NASA s Laser Risk Reduction Program, begun in 2002, has achieved many technology advances in only 3.5 years. The recent selection of several lidar proposals for Science and Exploration applications indicates that the LRRP goal of enabling future space-based missions by lowering the technology risk has already begun to be met

Kavaya, Michael J.

Singh, Upendra N.

NASA Technical Reports Server

  
Enabling Laser and Lidar Technologies for NASA’s Science and Exploration 
Mission’s Applications 
 
 
Upendra N. Singh and Michael J. Kavaya 
NASA Langley Research Center, MS 468, Hampton, Virginia 23681 
 
 
 
Abstract – NASA’s Laser Risk Reduction Program, 
begun in 2002, has achieved many technology 
advances in only 3.5 years. The recent selection of 
several lidar proposals for Science and Exploration 
applications indicates that the LRRP goal of enabling 
future space-based missions by lowering the 
technology risk has already begun to be met. 
I. INTRODUCTION 
NASA entered a new era in the 1990’s with the approval 
of several space-based remote sensing missions 
employing laser radar (lidar) techniques. Following the 
steps of passive remote sensing and then active radar 
remote sensing, lidar (light detection and ranging) 
sensors were a logical next step, providing independence 
from natural light sources, and better spatial resolution 
and smaller sensor size than radar sensors. The shorter 
electromagnetic wavelengths of laser light also allowed 
signal reflectance from air molecules and aerosol 
particles. The smaller receiver apertures allowed the 
concept of scanning the sensor field of view. However,  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
technical problems with MOLA I, LITE, MOLA II, 
VCL, and SPARCLE during that decade led to concern 
at NASA about the risk of lidar missions. An external 
panel was convened to make recommendations to 
NASA. Their report in 2000 strongly advocated that 
NASA maintain in-house laser and lidar capability, and 
that NASA should work to lower the technology risk for 
all future lidar missions. NASA then formed an 
Integrated NASA Lidar Systems Strategy Team 
(INLSST), chaired by U. N. Singh at LaRC and W. S. 
Heaps at GSFC, to make specific recommendations for 
implementing the external panel’s advice. Their plan for 
a NASA Laser Risk Reduction Program (LRRP), to be 
lead by LaRC and GSFC with participation and 
collaboration from industry and academia, was approved 
by NASA’s Administrator in June 2001. Funding of the 
LRRP began in 2002. 
II. THE LRRP CONCEPT 
The LRRP implemented the recommendations to work 
on lidar technologies before mission approval and to  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 1. Connection between technology development and 6 priority measurements 
https://ntrs.nasa.gov/search.jsp?R=20050237878 2019-08-29T21:02:32+00:00Z
  
