US Space Surveillance Network
jbarker@arinc.com
Mon, 8 Jan 1996 17:33:07 -0500
The following information on the US Space Surveillance Network is=20
extracted from the Army Space Reference Text (1993). An unclassif=
ied=20
reference text prepared for the US Army Space Institute (now close=
d)=20
at Fort Leavenworth, Kansas.
=20
Jeff Barker
jbarker@arinc.com
----------------------
=20
SPACE SURVEILLANCE
Space surveillance provides information on what is orbiting Ear=
th. =20
This information includes each object's orbital parameters, size a=
nd=20
shape, and other data useful for determining its purpose. Active =
and=20
inactive satellites, along with space debris such as boosters,=20
shrouds, and other objects are tracked. The smallest object that =
can=20
be tracked is about 4 inches (10 cm) in diameter. Space surveilla=
nce=20
provides essential information to the operators of space systems,=20
helps to determine the capabilities of potential adversaries, pred=
icts=20
the orbits of objects in space to include warning of potential=20
collisions, provides warning of an attack on a U.S. space system, =
and=20
predicts space object reentry impact points. In addition, message=
s=20
are sent to tactical commanders to warn them when they can be obse=
rved=20
by a potential adversary's space systems.=20
=20
SPACE SURVEILLANCE NETWORK
The U.S. Space Surveillance Network (SSN) is a collection of ra=
dar=20
and optical sensors used to detect, track and identify objects in=20
space. Although referred to as a network, the Space Surveillance=20
Network was not originally planned as such. As various sensors be=
came=20
available, their particular capabilities were used to contribute t=
o=20
the space surveillance mission. The Space Surveillance Network ca=
nnot=20
continuously track all satellites, therefore the Space Surveillanc=
e=20
Center prepares a prioritized list of satellites to track. Genera=
lly,=20
satellites with high interest missions or unstable orbits (objects=
=20
about to deorbit) will have higher priority data collection=20
requirements than other satellites.=20
The Space Surveillance Network is organized into three categori=
es=20
of sensors:=20
=FA Dedicated Government owned sensors with a primary mission of=
space=20
surveillance.
=FA Collateral Government owned sensors with a primary mission o=
ther=20
than space surveillance.
=FA Contributing Owned and operated by other agencies but which=20
provide surveillance data when not performing their primary missio=
n.
=20
SPACE SURVEILLANCE CENTER
The Space Surveillance Center (SSC), operated by the U.S. Space=
=20
Command, is located in Cheyenne Mountain, Colorado. The SSC maint=
ains=20
a database on all identifiable objects in Earth orbit. The databa=
se=20
includes about 10,000 objects. The SSC provides a variety of rout=
ine=20
and special reports to operational military commands, NASA, NOAA,=20
other organizations and the scientific community.
=20
TRACKING OF SPACE OBJECTS
Tracking space objects is an iterative process. The SSC starts=
the=20
process by developing a predicted element set (orbital parameters)=
of=20
the object's orbit. The Space Surveillance Center sends the eleme=
nt=20
set to selected sensors in the SSN. The sensors search the skies =
in=20
the predicted location, at the predicted time. If the prediction =
is=20
close, the sensor will detect and track the object. The tracking =
data=20
are sent back to SSC for processing and analysis. The SSC uses th=
is=20
information to compute a new element set, or prediction. This=20
prediction is then sent back out to the sensors, and the cycle is=20
repeated.
=20
SPACE OBJECT IDENTIFICATION (SOI)
The Space Surveillance Network sensors also collect information=
=20
which is used to perform Space Object Identification (SOI). SOI i=
s=20
the analysis of data from sensors to determine a satellite's size,=
=20
shape, motion, orientation and operational status. SOI is a techn=
ical=20
discipline that is similar to imagery interpretation.
=20
DEDICATED SENSORS
=20
Dedicated Optical Sensors
Optical sensors are basically telescopes, gathering light refle=
cted=20
off an object in space. Like all telescopes, they have limitation=
s;=20
for example, they cannot track objects in Earth's shadow unless th=
ey=20
are emitting light. Cloud cover, fog, atmospheric pollution, ligh=
t=20
glow from cities or a full moon degrade or prevent observations. =
The=20
size of the object to be tracked and its distance from Earth are a=
lso=20
limiting factors. =20
=20
Baker Nunn Camera
The Baker Nunn camera is a large telescope with a camera attach=
ed. =20
Imagery is recorded on film. Two to four hours are required for o=
n=20
site film processing and image analysis after which data is=20
transmitted to the Space Surveillance Center. The system can imag=
e=20
satellites ranging in altitude from 3,000 miles to 22,300 miles=20
(geostationary) and somewhat beyond. The position a space object =
in=20
the photo is determined by analyzing the star background. Baker Nu=
nn=20
cameras are in operation in San Vito, Italy and in Saint Margarets=
,=20
Newfoundland (operated by Canada). Many other Baker Nunn cameras =
have=20
been replaced by GEODSS.
