Solid State Light Evaluation in the US Lab Mockup - NASA · Solid State Light Evaluation in the US...

NASA/TM–2009–214784

Solid State Light Evaluation in the US Lab Mockup James C. Maida Space Human Factors Lab – Flight Projects Division NASA Johnson Space Center Houston, Texas 77058 Charles Bowen Space Human Factors Lab – Flight Projects Division NASA Johnson Space Center Houston, Texas 77058 Chuck Wheelwright (retired) Space Human Factors Lab – Flight Projects Division NASA Johnson Space Center Houston, Texas 77058

March 2009

THE NASA STI PROGRAM OFFICE . . . IN PROFILE Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA’s scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA’s institutional mechanism for disseminating the results of its research and development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report types: • TECHNICAL PUBLICATION. Reports of

completed research or a major significant phase of research that present the results of NASA programs and include extensive data or theoretical analysis. Includes compilations of significant scientific and technical data and information deemed to be of continuing reference value. NASA’s counterpart of peer-reviewed formal professional papers but has less stringent limitations on manuscript length and extent of graphic presentations.

• TECHNICAL MEMORANDUM. Scientific and

technical findings that are preliminary or of specialized interest, e.g., quick release reports, working papers, and bibliographies that contain minimal annotation. Does not contain extensive analysis.

• CONTRACTOR REPORT. Scientific and

technical findings by NASA-sponsored contractors and grantees.

• CONFERENCE PUBLICATION. Collected papers from scientific and technical conferences, symposia, seminars, or other meetings sponsored or cosponsored by NASA.

• SPECIAL PUBLICATION. Scientific, technical,

or historical information from NASA programs, projects, and mission, often concerned with subjects having substantial public interest.

• TECHNICAL TRANSLATION. English-

language translations of foreign scientific and technical material pertinent to NASA’s mission.

Specialized services that complement the STI Program Office’s diverse offerings include creating custom thesauri, building customized databases, organizing and publishing research results . . . even providing videos. For more information about the NASA STI Program Office, see the following: • Access the NASA STI Program Home Page at

http://www.sti.nasa.gov • E-mail your question via the internet to

[email protected] • Fax your question to the NASA Access Help

Desk at (301) 621-0134 • Telephone the NASA Access Help Desk at (301)

621-0390 • Write to: NASA Access Help Desk NASA Center for AeroSpace Information 7115 Standard Hanover, MD 21076-1320

NASA/TM–2009–214784

Solid State Light Evaluation in the US Lab Mockup James C. Maida Space Human Factors Lab – Flight Projects Division NASA Johnson Space Center Houston, Texas 77058 Charles Bowen Space Human Factors Lab – Flight Projects Division NASA Johnson Space Center Houston, Texas 77058 Chuck Wheelwright (retired) Space Human Factors Lab – Flight Projects Division NASA Johnson Space Center Houston, Texas 77058

March 2009

Available from:

NASA Center for AeroSpace Information National Technical Information Service 7115 Standard Drive 5285 Port Royal Road Hanover, MD 21076-1320 Springfield, VA 22161 301-621-0390 703-605-6000

This report is also available in electronic form at http://ston.jsc.nasa.gov/collections/TRS/

i

Contents

1.0 Background ....................................................................................................................... 1 2.0 Experimental Conditions Apparatus.................................................................................. 2 3.0 Experiment Procedure ....................................................................................................... 7 4.0 Results .............................................................................................................................. 7 Appendix A: Response Worksheets ............................................................................................. 15 Appendix B: Rating Survey Responses........................................................................................ 18 Appendix C: Contrast Sensitivity and the Perception of SSL Glare ............................................ 19

