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Primary Quantities Measured with System Typical |
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The WSI is designed and built by the Marine Physical Lab. The primary components of the system are listed below.
Fisheye Lens - 180Ì field of view
Filter Changer with spectral and neutral density filter wheels
Shutter - Electically driven mechanical shutter
Digital CCD Camera - Photometrics 16-bit with fiber optic taper, cooled to -40C with a 3-stage thermo-electric cooler
Purged Camera Housing to enclose above components
Arc with Arc Drive (along East-West axis)
Trolley and Trolley Drive (along North-South axis)
Sunshade
Weatherproof housing to enclose camera system and the following components:
Camera Electronics Unit
Air cooler/heater to maintain system and electronics temperatures
Temperature Controller
Liquid Coolant system with Flow Meter and Flow Switch to remove heat from back of the CCD thermo-electric cooler
Desiccant
Relative Humidity Sensor
Dome defroster (some units)
Sensor Accessory Control Panel
Occultor Accessory Control Panel
Field Hardened PC Computer and boards
Monitor
This section lists physical parameters describing the WSI. Some measured characteristics may vary slightly.
Sensor
Dimensions: 28" W x 36" D x 36" H
Sensor Weight: 410 lb
Sensor Power: 614 watts (79 must be on UPS)
Controller Dimensions: 26" W x 26" D x 52" H
Controller Weight: 450 lb
Controller Power: 150 watts (must be on UPS)
Spectral
Filters at 450 nm, 650 nm, 800 nm and open hole
Spectral passband width: 70 nm
Neutral Density Filters at 0, 2, and 3 logs (decades) neutral density
Fisheye-Nikkor 8mm f/2.8 lens
Angular resolution: 1/3Ì
Field of view 180Ì (typically 181Ì)
CCD: Thomson TH7895B, Grade 1 xx
512 x 512 pixels
16 bit A/D readout at 40,000 pixels/second
25 mm to 11 mm fiber optic reducer
CCD
cooled to -35ÌC to -40ÌC via 3-stage Peltier cooler and liquid coolant
Environmental Housing held at 60ÌF via an air conditioner/heater
Camera electronics (including A/D and pre-amp) held to 60ÌF
Measures
all sky conditions, including full sun to starlight
Dynamic Range (overall): 10.6 log or 40000000000:1
Dynamic Range (single image): 45800:1 xx
Readout Noise: 1.6 counts out of 65,536 grey levels
Uniformity (Spatial Variation): 1.6% (correctable)
Precision (Temporal Variation): 0.2%
Nonlinearity: < 1% up to signal 10k, < 3% up to signal 50k (correctable)
Pixel Resolution: 0.36Ì
Avg. Deviation from Equi-Distant: 1.2Ì (correctable)
Image
Exposure Time: Variable, 100 msec day, 1 min starlight
Automated Exposure Adjustment based on solar/lunar conditions
Solar/Lunar Occultor to shade lens and optical dome
Automated Occultor Position based on solar/lunar position
Self-checks for proper readouts and data acquisition
Automated self-shutdown under pre-defined conditions
Automated recovery from power down when power return
Produced
by the Marine Physical Laboratory, SIO.
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