Total Sky Imager (TSI)

The Total Sky Imager (TSI) provides continuous digitization of the sky and computes cloud amount for each image. The TSI was developed at Penn State University and the Pacific Northwest National Laboratory. The spherical dome control system was designed by the Geophysical Instruments and Measurements group at Brookhaven National Laboratory. After validation, the instrument was commercialized and is now sold by Yankee Environmental Systems (YES).

 

The TSI camera is a web-ready device, connects directly to an ethernet LAN, and can be accessed with an ordinary web browser such as Netscape. The dome rotates under computer control so that the black strip always occludes the sun. When on a ship, ship heading can be transmitted to the dome computer so the strip will stay properly aligned. If the ship is rocking severly, the width of the strip might need to be increased. The example below (Nauru99 day 184) shows an actual image and, on the right, the analyzed image where clouds are marked as white pixels. The TSI software produces both images and a quantitative estimate of cloud fraction each one minute of the day.

 

 

CHARACTERISTICS OF THE TSI   1. Sky images can be taken as often as every minute or much longer.   2. Digitization software discerns thick cloud, thin cloud, or sky.   3. Cloud fraction automatically computed.   4. With navigation input (lat, lon, heading) the system can be operated from a moving ship.   5. YES images software can be operated from many computers.

 

 

SHIPBOARD CONNECTION USING LAN AND SERIAL RS232

                       

The TSI base computer receives data on latitude, longitude, and ship heading and uses these to process images. It also sends the navigation data to the dome control computer which computes the correct position for the dome to properly align the black strip under the solar disk. Otherwise the sun's image would harm the CCD camera.

 

 

SHIPBOARD CONNECTION USING ONLY LAN WITH LAN-TO-SERIAL CONVERTERS