Figures

Figure 1. Transverse partition as viewed from SSL side............................................................ 3 Figure 2. Workstation, GLA side of partition. ........................................................................... 3 Figure 3. Node 1 end cone surfaces. .......................................................................................... 4 Figure 4. Fluorescent GLA spectra ............................................................................................ 5 Figure 5. Filtered and unfiltered SSL spectra............................................................................. 5 Figure 6. Text sample, wire cable, and computer....................................................................... 6 Figure 7. .................................................................................................................................... 8 Figure 8. .................................................................................................................................... 8 Figure 9. .................................................................................................................................... 9 Figure 10. .................................................................................................................................... 9 Figure 11. .................................................................................................................................. 10 Figure 12. .................................................................................................................................. 10 Figure 13. .................................................................................................................................. 11 Figure 14. .................................................................................................................................. 11 Figure 15. .................................................................................................................................. 12 Figure 16. .................................................................................................................................. 12 Figure 17. .................................................................................................................................. 13 Figure 18. .................................................................................................................................. 13 Figure 19. .................................................................................................................................. 14 Figure 20. Human contrast sensitivity function ......................................................................... 19

ii

Acronyms

CCT correlated color temperature GLAs general luminaire assemblies ISS International Space Station JSC Johnson Space Center LED light-emitting diode SSL solid state light

1

1.0 Background

This document constitutes the publication of work performed by the Space Human Factors Laboratory (mail code SF5 at the time) at Johnson Space Center (JSC) in the months of June and July 2000. Originally, the report was to be a document for internal consumption at JSC as it was seen as preliminary work for the development of solid state illumination for general lighting on future space vehicles and the International Space Station (ISS). Due to funding constraints, immediate follow-on efforts were delayed and the need for publication of this document was overcome by other events. However, in recent years and with the development and deployment of a solid state light (SSL) luminaire prototype on the ISS, the time was overdue for publishing this information for general distribution and reference.

SSLs are being developed to potentially replace the general luminaire assemblies (GLAs) currently in service in the ISS and included in designs of modules for the ISS. The SSLs consist of arrays of light emitting diodes (LEDs), small solid state electronic devices that produce visible light in proportion to the electrical current flowing through them. Recent progressive advances in electrical power-to-light conversion efficiency in LED technology have allowed the consideration of LEDs as replacements for incandescent and fluorescent light sources in many circumstances, and their inherent advantages in ruggedness, reliability, and life expectancy make them attractive for applications in spacecraft. One potential area of application for the SSLs is in the US Laboratory Module of the ISS. This study addresses the suitability of the SSLs as replacements for the GLAs in this application.

Three human factors questions were addressed by the study. First was whether the illumination level provided by the mockup GLAs was adequate for the performance of the visual tasks and whether there was any difference in performance under illumination from SSLs adjusted to a comparable level. The second question addressed the importance of the spectral characteristics of the illumination for the visual tasks being studied. The third question involved whether the astronauts sensed any differences in the way they perceived the US Laboratory Module environment with GLA or SSL lighting.

2

2.0 Experimental Conditions and Apparatus

The evaluation was designed to take a “quick look,” from the human factors standpoint, at the suitability of SSLs as replacements for the GLAs in the US Laboratory Module working environment. Three visual tasks for the evaluation were selected to broadly represent some of those likely to be encountered in this environment: (1) reading printed text and equipment legends; (2) interacting with computers; and (3) comparing/judging colors. Special attention was paid to controlling the light levels and spectral characteristics during the performance of the visual tasks. Participants were drawn from the pool of astronauts training for ISS missions at JSC.

The environment for the experiment was the US Laboratory Module mockup of the Space Station Mockup Test Facility. Standard lighting for the module is provided by 12 GLAs. For the experiment, six Sylvania mockup GLAs were installed. A removable temporary Foamcore partition was installed transversely at the midpoint of the module (figure 1), and the six GLAs above Bay 04 through Bay 06 were replaced with SSLs. This allowed two sets of isolated lighting conditions to be produced simultaneously in the two halves of the module. An access door was constructed in the partition to allow the experiment conductor and participant rapid access to both sides of the partition. Removable work surfaces were fitted to the starboard rack of Bay 02 on the GLA side of the partition (figure 2) and to the port rack of Bay 05 on the SSL side (figure 1). The vertical rack surface above and behind the work surface on the GLA side (figure 2) was covered with Foamcore material to approximate the reflective characteristics of the rack panels adjacent to the work surface on the SSL side. The blue end cone surfaces at the Node 1 end of the Lab Module were also covered with Foamcore (figure 3) to more nearly match the reflective characteristics of the Node 2 end cone.

