PDS_VERSION_ID         = PDS3                                                 
RECORD_TYPE            = STREAM                                               
OBJECT                 = TEXT                                                 
  PUBLICATION_DATE     = 2008-12-23                                           
  NOTE                 = "                                                    
      TRIG_AC.TXT describes the RPWS instrument configuration for the         
      Medium Frequency Receiver (MFR), the Wideband Reciever (WBR), the       
      Sounder, and the Dust detector algorithm when using Trigger AC."        
END_OBJECT           = TEXT                                                   
END                                                                           

Trigger AC Description                                                        
                                                                              
Sequence:  C37, ...                                                           
Trigger AC ( 10 KHz WBR for Ring-Plane Crossing )                             
                                                                              
This trigger is designed to overlay 10-KHz Wideband Receiver data on top of   
a standard background trigger, such as 8A (Survey), 8E (night-time survey),   
or A0 (SEDDF).  Data acquisition continues for all receivers, with the        
exception of the dust detector and the sounder, which are disabled during     
this trigger's operation.  In addition, the MFR is switched to the EZ         
antenna to avoid interfering with the WBR, which is assumed to be connected   
to the EX antenna.  It is assumed that the WBR is pre-configured before this  
trigger is executed, except that the 10-KHz band selection is done by the     
trigger.  The standard setup done for the WBR by the background triggers is   
detailed below.                                                               
A very specific bitrate is targeted with this trigger, by specifying that     
the number of compressed WBR data bytes be exactly 1150.  Depending upon how  
well the Data Compression Chip is able to compress the data, this will be     
expanded to perhaps 2K or 3K data samples.  The intended bitrate for the      
trigger is 75 kbps.  It can be cut to a half or a fourth of this via a        
73MEM_TWEAK command following the trigger.                                    
                                                                              
Receiver  Frequency Range  Sensor  Snapshot Spacing  Sample Size              
--------  ---------------  ------  ----------------  -----------              
WBR       0 - 10 KHz       EX      0.125 second      varies                   
MFR       25 - 12 KHz      EZ, BZ  32 seconds                                 
                                                                              
                                                                              
                                                                              
Other notes:                                                                  
                                                                              
There is a 60-second delay following the execution of this trigger, and       
preceding the start of the WBR data acquisition.  This allows time for the    
MFR to switch antennas and the sounder to finish any pending operation.       
                                                                              
This trigger will work with most non-direction-finding triggers, such as      
Trigger 28 (Interplanetary Cruise), but its intended bitrate may vary.        
                                                                              
In C37, this trigger was used to determine if the BX antenna might be used    
by the WBR as a cyclic trigger for use during direction-finding modes.  This  
was done by "tweaking" the trigger AC setup with the BX-antenna command.