NASA's Coastal and Ocean Airborne Science Testbed (COAST): Early ResultsL. Guild1, J. Dungan1, M. Edwards1, P. Russell1, J. Morrow2, S. Hooker3, J. Myers4, R. Kudela5, S. Dunagan1, M. Soulage6, J. Livingston7, R. Johnson1, T. Ellis4, N. Clinton4, R. Dominguez4, B. Lobitz8, K. Martin1, E. Fraim4, P. Zell1,

R.Berthold1, C. Smith1, K. Vassigh1, A. Demo1, W. Gore1, and J. Torres9

AbstractThe NASA Coastal and Ocean Airborne Science Testbed (COAST) project advances coastal ecosystems research and ocean color calibration and validation capability by providing a unique airborne payload optimized for remote sensing in the optically complex coastal zone. The COAST instrument suite combines a customized imaging spectrometer, sunphotometer system, and a new bio-optical radiometer package to obtain ocean/coastal/atmosphere data simultaneously in flight for the first time. The imaging spectrometer (Headwall) is optimized in the blue region of the spectrum to emphasize remote sensing of marine and freshwater ecosystems. Simultaneous measurements supporting empirical atmospheric correction of image data is accomplished using the Ames Airborne Tracking Sunphotometer (AATS-14). Coastal Airborne In situ Radiometers (C-AIR, Biospherical Instruments, Inc.), developed for COAST for airborne campaigns from field-deployed microradiometer instrumentation, provide measurements of apparent optical properties at the land/ocean boundary including optically shallow aquatic ecosystems. Ship-based measurements allowed validation of airborne measurements. Radiative transfer modeling on in-water measurements from the HyperPro and Compact-Optical Profiling System (C-OPS, the in-water companion to C-AIR) profiling systems allows for comparison of airborne and in-situ water leaving radiance measurements. Results of the October 2011 Monterey Bay COAST mission include preliminary data on coastal ocean color products, coincident spatial and temporal data on aerosol optical depth and water vapor column content, as well as derived exact water-leaving radiances.

Science Traceability Matrix

COAST Mission

Payload

Measures: Solar direct-beam transmission (T) at 14 wavelengths, 353-2139 nm

Ames Airborne Tracking Sunphotometer (AATS)Coastal Airborne In-situ Radiometers (C-AIR)

Data products: Aerosol optical depth (AOD) at 13

channels, 353-2139 nm Water vapor column content [using

T(940 nm)] Aerosol extinction, 340-2139 nm Water vapor density

Science Mission October 2011

Left: Flight path for October 28, 2011. Right: Flight path showing spiral descent from 6000 ft to 100 ft flight lines. Flight planning included timing within +/- 30 min of satellite overpass.

Raw data at 555 nm for global irradiance (Es), sky radiance (Li) reaching the sea surface, and radiance from the sea surface, called total radiance (LT) for four flight lines on Oct. 28, 2011. UTC is +7hrs from local time in October.

C-AIR measurements of the downward irradiance (Es), sky radiance away from the sun (Li) and total surface radiance (Lt) for each 30 second segment of all flight lines showed small vari-ances, but were mostly spectrally similar.

Shown are spectra from 30 second segments processed for glint avoidance by PROSIT along flight line 7, Oct. 28, 2011 at ~6000 ft.

Preliminary Data

Left: Aerosol optical depths (AOD) calculated from AATS-14 measurements for horizontal transects on 28 Oct. at altitudes 0.024 km ASL (top left) and 1.877 km ASL (bottom left). The AATS-14 channel center wavelengths (in μm) are given in the legend. Right: Corresponding mean AOD spectra (symbols) and log(AOD) vs. log(wavelength) quadratic fits (dashed lines) calculated for the total column above the aircraft for the low (blue) and high (red) flight legs, and for the layer (green) bounded by the two altitudes.

Vertical profiles of columnar water vapor (left), spectral AOD (middle), and spectral aerosol extinction (right) calculated from AATS-14 measurements acquired during a spiral descent over Monterey Bay on 28 October.

C-AIR

Scientific Outcomes• A flight-tested instrument suite suitable for cal/val activities for future satellite missions, as well as currently operating and developing missions.• Advanced payload capabilities for airborne carrier platforms including UASs.• A multi-sensor ocean/atmosphere data set available for improved atmospheric calibration and in-water algorithms.• Methodologies for empirical atmospheric correction developed for future airborne imagers of this type (e.g., NASA PRISM) when they come online.• Methods to address the biological properties of important coastal zone ecosystems.• Enabling technology for a broad range of research activities in the coastal zone to support the scientific community’s research goals and objectives.