=20
Ground Based Electro Optical Deep Space Surveillance System=20
(GEODSS)
GEODSS is an electronically enhanced telescope that uses low li=
ght=20
level television cameras and a computer instead of film. Sensor d=
ata=20
are stored on magnetic media for analysis locally or the data are=20
transmitted in near real time to the Space Surveillance Center for=
=20
analysis, if required. The GEODSS sensors are more sensitive than=
the=20
Baker Nunn cameras, therefore they can detect, image and track sma=
ller=20
and dimmer objects. The system can image objects in space with an=
=20
altitude of more than 22,000 miles. The GEODSS sensors provide va=
ry=20
accurate data which make them excellent for providing data to main=
tain=20
the space object catalog. The sensors only operate at night. Wea=
ther=20
conditions and a full moon restrict viewing opportunities. Each=20
GEODSS site has three telescopes, each facing a different section =
of=20
the sky. There are four GEODSS sites:
=FA Cicero, New Mexico
=FA Choe Jong San (near Taegu), Korea
=FA Maui, Hawaii
=FA Diego Garcia, Indian Ocean
A fifth GEODSS site in Portugal has been proposed. It would=20
replace the two remaining Baker Nunn sites.=20
=20
Maui Optical Tracking and Identification Facility (MOTIF)
MOTIF is an optical sensor similar to the GEODSS with an added =
Long=20
Wave Infrared (LWIR) detection system. It performs near Earth and=
=20
deep space surveillance and Space Object Identification. The rang=
e is=20
similar to that of the GEODSS. The sensor is only operated at nig=
ht. =20
Clouds, high winds, high humidity and a full moon restrict viewing=
=20
opportunities. MOTIF is collocated with the GEODSS site in Maui,=20
Hawaii.
=20
Dedicated Radar Systems
=20
Navy Space Surveillance (NAVSPASUR) System
The NAVSPASUR system consists of three transmitters and six=20
receivers located along the 33d parallel in the U.S. The transmit=
ters=20
emit a vertical continuous beam which forms an electronic fence. =
When=20
an object passes through one of the transmitter's waves in space a=
nd=20
two or more geographically separated receivers detect the reflecte=
d=20
energy, the object's location can be determined by triangulation=20
derived by interferometric techniques. This is essentially the sa=
me=20
process that bistatic radars use. Once the object's location and=20
general direction of movement are determined, NAVSPASUR operators=20
notify the Space Surveillance Center, which can then notify a trac=
king=20
radar to make more precise determinations of the object's=20
characteristics. The range of this fence is 5,000 miles in length=
and=20
can detect objects up to 15,000 miles out in space. The space obj=
ect=20
in orbit must have an inclination of greater than 33 degrees in or=
der=20
to pass through the electronic fence. It does not track, it only=20
detects. More than one million detections are made every month.
Transmitters are located at Gila River, Arizona; Lake Kickapoo,=
=20
Texas; and Jordan Lake, Alabama. Receivers are located at Fort=20
Stewart, Georgia; Hawkinsville, Georgia; Silver Lake, Mississippi;=
Red=20
River, Arkansas; Elephant Butte, New Mexico; and San Diego,=20
California. =20
NAVSPASUR headquarters is at Dahlgren, Virginia. The headquart=
ers=20
is also the Alternate Space Defense Operations Center and the=20
Alternate Space Surveillance Center.=20
=20
AN/FPS 85, Phased Array Radar
The AN/FPS 85 Phased Array Radar is located at Eglin AFB, Flori=
da. =20
The radar is housed in a wedge shaped building that is 318 feet lo=
ng. =20
The transmitter side has 5,928 elements and is 126 feet tall. The=
=20
receiver side has 19,500 elements and is 192 feet tall. The radar=
was=20
originally built to detect Sea Launched Ballistic Missiles (SLBM).=
It=20
became a dedicated space sensor in 1988, when the PAVE PAWS radar =
at=20
Warner Robins AFB, Georgia became operational. The radar has the=20
capability to track near Earth and deep space objects simultaneous=
ly. =20
Approximately 95% of objects in low Earth orbit pass through this=20
radar's coverage. =20
=20
Saipan Space Surveillance Station =20
The Saipan Space Surveillance Station, on the Pacific island of=
=20
Saipan, is well suited to monitor launches from China and the cent=
ral=20
Asian land mass . It transmits a single radar beam toward its tar=
get=20
in space. From the reflected energy the systems is able to calcul=
ate=20
the size, orientation, altitude, speed and direction of movement. =
The=20
system is not suitable for searching the sky for satellites. The=20
radar must first be queued so that it is pointed in the correct=20
position. The radar can track an object in space with high precis=
ion,=20
but it can only track one object at a time. =20
=20
Deep Space Tracking System (DSTS)
The Deep Space Tracking System uses sensitive, highly accurate,=
60=20
foot dish antennas to detect and track S band radio signals=20
transmitted by radio beacons on most satellites. There are DSTS=20
receivers located at Griffiss Air Force Base, New York; RAF Feltwe=
ll,=20
Great Britain; and Misawa Air Base, Japan. These sites are expect=
ed=20
to become operational in 1993 and 1994. The signals transmitted b=
y=20
most satellites are not significantly affected by weather and can=20
operate during the day and at night. The system is capable of=20
tracking many satellites in a short amount of time. This will allo=
w=20
the other optical and radar sensors to detect and track other=20
unidentified objects in space. Since they rely on transmissions f=
rom=20
the satellites, they cannot detect or track space debris or totall=
y=20
inactive satellites.
