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13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Shortwave Array Spectroradiometer–Zenith (SASZe) Instrument Handbook

The Shortwave Array Spectroradiometer – Zenith (SASZe) provides measurements of zenith spectral shortwave radiance at 1Hz over a continuous spectral range from approximately 300 nm to 1700 nm. The SASZe design connects an optical collector located outdoors to a pair of spectrometers and data collections system located indoors within a climate-controlled building via an umbilical cable of fiber optic and electrical cables. The light collector incorporates a collimator yielding a 1-degree Full Width at Half Maximum (FWHM) field of view. The data-acquisition electronics and spectrometers include an in-line fiber optic shutter and two Avantes fiber-coupled grating spectroradiometers within a temperature-controlled container. The Avantes Avaspec ULS 2048 charge-coupled device (CCD) spectrometer covers the wavelength range from about 300-1100 nm with a pixel spacing of less than 0.6 nm and a spectral resolution of about 2.4 nm FWHM. The Avantes Avaspec NIR256-1.7 spectrometer covers the wavelength range from about 950 nm to 1700 nm with a pixel spacing of less than 4 nm and a spectral resolution of about 6 nm FWHM.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Observation of the spectrally invariant properties of clouds in cloudy-to-clear transition zones during the MAGIC field campaign

We use the spectrally invariant method to study the variability of cloud optical thickness τ and droplet effective radius reff in transition zones (between the cloudy and clear sky columns) observed from Solar Spectral Flux Radiometer (SSFR) and Shortwave Array Spectroradiometer-Zenith (SASZe) during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The measurements from the SSFR and the SASZe are different, however inter-instrument differences of self-normalized measurements (divided by their own spectra at a fixed time) are small. The spectrally invariant method approximates the spectra in the cloud transition zone as a linear combination of definitely clear and cloudy spectra, where the coefficients, slope and intercept, character-ize the spectrally invariant properties of the transition zone. Simulation results from the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model demonstrate that (1) the slope of the visible band is positively correlated with the cloud optical thickness τ while the intercept of the near-infrared band has high negative cor-relation with the cloud drop effective radius reff even without the exact knowledge of τ; (2) the above relations hold for all Solar Zenith Angle (SZA) and for cloud-contaminated skies. In observations using redundant measure-ments from SSFR and SASZe, we find that during cloudy-to-clear transitions, (a) the slopes of the visible band de-crease, and (b) the intercepts of the near-infrared band remain almost constant near cloud edges. The findings in simulations and observations suggest that, while the optical thickness decreases during the cloudy-to-clear transition, the cloud drop effective radius does not change when cloud edges are approached. These results sup-port the hypothesis that inhomogeneous mixing dominates near cloud edges in the studied cases.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

sashevis (b1)

The shortwave array spectroradiometer—hemispheric (SASHE) uses a hemispheric spectralon diffuser and rotating shadowband similar to the MFRSR and RSS instruments, so it also provides spectrally resolved, direct-normal, diffuse-horizontal, and total-horizontal irradiances, and can be calibrated in situ via Langley regression. The SASHE incorporates two Avantes fiber-coupled spectroradiometers (Avaspec ULS 2048 CCD and Avaspec NIR256-1.7) for visible and near-infrared detection in the wavelength range 350-1700 nm. The spectral resolution is 2.4 nm for the ULS 2048 CCD and 6 nm for the NIR256-1.7. Like the SWS and SASZE, an external collector mounted outdoors is connected via fiber-optic cable to a pair of spectroradiometers housed indoors, so the entire spectral range is measured simultaneously for both spectroradiometers. For the typical shadowband measurement, the spectroradiometers are operated with one measurement per second, but the entire shadowband sequence takes about 20 seconds, so this is the measurement interval for the irradiances. The SASHE operating sequence is configurable and supports alternate programmed sequences as a function of solar zenith angle. For example, it currently employs different sequences for high sun angles, low sun angles, and twilight conditions when the sun is below the horizon but the sky is not yet fully dark. It also includes a mode where visible spectra are collected rapidly while the band is moved over a range of near-sun angles to characterize the forward-scattered radiation. The SASHE data are preliminarily calibrated through comparison with calibrated lamps. The accuracy of irradiance produced by the SASHE is expected to be better than ±5%, which includes calibration and instrument stability errors. Under suitably uniform atmospheric conditions, higher calibration accuracy and precisions (±1%) can be obtained when the responsivity is tied to the solar extraterrestrial irradiance via Langley regression plots. This approach is recommended when high-precision measurements of optical depth are required.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