AATS-14

Acknowledgements• Naval Postgraduate School Center for Interdisciplinary Remotely

Piloted Aircraft Systems (CIRPAS) Twin Otter Team.• UC Santa Cruz and Moss Landing RV John Martin field team.• UC Davis Spectral Measurements Team: Mui Lay, George Scheer,

and Susan Ustin.COAST Team at NPS CIRPAS in Marina, CA.

1NASA Ames Research Center, Moffett Field, CA 94035; 2Biospherical Instruments Inc., San Diego, CA 92110; 3NASA GSFC, MD 20771; 4UC Santa Cruz/NASA, Moffett Field, CA 94035; 5UC Santa Cruz, Santa Cruz, CA, 95064; 6Universities Space Research Association/NASA Ames Research Center, Moffett Field, CA, 94035; 7SRI International/NASA Ames Research Center, Moffett Field, CA 94035; 8Univ. Corporation at Monterey Bay/NASA Ames Research Center, Moffett Field, CA 94035; 9NASA Postdoctoral Program/NASA Ames Research Center, Moffett Field, CA 94035

Monterey Bay has both open ocean and optically complex water masses, so the full dynamic range of the sensor suite and protocols being used in the field can be evaluated.

The mission consisted of flying the imaging spectrometer, together with the AATS-14 and C-AIR on the CIRPAS Twin Otter, over an instrumented surface to evaluate the sensor suite. The AATS-14 provides a simultaneous empirical characterization of the atmospheric column (AOD and water vapor) that will be used for atmospheric correction.

During flights, we obtained MODIS Aqua and Terra, HICO, and MERIS data corresponding to contemporaneous deployment of the ship-based measurements from the R/V John Martin (Moss Landing Marine Lab). Satellite observations will be used to compare accuracy of radiance retrievals and derived products versus the Headwall imaging spectrometer, C-AIR, and the in situ measurements.

Blue: C-OPSBlack: HyperPro IIRed: Headwall

Comparison of Headwall (3x3 avg) reflectance processed using Tafkaa atmospheric correction, 3 consecutive casts of C-OPS, and 3 consecutive casts of HyperPro II for red tide (above) and low biomass (below) stations. All spectra matched reasonably well. The C-OPS has lower variance and less noise at the blue and red end of the spectrum, but misses the peak reflectances in red tide waters (above).

Example of the vertical resolution achieved by the C-OPS profiler (unbinned reflectance data for the first 0.5 m of the cast is shown)

100 ft!

Three 19-channel microradiometers:1. with cosine collector for measuring solar irradiance (Es) 2. Sky radiance (Li) and3. Total radiance (Lt)

Spectral range: 320-780 nm with 10 nm bandwidth to include channels centered around 412, 443, 490, 510, 555, 665, and 683 nm to match satellite (NASA MODIS) bands used for ocean color remote sensing.

Physical FOV radiance instrument: 1.25° half-angle, 0.7° slope angle

The Es and Li radiometers are mounted within a fairing on top of the aircraft. The Li radiometer is mounted 40 deg off zenith. The Lt radiometer is mounted at 40 deg off nadir alongside the imaging spectrometer.

Ship-based Measurements• Underway T, S, Fluorescence• At each station (2-3 stations per

day):– Size fractionated chlorophyll,

flow cytometry counts– CDOM, absorption spectra,

nutrients– Sunphotometer spectra– HyperPro cast, C-OPS cast

– Water-leaving radiance, profile data

– Backscatter/ac-s casts– ASD surface reflectance

Top: True color composite of the Headwall imaging spectrometer raw data showing 450nm (red), 550 (green), and 680 (blue). Pixel resolution is ~4m from ~6000ft AGL and swath width is 1.7km.Insert: Enhanced raw data showing algal bloom in red.

NImaging Spectrometer

Line 7 Line 8 Line 9 Line 10

A Science Traceability Matrix provides a project trace from the science goals to the instrument requirements and projected instrument performance. Colored box outlines indicate the path through the matrix to meet science requirements.

Funding: NASA HOPE, Science Mission Directorate, Office of Chief Engineer, and SMD/Earth Science Division