the minimum values of the spectra plotted in figures 73–86. Therefore, 

the high frequency spectral flattening is not a sensor noise floor effect, even at the lowest 

spectral energies. It also does not appear to be due to excessive aliasing. The transition of 

aliasing seems to be very rapid in many of the figures (e.g., figures 85 and 86), yet appears 

extended in some cases (e.g., figures 80 and 86). Since these cannot be due to roundoff effects 

they are perhaps due to the analog processing limitations of the sensor at low wind speeds. The 

times when this effect is the most pronounced apparently correspond to mean winds below 2 m/s. 
51 

The worst cases apparently occur when the wind speed is approximately 0.5 m/s, regardless of 

the time of day. 

It should be noted that, although the highest frequencies seem to show the potential for 

corruption due to unknown sources, the frequency range between about 1/3 Hz and 3 Hz appears 

to consistently show nearly log-linear form, even if this spectral dependence does not exactly 

match a -5/3rds theoretical dependence expected. The implications for SBL studies is that 

regardless of the disturbance of the vertical profile due to the stability, the spectra appear stable. 

5. Conclusion 

The NATO RTG-40 Active Imager Land Field Trials, conducted at the WSMR HELSTF range, 

represent the type of complex measurement program that can be accomplished given the mutual 

support and cooperation of coordinated agencies. The success of this program will lead to 

improved modeling of active imager systems by NATO countries and the advance of this 

promising technology. 

At the same time, ARL has obtained a valuable data resource that shows the promise of revealing 

various aspects of diurnal patterns of structure within the surface layer atmosphere of a desert 

environment. Initial analysis has shown the quality of the sonic anemometer data taken. The 

consistency of the vertical fluxes of heat and momentum between different tower levels indicates 

that except for certain cold weather conditions the sensors were performing accurately. Results 

also indicate an effective method is available to estimate the refractive index structure parameter, 

2 Cn . The sonic anemometer also may be sufficient to characterize the surface layer, as it seems 

well suited to evaluation of the sensible heat flux, momentum flux, and spectral fluctuation 

properties of temperature and wind. Such properties are the basis for characterizing the dynamic 

similarity state of the surface layer (at least under daytime conditions). Further analyses using 

this data set are recommended, and ongoing, but for purposes of closure for this report, the 

analysis has been restricted to the results presented. 
52 

References 

Beland. Propagation through Atmospheric Turbulence. Chapter 6 of The Infrared Handbook, 

Wolfe, W.L., Zissis, G. J., Eds; ERIM: Ann Arbor, MI, 1989. 

Ishimaru, A. Wave Propagation and Scattering in Random Media. Volume 2; Academic Press: 

New York, 1978. 

Kaimal, J.C.; Wyngaard, J.C.; Izumi,Y.; Cot’e, O.R. Spectral Characteristics of Surface-Layer 

Turbulence. Q. J. Roy. Met. Soc. 1972, 98, 563-589. 

List, R.J., Smithsonian Meteorological Tables, Smithsonian Inst., Washington, DC, 1951. 

Ludeman, L.C., Fundamentals of Digital Signal Processing, J. Wiley & Sons, New York, 1986. 

Panofsky, H.A., and J.A. Dutton, Atmospheric Turbulence: models and methods for engineering 

applications, J. Wiley & Sons, New York, 1984. 

Tatarskii, V.I. Wave Propagation in a Turbulent Medium, Silverman, R.A., Translator; McGrawHill Book Company, Inc.: New York, 1961. 

Tofsted, D. H. Turbulence Simulation: On Phase and Deflector Screen Generation; ARL-TR1886; U.S. Army Research Laboratory: White Sands Missile Range, NM, 2001. 

Tofsted, D. H. Turbulence Simulation: Outer Scale Effects on the Refractive Index Spectrum; 

ARL-TR-348; U.S. Army Research Laboratory: White Sands Missile Range, NM, 2000. 

Vickers, D.; Mahrt, L. The Cospectral Gap and Turbulent Flux Calculations. J. Atmos. and 

Ocean. Tech. 2003, 20, 660-672. 