sashemfr (b1)

The shortwave array spectroradiometer—hemispheric (SASHE) uses a hemispheric spectralon diffuser and rotating shadowband similar to the MFRSR and RSS instruments, so it also provides spectrally resolved, direct-normal, diffuse-horizontal, and total-horizontal irradiances, and can be calibrated in situ via Langley regression. The SASHE incorporates two Avantes fiber-coupled spectroradiometers (Avaspec ULS 2048 CCD and Avaspec NIR256-1.7) for visible and near-infrared detection in the wavelength range 350-1700 nm. The spectral resolution is 2.4 nm for the ULS 2048 CCD and 6 nm for the NIR256-1.7. Like the SWS and SASZE, an external collector mounted outdoors is connected via fiber-optic cable to a pair of spectroradiometers housed indoors, so the entire spectral range is measured simultaneously for both spectroradiometers. For the typical shadowband measurement, the spectroradiometers are operated with one measurement per second, but the entire shadowband sequence takes about 20 seconds, so this is the measurement interval for the irradiances. The SASHE operating sequence is configurable and supports alternate programmed sequences as a function of solar zenith angle. For example, it currently employs different sequences for high sun angles, low sun angles, and twilight conditions when the sun is below the horizon but the sky is not yet fully dark. It also includes a mode where visible spectra are collected rapidly while the band is moved over a range of near-sun angles to characterize the forward-scattered radiation. The SASHE data are preliminarily calibrated through comparison with calibrated lamps. The accuracy of irradiance produced by the SASHE is expected to be better than ±5%, which includes calibration and instrument stability errors. Under suitably uniform atmospheric conditions, higher calibration accuracy and precisions (±1%) can be obtained when the responsivity is tied to the solar extraterrestrial irradiance via Langley regression plots. This approach is recommended when high-precision measurements of optical depth are required.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

sashenir (b1)

The shortwave array spectroradiometer—hemispheric (SASHE) uses a hemispheric spectralon diffuser and rotating shadowband similar to the MFRSR and RSS instruments, so it also provides spectrally resolved, direct-normal, diffuse-horizontal, and total-horizontal irradiances, and can be calibrated in situ via Langley regression. The SASHE incorporates two Avantes fiber-coupled spectroradiometers (Avaspec ULS 2048 CCD and Avaspec NIR256-1.7) for visible and near-infrared detection in the wavelength range 350-1700 nm. The spectral resolution is 2.4 nm for the ULS 2048 CCD and 6 nm for the NIR256-1.7. Like the SWS and SASZE, an external collector mounted outdoors is connected via fiber-optic cable to a pair of spectroradiometers housed indoors, so the entire spectral range is measured simultaneously for both spectroradiometers. For the typical shadowband measurement, the spectroradiometers are operated with one measurement per second, but the entire shadowband sequence takes about 20 seconds, so this is the measurement interval for the irradiances. The SASHE operating sequence is configurable and supports alternate programmed sequences as a function of solar zenith angle. For example, it currently employs different sequences for high sun angles, low sun angles, and twilight conditions when the sun is below the horizon but the sky is not yet fully dark. It also includes a mode where visible spectra are collected rapidly while the band is moved over a range of near-sun angles to characterize the forward-scattered radiation. The SASHE data are preliminarily calibrated through comparison with calibrated lamps. The accuracy of irradiance produced by the SASHE is expected to be better than ±5%, which includes calibration and instrument stability errors. Under suitably uniform atmospheric conditions, higher calibration accuracy and precisions (±1%) can be obtained when the responsivity is tied to the solar extraterrestrial irradiance via Langley regression plots. This approach is recommended when high-precision measurements of optical depth are required.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2011

sashenirlowsun (a0)

