PDS_VERSION_ID       = PDS3                                                   
RECORD_TYPE          = UNDEFINED                                              
START_TIME           = 1997-02-15T00:00:00                                    
STOP_TIME            = 1998-01-15T21:21:23                                    
INSTRUMENT_HOST_NAME = "CLEMENTINE 1"                                         
TARGET_NAME          = MOON                                                   
^ADOBE_PDF_DOCUMENT  = "OFFSQNT.PDF"                                          
                                                                              
DESCRIPTION          = "Document describes small polarization-dependent       
                        pointing offsets for NASA Deep Space Network (DSN)    
                        beam waveguide antennas.  Document was sent by        
                        Mike Wert of the DSN to Sal Abbate, accompanied       
                        by the note below.  Abbate then forwarded both to     
                        Stanford where analysis was being carried out.        
                                                                              
                        The 'article' mentioned in the first paragraph is     
                        this document.  No ASCII text version was available   
                        at the time the archive was constructed.              
                                                                              
                        No beam waveguide antennas were used for the          
                        Clementine bistatic radar experiment; but 'squint'    
                        concepts may still be useful for understanding        
                        differences in system noise when the 70-m antennas    
                        were pointing at the lunar limb.                      
                                                                              
  Sal,                                                                        
                                                                              
  As you requested to assist in your understanding of differences in the      
  microwave noise observed between the two circular polarizations at S-band   
  at DSS14 during DSPSE bi-static lunar radar, I have researched the          
  literature and found the attached article which explains the theory of      
  offset-feed-induced-polarization-squint.  The research attached was for     
  the specific case of the new DSN beam-waveguide antennas, but the theory    
  applies to the reflex optics used to illuminate the SPD cone S-band feed    
  with the DSS14 cassegrain telescope.                                        
                                                                              
  I have not 'run' the equations from the attached article for the specific   
  optical constants for DSS14, but from field calibration results from        
  Mr. D. Girdner, GDSCC, the following empirical results are available:       
                                                                              
  1. DSS14 S-band pointing is typically RCP-compensated                       
                                                                              
  2. The LCP beam from DSS14 would be about 0.009 degrees positive in         
  elevation  from the RCP beam -- which is in agreement qualitatively with    
  the attached paper (i.e. squint in the plane transverse to the plane        
  containing the optic axis and the feed offset, and to the right for LCP     
  radiation looking out along the beam)                                       
                                                                              
  3. The DSS14 main-lobe at S-band is about 0.1 deg wide (full-width at       
  half-power)                                                                 
                                                                              
  4. The difference in received noise from the lunar disk from the two        
  beams will depend on the aim point(s) used.                                 
                                                                              
  If you can provide the aim point(s) used, a rough expected noise            
  temperature set could be approximated.  The observed squint at DSS14        
  could also be compared with the theoretical value to further qualify        
  the noise expectation approximation.                                        
                                                                              
  Regards,                                                                    
  Mike Wert"                                                                  
                                                                              
                                                                              
OBJECT              = ADOBE_PDF_DOCUMENT                                      
 DOCUMENT_NAME       = "BEAM SQUINT DUE TO CIRCULAR POLARIZATION IN A         
                         BEAM-WAVEGUIDE ANTENNA"                              
 PUBLICATION_DATE    = 1997-02-15                                             
 DOCUMENT_TOPIC_TYPE = "INSTRUMENT DESCRIPTION"                               
 INTERCHANGE_FORMAT  = BINARY                                                 
 DOCUMENT_FORMAT     = "ADOBE PDF"                                            
 FILES               = 1                                                      
                                                                              
END_OBJECT          = ADOBE_PDF_DOCUMENT                                      
                                                                              
END