Towards an Autonomous Airborne Sun/Sky Scanning Spectrometer
Beat Schmid (SGG/BAER), Nicholas Truong (SGG/BAER), Teck Meriam (SGG/BAER*), Philip Russell (SGG), and Jens Redemann (SGG/BAER)
*Now at KLA Tencor
Atmospheric aerosols (particles 10 nm to 10 mm) play a crucial role in the Earth’s radiation balance and may hold the key to combating global warming. However, more knowledge is needed about aerosol sources, distributions and properties. This requires continuous observations from satellites, networks of ground-based instruments, and dedicated field experiments.
More information on aerosol particles (size, refractive index) can be obtained by measuring scattered light in addition to the direct solar beam
Entrance aperture Optical fiber
Sun-tracking head
Altair UAV
The existing Ames airborne tracking sunphotometers (AATS) make sunlight transmission measurements at 6 or 14 discrete wavelengths from which we derive information on aerosols, water vapor and ozone. The AATS measuements have been used extensively to validate measurements from satellite-, aircraft- and surface-based instruments. NASA Ames has been the world leader in airborne sunphometry since 1985. The AERONET (AErosol RObotic NETwork) program is a global, federated ground-based network of Sun/Sky radiometers initiated by NASA.
Instrument Block Diagram
“Heart” of prototype is a Spectrometer: •Zeiss MCS with Tec5 Electronics •Hamamatsu CCD S7031-1006 1044x64 pixels •Spectral range: l=220-1000 nm •Spectral distance of pixel: Dl ~ 0.8 nm •Resolution: Dl =1.7 - 2.5 nm
Ames Airborne Tracking Sunphotometer (AATS-14) And Its Use
SAGE II, III
AATS-14
Volcanic Volcanic Emissions Emissions Urban Urban Pollution Pollution
Terra, Aqua, Aura
Desert Dust Desert Dust
In the project we build a ground-based prototype to address key technical challenges we encounter when designing the smaller, lighter, fully autonomous, more capable instrument described above. The challenges are: a) Dynamic range of the detection system, b) Suppression of unwanted stray light when measuring sky radiance a few degrees away from the Sun, c) In-flight self-cleaning of the optical window.
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P. Russell, Ames Seminar, 24 January 2002
H20 H20 O3 O3
Biomass Biomass Smoke Smoke
10/8/2004 3:58:54 PM
(Dimensions in mm)
NASA Ames Airborne Sunphotometer-Satellite Group Major Aerosol Field Campaigns, 1996-2004
TARFOX, 1996 ICARTT, 2004 ADAM, 2003 EVE, 2004
Spectra from various light sources
1 0.9 Halogen Red Laser Blue LED Fluorescent
SOLVE II, 2003
CLAMS, 2001
ACE-Asia, 2001
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ACE-2, 1997
Arbitrary Units
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 200
ARM Aerosol IOP, 2003
PRIDE, 2000
SAFARI, 2000
An airborne instrument that measures a continuous spectrum of the direct solar beam and of the scattered sunlight as a function of angular distance from the Sun will deliver considerably more information on atmospheric aerosols and gases but does not currently exist.
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Wavelength (nm)