The shortwave array spectroradiometer—hemispheric (SASHE) uses a hemispheric spectralon diffuser and rotating shadowband similar to the MFRSR and RSS instruments, so it also provides spectrally resolved, direct-normal, diffuse-horizontal, and total-horizontal irradiances, and can be calibrated in situ via Langley regression. The SASHE incorporates two Avantes fiber-coupled spectroradiometers (Avaspec ULS 2048 CCD and Avaspec NIR256-1.7) for visible and near-infrared detection in the wavelength range 350-1700 nm. The spectral resolution is 2.4 nm for the ULS 2048 CCD and 6 nm for the NIR256-1.7. Like the SWS and SASZE, an external collector mounted outdoors is connected via fiber-optic cable to a pair of spectroradiometers housed indoors, so the entire spectral range is measured simultaneously for both spectroradiometers. For the typical shadowband measurement, the spectroradiometers are operated with one measurement per second, but the entire shadowband sequence takes about 20 seconds, so this is the measurement interval for the irradiances. The SASHE operating sequence is configurable and supports alternate programmed sequences as a function of solar zenith angle. For example, it currently employs different sequences for high sun angles, low sun angles, and twilight conditions when the sun is below the horizon but the sky is not yet fully dark. It also includes a mode where visible spectra are collected rapidly while the band is moved over a range of near-sun angles to characterize the forward-scattered radiation. The SASHE data are preliminarily calibrated through comparison with calibrated lamps. The accuracy of irradiance produced by the SASHE is expected to be better than ±5%, which includes calibration and instrument stability errors. Under suitably uniform atmospheric conditions, higher calibration accuracy and precisions (±1%) can be obtained when the responsivity is tied to the solar extraterrestrial irradiance via Langley regression plots. This approach is recommended when high-precision measurements of optical depth are required.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2011

sashevislowsun (a0)

The shortwave array spectroradiometer—hemispheric (SASHE) uses a hemispheric spectralon diffuser and rotating shadowband similar to the MFRSR and RSS instruments, so it also provides spectrally resolved, direct-normal, diffuse-horizontal, and total-horizontal irradiances, and can be calibrated in situ via Langley regression. The SASHE incorporates two Avantes fiber-coupled spectroradiometers (Avaspec ULS 2048 CCD and Avaspec NIR256-1.7) for visible and near-infrared detection in the wavelength range 350-1700 nm. The spectral resolution is 2.4 nm for the ULS 2048 CCD and 6 nm for the NIR256-1.7. Like the SWS and SASZE, an external collector mounted outdoors is connected via fiber-optic cable to a pair of spectroradiometers housed indoors, so the entire spectral range is measured simultaneously for both spectroradiometers. For the typical shadowband measurement, the spectroradiometers are operated with one measurement per second, but the entire shadowband sequence takes about 20 seconds, so this is the measurement interval for the irradiances. The SASHE operating sequence is configurable and supports alternate programmed sequences as a function of solar zenith angle. For example, it currently employs different sequences for high sun angles, low sun angles, and twilight conditions when the sun is below the horizon but the sky is not yet fully dark. It also includes a mode where visible spectra are collected rapidly while the band is moved over a range of near-sun angles to characterize the forward-scattered radiation. The SASHE data are preliminarily calibrated through comparison with calibrated lamps. The accuracy of irradiance produced by the SASHE is expected to be better than ±5%, which includes calibration and instrument stability errors. Under suitably uniform atmospheric conditions, higher calibration accuracy and precisions (±1%) can be obtained when the responsivity is tied to the solar extraterrestrial irradiance via Langley regression plots. This approach is recommended when high-precision measurements of optical depth are required.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2011

sashevishisun (a0)