Wyngaard, J. C. On Surface Layer Turbulence. Chapter 3 of Workshop on Micrometeorology, 

Haugen, D. A., Ed.; American Meteorological Society: Boston, MA, 1972. 
53 

Appendix: Scintillometer Calibrations 

Calibration of the four Model IV-L, Lockheed Atmospheric Scintillometer, were performed both 

pre and post RTG-40 test. These units (most are circa era 1986 manufacture) were properly 

cleaned, aligned, and adjusted optically, and an electrical calibration was carefully performed. 

The instruments are designed to operate over ranges of 900 to 1200 m, measuring Cn

2

 over a 

range of 1×10-12 to1×10-16 m-2/3. 

The electrical calibration was performed in accordance with manufacturer’s guidance, using a 

voltage standard and a precision voltage meter. Since calibration parameters were set to the 

manufacturer’s specifications prior to the RTG-40 test, the following table lists post calibration 

values only. The voltages represent alignment drift for each adjustment required during voltage 

calibration for each of the four receivers. As shown in table A-1, Scintillometer Serial Number 1 

(4 m level, facing South during test) showed a deviation of + 0.9% from manufacturers 

specifications; Scintillometer Serial Number 2 (2 m level, facing North during test) showed a 

deviation of +1.3% from manufacturers specifications; Scintillometer Serial Number 10 (4 m 

level, facing North during test) showed a deviation of +1.6% from manufacturers specifications, 

and Scintillometer Serial Number 11 (2 m level, facing South during test) showed a deviation of 

+1.2% from manufacturers specifications. However, the output at the BNC connector, 

representing the actual Cn

2

 value recorded as data, showed deviations from the specified values 

of no more than +/- 0.2% across the calibration voltage range. Considering the following 

corresponding voltage to Cn

2 equivalence; 1 volt =1×10-12, 0.1 volt =1×10-14, and 

0.01 volt =1×10-16, then 0.002 volt equals ~1.6×10-17 Cn

2

 error at low Cn

2

 periods. This is 

presumably small, but other problems are noted with the 4 m North sensor in the analysis 

section. 
54 

Table A-1. Alignment drift for each sensor. 

Scintillometer 

 Serial No. 1 

AGC Card U1 A/D Before adjustment(Mfg. 

Spec. w/0.100VDC input – 

Nominal = 0.00VDC output) 

Output Amp Adj. Before 

adjustment (Mfg. Spec. 

w/1.00VDC input – Nominal = 

2.00Vdc output) 

 0.012 V 2.013V 

 

Cn

2 Card 

Input Amplifier 

Balance Before 

adjustment (Nominal 

= 0.00 +/-5 mv ) 

Cn

2

 voltage at 

BNC after 

adjustment 

(Nominal = 

1.000) 

Output Amplifier 

Adjust (Mfg. Spec. 

w/0.100VDC input – 

Nominal = 0.00VDC 

output) 

Output Amplifier 

Adjust (Mfg. Spec. 

w/1.00VDC input – 

Nominal = 2.00VDC 

output) 

 0.002V 1.000 0.000V 2.018V adj. no lower 

Scintillometer 

Serial No. 2 

AGC Card U1 A/D Before adjustment(Mfg. 

Spec. w/0.100VDC input – 

Nominal = 0.00VDC output) 

Output Amp Adj. Before 

adjustment (Mfg. Spec. 

w/1.00VDC input – Nominal 

= 2.00Vdc output) 

 0.002 V 2.016V 

 

Cn

2 Card 

Input Amplifier 

Balance Before 

adjustment (Nominal 

= 0.00 +/-5 mv ) 

Cn

2

 voltage at 

BNC after 

adjustment 

(Nominal = 

1.000) 

Output Amplifier 

Adjust (Mfg. Spec. 

w/0.100VDC input – 

Nominal = 0.00VDC 

output) 

Output Amplifier 

Adjust (Mfg. Spec. 

w/1.00VDC input 

Nominal = 2.00VDC 

output) 

 0.006 V 0.998V 0.001V 2.027V 

Scintillometer 

Serial No.10 

AGC Card U1 A/D Before adjustment(Mfg. 