maintain in-house capability by using the strengths in 1-
micron solid-state lasers at GSFC and the strengths in 2-
micron solid-state lasers at LaRC to work on 
fundamental issues concerning these two laser 
technologies, as listed on the left side of Figure 1. With 
additional work on wavelength conversion technologies, 
the four lidar techniques of altimetry, Doppler, 
Differential Absorption Lidar (DIAL), and basic lidar 
backscattered signal strength profiling would be able to 
make 6 high priority earth science measurements: 
surface and ice mapping, horizontal vector wind profiles, 
river currents, CO2 profiles, O3 profiles, and 
aerosols/clouds. Figure 2 depicts the enabled lidar 
techniques and measurements. Through collaboration  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
and communication between LaRC and GSFC of 
questions, capabilities, and results, the advancement of 
the commonly needed areas of laser and wavelength 
conversion development would proceed faster and 
without duplicated effort. The goal of the LRRP is to 
advance the technologies to the point that science 
mission proposals could be confident of acceptable risk 
upon selection. 
III. LRRP TASKS AT LARC 
The main thrust of the LRRP effort at LaRC has been the 
development and risk reduction of the solid-state, diode-
pumped, 2-micron pulsed laser. The Ho:Tm:LuLF based 
laser will enable the measurement of wind, CO2, 
aerosols, clouds, and river flow. LaRC is the world 
leader in high pulse-energy 2-micron laser technology. 
However, the laser needed development in the areas of 
pulse energy, beam quality, heat removal, efficiency, and 
packaging. Another thrust at LaRC has been the laser 
diode arrays that are used to pump the 2-micron laser. 
The external panel, as well as NASA engineers, were 
very concerned about the lack of several commercial 
vendors providing space qualified LDAs, and the ability 
of the LDAs to have long life in space. This concern has 
been validated by the technical problems with the LDAs 
that occurred after launch of the ICESAT mission in 
2003. Both LaRC and GSFC have been working on 
LDAs in parallel, with emphases on the specific LDAs  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
needed to pump the 2 and 1 micron laser, respectively. A 
third LaRC thrust has been in technologies to convert the 
1 micron photons of the Nd:YAG laser to UV 
wavelengths needed for the DIAL measurement of 
ozone. Efficient and reliable conversion to pulse 
energies near 200 mJ with small components is desired. 
This task also was shared by LaRC and GSFC, with 
LaRC concentrating on high pulse energy techniques, 
and GSFC concentrating on high pulse repetition 
frequency techniques. An additional LRRP task at LaRC 
involved advancement of the receiver technologies for 
both coherent and direct detection lidar remote sensing 
at 2 microns. Any improvement in the detection 
efficiency allows either better measurement sensitivity 
Backscatter Lidar
• Cloud 
• Aerosol
Differential Absorption Lidar (DIAL)
• Ozone
• Carbon Dioxide
Doppler Lidar
• Wind Fields
• River Flow
Altimetry Lidar
• Ice Sheet Mass Balance 
• Vegetation Canopy
• Land Topography
fDoppler
Frequency
Transmit
Pulse
Return
Velocity = (λ/2) fDoppler
TArrival
Time
Transmit
Pulse
Return
Range = (c/2)TArrival
TArrival
Time
Transmit
Pulse
Return
Density = IS/IT
Range = (c/2)Tarrival
IT
IS
λoff λon
Transmit
Pulses
Returns
Concentration = 
log[ I(λon)/ I(λoff)]
Wavelength
Figure 2. Depiction of four techniques of lidar remote sensing using two lidar technologies 
  
with the same size laser and receiver mirror, or the same 
measurement sensitivity with a smaller laser and/or 
mirror. Since the laser and mirror sizes translate into 
cost, power, mass, volume, and heat removal; improved 
detection efficiency translates into a large mission 
benefit. Table 1 shows a summary of the LRRP thrusts at 
LaRC. 
Table 1. LRRP Thrust Areas at LaRC 
Thrust 
Area 
Areas of Risk 
Reduction 
Enabled 
Measurements 
Pulsed 
Laser 
Pulse energy 
Heat removal 
Efficiency 
Beam quality 
Damage 
Contamination 
Lifetime 
Packaging 
Earth: Wind, CO2, 
Aerosols, 
Clouds 
 
Mars: Wind, 
Density, Dust 
Pump Laser 
Diode 
Arrays 
Materials 
Architecture 
Lifetime 
Space 
qualification 
Availability 
All 2 micron laser 
measurements 
above 
Wavelength 
Conversion 
to UV 
Efficiency 
Pulse energy 
Damage 
Lifetime 
Ozone, Aerosols, 
Clouds 
2-Micron 
Direct 
Detector 
Responsivity 
Noise 
Active area 
Direct detection 
CO2, Aerosols, 
Clouds 
2-Micron 
Coherent 
Receiver 
Quantum 
efficiency 
Packaging 
Earth: Wind, CO2, 
Aerosols, Clouds 
 
Mars: Wind, 
Density, Dust 
 
Space only permits a sampling of the accomplishments 
to be mentioned here. 
IV. SELECTED ACCOMPLISHMENTS 
There has been a lot of hard work and many outstanding 
accomplishments to date by the outstanding LaRC team 
of technicians, engineers, and scientists involved with 
LRRP.  
Pulsed Laser 
The 2-micron laser activity which has been carried on 
under the LRRP builds on the coherent detection lidar 
technology developed for the SPARCLE (SPAce 
Readiness Coherent Lidar Experiment) Shuttle mission 
to measure winds. At that time, 100 mJ of single-mode 
2-micron pulse energy was the state-of-the-art [1]. Since 
then a new laser material with a 20% efficiency 
improvement over prior art has been formulated and 
demonstrated [2-4], exceeding 1 J pulse energy in a 
single pulse and 1.5 J in a double pulse in recent tests [5-
6]. Besides high energy and efficiency, another key 
requirement for space is conduction only cooling (as 
opposed to liquid cooling) of the laser structure. An all 
conductively-cooled laser architecture was recently 
demonstrated with more than ~100 mJ pulse energy and 
near diffraction limited beam quality [7]. 
 
