B^£ 
y&iv::>     „/w3c  **£:# 
fmii'' 
United  Slates  Air  Force 
OFFICE  OF  PUBLIC  AFFAIRS,  AIR  FORCE  SYSTEMS  COMMAND,  ANDREWS  AF6,  MD  20334,  (301)  981-4137 
DEFENSE  METEOROLOGICAL  SATELLITE  PROGRAM 
(DMSP) 
(USAF  Photo  79-6-5 18C) 
(PA  No.  019.82  -  Current  as  of  April  1982)
DEFENSE  METEOROLOGICAL  SATELLITE  PROGRAM 
Accurate  weather  forecasts  have  always  been  a  basic  need  of  military 
commanders,  and  the  Defense  Meteorological  Satellite  Program  (DMSP)  is  essential  to 
meet  these  requirements. 
Using  data  from  these  satellites,  military  weather  forecasters  detect  and  observe 
developing  cloud  patterns  and  follow  existing  weather  systems.  The  data  help  identify 
severe  weather  such  as  thunderstorms,  determine  the  intensity  of  hurricanes  and 
typhoons,  rjid  provide  visible  and  infrared  imagery  to  form  three-dimensional  cloud  plural 
analyses  of  various  weather  conditions.  An  important  feature  of  this  imagery  is  its  near 
constant  resolution. 
While  the  primary  mission  of  DMSP  satellites  is  gathering  weather  data  for 
military  uses,  its  information  is  actually  a  national  resource.  Data  gathered  by  the 
satellites  are  made  available  to  the  civilian  community  through  the  Commerce 
Department's  National  Oceanic  and  Atmospheric  Administration  (NOAA). 
DMSP  satellites  are  capable  of  providing  weather  data  on  a  real-time  basis  to  the 
Air  Weather  Service  and  Navy  and  can  store  these  data  in  on-board  recorders  for  later 
transmission  to  Air  Force  readout  sites  at  Fairchild  AFB,  WA,  or  Loring  AFB,  ME.  These 
sites,  as  well  as  the  Command  Contro.1  Center  at  Offutt  AFB,  NE,  are  operated  by  the 
Strategic  Air  Command's  (SAC)  4000th  Satellite  Operations  Group.  Recorded  data  are 
also  received  in  Hawaii  at  a  remote  tracking  station  managed  by  the  Air  Force  Satellite 
Control  Facility  (SCF)  at  Sunnyvale  AFS,  CA.  The  recorded  data  are  then  relayed  by 
satellite  from  both  readout  sites  and  the  SCF's  Hawaii  Tracking  Station  to  the  Air  Force 
Global  Weather  Central  at  Offutt. 
TERMINALS:    Mobile  ground  terminals  provide  military  commanders  in  the  field  with 
photographic-quality  prints  of  cloud  cover  four  times  a  day.    The  Mark  IV  mobile  ground 
terminal  is  a  compact  unit  consisting  of  the  19  ft.  (3  m)  parabolic  antenna,  the  Mark  IV 
van  and  an  auxiliary  power  generator.    With  the  antenna  stored  in  the  van  the  Mark  IV 
transportable  terminal  is  compact  enough  to  carry  in  a  C-130  aircraft. 
As  DMSP  satellites  pass  overhead,  the  mobile  ground  terminals  receive  pictures  of 
a  section  of  the  earth  and  its  cloud  cover.  Weather  data  transmitted  from  the  DMSP 
satellites  to  the  ground  terminal  can  be  gridded  and  labeled  for  clarification.  Mark  IV 
technology  also  permits  weather  watchers  to  enlarge  and  print  selected  portions  of 
infrared  and  visual  weather  data  from  both  the  military  DMSP  and  civilian  NOAA 
satellites. 
ORBIT;  The  satellites  —  there  are  normally  two  in  orbit  at  any  one  time  —  orbit  at  an 
altitude  of  approximately  450  nm  (833  km)  in  a  near-polar,  sun-synchronous  orbit.  They 
take  about  101  minutes  to  complete  their  orbits,  and  each  scans  a  1,600  nm  (2,960  km) 
wide  area.    Each  satellite  can  cover  the  entire  earth  in  about  12  hours. 
