Daylight Visible/NIR WSI
The Daylight Visible/NIR WSI is a modern (2000) version of the earlier Day-only WSI used in the mid-to-late 80’s, and is somewhat simpler and less costly than the Day/Night WSI. Like the Day/Night WSI, this smaller version automatically acquires full 180 degree field of view imagery at computer controlled intervals, but only from dawn to dusk. It is an all-weather system fully capable of extended, unattended operations. A picture of the system is shown below, along with a striking image of cirrus acquired near sunset.
Specific characteristics of the system are discussed below.
The control system includes an accessory control panel (ACP), built by MPL, which controls the filter changer and occultor either manually or via the computer. The computer is a Dell Optiplex GX1p, operating in a Windows NT environment. The system includes a Digital IO card and a GPS card for acquiring accurate time and location. The ACP is shown below.
The system includes software for full automated control of data acquisition. It includes several options regarding filter selection and image acquisition intervals. It includes algorithms to identify reasonable selections of gain and exposure, as well as algorithms to identify the occultor selection to use. The software was written by MPL to run within the environment of the V++ image processing software provided by Photometrics. Data processing software processes the red/blue data to yield cloud decision images, cloud fraction, and related parameters. The processing software also can provide calibrated radiance distributions as well as irradiances for the full image and selected regions of interest for any of the filters. The processing software was also developed at MPL and runs within the V++ environment.
This system can be adapted for a number of applications, and is designed for applications requiring daytime data at high spatial resolution in several spectral filters. The system was developed for Deutsche Wetterdienst.
by the Marine Physical Laboratory, SIO.