environmental   software   is   interfaced   with   NTDS, shipboard Aerographer’s Mates have indirect access to the   bathythermograph   output. On   temporary deployment, mobile environmental team members may need  to  manually  enter  the  bathythermograph  output into   the   Mobile   Oceanography   Support   System (MOSS) terminal. The   AN/BQH-7A   may   be   connected   to   two launchers at the same time, although only one is used for each  sounding. This  system  uses  both  a  hand-held LM3A  launcher  (fig.  2-6)  and  the  MX-8577/SSQ-61 through-the-hull   launcher.   The   hand-held   launcher may  also  be  used  with  all  of  the  AN/SSQ-(series) systems. The   same   T-4   XBT   probe   is   used   with   the AN/BQH-7A   system.   In   addition,   the   AN/BQH-7A also  accepts  the  T-5  6,000-foot-deep  ocean  scientific probe,  the  T-7  2,500-foot  improved  sonar  prediction probe,  and  other  specialized  probes.  By  using  any  of these probes, you can make the chart recording as either a depth/temperature trace or as a depth/sound velocity trace.  Selection  is  made  with  the  “strip  chart  output” selector   switch,   located   just   above   the   chart   door. Sound  velocity  is  internally  calculated  based  on  the measured temperature and a standard salinity of 35%. The   tape   may   be   replayed   to   produce   either   a temperature  or  a  sound  velocity  trace.  Normally,  the temperature  trace  is  recorded  first,  evaluated  and encoded for transmission, and then the sound velocity trace is recorded for direct use by the shipboard Sonar Technicians. The  AN/BQH-7A  also  uses  a  different  type  of probe called an Expendable Sound Velocimeter (XSV) probe.  The  standard  model  is  the  XSV-01,  that conducts  sound  velocity  measurements  to  2,790  feet (850 meters), and is shown in figure 2-7. An XSV probe uses a special sensor that produces an internal acoustic signal.  The  integrated  circuitry  of  the  probe  then calculates  the  sound  speed,  factoring  in  the  temperature, pressure,  and  salinity  of  the  water.  The  sound  speed values produced by an XSV are direct measurements. When  this  probe  is  used,  the  chart  output  selector  is disabled and only a sound velocity profile is produced. These  probes  are  recommended  in  areas  where  the salinity  of  seawater  is  historically  different  from  the standard  35%,  and  when  salinity  varies  with  depth. When  soundings  are  conducted  by  using  this  type  of probe,   a   standard   temperature   probe   must   still   be dropped to fulfill data collection requirements. Detailed  operating  procedures  are  covered  in  the operator/technical   manual   Technical   Manual   for Figure  2-6.—LM3A  hand-held  launcher. Bathythermograph/Sound    Velocimeter    AN/BQH-7A Oceanographic  Data  System  Surface  Ship  Application, NAVSEA   SE365-BA-MMO-010/BQH-7A. Maintenance Preventive   and   corrective   maintenance   are thoroughly  covered  in  the  operator/technical  manual. Preventive   maintenance   includes   recommended weekly testing of the system output using a test probe, a  monthly  launcher  cleaning  and  inspection,  a quarterly  test  device  performance  procedure,  a semiannual  recorder  and  processor  cleaning  and inspection,   and   an  annual   check   of   the   cable’s signal/ground continuity and insulation resistance. At the  beginning  of  each  sounding,  the  operator  must ensure  that  the  ready-for-launch  mode  stylus  alignment is  made.  With  an  XBT  probe  in  the  “temperature” mode, align the stylus at 62.0°F (±0.3°F). and with an XSV probe, align the stylus at 4,962 feet per second. Columns are predrawn on each recording chart for these readings as well as for other calibration measurements. 2-8