3

Figure 1. Transverse partition as viewed from SSL side.

Figure 2. Workstation, GLA side of partition.

4

During the experiment, all individual dimmer controls on the GLAs were adjusted for maximum brightness, and the illumination from the SSLs was adjusted to produce equivalent illuminance readings (22 to 23 foot-candles [fc]) in the centers of the work surfaces on both sides of the partition. Illuminance readings on equipment rack surfaces throughout the module exceeded the work surface values by as much as 10 fc near the “tops” of the racks beneath the luminaires, while readings on the rack surfaces near the floor were as low as 5.6 fc. Ganged control of illumination from the SSLs was effected by adjusting the common direct current voltage applied to the SSL luminaires. Time for SSL thermal stabilization was allowed following adjustments in power supply settings to minimize variations in SSL illumination. Electrical current drawn by the SSLs and work surface light levels were monitored throughout the experiment sessions.

A set of filters were constructed for use with the SSLs in the second session of the experiment. These were designed to adjust the correlated color temperature (CCT) of the SSLs to approximate the CCT of the GLAs. The CCT of the Sylvania GLAs was measured to be 4324°K, whereas the CCT of the SSLs was measured to be 6700°K and 4166°K for the unfiltered and filtered cases, respectively. The filter material used was Rosco International Type 3442, a commercial stabilized gelatin stage lighting filter film. Color characteristics of the lights used in the experiment were measured with a Photo Research Model 650 colorimeter. Visible spectra for the lights are shown in figures 4 and 5.

5

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

380 420 460 500 540 580 620 660 700 740 780

W avelength (nm)

Rad

ianc

e (W

/m2/

sr)

Figure 4. Fluorescent GLA spectra.

Figure 5. Filtered and unfiltered SSL spectra.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

380 420 460 500 540 580 620 660 700 740 780

W avelength (nm)

Rad

ianc

e (W

/m2 /s

r)

Unfilte red

Filte red

6

Text samples were prepared for the participants to read under the various experimental lighting conditions. These were drawn from current short summaries of technical papers on various topics published in Science News. Each article was transcribed and printed on white paper in 10-point sans serif (Arial) font. Transcribed text was single spaced, providing a greater challenge to the reader.

The laptop computer used in the experiment was a Fujitsu Lifebook Model L470 (figure 6), having a 9-inch diagonal back-lighted LCD color display. The settings for the display brightness and contrast were fixed during the experiment to produce approximately 16.5fL, 11.0fL, 6.7fL brightness readings for the respective white, gray, and black areas of the survey display. All survey prompts were displayed and responses and comments were recorded by means of the computer. Software supporting these activities consisted of a group of Microsoft Excel spreadsheets including option buttons for survey responses and text boxes for comment entries. Spreadsheet contents are represented in their initialized state in Appendix A. Once a selection was made from a group of buttons, it remained active until the end of the session or an alternate button was selected.

Challenges to color rendering under the experimental lighting conditions were explored by having the participants examine a cable with multicolored insulated 22 American Wire Gauge wires to judge the ease of identifying (naming) colors and the ease of differentiating between the colors.

Figure 6. Text sample, wire cable, and computer.

7

3.0 Experiment Procedure

The participants performed the experiment in two sessions. In each session, responses to one of the forms of the SSL were examined along with the responses to the GLAs. The SSLs used in the first session were unfiltered, and the second session used the same SSLs fitted with filters to alter the light spectrum to approximate the CCT of the GLAs. This arrangement precluded complete balancing of the order of presentation of the different lighting conditions, but it eliminated the considerable time required to install or remove the filters, thereby reducing the time required of the participants to complete the experiment. Within each session, however, the order of presentation of the GLA or SSL conditions was randomly balanced, with half the participants experiencing each order.