SIZE;  The  Block  5D-2  satellite  weighs  approximately  1,660  lb.  (732  kg),  including 
approximately  400  lb.  (180  kg)  of  sensor  payload  and  is  21  ft.  (6.2  m)  long  with  solar  array 
deployed.
HURRICANE  FREDERIC  IN  THE  GULF  OF  MEXICO 
(US AF  Photo  114840) 
SPACECRAFT:  A  launch  vehicle  upper  stage  is  integrated  into  the  satellite  with  the 
spacecraft  providing  for  ascent  phase  guidance  for  the  upper  stage  from  liftoff  through 
orbit  insertion,  as  well  as  electrical  power,  telemetry,  altitude  control  and  propulsion. 
The  spacecraft  is  divided  into  four  major  sections: 
-  a  precision  mounting  platform   for  sensors  and  other  equipment  requiring 
precise  alignment, 
-  an  equipment  support  module  which  encloses  the  bulk  of  the  electronics, 
-  a  reaction  control  equipment  support  structure  containing  the  spent  upper- 
stage  rocket  motor  and  supporting  the  ascent  phase  reaction  control  equipment,  and 
-  a  solar  array. 
-    3    -
LAUNCH  VEHICLE:   Block  5D-Z  satellites  will  be  launched  on  Atlas  boosters. 
ORBITAL  CONTROL:  Spacecraft  three-axis  attitude  control  is  maintained  by  automatic 
momentum  exchange  between  three  momentum  wheels.  On-board  magnetic  coils  provide 
controlled  interaction  with  the  earth's  magnetic  field  to  prevent  accumulation  of  secular 
momentum.   The  momentum  wheels  are  backed  by  a  fourth  skewed  unit  for  redundancy. 
POWER:  The  power  subsystem  is  a  direct  energy  transfer  system.  Power  from  the  solar 
cell  array  is  either  conditioned  for  direct  use  by  the  spacecraft  components,  stored  in 
nickel-cadmium  storage  batteries  or  shunted  through  resistive  power  dissipators  on  the 
array.   The  Block  5D-2  will  support  power  requirements  up  to  370  watts. 
IMAGERY:  The  Operational  Linescan  System  (OLS)  is  the  primary  sensor  on  board  the 
spacecraft,  providing  visual  and  infrared  imagery.  The  OLS  uses  a  linescanning 
radiometer  to  take  visual  and  infrared  (day  and  night)  imagery  in  both  .3  nm  (.55  km)  and 
1.5  nm  (3  km)  resolution.  These  data  are  used  to  analyze  cloud  patterns  in  support  of  a 
wide  range  of  military  requirements. 
A  major  improvement  of  the  OLS  over  past  generation  scanning  radiometers  is  its 
ability  to  produce  imagery  with  a  near  constant  resolution  across  scan.  This  is 
accomplished  by  using  segmented  visual  and  infrared  detectors  and  employing  a  detector 
switching  technique  as  the  OLS  scans  away  from  satellite  subpoint  nadir  towards  the 
edge-of-scan.  This  detector  switching  is  combined  with  a  basic  sinusoidal  scam  pattern  to 
produce  the  near  constant  resolution. 
An  additional  imaging  system  will  be  flown  starting  on  the  fourth  5D-2  satellite. 
Called  the  SSM/I  (Mission  Sensor  System,  Microwave  Imager),  the  sensor  is  a  passive 
microwave  radiometer  that  detects  and  images  microwave  energy  emitted  by  the 
atmosphere  and  the  surface  of  the  earth.  These  measurements  will  provide  military 
meteorologists  information  about  ocean-surface  wind  speed,  ice  coverage  and  age,  areas 
and  intensity  of  precipitation,  amount  of  water  and  clouds,  and  soil  moisture.  The 
Microwave  Imager  is  described  in  more  detail  in  a  separate  fact  sheet. 
