CURRENT  CAPABILITIES  AND  FUTURE 
REQUIREMENTS  OF  THE  AIR  FORCE  SPACE 
SURVEILLANCE  NETWORK 
DENNIS  K.  HARDEN, 
CAPT,  ORBITAL  ANALYST  LEADER,  HQ  USSPACECOM/SSC 
PETERSON  AIR  FORCE  BASE,  COLORADO 
Prepared  for  Presentation  at  the 
Tenth  Air  University  Aerospace  Power  Symposium 
"The  Impace  of  Space  on  Aerospace  Doctrine" 
Air  War  College 
Maxwell  Air  Force  Base,  Alabama 
10-12  March  1986 
The  views  end    conclusions  expressed  in  this  paper  are  those  of 
the  author(s)  and  do  not  reflect  the  official  policy  or  position 
of  the  Department  of  Defense  or  the  United  States  Government.
When  the  Soviet  Union  launched  Sputnik  1  on  4  October  1957 
it  was  a  complete  surprise  to  the  US.   It  was  immediately 
realized  that  the  US  had  almost  no  means  of  detecting,  trackinq 
or  identifying  man-made  objects  in  space.   As  a  result  a  crash 
program  was  initiated  to  develop  and  deploy  a  system  of  sensors 
capable  of  maintaining  surveillance  on  man-made  earth  orbiting 
obj  ects . 
The  first  network  of  spacetrack  sensors  consisted  of  the 
Naval  Space  Surveillance  (NAVSPASUR)  system,  developed  by  the 
Advanced  Research  Projects  Agency  and  the  Baker-Nunn  cameras 
which  had  been  developed  by  the  Smithsonian  for  the  purpose  of 
tracking  Vanguard,  initially  scheduled  for  launch  in  1957.   These 
sensors  were  combined  to  form  the  Space  Data  and  Tracking  System 
(SPADATS)  and  assigned  operationally  to  NORAD  on  7  November  I960, 
by  the  Joint  Chiefs  of  Staff. 
This  system,  now  known  as  the  Space  Surveillance  Network 
(SSN),  has  expanded  rapidly  over  the  past  25  years.   The  evolu- 
tion can  be  divided  into  three  phases.   Phase  one  which  began  in 
1960  lasted  until  the  end  of  1963.   During  this  time  the  existing 
sensors  were  supplemented  by  radars  of  the  Ballistic  Missile 
Early  Warning  System  (BMEWS) .   These  radars,  although  designed  to 
warn  of  missile  attack,  had  space  surveillance  capabilities.   By 
the  end  of  1963  the  SSN  was  tracking  about  400  man-made  space 
objects . 
Phase  two  began  in  1964  and  lasted  through  1971.   There  were 
two  driving  factors  during  this  phase.   The  first  was  a  need  to 
increase  the  accuracy  of  positional  data  from  the  SSN  to  support 
an  anti-satellite  (ASAT)  system  the  Air  Force  had  been  directed 
to  deploy.   The  second  was  the  need  to  determine  ,he  reentry  and 
impact  points  of  decaying  satellites.   This  requirement  was  for- 
malized in  the  1967  Outer  Space  Treaty  which  made  States  respon- 
sible for  damage  caused  by  reentering  objects.   These  new 
requirements  lead  to  two  significant  improvements.   One  was  the 
Space  Defense  Center  (SDC)  which  was  established  in  the  NORAD 
Cheyenne  Mountain  Complex  in  1966.   With  the  powerful  soft- 
ware developed  for  the  SDC,  the  SDC  was  providing  data  to  users 
on  almost  1900  orbiting  satellites. 
The  second  upgrade  during  this  phase  was  the  addition  of  the 
FPS-85  radar  at  Eglin  AFB ,  Florida.   This  was  the  first  radar 
designed  exclusively  for  satellite  surveillance.   Because  of  its 
location  it  was  capable  of  tracking  most  satellites,  especially 
low  inclination  satellites.   Many  "unknown"  satellites  were  added 
to  the  catalog  after  the  FPS-85  became  operational. 
Phase  three  which  began  in  1971  is  continuing  today.   Figure 
1  shows  the  SSN  as  it  now  exists.   The  total  number  of  sensors  is 
23  with  two  more  PAVE  PAWS,  phased  array  radars  scheduled  to  be 
added,  one  in  Texas,  one  in  Georgia.   The  23  sensors  function  in 
one  of  three  modes,  dedicated,  collateral  or  contributing.