Serendipitously, there is a very strong carbon dioxide 
(CO2) absorption line within the tuning range of this 2-
micron laser and this presents the opportunity to 
simultaneously measure CO2 along with wind, aerosols, 
dust, etc. The temperature profile can be obtained also 
by using both temperature independent and temperature 
dependent CO2 absorption lines. By transmitting both an 
on- and an off-resonant laser wavelength, the DIAL 
technique can measure CO2 concentration profiles.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 3. Drawing and photograph of the diode-pumped 
laser oscillator head 
 
Several steps towards such a multi-use lidar application 
have already been accomplished. Frequency control and 
locking of the laser wavelength to the CO2 absorption 
line has been demonstrated [8-10]. Double pulse 
operation of the 2-micron laser has been accomplished, 
which extracts more optical energy from the laser, thus 
raising efficiency, and opening the possibility of 
obtaining both DIAL laser wavelengths from each laser 
firing [11]. Recently, a DIAL measurement of CO2 was 
performed with the resonant and off-resonant DIAL 
wavelengths alternated at a 5-Hz rate, thus simulating 
the advantages of the double pulse laser technique. Since 
this technique greatly reduces the error from atmospheric 
fluctuations, a best ever precision of 1.5% for a CO2 
  
measurement was produced, though from a static 
platform [12]. Since CO2 comprises ~95% of the 
Martian atmosphere its measurement can be used to infer 
density profiles. The Martian troposphere is 40 km in 
depth and the altitude variations of CO2 could exceed 
two orders of magnitude. The strength of the 2-micron 
absorption lines in CO2 permits the use of off-line center 
DIAL techniques, leading to much greater dynamic 
range of the measurement, so that vertical profiling of 
density is possible through a significant portion of the 
atmospheric column. 
 
Current activities on the pulsed laser include completion 
of an all-conductively-cooled amplifier, phase conjugate 
mirror development for improved beam quality of the 
amplifier output, and compact, rugged packaging. 
 
Pump Laser Diode Arrays 
As indicated in Table 1, the pump laser diode arrays 
(LDA) are crucial to successfully utilizing the solid-state 
pulsed laser technology in space. Several of NASA’s 
space lidar missions have had trouble with the LDAs, 
most recently the ICESat mission. Recently, it was 
learned that the upcoming European Space Agency 
(ESA) Atmospheric Dynamics Mission (ADM) is also 
having technical problems with the LDAs. These 
missions all employ 1-micron lasers. The pulse duration 
needed to pump the 2-micron laser is 7 times longer than 
needed by the 1-micron laser, thereby increasing the 
LDA thermal transients and possibly decreasing lifetime. 
Both LDA Characterization and Lifetime Test Facilities 
have been designed, assembled, and put into intensive 
service. The lifetime facility can test up to 12 LDAs 
simultaneously. The experience at GSFC in setting up 
 
 
 
 
 
 
 
 
Figure 4. LDA lifetime test facility at LaRC 
 
similar facilities was leveraged by LaRC. LaRC has also 
worked heavily with industry to discuss the 
characterization and lifetime results of current LDAs, 
and to discuss ways to improve the LDAs [13]. Failure 
mechanisms being considered include laser bar material 
defect, thermal cycling, solder creep/migration, solder 
de-bonding, and bond wire failure. An improved LDA 
architecture using diamond in the LDA package in place 
of the standard BeO/Cu was developed by teaming with 
Northrup Grumman/CEO. Test show that the thermal 
resistance has been reduced by 17%, which should 
translate into a large improvement in lifetime. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 5. LDA data showing reduced thermal resistance 
 
Wavelength Conversion to UV 
The LaRC approach for generating the two UV 
wavelength (308 & 320 nm) laser pulses necessary to 
profile ozone concentration is to use Optical Parametric 
Oscillator (OPO) and Sum Frequency Generation (SFG) 
nonlinear optics technologies. LaRC has teamed with 
Sandia National Lab and Fibertek to accomplish this. 
Fibertek is fabricating a > 1J Nd:YAG laser for LaRC 
with the strict beam qualities needed to pump the 
nonlinear optical processes. Sandia has perfected models 
of the nonlinear processes and used these models to 
invent a novel OPO architecture (see Figure 6), and to 
provide guidance for the overall UV generation system. 
Up to 190 mJ pulse energy at 320 nm has already been 
demonstrated. Integration and demonstration of the 
components is planned at LaRC. 
 