The same sequence of tasks was used for both lighting conditions in each session. First, the participant was provided with a printed page of black-on-white printed text. After reading the passage, the participant completed the rating survey on the computer. A second rating survey relating to the ease of computer use in the lighting environment followed the text reading. Once the reading and computer use surveys were completed, the participant was provided with an electrical cable comprised of wires with multicolored insulation. The participant examined the colored wires and again turned to the computer to complete the last portion of the rating survey, which related to the ease of color judgment and the overall module lighting characteristics.

4.0 Results

The use of an Excel spreadsheet for collecting the ratings allowed relative ease in categorizing, counting, and graphically representing the response frequencies. A tabulation of responses to the rating survey items is included as Appendix B.

The survey responses and comments were interpreted to indicate the following results:

• The SSL is a suitable replacement for the GLA. • The CCT of the evaluated SSLs is acceptable for the tasks performed. • Glare in the US Laboratory Module is not significant with either GLA or SSL

lighting. • The availability of higher light intensity than that provided by the current GLA

would be beneficial. • SSL fixtures should be made available for long-term evaluations and routine

mockup training activities. Responses to survey items are summarized in figures 7 through 19. In these charts, the response categories “strongly agree” and “somewhat agree” are combined as “agree.” Similarly, the “strongly disagree” and “somewhat disagree” categories are lumped together as “disagree.”

8

Figure 7

Figure 8

The color of the lighting distracts me while reading black-on-white text.

0

2

4

6

8

10

12

GLA SSL Filtered SSL

Res

pons

e C

ount

AgreeAmbivalentDisagree

The module lighting is bright enough to read black-

on-white text comfortably.

0

2

4

6

8

10

12


Res

po

nse

Cou

nt

Agree Ambivalent Disagree

9

Figure 9

Figure 10

The module lighting seems harsh or glaring when I am reading black-on-white text.

0

2

4

6

8

10

12


Res

pons

e C

ount


The distribution of light within the module is satisfactory for reading black-on-white text.

0

2

4

6

8

10

12


Res

pons

e C

ount


10

Figure 11

Figure 12

The module lighting is bright enough to allow me to use the computer comfortably.

0

2

4

6

8

10

12


Res

pons

e C

ount


The color of the lighting distracts me while I am using the computer.

0

2

4

6

8

10

12


Res

pons

e C

ount


11

Figure 13

Figure 14

The module lighting seems harsh or glaring when I am using the computer.

0

2

4

6

8

10


Res

pons

e C

ount


The distribution of light within the module is satisfactory for using the computer.

0

2

4

6

8

10

12


Res

pons

e C

ount


12

Figure 15

Figure 16

The lighting makes it difficult to distinguish some wire colors from others.

0

2

4

6

8

10

12


Res

pons

e C

ount


The lighting makes it difficult to identify the colors of some of the wires.

0

2

4

6

8

10


Res

pons

e C

ount


13

Figure 17

Figure 18

The overall illumination allows easy reading of labels on equipment throughout the module.

0123456789


Res

pons

e C

ount


The distribution of light within the module is satisfactory.

0

2

4

6

8

10


Res

pons

e C

ount


14

Figure 19

The color of the lighting makes the module seem warm/cold.

0123456789


Res

pons

e C

ount

WarmAmbivalentCold

15

Appendix A. Response Worksheets

Com ple te ly agree

S om ew hat agree

Ne ither agree nor disagree

S om ew hat disagree

Com ple te ly disagree

The m odule lighting seem s harsh or gla r ing w hen I am reading black-on-w hite text.

Com ple te ly agree

S om ew hat agree




The lighting conditions for reading black-on-w hite text a re uniform throughout the m odule .

Com ple te ly agree

S om ew hat agree




The m odule lighting is br ight enough to read black-on-w hite text com fortably.

Com ple te ly agree

S om ew hat agree




The color of the lighting distracts m e w hile I am reading black-on-w hite text.

Comments regard ing read ing b lack-on-white text:

P lease read the p rinted a rtic le and then answer the fo llowing questions:

16

The m odule lighting is br ight enough to a llow m e to use the com puter com fortably.