The  dedicated  sensors  are  those  sensors  controlled  by  NORAD 
with  a  primary  mission  of  spacetrack  support.   The  dedicated  sen- 
sors consist  of  three  optical  and  two  radar  systems.   The  optical 
sensors  are  the  Baker-Nunn  cameras,  the  Ground-Based 
Electro-Optical  Deep-Space  Surveillance  (GEODSS)  system,  and  the 
Maui  Optical  Tracking  and  Identification  Facility  (MOTIF).   Radar 
components  of  the  dedicated  network  are  NAVSPASUR  and  the  Global 
Positioning  System-10  (GPS-10)  located  at  San  Miguel,  Republic  of 
the  Phillipines. 
Collateral  sensors  are  those  sensors  controlled  by  NORAD,  but 
with  a  primary  mission  other  then  spacetrack,  usually  missile 
warning.   These  sensor  types  include  the  FPS-85;  Cobra  Dane  at 
Shemya,  Alaska;  three  BMEWS  at  Alaska,  Greenland  and  England;  The 
Perimeter  Attack  Radar  Characterization  System  (PARCS)  in  North 
Dakota;  the  FPS-79  at  Pirinclik,  Turkey;  and  the  PAVE  PAWS, 
phased  arrays  in  California  and  Massachusetts. 
Finally,  there  are  the  contributing  sensors.   These  sensors 
are  not  controlled  by  NORAD.   Instead,  they  are  under  contract  to 
provide  information  when  requested.   The  sensor  names  and  loca- 
tions include  Kaena  Point,  Hawaii;  ALTAIR  and  ALCOR  at  the 
Kwajaln  Altoll;  Millstone  and  Haystack  in  Massachusetts;  and 
Ascension  and  Antigua  Islands. 
All  of  the  data  obtained  from  the  SSN,  over  30,000  obser- 
vations daily,  is  fed  to  the  NORAD  Space  Surveillance  Center 
(NSSC)  located  in  NORADs  Cheyenne  Mountain  Complex.   The  NSSC 
mission  is  to  detect,  track,  identify,  and  maintain  surveillance 
on  all  man-made  objects  in  earth  orbit.   The  data  received  by  the 
NSSC  is  also  used  for  foreign  satellite  identification,  satellite 
maneuver  processing,  collision  avoidance,  decay/impact  predic- 
tion, targeting  for  the  US  Anti-satellite  (ASAT)  system,  and 
attack  assessment  for  both  the  US  and  Soviet  ASAT  systems.   The 
NSSC  maintains  an  accurate,  current  catalog  of  all  space  objects 
and  provides  this  data  to  numerous  cooperating  agencies, 
including  the  Johnson  Space  Center,  Goddard  Space  Flight  Center, 
and  the  Air  Force  Satellite  Control  Facility. 
FUTURE  REQUIREMENTS 
Future  requirements  to  support  the  space  surveillance  mission 
will  be  dependent  upon  many  factors.   Perhaps  the  most  signifi- 
cant of  these  factors  are  the  projected  growth  of  the  satellite 
population,  and  the  need  for  surveillance  on  smaller  objects.   An 
analysis  of  these  requirements  reveals  future  deficiencies  in  the 
SSN  capability  to  support  the  surveillance  mission,  especially  in 
the  areas  of  collision  avoidance  and  Deep-Space  (DS)  satellite 
(period  >  225  min)  tracking.
To  understand  the  future  requirements  of  the  SSN  both  the  US 
and  the  USSR  space  programs  must  be  examined.   It  is  necessary  to 
appreciate  the  extent  of  reliance  by  both  nations  militaries  to 
accomplish  communications,  navigation,  reconnaissance,  early 
warning,  nuclear  explosion  detection,  weather  forecasting  and 
geodetics.   Satellites  allow  for  these  functions  to  be 
accomplished  in  an  economical,  technically  superior  manner. 
The  Soviet  Union  normally  maintains  110-120  satellites  in  an 
operational  status.  The  USSR  spent  approximately  $35  billion  on 
space  activities  in  1984.  The  USSR  conducted  9  7  space  launches, 
of  which  about  70  percent  were  military  related. 
The  robust  nature  of  the  Soviet  space  program  indicates  a 
quest  for  military  superiority.   The  USSR  is  developing  several 
new  space  vehicles.   These  vehicles  include  a  heavy-lift  launch 
vehicle,  equivalent  to  the  Saturn  5;  a  medium  lift  vehicle, 
evidently  designed  for  high  launch  rates;  and  a  Space 
Transportation  System  (STS)  which  closely  resembles  the  US 
shuttle. 