0
1
2
3
4
5
6
7
8
0 1 2 3 4 5 6
Dissipated Heat (W )
R
el
at
iv
eT
em
p 
R
is
e 
(o C
)
Cu/Beo Package 
Rth = 1.88 oC/W
Diamond Package
Rth = 1.56 oC/W
0.0
0.5
1.0
1.5
41.00 41.50 42.00 42.50 43.00 43.50 44.00 44.50 45.00
Time (sec)
R
el
at
iv
e 
Te
m
pe
ra
tu
re
 (o
C
)
1.43 sec
0.92 sec
Diamond Package
BeO/Cu Package
  
V. LRRP TECHNOLOGY SPINOFFS 
Figure 7 depicts how the technologies being developed 
at LaRC and GSFC by the LRRP plus some additional 
lidar technologies may be combined to enable several 
measurements desired by NASA’s Science Mission  
 
 
 
 
 
 
 
 
 
Figure 6. Novel OPO arrangement invented at Sandia 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Directorate (SMD) and Exploration Systems Mission 
Directorate (ESMD). Not shown in the figure are many 
applications for other US Agencies, such as NOAA, 
DOD, EPA, Homeland Security, etc. During FY04, 
LaRC and GSFC teamed on a proposal to the ESMD. 
LaRC proposed to apply the 2-micron laser technology, 
and the coherent detection wind measurement and CO2 
measurement techniques for demonstrating a prototype 
Mars Orbiter Lidar for obtaining wind, density, and dust 
climatologies of Mars. This proposal was selected. Also 
during FY04, the SMD requested Instrument Incubator 
Program (IIP) proposals to advance technology in the 
TRL 3-5 range. Of the 5 proposals selected from LaRC, 
4 proposals received assistance from the LRRP 
technology development at LaRC and GSFC. A 
tropospheric wind proposal benefited from the LRRP 
effort at LaRC on the 2-micron laser, the LDAs, and the 
heterodyne receiver. A CO2 proposal benefited from the 
advancement at LaRC of the same laser and LDAs, and 
also from the direct detection detector advancement and 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Double λ/2
803 nm, 532 nm
Output
coupler
Pump in
λ/2 803 nm
Pump out
Lidar Technologies 
Scanner
Receiver
AutoAlign
Pointing
Telescope
Detector
SMD  ESMD 
CO2 Profiling X
Global Winds X
Ozone Profiling X
Chem/Bio Sensing X
Landing/Rendezvous X
Water Vapor Profiling X
Laser  Transmitter Technologies Measurements 
XRanging/Altimetry X
Clouds/Aerosols X
Customers 
X
2-Micron Lidar
Transmitter
Frequency
Controller
Amplifier
IR
Wavelength 
Converter
UV
Wavelength
Converter
1-Micron Lidar
Transmitter
X
X
X
X
Surface Material/State XX
Figure 7. Flow of LRRP technologies to NASA’s desired measurements 
  
the CO2 measurement demonstrations. Two selected IIP 
proposals at LaRC are for ozone measurement. One 
benefited from the wavelength conversion to UV 
activities at LaRC, and the other benefited from the 
complementary activities at GSFC. 
 
VI. CONCLUSIONS 
NASA responded to concerns about the perceived risks 
of future space-based lidar missions by commissioning 
an external review panel. The panel made excellent 
recommendations which NASA implemented through 
the LRRP. The collaboration between LaRC, GSFC, 
industry and academia has proved to work well, and the 
LRRP activities have been shown to be very valuable. 
Several proposals have already been selected which 
benefited from LRRP advances. Continuation of the 
LRRP for a few more years would permit many 
activities, such as the LDA improvement, space 
qualification, and availability task, and the radiation and 
contamination tasks, to take advantage of the teams and 
laboratories in place to provide a large benefit to NASA 
for a small cost. 
 