Spec. w/0.100VDC input – 

Nominal = 0.00VDC output) 

Output Amp Adj. Before 

adjustment (Mfg. Spec. 

w/1.00VDC input – Nominal 

= 2.00Vdc output) 

 0.002 VDC 2.006VDC 

 

Cn

2 Card 

Input Amplifier 

Balance Before 

adjustment (Nominal 

= 0.00 +/-5 mv ) 

Cn

2

 voltage at 

BNC after 

adjustment 

(Nominal = 

1.000) 

Output Amplifier 

Adjust (Mfg. Spec. 

w/0.100VDC input – 

Nominal = 0.00VDC 

output) 

Output Amplifier 

Adjust (Mfg. Spec. 

w/1.00VDC input 

Nominal = 2.00VDC 

output) 

 0.006 V 1.002 0.002V 2.032V adj. no lower 

Scintillometer 

Serial No. 11 

AGC Card U1 A/D Before adjustment(Mfg. 

Spec. w/0.100VDC input – 

Nominal = 0.00VDC output) 

Output Amp Adj. Before 

adjustment (Mfg. Spec. 

w/1.00VDC input – Nominal 

= 2.00VDC output) 

 0.002 V 2.024V 

 

Cn

2 Card 

Input Amplifier 

Balance Before 

adjustment (Nominal 

= 0.00 +/-5 mv ) 

Cn

2

 voltage at 

BNC after 

adjustment 

(Nominal = 

1.000) 

Output Amplifier 

Adjust (Mfg. Spec. 

w/0.100VDC input – 

Nominal = 0.00VDC 

output) 

Output Amplifier 

Adjust (Mfg. Spec. 

w/1.00VDC input 

Nominal = 2.00VDC 

output) 

 0.000V 0.999V 0.006V 2.011V adj. no lower 
55 

Acronyms and Abbreviations 

2-D two dimensional 

3-D three-dimensional 

AFRL Air Force Research Laboratory 

AGL above ground level 

AR Army Regulations 

ARL U.S. Army Research Laboratory 

ASCII American Standard Code for Information Interchange 

BIL Burst Illumination Laser 

CERDEC Communications Electronics Research Development and Engineering Command 

cm centimeter 

DASYS Danish system 

ELVISS Enhanced Low light level and VIsible Surveillance System 

EOVAF Electro-Optical Vulnerability analysis Facility 

FFT Fast Fourier Transform 

FRS Family Radio Service 

ft feet or foot 

FWHM Full Width at Half Maximum 

GPS Global Positioning System 

HELSTF High Energy Laser System Test Facility 

HWY Highway 

Hz hertz 

ID identification 

IR infrared 

km kilometer 
56 

LASSIE Land-based Active System & Surveillance Image Enhancement 

LGS Laser Ground Safety 

LOS line-of-sight 

LSTC Laser System Test Center 

m meter 

met meteorological 

MFS Missile Flight Safety 

MOA memorandum of agreement 

mrad milliard 

NATO North Atlantic Treaty Organization 

NIR near infrared 

nm nanometer 

NVESD Night Vision and Electronic Sensors Directorate of CERDEC 

OA observation area 

OD optical density 

ORD Operational Requirements Document 

PC personal computer 

PPE personal protective equipment 

RTG Research Technology Group 

s second 

SBL stable boundary layer 

SIM Sensor Interface Module 

SLAD Survivability/Lethality Analysis Directorate 

SOP Standard Operating Procedure 

SOP Safety Operating Procedure 

SQL Structured Query Language 

SWIR Short-wave IR 
57 

TTL transistor-transistor logic 

U.K. United Kingdom 

UXO unexploded ordinance 

WSMR White Sands Missile Range 

NOTE: Also see abbreviations given in table 5 for reference points at test site.
58 

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2275 D Street 

WPAFB OH 45433-7226 

Dr. Andy Goroch 1 CD/1 HC 

Naval Research Laboratory 

Marine Meteorology Division, Code 7543 

7 Grace Hopper Ave 

Monterey, CA 93943-5006 

U.S. Naval War College 1 CD 

War Gaming Department (Code 33) 