T he color of the lighting dis tracts m e w hile I am us ing the com puter.

The m odule lighting seem s harsh or gla r ing w hen I am us ing the com puter.

The lighting conditions for com puter use a re uniform throughout the m odule .

Com ple te ly agree

S om ew hat agree




Com ple te ly agree

S om ew hat agree




Com ple te ly agree

S om ew hat agree




Com ple te ly agree

S om ew hat agree




Comments regard ing compute r use :

17

The overa ll illum ination a llow s easy reading of labe ls on equipm ent throughout the m odule .

T he diffe rence in br ightness betw een lighter and darker a reas in the m odule is sa tis factory.

T he color of the lighting m akes it difficult to distinguish w ire co lors.

Com plete ly agree

S om ew hat agree



Com plete ly disagree

Com ple te ly agree

S om ew hat agree




Com ple te ly agree

S om ew hat agree




T he color of the lighting m akes the m odule seem :

W arm

S om ew hat w arm

Ne ither w arm nor co ld

S om ew hat co ld

Cold

Comments:

Please perfo rm the wire matching task and then answer the fo llowing questions:

18

Appendix B: Rating Survey Responses

Response Frequencies Light Question Comp. S’what S’what Comp. No Type Category Question agree agree Ambiv. disagree disagree Resp.

Bright enough? 5 2 1 3 1 0 Text Color distracting? 0 1 3 1 7 0 Reading Harsh or glaring? 0 0 2 2 8 0 Brightness ratio OK? 4 3 1 3 0 1 Bright enough? 8 2 0 1 0 1 Computer Color distracting? 0 1 2 2 6 1

GLA Use Harsh or glaring? 0 2 2 3 4 1 Brightness ratio OK? 5 4 1 1 0 1 Color distinguishing problem? 2 2 0 3 5 0 Color Color naming problem? 2 2 0 3 4 1 & Easy to read labels? 5 3 0 4 0 0 Overall Brightness ratio OK? 4 3 0 4 1 0 Warm (agree)/cold? 1 2 5 3 1 0 Bright enough? 6 3 1 0 1 1 Text Color distracting? 0 1 1 2 8 0 Reading Harsh or glaring? 1 3 2 1 5 0 Brightness ratio OK? 7 2 0 2 0 1 Bright enough? 7 3 0 0 0 2 Computer Color distracting? 0 1 0 3 7 1

SSL Use Harsh or glaring? 0 4 1 1 5 1 Brightness ratio OK? 6 3 2 0 0 1 Color distinguishing problem? 0 1 1 2 5 3 Color Color naming problem? 0 4 0 1 6 1 & Easy to read labels? 4 4 0 4 0 0 Overall Brightness ratio OK? 4 4 2 2 0 0 Warm (agree)/cold? 2 1 5 3 1 0 Bright enough? 6 4 0 1 1 0 Text Color distracting? 1 0 2 3 6 0 Reading Harsh or glaring? 0 1 2 4 5 0 Brightness ratio OK? 5 6 0 1 0 0

SSL Bright enough? 8 1 1 0 0 2 with Computer Color distracting? 0 2 1 3 5 1 Filter Use Harsh or glaring? 0 1 0 6 3 2

Brightness ratio OK? 5 5 0 0 1 1 Color distinguishing problem? 5 5 0 0 1 0 Color Color naming problem? 0 3 0 2 7 0 & Easy to read labels? 0 3 2 1 6 0 Overall Brightness ratio OK? 4 5 1 2 0 0 Warm (agree)/cold? 3 5 1 3 0 0

19

Appendix C. Contrast Sensitivity and the Perception of SSL Glare

Glare is predicted when a light source or reflective surface in the observer’s field of view exceeds the surrounding brightness by a ratio of 12:1 or more. An additional factor not usually considered in predicting glare is the human contrast sensitivity function. This characteristic, shown in figure 20, relates the sensitivity of the human visual system to periodic spatial variations in contrast (brightness). The graph of figure 20 shows that humans respond most strongly to variations in contrast in the spatial frequency range from about two to four cycles per degree of visual angle.