VII. ACKNOWLEDGEMENTS 
The authors would like to acknowledge the funding and 
management support provided by NASA’s Science 
Mission Directorate (SMD), Exploration Systems 
Mission Directorate (ESMD) and Earth Science 
Technology Office (ESTO).  
 
VIII. REFERENCES 
1. J. Yu, U. Singh, N. Barnes, and M. Petros, “125-mJ diode-
pumped injection-seeded Ho:Tm:YLF laser”, Opt. Lett. 23, 780, 
1998. 
2. M. Jani, N. Barnes, K. Murray, D. Hart, G. Quarles, and V. 
Castillo, “Diode-Pumped Ho:Tm:LuLiF4 Laser at Room 
Temperature,” IEEE J. Quantum Electron. 33, 112, 1997. 
3. M. Petros, J. Yu, S. Chen, U. Singh, B. Walsh, Y. Bai, and N. 
Barnes, “Diode pumped 135 mJ Ho:Tm:LuLF Oscillator,” 
Advanced Solid-State Photonics, TOPS 83, 309-314, 2003. 
4. B. Walsh, N. Barnes, M. Petros, J. Yu, and U. Singh, 
“Spectroscopy and modeling of solid state lanthanide lasers: 
Application to trivalent Tm3+ and Ho3+ in YLiF4 and LuLiF4,” 
J. Appl. Phys. 95, 3255, 2004. 
5. S. Chen, J. Yu, U. Singh, M. Petros, and Y. Bai, “Joule Level 
Double-pulsed Ho:Tm:LuLF Master-Oscillator-Power-Amplifier 
(MOPA) for Potential Spaceborne Lidar Applications,” SPIE's 
Fourth International Asia-Pacific Environmental Remote Sensing 
Symposium, Honolulu, HI, 8-12 November 2004. 
6. S. Chen, J. Yu, M. Petros. Y. Bai, B. C. Trieu, M. J. Kavaya, and 
U. N. Singh, “One-Joule Double-pulsed Ho:Tm:LuLF Master-
Oscillator-Power-Amplifier (MOPA),” Advanced Solid-State 
Photonics 20th Anniversary Meeting, Vienna, Austria, 6-9 
February 2005 
7. M. Petros, J. Yu, T. Melak, B. Trieu, S. Chen, U. Singh, and Y. 
Bai, “Totally conductive cooled, diode pumped, 2 micron laser 
transmitter”, SPIE's Fourth International Asia-Pacific 
Environmental Remote Sensing Symposium, Honolulu, HI, 8-12 
November 2004. 
8. G. Koch, A. Dharamsi, C. Fitzgerald, and J. McCarthy, 
“Frequency Stabilization of a Ho:Tm:YLF laser to absorption 
lines of carbon dioxide,” Appl. Opt. 39, 3664, 2000. 
9. G. Koch, M. Petros, J. Yu, and U. Singh, “Precise wavelength 
control of a single-frequency pulsed Ho:Tm:YLF laser,” Appl. 
Opt. 41, 1718, 2002. 
10. G. Koch, “Automatic laser frequency locking to gas absorption 
lines,” Opt. Eng. 42, 1690-1693, 2003 
11. J. Yu, A. Braud, and M. Petros, “600-mJ, double-pulse 2-micron 
laser,” Opt. Lett. 28, 540, 2003. 
12. G. Koch, B. Barnes, M. Petros, J. Beyon, F. Amzajerdian, J. Yu, 
R. Davis, S. Ismail, S. Vay, M. Kavaya, and U. Singh, “Coherent 
Differential Absorption Lidar Measurements of CO2,” Appl. Opt. 
43, 5092-5099, 2004. 
13. F. Amzajerdian, B. L. Meadows, N. R. Baker, R. S. Baggott, U. 
N. Singh, and M. J. Kavaya, “Advancement of High Power 
Quasi-CW Laser Diode Arrays For Space-based Instruments,” 
SPIE's Fourth International Asia-Pacific Environmental Remote 
Sensing Symposium, Honolulu, HI, 8-12 November 2004. 


Enabling Laser and Lidar Technologies for NASA's Science and Exploration Mission's Applications

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