TEMPERATURE/MOISTURE  MEASUREMENTS:  The  infrared  temperature/moisture 
sounder  measures  infrared  radiation  emitted  from  different  heights  within  the 
atmosphere,  allowing  forecasters  to  plot  curves  of  temperature  and  water  vapor  versus 
altitude.  A  microwave  temperature  sounder  is  also  used  to  measure  microwave  radiation 
emitted  from  different  heights  within  the  atmosphere.  This  instrument  allows 
forecasters  to  plot  curves  of  temperature  versus  altitude  even  over  cloudy  regions  of  the 
globe. 
IONOSPHERIC  MEASUREMENTS:  Three  sensors  observe  the  state  of  the  earth's 
ionosphere.  The  first,  called  a  precipitating  electron  and  proton  spectrometer,  is  used  to 
count  electrons  and  protons  at  different  energies  spiralling  down  ("precipitating")  along 
the  earth's  magnetic  field  lines.  These  data  are  used  to  accurately  forecast  the  location 
and  intensity  of  the  aurora  and  to  aid  radar  operations  and  long-range  ground 
communications  in  the  Northern  Hemisphere.  Another  sensor  measures  energy  in  the 
high  energy  gamma  and  x-ray  portion  of  the  spectrum.  Aurora  emit  in  this  part  of  the 
spectrum.  A  third  ionospheric  sensor,  the  ionspheric  plasma  monitor,  measures  electron 
and  ion  densities  and  temperatures  at  spacecraft  altitude.  Data  from  this  sensor  is  used 
in  ionospheric  weather  models  to  predict  the  state  of  the  ionosphere  as  it  affects 
communications  and  navigation. 
-    4    -
IONOSPHERIC  MEASUREMENTS 
Three  sensors  observe  the  state  of  the  earth's  ionosphere.  The  first,  called  a 
precipitating  electron  and  proton  spectrometer,  is  used  to  count  electrons  and  protons  at 
different  energies  spiralling  down  ("precipitating")  along  the  earth's  magnetic  field 
lines.  These  data  are  used  to  accurately  forecast  the  location  and  intensity  of  the  aurora 
and  to  aid  radar  operations  and  long-range  ground  communications  in  the  Northern 
Hemisphere.  Another  sensor  measures  energy  in  the  high  energy  gamma  and  x-ray 
portion  of  the  spectrum.  Aurora  emit  in  this  part  of  the  spectrum.  A  third  ionospheric 
sensor,  the  ionspheric  plasma  monitor,  measures  electron  and  ion  densities  and 
temperatures  at  spacecraft  altitude.  Data  from  this  sensor  is  used  in  ionospheric 
weather  models  to  predict  the  state  of  the  ionosphere  as  it  affects  communications  and 
navigation. 
CONTRACTORS; 
Spacecraft  —  RCA  Government  Systems  Division,  Astro-Electronics,  Princeton, 
New  Jersey. 
Primary  Sensor  —  Westinghouse  Electric  Corp.,  Defense  &  Electronics  Systems 
Center,  Baltimore,  Maryland. 
Special  Sensors  —  Barnes  Engineering  Co.,  Stanford,  CT;  Aerojet  Electro-Systems 
Co.,  Azusa,  CA;  Hughes  Aircraft  Co.,  Space  &  Communcations  Group,  El  Segundo, 
California. 
Ground  Terminals  —  Harris  Corp.,  Government  Systems  Group,  Melbourne, 
Florida. 
Launch  Vehicle  —  McDonnell  Douglas  Astronautics  Co.,  Huntington  Beach, 
California. 
For  additional  information,  contact:  For  photographs,  write: 
Space  Division  Director  of  Operations 
Office  of  Public  Affairs  (SD/PA)  1361  Audiovisual  Sqdn. 
P.O.  Box  92960,  Worldway  Postal  Cntr  1221  So.  Fern  St. 
Los  Angeles  ,  CA   90009  Arlington,  VA  22202 
(213)  643-0030 
-    5    -