PDS_VERSION_ID        = PDS3                                                  
RECORD_TYPE           = STREAM                                                
OBJECT                = TEXT                                                  
  INTERCHANGE_FORMAT    = ASCII                                               
  PUBLICATION_DATE      = 1997-07-09                                          
  NOTE                  = "Internal memo describing system temperature        
                           determinations using data acquired during          
                           the Clementine bistatic radar experiment           
                           at DSS 43.  Since DSS 43 data are not              
                           included in this archive, the results              
                           are not directly applicable."                      
END_OBJECT            = TEXT                                                  
END                                                                           
                                                                              
                                                                              
                                                                              
                                                                              
Amplitude Calibration from 41000626 data                                      
========================================                                      
                                                                              
     Ambient load temperature was reported as                                 
                                                                              
                      Tamb = 20.5C = 293.5K                             (1)   
                                                                              
                                                                              
Channel 1 (RCP)                                                               
---------------                                                               
                                                                              
     After correction for Channel 1 (RCP) attenuator changes, compare power   
levels with ambient load connected (23658-23768 secs and 23789-23940 secs)    
to power levels with antenna pointed to sky (23183-23573 secs).  Ambient      
load raises noise power by 11.9 dB -- a factor of 15.488 -- the "Y-factor".   
                                                                              
     If noise power generated in front end of receiver (e.g., maser and       
DSN antenna itself) is  Trcvr  and cosmic noise is  Tsky, then for RCP        
                                                                              
                     Trcvr + Tamb                                             
                     ------------ = 15.488                              (2)   
                     Trcvr + Tsky                                             
                                                                              
The quantity we are interested in is  Trcvr + Tsky,  since this is the        
source of noise power coming from the receiver in the absence of              
spacecraft signal, microwave thermal emission from the lunar surface, or      
radio echo.  We can rearrange terms in (2) to give                            
                                                                              
                  Trcvr + Tsky = (Tamb - Tsky)/14.488                   (3)   
                                                                              
At microwave frequencies, the sky typically has a temperature on the order    
of 3K, so  Tsky << Tamb.  In fact, we can make a small table to see the       
effects:                                                                      
                                                                              
                    Tsky      Trcvr + Tsky                                    
                    ----      ------------                                    
                     0K          20.26K                                       
                     1K          20.19K                                       
                     3K          20.05K                                       
                     5K          19.91K                                       
                                                                              
Since the Tamb report may easily be in error by 1C and the Y-factor may       
easily be in error by 0.1 dB (2%), we take our estimate of system             
temperature on Channel 1 to be                                                
                                                                              
                    Trcvr + Tsky = 20.0 +/- 0.5K                       (4)    
                                                                              
                                                                              
Channel 3 (LCP)                                                               
---------------                                                               
                                                                              
     After correction for Channel 3 (LCP) attenuator changes, compare power   
levels with ambient load connected (23770-23787 secs and 23942-24142 secs)    
to power levels with antenna pointed to sky (23183-23436 secs).  Ambient      
load raises noise power by 11.6 dB -- a factor of 14.454 -- the "Y-factor".   
                                                                              
     Following the same steps as for Channel 1, we arrive at                  
                                                                              
                  Trcvr + Tsky = (Tamb - Tsky)/13.454                   (3)   
                                                                              
A similar table shows:                                                        
                                                                              
                    Tsky      Trcvr + Tsky                                    
                    ----      ------------                                    
                     0K          21.82K                                       
                     1K          21.74K                                       
                     3K          21.59K                                       
                     5K          21.44K                                       
                                                                              
We take our estimate of system temperature on Channel 3 to be                 
                                                                              
                    Trcvr + Tsky = 21.6 +/- 0.5K                       (4)    
                                                                              
                                                                              
Relative Amplitudes                                                           
-------------------                                                           
                                                                              
     Execution of PREPPOWER on the first 100 sec of samples for each          
polarization yields relative power measurements of 610 for RCP and 662        
for LCP.  Over this time interval, the attenuators on both channels           
were set to 33.  The ratio of these powers is indistinguishable from          
the ratio of the two system temperatures.  We can adopt attenuator            
settings of 33 dB as our reference level (GAIN = 1.0) on each channel.