DOI: 10.48322/qvhw-xp72
title: Voyager 2 Planetary Radio Astronomy (PRA) Lowband Receiver Jupiter encounter, 6 sec resolution
title: VG2-J-PRA-3-RDR-LOWBAND-6SEC-V1.0

description: 
	   (Description based on material from VG2_PRA_JUP_HRES_DS.CAT)

      Voyager 2 Radio Astronomy (PRA) data from the Jupiter encounter (1979-04-25 to 1979-08-04).  
      The data set provides 6 second high resolution lowband radio mean power data. The data 
      are provided for 70 instrument channels, covering 1.2 to 1326.0 kHz.
 
       This data set (VG2-J-PRA-3-RDR-LOWBAND-6SEC-V1.0) contains              
      data acquired by the Voyager-2 Planetary Radio Astronomy (PRA)          
      instrument during the Jupiter encounter. The bounding time              
      interval set for most Voyager 2 Jupiter PDS data sets is the            
      Voyager project defined 'far encounter' mission phase boundary          
      (1979-07-02 to 1979-08-03). Since, however, the PRA instrument          
      is able to observe planetary phenomenon at much larger ranges           
      than other fields and particles experiments, this boundary is           
      artificial with respect to PRA. Hence, PRA lowband data                 
      provided here cover the entire Jupiter Encounter Phase                  
      (1979-04-25 to 1979-08-04). Data from beyond the far encounter          
      interval is contained in the cruise data archive which is               
      available from the NSSDC.                                               
                                                                             
      VG2-J-PRA-3-RDR-LOWBAND-6SEC-V1.0 contains data at the highest          
      time resolution possible during normal operations. The normal           
      mode of PRA operations during the planetary encounters was to           
      sweep through the two radio receiver bands, high band (40.5 to          
      1.5 MHz in 128 channels spaced 0.3072 MHz apart) and low band           
      (1326.0 to 1.2 kHz in 70 channels spaced 19.2 kHz apart) in a           
      period of 6 seconds. The receivers measured, on alternate               
      samples, the left hand circular and right hand circular (radio          
      definition) power.                                                      
                                                                              
      Measured Parameters                                           
          
      ===================                                                     

      The data here are from the low frequency receiver band and are          
      'packaged' into spacecraft major frame records. Each major              
      frame is 48 seconds long or eight sweeps through the PRA                
      receiver. The data are calibrated and are given in units of             
      'millibels' which is 1000 times the log of the received power.          
      Zero millbels corresponds to approximately 1.4 x 10^-21 W m^-2          
      Hz^-1, however, this value is never seen in practice. The               
      minimum values detected, which includes receiver internal and           
      spacecraft generated noise, are about 2300 to 2400 millibels,           
      or about 3.5 x 10^-19 W m^-2 Hz^-1; even higher values are seen         
      at the very lowest frequencies.                                         
                                                                              
      The data format is ASCII and consists of a time indicator               
      followed by an array containing the eight low band sweeps. Time         
      is spacecraft event time (SCET) which is basically universal            
      time at the spacecraft. Specifically, time is in the form of            
      YYMMDD and seconds into YYMMDD. Both are written as I6.                 
      Example: July 1, 1979 at 12 hours SCET would be 790701, 43200.          
      The seconds correspond, to the nearest second, to the start of          
      the sweep (which occurs in PRA high band). The first value in           
      low band (1326.0 kHz) occurs some 3.9 seconds after this time           
      and samples at successively lower frequencies are spaced 0.03           
      seconds apart. Only one time is given for the entire major              
      frame, thus the start of each sweep is the time given plus 6            
      times the sweep number minus 1 (i.e., 0 through 7).                     
                                                                              
      The data array is dimensioned as 71 X 8 and written as I4               
      format (i.e. 568I4). The '8' corresponds to the eight PRA               
      sweeps. The lowest 68 of the 70 low band channels (1287.6               
      to 1.2 kHz) are in positions 2-69.  Positions 70-71 should be           
      ignored. Missing or bad data values are set to zero. In                 
      position 1 of each sweep is a status word where the 12 least            
      significant bits have used, although not all 12 have meaning            
      for PRA low band. Numbering those bits 0 for least significant          
      to 11 for most significant, the bits that have meaning are as           
      follows:                                                                

      bit                                                                     

       0: 15 dB attenuator in use when equal to 1                             

       1: 30 dB attenuator in use when equal to 1                             

       2: 45 dB attenuator in use when equal to 1                             

       9,10 (together): polarization of first channel sampled (1326.0         
                        kHz) according to the scheme:                         