The shortwave array spectroradiometer—hemispheric (SASHE) uses a hemispheric spectralon diffuser and rotating shadowband similar to the MFRSR and RSS instruments, so it also provides spectrally resolved, direct-normal, diffuse-horizontal, and total-horizontal irradiances, and can be calibrated in situ via Langley regression. The SASHE incorporates two Avantes fiber-coupled spectroradiometers (Avaspec ULS 2048 CCD and Avaspec NIR256-1.7) for visible and near-infrared detection in the wavelength range 350-1700 nm. The spectral resolution is 2.4 nm for the ULS 2048 CCD and 6 nm for the NIR256-1.7. Like the SWS and SASZE, an external collector mounted outdoors is connected via fiber-optic cable to a pair of spectroradiometers housed indoors, so the entire spectral range is measured simultaneously for both spectroradiometers. For the typical shadowband measurement, the spectroradiometers are operated with one measurement per second, but the entire shadowband sequence takes about 20 seconds, so this is the measurement interval for the irradiances. The SASHE operating sequence is configurable and supports alternate programmed sequences as a function of solar zenith angle. For example, it currently employs different sequences for high sun angles, low sun angles, and twilight conditions when the sun is below the horizon but the sky is not yet fully dark. It also includes a mode where visible spectra are collected rapidly while the band is moved over a range of near-sun angles to characterize the forward-scattered radiation. The SASHE data are preliminarily calibrated through comparison with calibrated lamps. The accuracy of irradiance produced by the SASHE is expected to be better than ±5%, which includes calibration and instrument stability errors. Under suitably uniform atmospheric conditions, higher calibration accuracy and precisions (±1%) can be obtained when the responsivity is tied to the solar extraterrestrial irradiance via Langley regression plots. This approach is recommended when high-precision measurements of optical depth are required.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2011

sashenirhisun (a0)

The shortwave array spectroradiometer—hemispheric (SASHE) uses a hemispheric spectralon diffuser and rotating shadowband similar to the MFRSR and RSS instruments, so it also provides spectrally resolved, direct-normal, diffuse-horizontal, and total-horizontal irradiances, and can be calibrated in situ via Langley regression. The SASHE incorporates two Avantes fiber-coupled spectroradiometers (Avaspec ULS 2048 CCD and Avaspec NIR256-1.7) for visible and near-infrared detection in the wavelength range 350-1700 nm. The spectral resolution is 2.4 nm for the ULS 2048 CCD and 6 nm for the NIR256-1.7. Like the SWS and SASZE, an external collector mounted outdoors is connected via fiber-optic cable to a pair of spectroradiometers housed indoors, so the entire spectral range is measured simultaneously for both spectroradiometers. For the typical shadowband measurement, the spectroradiometers are operated with one measurement per second, but the entire shadowband sequence takes about 20 seconds, so this is the measurement interval for the irradiances. The SASHE operating sequence is configurable and supports alternate programmed sequences as a function of solar zenith angle. For example, it currently employs different sequences for high sun angles, low sun angles, and twilight conditions when the sun is below the horizon but the sky is not yet fully dark. It also includes a mode where visible spectra are collected rapidly while the band is moved over a range of near-sun angles to characterize the forward-scattered radiation. The SASHE data are preliminarily calibrated through comparison with calibrated lamps. The accuracy of irradiance produced by the SASHE is expected to be better than ±5%, which includes calibration and instrument stability errors. Under suitably uniform atmospheric conditions, higher calibration accuracy and precisions (±1%) can be obtained when the responsivity is tied to the solar extraterrestrial irradiance via Langley regression plots. This approach is recommended when high-precision measurements of optical depth are required.

54 ENVIRONMENTAL SCIENCES↗