When considered from the standpoint of contrast sensitivity, the periodic spacing of rows of LEDs arrayed in an SSL may conspire with the interior dimensions of a habitable structure such as the US Laboratory Module to exacerbate the perception of glare from the luminaire. The visual angle, α , between two points S distance apart from one another and viewed from a distance D is calculated as ( )12 tan 2S Dα −= . For example, assuming that the spacing between rows of

LEDs in the SSL is 0.3 inch (similar to the row spacing in the SSLs used in this experiment), and that viewing distances range from 2 feet to 7 feet, the row spacing in terms of visual angle occupies from 0.205º to 0.716º. Since the fundamental spatial frequency corresponding to the LED spacing, sf , is the reciprocal of the visual angle α , the range of fundamental spatial

frequencies corresponding to this range for α in cycles per degree (~/°) is

{ }1.4~/ 4.9~/sf° ≤ ≤ ° . The range for sf in this example thus brackets the peak of the contrast

sensitivity function, possibly increasing the likelihood of the perception of glare. The spacing of point source illumination elements in arrays to form luminaires might well be considered in relation to the dimensions of the space in which they may be viewed when designing for increased visual comfort.

Figure 20. Human contrast sensitivity function.

Reference: Owsley, Cynthia, Robert Sekuler, and Dennis Siemsen (1983). Contrast sensitivity throughout adulthood. Vision Research 23(7), 689-699.

10

100

1000

0.1 1 10 100

Spatial Frequency (cycles/degree)

Con

tras

t Sen

sitiv

ity

Age 20-30Age 60-70

REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

1. AGENCY USE ONLY (Leave Blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED March 2009 NASA Technical Memorandum

4. TITLE AND SUBTITLE 5. FUNDING NUMBERSSolid State Light Evaluation in the US Lab Mockup

6. AUTHOR(S) James C. Maida, Charles Bowen, Chuck Wheelwright NASA Johnson Space Center, Houston, TX 77058

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBERS

Lyndon B. Johnson Space Center Houston, Texas 77058

S-1036

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY REPORT NUMBER

National Aeronautics and Space Administration Washington, DC 20546-0001

TM–2009–214784

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Available from the NASA Center for AeroSpace Information (CASI) 7115 Standard Hanover, MD 21076-1320 Category: 18

13. ABSTRACT (Maximum 200 words) Solid state lights (SSLs) are being developed to potentially replace the general luminaire assemblies (GLAs) currently in service in the ISS and included in designs of modules for the ISS. The SSLs consist of arrays of light emitting diodes (LEDs), small solid state electronic devices that produce visible light in proportion to the electrical current flowing through them. Recent progressive advances in electrical power-to-light conversion efficiency in LED technology have allowed the consideration of LEDs as replacements for incandescent and fluorescent light sources in many circumstances, and their inherent advantages in ruggedness, reliability, and life expectancy make them attractive for applications in spacecraft. One potential area of application for the SSLs is in the US Laboratory Module of the ISS. This study addresses the suitability of the SSLs as replacements for the GLAs in this application.

14. SUBJECT TERMS 15. NUMBER OF PAGES

16. PRICE CODE

light sources, lighting equipment, aircraft lights, illuminating, US Laboratory Module 28

17. SECURITY CLASSIFICATION OF REPORT

18. SECURITY CLASSIFICATION OF THIS PAGE

19. SECURITY CLASSIFICATION OF ABSTRACT

20. LIMITATION OF ABSTRACT

Unclassified Unclassified Unclassified Unlimited Standard Form 298 (Rev Feb 89) (MS Word Mar 97) Prescribed by ANSI Std. 239-18 298-102

NSN 7540-01-280-5500

Solid State Light Evaluation in the US Lab Mockup - NASA · Solid State Light Evaluation in the US...

Documents

Transcript of Solid State Light Evaluation in the US Lab Mockup - NASA · Solid State Light Evaluation in the US...