The  US  military  space  program  is  also  expanding.   Recognizing 
the  importance  of  space,  the  Air  Force  established  the  Space 
Command  in  1982.   The  Navy  quickly  followed  by  forming  a  Naval 
Space  Command .   This  year  a  Unified  US  Space  Command  was  created 
with  a  headquarters  in  Colorado  Springs,  Colorado.   The  FY  1984 
military  spaco  budget  was  $10.5  billion.   A  Consolidated  Space 
Operations  Center  (CSOC)  is  presently  under  construction  and  due 
to  be  activated  in  1986.   From  the  CSOC^BHHBBB  STS  and  military 
satellite  missions  will  be  controlled.   In  conjunction  with  the 
expanding  role  of  the  military  in  space,  a  launch  complex  for  the 
STS  is  being  completed  at  Vandenberg  AFB ,  California.   From  this 
location  it  will  be  possible  to  launch  the  STS  on  polar  orbit 
missions.   Finally,  the  Strategic  Defense  Initiative  is  bringing 
the  military  into  space.   The  total  cost  of  this  program  if 
pursued  to  completion  could  exceed  $400  billion. 
COLLISION  AVOIDANCE 
As  our  dependence  on  satellites,  the  STS,  and  possible  future 
manned  platforms  becomes  even  greater,  the  credibility  of  colli- 
sion avoidance  data  becomes  critical.   There  is  substantial  evi- 
dence that  at  least  two  satellite  breakups  have  been  the  result 
of  collision  with  space  debris. 
To  date  there  have  been  at  least  70  known  explosions  of 
orbiting  objects.   At  least  11  other  breakups  resulting  in  a 
large  number  for  fragments  have  also  occurred.   Almost  50  percent 
of  the  objects  cataloged  originated  from  these  events.
Orbiting  debris  are  beginning  to  pose  an    increasingly  signi- 
ficant hazard  to  active  payloads.   The  degree  of  hazard  is  depen- 
dent upon  the  payload  size,  the  number  of  debris  fragments 
operating  in  the  same  environment,  and  the  length  of  time  on 
orbit.   The  NSSC  presently  maintains  data  on  over  6000  objects. 
Most  are  larger  than  10  cm  in  diameter.   The  probability  of 
collision,  of  a  payload,  with  these  objects  is  small.   For  the 
STS  it  is  approximately  4x10-6  for  a  seven  day  flight. 
There  is  a  second,  more  significant  threat  to  spacecraft. 
This  threat  is  from  the  untracked  satellite  population.   The 
number  of  these  objects  must  be  much  higher  than  that  of  the 
trackable  objects.   Based  upon  the  number  of  objects  4  cm  and 
larger  which  are  newly  detected  just  prior  to  decay,  the  probabi- 
lities of  collision  are  increased  substantially.   When  these 
smaller,  uncataloged  objects  are  taken  into  account  the  estimate 
for  collision  of  a  large  satellite  in  one  year  is  0.016  in  an 
850  km  orbit  (figure  2).   The  danger  is  substantial  from  even 
smaller  particles.   Studies  have  shown  that  particles  as  small  as 
1  cm  could,  in  a  collision,  penetrate  a  5  cm  thickness  of 
aluminum . 
Perhaps  that  most  important  aspect  of  the  debris  problem  is 
its  self-propigating  nature.   Hundreds  of  objects  can  result  from 
a  single  collision.   Each  of  these  new  objects,  in  turn, 
increases  the  probabilities  of  other  collisions.   It  is  predicted 
that  the  number  of  objects  tracked  will  increase  by  three  the 
eight  times  over  the  next  20  years.   Figure  3  shows  that  by  the 
1990s  the  chances  of  orbital  collision  will  be  significant. 
Long-term  solutions  to  the  problem  of  space  debris  have  not 
yet  been  formed.   For  the  near-term,  however,  the  credibility  of 
collision  avoidance  information  for  operational  payloads  must  be 
improved.   This  will  necessitate  improvements  to  the  SSN.   The 
capability  to  track  smaller  objects  must  be  added.   To  support 
these  new  objects  more  powerful  computing  systems  are  necessary 
at  the  NSSC.   Only  with  this  new  data  available  will  collision 
avoidance  for  payloads  remain  viable, 
DEEP-SPACE  SURVEILLANCE 
A  second  critical  area  of  concern  also  exists  for  the  SSN. 
