coefficients printed on the nonperforated strip attached to the punch-tape may also be entered manually. TELEMETRY  AND  RECEIVER  CHECK The  receiver  may  be  retuned  to  the  radiosonde, following the procedures in the operator’s manual, and the wide-band or narrow-band receiver mode selected. The  wide-band  mode  is  always  used  unless  locally produced radio interference requires use of the narrow- band  mode.  Normally,  both  the  radiosonde  and  the receiver  should  be  retuned,  to  try  to  avoid  the interference  before  selecting  the  narrow-band  mode. The best reception of the radiosonde is indicated by five asterisks  in  the  reception  LCD  window,  with  fewer asterisks  indicating  weaker  reception.  The  absence  of any asterisks indicates the signal is about to be lost. NAVAID  SYSTEM  SIGNAL  RECEPTION CHECK Navigation-aid radio signal strength from the eight Omega  stations  are  checked  following  procedures  listed in the operator’s manuals. If the receiver or transmitter is, or will move to within 60 nautical miles of one of the NAVAID transmitter sites, the receiver/processor will not  process  the  signal  properly  and  could  cause incorrect wind data. The station must be deleted from the   program   before   the   sounding   begins.   Use   the "SYSGEN"  program  edit  mode  as  described  in  the operator’s  manual  to  delete  a  nearby  Omega  station. Upgraded MRS units and radiosondes use GPS, which is  more  reliable  and  accurate  than  the  VLF-Omega system. RELEASE   AUTHORIZATION After the instrument checks have been completed and  the  radiosonde  is  attached  to  the  balloon,  the operator  must  contact  the  air  traffic  controller  in  the shore-station  control  tower  to  obtain  “permission  to release  a  meteorological  balloon.”  The  air  traffic controllers  are  responsible  for  transmitting  any NOTAMs (Notice To Airmen) that may be required at Naval and Marine Corps air stations. Aboard ship, the operator must contact the officer of the deck (OOD) for permission  to  release  a  meteorological  balloon.  The OOD has the responsibility for contacting the Tactical Action  Officer  (TAO),  the  shipboard  air  traffic controllers,  and  the  Air  Boss  to  obtain  release authorization, and then to relay the authorization to the observer. Since the shipboard process involves several different departments, each of which may be extremely busy  with  normal  ship  handling  and  flight-quarters evolutions, it is best to obtain authorization well before release   time.   Keep   in   mind   that   certain   electronic emissions control (EMCON) restrictions may preclude a radiosonde launch. SURFACE  WEATHER  OBSERVATION Just  before  release  of  a  meteorological  balloon,  a weather  observation  must  be  made.  Data  from  the surface  weather  observation  is  entered  into  the receiver/processor  either  before  or  after  release,  but before the radiosonde instrument has passed the 14,000- foot height. The surface observation data entry routine will prompt the operator to enter the station pressure in whole hectopascals, the air temperature to the nearest 1/10 Celsius degree, the relative humidity to the nearest percent, true wind direction to the nearest degree, wind speed  to  the  nearest  knot,  and  the  cloud  group N_hC_LhC_MC_H,  as  described  later  in  this  chapter. The surface observation data should be compared to the surface raw data received from the radiosonde and displayed by the computer.  If the comparison values are outside the range plus or minus 1°C for temperature and 10%  relative  humidity,  the  radiosonde  should  be allowed  to  acclimate  an  additional  5  minutes.  If  the radiosonde fails this check, another radiosonde should be used. BALLOON  RELEASE When  the  balloon  is  released,  the  radiosonde reports  a  decrease  in  pressure  to  the  data  processor, which  automatically  starts  the  data  recording  and processing    function. Data  will  print  out  or  be transmitted to a computer 8 to 10 minutes after release. During   ascent   through   the   first   15,000   feet,   the radiosonde   instrument   is   most   susceptible   to interference and loss of NAVAID/GPS signals used to determine  winds.  To  determine  accurate  winds,  the receiver   should   be   maintained   continuously   in   the “track” mode during this time. 1-10 Q19. Q20. Q21. Q22. Q23. REVIEW  QUESTIONS How are RS-80 radiosondes powered? How can the radiosonde frequency be adjusted? How  is  high  quality  reception  indicated  by  the MRS? Aboard ship, what person authorizes the release of a radiosonde balloon? What  should  be  done  with  the  surface observation   data   before   a   radiosonde   is released?