Galileo Solid State Imaging Camera


Quick Reference Index



Color Picture of SSI Camera

Schematic of SSI Camera



Overview of the properties of the Galileo SSI camera
General
Mass 28 kg
Peak power 23 W
Dimensions 90 x 25 x 30 cm³
 
Optical
Focal length 1500 mm
Field-of-view 8.1 mrad
Angular resolution 10.16 µrad/pixel
Camera speed F/8.5 T/10.8 at 576 nm
Filter positions 8
Minimum exposure time 4.167 ms
Maximum exposure time 51.2 s
 
Detector
Type Silicon Virtual Phase CCD
Dimensions 12.19 x 12.19 mm
Pixel density 65.6 pixels/mm
Pixel format 800 x 800
Pixel full-well capacity 108,000 e¯ (normal modes)
432,000 e¯ (summation mode)
Noise floor ±30 e¯
Signal digitization 8 bits, 256 DN
1 DN (low gain state) 379 e¯
Gain state factors 1:4.8:9.8
Nonlinearity 0.2 DN (normal modes)
0.45 DN (summation mode)
Charge transfer efficiency 0.99997
Dark counts <10 e¯/s·pixel
 
Frame times for operating modes
Summation mode (2 x 2 pixel) 2.333 s
15.1667 s
Normal modes* 60.667 s
30.333 s
Full-resolution record mode 8.667 s
 
Tape recorder characteristics for SSI data
Transfer rate 8.064x10^5 bits/s
Maximum storage (images):  
   Summation mode 478
   60 2/3 128
   30 1/3 compressed 257
   8 2/3 128
   8 2/3 compressed 257

*Normal modes can either be recorded or channelled directly for real-time transmission. The summation mode must be recorded. In the normal modes the data can, if necessary, be compressed by a factor of approximately 2.5 in either an information preserving fassion (lines may be truncated), or in a non-information preserving (lines are complete but pixel values may lose accuracy).



FLIGHT CCD SUMMARY TABLE
FULL WELL (FULL RES.) 113000 e¯
FULL WELL (SUMMATION) 405000 e¯
NOISE FLOOR (INV.) 74 e¯
NOISE FLOOR (NON-INV.) 30 e¯
NOISE FLOOR (SUMMATION INV.) 119 e¯
NOISE FLOOR (SUMMATION NON-INV.) 45 e¯
PARALLEL SPURIOUS (INV.) 1700 e¯
PARALLEL SPURIOUS (NON-INV.) 250 e¯
GAMMA (FULL RES.) 1.002 ±0.002
GAMMA (SUMMATION) 0.995 ±0.005
NON-LINEARITY (FULL RES.) gamma=1 0.9%
NON-LINEARITY (SUMMATION) gamma=1 2.9% *
DARK CURRENT 0
CTF @NYQUIST (FULL RES.) 0.39
CTF @0.8 NYQUIST (SUMMATION) 0.68
Q.E. @400 nm 0.39
Q.E. PEAK (~700 nm) 0.45
Q.E. @1000 nm 0.014
#DK SPIKES > 1000e¯ @60 sec. 7
PIXEL NON-UNIFORMITY 0.48%

* FOR LEFT HALF OF FRAME ONLY, RIGHT SIDE HAS NON-LINEARITY OF UP TO 4.6%



Exposure Intervals
Exposure Number Exposure Time (ms)
Phase 1
Exposure Time (ms)
Phase 2
Exposure Limit
0 0 0
1 4-1/6 4-1/6
2 6-1/4 6-1/4
3 8-1/3 4-1/6
4 12-1/2 12-1/2
5 16-2/3 12-1/2
6 25 20-5/6
7 33-1/3 29-1/6
8 50 45-5/6
9 66-2/3 62-1/2
10 100 95-5/6
11 133-1/3 129-1/6
12 200 195-5/6
13 266-2/3 262-1/2
14 400 395-5/6 Longest normal exposure for 2-1/3 s mode
15 533-1/3 529-1/6 Longest normal exposure for 15-1/6 s mode
16 800 795-5/6 Longest normal exposure in 8-2/3 s, 30-1/3 s and 60-2/3 s mode
17 1,066-2/3 1,062-1/2
18 1,600 1,595-5/6 Longest extended exposure, 2-1/3 s mode
19 2,133-1/3 2,129-1/6
20 3,200 3,195-5/6
21 4,266-2/3 4,262-1/2
22 6,400 6,395-5/6 Longest extended exposure, 8-2/3 s mode
23 8,533-1/3 8,529-1/6
24 12,800 12,795-5/6 Longest extended exposure, 15-1/6 s mode
25 17,066-2/3 17,062-1/2
26 25,600 25,595-5/6 Longest extended exposure, 30-1/3 s mode
27 34,133-1/3 34,129-1/6
28 51,200 51,195-5/6 Longest extended exposure, 60-2/3 s mode
29 0 0 Exposure number 29 occurring in image parameter telemetry is used to identify dark current calibration frames. This exposure number also causes picture count to increment.
30 0 0
31 0 0