This  is  the  capability  to  support  the  future  DS  surveillance 
requirements.   The  DS  satellite  population,  satellites  with 
periods  great  than  225  rains,  is  expected  to  grow  dramatically, 
increasing  by  200  percent  in  the  next  15  years  (Figure  4). 
There  are  presently  nine  sensors  tasked  to  maintain  obser- 
vational data  on  these  satellites.   These  sensors  are  the  FPS-85; 
the  FPS-79  at  Pirinclik,  Turkey;  Millstone;  ALTAIR;  GEODSS;  and 
the  Baker-Nunn  cameras.   The  FPS-85,  which  provides  40  percent
of  the  total  number  of  DS  observations,  and  the  Baker-Nunn 
cameras  are  scheduled  to  be  closed  before  1990.   There  are  three 
operational  GEODSS  located  in  New  Mexico,  Hawaii,  and  Korea.   Two 
additional  GEODSS  should  be  operational  in  1987.   When  capabili- 
ties of  the  GEODSS,  the  FPS-79,  Millstone  and  ALCOR  are  examined, 
it  is  evident  that  the  DS  surveillance  network  can  support  only  a 
finite  number  of  objects  per  day.   Figure  5  shows  a  hypothetical 
tasking-response  curve  for  a  GEODSS  site.   Due  to  equipment  and 
weather  limitations  a  given  site  can  support  only  a  finite  number 
of  satellites  tasked  before  the  response  curve  flattens.   A  radar 
site  shews  similiar  limitations  due  to  the  time  require  to  obtain 
observations  on  DS  satellites,   If  the  DS  population  continues  to 
grow  at  the  expected  rate,  this  finite  number  will  eventually  be 
exceeded  perhaps  before  additional  operational  sensors  are 
available. 
SOLUTIONS 
The  problem  of  tracking,  small  objects  will  be  especially 
acute  after  closure  of  the  FPS-85.  The  FPS-85  and  PARCS  with 
augmentation  from  NAVSPASUR  provide  most  data  on  smaller  objects. 
Consideration  should  be  given  to  the  deployment  of  an  addi- 
tional sensor  to  alleviate  the  debris  problem,  A  C-Band  radar 
located  with  Southeast  PAVE  PAWS  would  be  of  great  assistance 
because  of  the  accuracy  of  the  tracking  data.   The  addition  of  a 
PACBAR  III  at  Guam  or  Saipan  would  help,  especially  with  low 
inclination  objects. 
The  best  near-earth  solution  would  be  to  retain  the  FPS-85  in 
a  solely  spacetrack  role.   Perhaps  as  a  contract  sensor.   If  this 
should  occur  the  problems  of  equipment  and  maintenance  for  this 
old  system  should  be  addressed.   Also,  as  a  near-earth  solution 
one  of  the  two  new  PAVE  PAWS  could  be  extensively  modified  to 
support  satellite  surveillance.   This  would  create  a  unique 
system  however  with  its  inherent  problems.   Finally,  the  NSSC 
must  be  upgraded  to  accomodate  the  increased  number  of  obser- 
vations a  more  powerful  SSN  would  provide. 
Probably  the  most  viable  alternative  to  the  DS  problem  is 
accelerated  development  of  the  Space  Based  Surveillance  System 
(SBSS).   A  NASA  symposium  on  debris  concluded  that  a  SBSS  would 
be  capable  of  detecting  particles  as  small  as  lmm.   Most  advan- 
tages of  all  it  would  not  be  subject  to  the  weather  constraints 
inherent  in  the  GEODSS  system.   Once  SBSS  is  deployed  the  DS  sur- 
veillance problem  should  be  solved. 
Military  satellites  are  crucial  to  the  security  of  the  US. 
In  many  cases  the  terrestrial  equivalent  of  the  services  these 
satellite  provide  has  atrophied  or  no  longer  exists.   The  SSN 
must  be  improved  to  allow  for  the  protection  and  defense  of  our 
national  space  assets.   The  cornerstone  is  complete  and  accurate 
space  surveillance.
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Satellites:  The  Creation  of :«  Debris  Hell."  J.  Geophysical  Kev.  Vol.  83.  No.  A6.  I  June  I V78.  and  Kcssler.  I). 
J..  "Sources  of  Orbital  Debris  jnd  ilic  Projected  environment  tor  future  Spacecraft."  P'esenicd  at  AiAA 
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