NASA Technical Memorandum 4520 Hazard Calculations of Diffuse Reflected Laser Radiation for the SELENE Program Gilda A. Miner Langley Research Center Hampton, Virginia Phillip D. Babb The Bionetics Corporation Hampton, Virginia ( _: A S A- T _I--.',,.5 2 0 _ HAZA_9 CALCULATIONS JF i'[FFIJS_ REFLECTED LA.£ER #,Ai IATI['_!,_ FqF_ Tt-4L SFL,,_£ PROGRAM N94-17265 Unclas f &SA National Aeronautics and Space Administration Office of Management Scientific and Technical Information Program 1993 Htl30 0193596 https://ntrs.nasa.gov/search.jsp?R=19940012812 2018-04-30T10:27:49+00:00Z
12
Embed
Hazard Calculations of Diffuse Reflected Laser Radiation · PDF fileNASA Technical Memorandum 4520 Hazard Calculations of Diffuse Reflected Laser Radiation for the SELENE Program Gilda
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
NASA Technical Memorandum 4520
Hazard Calculations of Diffuse
Reflected Laser Radiation for
the SELENE Program
Gilda A. Miner
Langley Research Center
Hampton, Virginia
Phillip D. Babb
The Bionetics Corporation
Hampton, Virginia
( _: A S A- T _I--.',,.5 2 0 _ HAZA_9 CALCULATIONS
The hazards from diffuse laser light reflections off water clouds, ice clouds,
and fog and from possible specular reflections off ice clouds were assessed with
the American National Standards (ANSI ZI36.1 1986) for the free-eleetron-lascr
parameters under consideration for the Segmented Efficient Laser Emission fi>r Non-
Nuclear Electricity (SELENE) Program. Diffuse laser reflection hazards exist for
water cloud surfaces less than 722 m in altitude and ice cloud surfaces less thtm
850 rn in altitude. Specular reflectimts front ice crystals in cirrus clouds are not
probable; however, any specular reflection is a hazard to ground observers. The
hazard to the laser operators and any ground observers during heavy fog conditions
is of such significant magnitude that the laser should 7_ot be operated in fog.
Introduction Symbols
Outdoor laser systems require two additional asafety concerns not associated with indoor laser Hsystems: (1) atmost)herie scattering and (2) safe-
viewing distances for specular and diffuse reflections
for both laser operators and ground observers. Be- Hefore an outdoor laser is operated, laser hazard levels
are calculated and intensity levels are measured tohelp establish safety proee<tures. Outdoor lasers have MPE
been successfully used by the military services with
the use of class 3 and class 4 systems in their laser
range finders, laser target designators, and direct firesimulators. Only one laser injury occurred with these
outdoor systems during the 1980's (ref. 1). MPEDIFF
In addition, LIDAR (light detecting and ranging)
has been use d suceessflflly since the early 1960's to
remotely study the atmosphere (ref. 2). Initially, MPEDIRru])y lasers were use(t to allalyze species a n(t impurity
concentrations of the atmosphere to distances up to
35 kin. Now, gigawatt Nd:YAG lasers are beingused to analyze impurities to distances of 100 kin. NHZ
Experiments measuring atmospheric polhltion aren
performed at night to detect return photons becausethe signal-to-noise ratio is too small during the day. prfThe concern that LIDAR reflections fronl clouds werea safety hazard generated many cloud mo<lels and Q
reflection experiments, r
The two types of reflected laser radiation are spec- rNHZ
ular and diffuse (ref. 3). When the beam front re-nmins intact and is as nmch a hazard as the pri-
nmry laser beam, the reflection is specular. When
the beam is reflected and scattered uniformly in all Tdirections, the reflection is diffuse. Most reflectionsfrom clouds and haze are considered diffuse.. This t
paper addresses the hazards of possible specular re- 0_,flections from ice-forming cirrus clouds and diffuse re-
flected laser radiation from water clouds, ice chmds,
and fog for the Segmented Efficient. Laser Emissionfor Non-Nuclear Electricity (SELENE) Program. A
beanl (]ianleter_ cnl
radiant exposure, surface density of
radiant energy received, J-cm 2
emergent imam radiant exposure at
range r, J-eln -2
maxilnum permissible exposure,level of laser radiation to which
a person can be exposed without
hazardous effect or biologicalchanges in eye or skin, J-en1-2
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 thiscollection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Intormation Operations and Reports, 1215 JeffersonDavis 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
October 1993 Technical Memorandum
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
HazaM Calculations of Diffuse Reflected Laser Radiation for the
SELENE Program WU 506-41-41-01
6. AUTHOR(S)
Gilda A. Miner and Phillip D. Babb
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
NASA Langley Research Center
Hampton, VA 23681-00(11
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
National Aeronautics and Space Administration
WaMdngton, DC 20546-0001
8. PERFORMING ORGANIZATION
REPORT NUMBER
L- 17008
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
NASA TM-4520
11. SUPPLEMENTARY NOTES
Miner: Langley Research Center, Hampton, VA; Babb: The Bionetics Corporation, Hami)ton, VA.
12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE
Unclassified Unlimited
Subject Category 36
13. ABSTRACT (Maximum 200 wards)
The hazards from diffuse laser light reflections off water clouds, ice clouds, and fog and from possible specularreflections off ice ehmds were a_ssessed with the American National Standards (ANSI Z136.1 1986) for thefree-eh,t:tron-laser parameters untter consideration for the Segmented Efficient Laser Emission for Non-NuclearElectricity (SELI_:NE) Program. Diffuse ltLser reflection hazards exist for water cloud surfaces less than 722 m
in altitude and ice cloud surfaces less than 850 ti1 in altitude. Specular reflections from ice crystals in cirrus
clouds are not probable; however, any specular reflection is a hazaM to ground observers. The hazard to the
laser operators and any ground observers during heavy fog conditions is of such significant magnitu(le that thel_ser should not be operated in fog.
14. SUBJECT TERMS
Diffuse la._er reflections by clouds; SELENE Program