Filter Data

Filter Data and SSI Absolute Sensitivity
Filter Name Filter Number Effective Wavelength (nm)** Passband (nm) *** +Sensitivity (w cm¯² ster¯¹ nm¯¹) *Sensitivity (DN ms¯¹)
Clear 0 625 440 5.84 X 10-8 30.9
Violet 3 414 45 2.06 X 10-6 0.900
Green 1 559 65 4.89 X 10-7 4.45
Red 2 664 60 3.74 X 10-7 4.86
"Methane" (7270) 6 731 10 3.79 X 10-6 0.411
"Continuum" 4 757 19 1.88 X 10-6 0.780
"Methane" (8890) 7 888 16 6.91 X 10-6 0.165
"Infrared" 5 990 50 5.99 X 10-6 0.152

+ Radiance needed to produce a signal of 1 DN ms-1 in the low gain state assuming constant spectral radiance across the filter bandpass.
* Sensitivity at 5.2 AU for a scene of unit reflectivity illuminated by sunlight.
** Assumes a solar spectrum.
*** Full-width at half maximum.


For the Science paper, the effective wavelengths of the SSI system response through various filters are quoted numerous times. The values quoted are in many cases not consistent with the latest SSI calibration results and are often inconsistent with each other.

Here are the latest best estimates of the SSI effective wavelengths in nm for several target bodies:

Clear Violet Green Red 727 756 889 1um
Solar 626 414 559 664 731 757 888 990
Avg Europa 636 416 559 664 731 757 888 989
Avg Gany 637 415 560 664 731 757 888 989
Avg Io 644 418 560 664 731 757 888 990
GRS 621 415 559 664 732 757 886 991

Also, the width of the red bandpass, quoted in the Io section of the paper, is +/-30 nm (FWHM) or +/-40 nm at the 10% of max response level or +/-45 nm at the 1% of max level, but not +/-60 nm.

The effective wavelengths are probably not known to better than 2 or 3 nm I would guess. I recommend that we either consistently use the above values for the solar spectrum everywhere in the paper or that the above wavelengths for each target body be used when discussing the individual targets in their respective sections, and that we not use any obsolete values.



SSI Spectral Response

SSI spectral response to a constant source of radiance of (pi)¯¹ watts m¯² ster¯¹ nm¯¹ through each of its eight filters.

SSI Spectral Response Tables



Limiting Stellar Magnitudes Through Clear Filter

Frame No. Exposure (sec) Gain Filter Lim. Mag.
1 0.200 10K Clear 10.2
2 0.133 10K Clear 9.8
3 0.100 10K Clear 9.4
4 0.050 10K Clear 8.7
5 0.100 100K Clear 7.4



Scattered Light Attenuation Models

Plot of the point spread functions for two SSI filters (990 and GRN). In the SSI lunar data, the largest ammount of attenuation due to scattered light is observed in the 990-filter data and the least ammount is observed in the GRN-filter data. For a given wavelength, this function describes attenuation of illumination on a single-source pixel due to scattered light (shown as the logarithm, or 10^-n, of the attenuation factor n in inverse steradians) in the 990-nm and 560-nm Galileo SSI filters. To determine the scattered light expected for a single pixel, multiply the attenuation factor for the pixel (at a desired distance) by the illumination at that pixel. For evaluation of scattered light for an entire image, contributions from individual source pixels are summed over the whole image.



Phase 1 Operating Modes



Virtual-phase CCD Schematic Diagram



Virtual-phase CCD Integration and Charge Transfer



Contact for Content: Kenneth P. Klaasen


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Homepage creator: Matthew Fishburn

Last updated: February 09, 2000