TWST: Cloud Properties Spectroradiometer
The Aerodyne TWST (Three-Waveband Spectrally-agile Technique) is a calibrated spectroradiometer that records the spectral radiance in the visible wavelength regime with high temporal resolution.
Three-Waveband Spectrally-agile Technique
The Aerodyne TWST (Three-Waveband Spectrally-agile Technique) is a calibrated spectroradiometer which stares at a narrow segment of the sky directly overhead, recording the spectral radiance in the visible wavelength regime with high temporal resolution.
There are two models of the TWST: the TWST COD – Sensor focuses on cloud optical depth measurements, while the TWST – CPS Sensor also captures Phase and Reff data.
TWST Cloud Optical Depth (COD) Sensor
TWST Cloud Optical Depth (COD) Sensor
Accurate and Precise Continuous Monitoring of Cloud Optical Depth (COD)
- Measures VIS spectra (400-1000 nm)
- Provides true 1 Hz sample rate
- Resolves thick/thin cloud ambiguity
- High temporal resolution; typical SNR (530 nm) > 1000 at 1 Hz
- Proven radiometric stability under harsh field conditions; frequent recalibration not required
- Sealed IP66 enclosure and backup battery allow for long-term autonomous field operation
- Includes radiometric calibration and a laptop computer fully loaded with executable software for control, data processing and user calibration
- Demonstrated agreement with co-located AERONET sensors within 1% when comparing in-band solar radiance at 440 and 870 nm
TWST – CPS Sensor
TWST – CPS Sensor
Accurate and Precise Continuous Monitoring of Cloud Properties: Optical Depth, Effective Radius, Phase
- Measures VIS spectra (400-1700 nm)
- Provides 1 Hz sample rate
- Resolves thick/thin cloud ambiguity
- High Temporal Resolution; Typical SNR (530 nm) > 1000 at 1 Hz
- Proven radiometric stability under harsh field conditions; frequent recalibration not required
- Sealed IP66 enclosure and backup battery allow for long-term autonomous field operation
- Includes radiometric calibration and a laptop computer fully loaded with executable software for control, data processing and user calibration
- Demonstrated agreement with co-located AERONET sensors within 1% when comparing in-band solar radiance at 440 and 870 nm
specifications
| TWST Measurement Specification | COD Sensor | CPS Sensor |
|---|---|---|
|
Spectral Range |
400-1000 nm |
400-1000 nm / 950-1700 nm |
|
Spectral Resolution |
~2 nm |
~2 nm / ~6 nm |
|
Field of View |
0.5 deg. FWHM |
.5 deg. FWHM |
|
Spectral Bands used in COD Retrieval |
440, 760, and 870 |
440, 760, and 870 or 780 nm |
|
COD Precision |
1% (typical, depends on update rate) |
1% (typical, depends on update rate) |
|
Operating Range |
Blue sky to COD > 100 |
Clear sky to COD > 100 |
|
Data Logging Rate |
1 Hz (typical), variable sampling internal from
1 to 60 seconds |
1 Hz (typical), variable sampling internal from
1 to 60 seconds |
|
Method for Phase Retrieval |
— |
1600 nm spectral band |
|
Phase Designations |
— |
Ice, Mixed, Liquid |
|
Method for Reff Retrieval |
— |
Minimization of error between spectral radiance measurements and forward model |
Atmosphere
Atmosphere
Cloud Properties
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TWST Applications
- Accumulation of COD, Phase, and Reff data for inclusion in climatology models
- Capture of cloud edges and fast evolution of cloud properties
- Study of cloud-aerosol interaction effects
- Collecting ground truth measurements for space-based earth-observing sensors
- Real-time measurement of COD for any event requiring a ‘GO – NO GO’ decision based upon knowledge of local cloud conditions