686 Cushing Road 

Newport, Rhode Island 02841-1207 

Naval Postgraduate School 1 CD 

J. D. Eagle 

OR/Er 

1 University Circle 

Monterey, CA 93943 

Naval Postgraduate School 1 CD 

R. K. Wood 

OR/Wd 

1 University Circle 

Monterey, CA 93943 

Naval Postgraduate School 1 CD 

G. Schacher 

Dept. of Physics 

1 University Circle 

Monterey, CA 93943 

Naval Postgraduate School 1 CD 

W. B. Maier II 

Dept. of Physics 

1 University Circle 

Monterey, CA 93943 

Ruth H. Hooker Research Library 1 CD 

4555 Overlook Ave, SW 

Washington, DC 20375 

JWARS 1 CD 

Attn: C. Burdick 

1555 Wilson Boulevard, Suite 619 

Arlington, VA 22209 

U.S. Army Research Laboratory 2 CDs 

AMSRD ARL CI OK TP Techl Lib 

APG, MD 21005 

Distribution Copies 

Northrop Grumman Information Technology 1 CD 

Melanie Gouveia 

55 Walkers Brook Dr 

Reading MA 01867 

Northrop Grumman Information Technology 1 CD 

Dr. Haig Iskenderian 

55 Walkers Brook Dr. 

Reading, MA 01867 

Anteon Corp. 1 CD 

Mike Adams 

46 Growing Rd 

Hudson, NH 03051 

SAIC 1 CD 

Attn: Mr. Delgado 

731 Lakepointe Centre Dr. 

O’Fallon, Ill 62269-3064 

Technical Reports Boulder Laboratories Library, 

MC 5 1 CD 

325 Broadway 

Boulder, CO 80305 

NCAR Library Serials 1 CD 

National Center for Atmospheric Research 

PO Box 3000 

Boulder CO 80307-3000 

U.S. Army Research Laboratory 1 CD/1 HC 

Attn: IMNE ALC IMS 

Mail & Records Mgmt 

Adelphi, MD 20783-1197 

Administrator 1 CD 

Defns Techl Info Ctr 

Attn: DTIC OCP (V Maddox) 

8725 John J Kingman Rd., Ste. 0944 

Ft Belvoir, VA 22060-6218 

U.S. Army Research Laboratory 2 CDs 

AMSRD ARL CI OK TL Techl Lib 

2800 Powder Mill Rd. 

Adelphi, MD 20783-1197 

US Army Night Vision & Electronic Sensors 

Directorate 1 CD/1 HC 

Sensor Performance Branch 

Attn: AMSRD-CER-NV-MS-SP (J. Reynolds) 

10221 Burbeck Road 

Fort Belvoir, VA 22060-5806 
60 

Distribution Copies

US Army Night Vision & Electronic Sensors 

Directorate 1 CD/1 HC 

Sensor Performance Branch 

Attn: AMSRD-CER-NV-MS-SP (R. Espinola) 

10221 Burbeck Road 

Fort Belvoir, VA 22060-5806 

US Army Night Vision & Electronic Sensors 

Directorate 1 CD/1 HC 

Sensor Performance Branch 

Attn: AMSRD-CER-NV-MS-SP (M. Friedman) 

10221 Burbeck Road 

Fort Belvoir, VA 22060-5806 

Dr. R. Rasmussen 1 CD 

National Center for Atmospheric Research 

P.O. Box 3000 

Boulder, CO 80307-3000 

Dr. E. Jacobs 1 CD/1 HC 

The University of Memphis 

Department of Electrical and Computer Engineering 

206 Engineering Science Bldg. 

Memphis, TN 38152-3180 

Endre Repasi Special Order (1 CD) 

FGAN-FOM 

Research Institute for Optronics and Pattern Recognition 

Gutleuthausstrasse 1 

76275 Ettlingen 

Germany 

Endre Repasi 1 CD 

FGAN-FOM 

Research Institute for Optronics and Pattern 

Recognition 

Gutleuthausstrasse 1 

76275 Ettlingen 

Germany 

Luc Forand 1 CD 

DRDC Valcartier 

2459 Pie XI Blvd North 

Quebec, QC 

Canada G3J 1X5 

TOTAL 58 CDs and 22 HCs