            +---------------------------+                                                                              
	        |            |    |value bit|
	        |            |    | 10=     |
	        |            |    | 0  |  1 |
            |value bit 9=|  0 | R  |  L |
            |            |  1 | L  |  R |
            +---------------------------+                                                                              
                                                                              
      Polarization at successively lower frequencies is opposite to           
      the frequency above it, i.e. either a LRLR or an RLRL pattern.          
      Successive 6-second sweeps start on the opposite polarization           
      as the previous sweep as indicated in the status bits. Note             
      that this polarization is the received polarization, not                
      necessarily the emitted polarization. Correct interpretation of         
      the received polarization depends on the antenna plane                  
      orientation relative to the radio source. A good description of         
      this concept can be found in Leblanc Y., Aubier M. G., Ortega-Molina A.,
      Lecacheux A., 1987, J.Geophys. Res. 92, 15125 and in Wang, L. and Carr, T.D.,
      Recalibration of the Voyager PRA antenna for polarization sense 
      measurement, Astron. Astrophys., 281, 945-954, 1994. and references therein.
                                                                              
      Missing or bad data values are set to zero. If the status word          
      is zero, any data in that receiver sweep should be discarded.           
                                                                              
      Data Coverage                                                  
         
      =============                                                           

      The data are stored as 4 ASCII tables (.TAB), each accompanied with a PDS     
      label file (.LBL) which describes properties of the data file.  Data          
      cover the following time intervals:                                           


      Volume ID: VGPR_1201                                                    

     +-------------------------------------------------------------------------+
     | Filename   |Records|              Start       |            Stop         |
     |-------------------------------------------------------------------------|
     | PRA_I.TAB  |  32707| 1979-04-25T00:00:04.000Z |1979-05-28T23:59:14.000Z | 
     | PRA_II.TAB |  34207| 1979-05-29T00:00:02.000Z |1979-06-23T23:59:59.000Z | 
     | PRA_III.TAB|  31652| 1979-06-24T00:00:47.000Z |1979-07-12T23:59:58.000Z | 
     | PRA_IV.TAB |  34416| 1979-07-13T00:00:46.000Z |1979-08-04T23:05:33.000Z |
     +-------------------------------------------------------------------------+                                                                              
                                                                              
      Confidence Level Overview                      
                         
      =========================                                               
                                                                              
      The accuracy of calibration in the PRA low band is                      
      approximately 2 dB, except at frequencies below 100 kHz where           
      it is somewhat worse. Interference from the Voyager power               
      subsystem is a major problem to the PRA instrument, affecting           
      many of the 70 low band channels. This interference manifests           
      itself by abrupt changes in background levels. Some channels,           
      notably 136 and 193 kHz, are almost always affected, whereas,           
      others are only affected for short intervals. Usually, this             
      interference is only a problem when the natural signals are             
      weak.                                                                 
                                                                              
Additional information associated with this data set is available in the      
following files:                                                              
                                                                              
+------------------------------------------------------------------------------------------------------------------------------------------+   
|                                   file                                                               |    contents                       |
|------------------------------------------------------------------------------------------------------|-----------------------------------|
|https://pds-ppi.igpp.ucla.edu/ditdos/download?id=pds://PPI/VGPR_1201/CATALOG/VG2_PRA_INST.CAT         | VG1 PRA instrument description    |
|https://pds-ppi.igpp.ucla.edu/ditdos/download?id=pds://PPI/VGPR_1201/CATALOG/VG2_PRA_JUP_HRES_DS.CAT  | data set description              |
|https://pds-ppi.igpp.ucla.edu/ditdos/download?id=pds://PPI/VGPR_1201/CATALOG/PERSON.CAT               | personnel information             | 
|https://pds-ppi.igpp.ucla.edu/ditdos/download?id=pds://PPI/VGPR_1201/CATALOG/REF.CAT                  | key reference description         | 
|https://pds-ppi.igpp.ucla.edu/ditdos/download?id=pds://PPI/VGPR_1201/DOCUMENT/INSTRUMENT              | ASCII and HTML versions of the PRA|   
|                                                                                                      | investigation description paper   |
+------------------------------------------------------------------------------------------------------------------------------------------+