DI I&T Testing Update, TV3   Thursday January 30, 2003	      CML              
                                                                              
At the end of last nightıs TV3 testing, the ITS CCD was                       
cooled down to ­20 C, enough to allow testing of its                          
photoresponse. An optical light source was constructed out                    
of a calibrated lamp shone through an integrating sphere into                 
the 8-Ball test vacuum chamber containing the ITS                             
instrument.                                                                   
                                                                              
The resulting images were very flat, within 2% RMS across                     
a quadrant. Quadrant to quadrant variations were systematic                   
left to right, and of about a 2% level, higher on the left. This              
is inconsistent with the pattern seen in the dark current as                  
well. This result suggests the 2 left readout amplifiers are of               
slightly higher gain than the 2 right readout amplifiers.                     
                                                                              
An exposure of 0.8 sec was found to give us near-saturation                   
at 17kDN/sec input flux. A (zero-second delay time, zero                      
second shutter ­ zero second shutter) measurement gave us a                   
response of 146 DN across the CCD, which corresponds to                       
an effective integration time of about 8 msec, not the 2.7                    
msec "effective" delay time expected as pixels are bucket-                    
brigaded across the chip to the amplifier as the array is read                
out; nor was any ramp signal found across the chip, as                        
would be naively expected ­ the pixels farthest from the                      
amplifier are exposed to the input light source longest. We                   
are still working this out. Don Hampton believes this is due                  
to the fact that we run 4 flushes per 0 second read.                          
                                                                              
The CCD uniformity looks very good. There are only a few                      
noticeably bad regions at ­20C, and only 1 or 2 of these                      
seem larger than 1-2 pixels across. The quadrant boundaries                   
are noticeable at the few percent level, which may cause                      
some difficulties for AutoNav tracking.                                       
                                                                              
The CCD dark current continued its exponential decrease                       
with temperature as we cooled, but the slope of the falloff                   
seemed less than expected. We found about 30 DN/sec dark                      
current at ­20 C, as compared to an optical flux on the                       
detector from our test setup of 17,000 DN/sec.                                
                                                                              
The diagnostic vibration of the HRI/MRI instruments +                         
platform continues this morning, in an attempt to pinpoint                    
the location of the weak link(s). The anticipation is that the                
system will be moved back to the cleanroom this afternoon.