=20
COLLATERAL SENSORS
=20
Ballistic Missile Early Warning System (BMEWS)
The primary mission of BMEWS is to provide early warning and at=
tack=20
assessment of missile attacks launched against CONUS and southern=20
Canada from the Asian land mass that pass over or near the North P=
ole.=20
The system also serves to provide SLBM and ICBM warning/attack=20
assessment for the United Kingdom and Europe. The radars are capa=
ble=20
of tracking multiple space objects, however the capability is limi=
ted=20
to relatively large objects in low Earth orbit. BMEWS sites are=20
located at:
=FA Thule, Greenland (Site 1) A phased array radar, installed in=
1987,=20
provides 240 degree coverage against large objects such as ICBMs o=
r=20
SLBMs.
=FA Clear AFB, Alaska (Site 2) This site is equipped with 1961=20
vintage radars. They have proven to be very reliable, with a=20
historical 99% availability rate. =20
=FA Royal Air Force Station, Fylingdales, Great Britain (Site 3) =
The=20
site was initially built in 1964. It has three phased array radar=
s=20
which provide 360 degree coverage for warning/attack assessment of=
=20
ICBM and SLBM attacks.
=20
PAVE PAWS
PAVE PAWS is a system of radar complexes with a primary mission=
to=20
provide warning/attack assessment of SLBM attack against CONUS and=
=20
southern Canada. Each site operates a dual faced phased array rad=
ar. =20
The two northern sites (Cape Cod and Beale) can also provide=20
warning/attack assessment of an ICBM attack from the Asian land ma=
ss. =20
Each site can also provide satellite tracking data for space=20
surveillance. The sensitivity of the radar limits detection and=20
tracking to low Earth orbits of relatively large objects. Sites a=
re=20
located at:
=FA Cape Cod AFS, Massachusetts
=FA Beale AFB, California
=FA Robins AFB, Georgia
=FA Eldorado AFS, Texas
Due to a reduced threat, the PAVE PAWS system does not operate =
at=20
all times.
=20
AN/FSP 108, COBRA DANE
COBRA DANE is the project name for a single faced phased array=20
radar located at Shemya AFB, Alaska. Its primary mission is=20
intelligence, with secondary emphasis being space surveillance. I=
t=20
can also perform warning/attack assessment for missile attacks. T=
he=20
radar operates in the L band which provides better accuracy and=20
sensitivity than Pave Paws. Due to its position, COBRA DANE provi=
des=20
important information on new foreign launches.
=20
AN/FSP 79, Pirinclik, Turkey
The AN/FSP 79 radar, located at Pirinclik, Turkey, has the same=
=20
general mission as COBRA DANE. This system has two detection rada=
rs=20
and a tracking radar. Two objects can be tracked simultaneously. =
It=20
is the only 24 hour a day deep space sensor in the eastern hemisph=
ere.=20
=20
=20
AN/FPQ 16, Perimeter Acquisition Radar Attack Characterization Sys=
tem=20
(PARCS)
PARCS is a left over from the Safeguard Anti Ballistic Missile=20
system at Cavalier AFB, North Dakota. Following the deactivation =
of=20
Safeguard, the Army transferred PARCS to the Air Force. The Air F=
orce=20
assigned the radar a primary mission of warning/attack assessment =
of=20
SLBM and ICBM attack against CONUS and southern Canada. Its singl=
e=20
faced phased array radar is pointed northward over the Hudson Bay.=
It=20
can provide valuable surveillance, tracking, reporting, and Space=20
Object Identification data for the Space Surveillance Network. In=
=20
June 1992, the Air Force deactivated the site and placed it in=20
extended storage.
=20
CONTRIBUTING SENSORS
=20
Millstone Hill Radar and Haystack Long Range Imaging Radar
These two radars, commonly referred to as the Millstone/Haystac=
k=20
Complex, are located in Lexington, Massachusetts. They are owned =
and=20
operated by Lincoln Laboratories of the Massachusetts Institute of=
=20
Technology (MIT). Millstone is a deep space radar that contribute=
s 80=20
hours per week to tracking for the Space Surveillance Center. =20
Haystack is a deep space imaging radar that provides wideband Spac=
e=20
Object Identification data to the Space Surveillance Center about =
once=20
every six weeks. In addition to the scheduled use of Haystack,=20
USSPACECOM has the option to call on it two additional times in a=20
year.
=20
Antigua =20
A tracking radar is installed on Antigua, British West Indies o=
ff=20
the coast of Venezuela. This radar is part of the Eastern Test Ra=
nge=20
which supports launches from the Eastern Space and Missile Center=20
(Cape Kennedy and Cape Canaveral, Florida). The radar is very=20
accurate, but has a limited search capability.
=20
Ascension Island
A tracking radar, similar to the one on Antigua, is installed o=
n=20
this island located off the coast of Africa near the Equator. It =
also=20
is part of the Eastern Test Range.
=20
ALTAIR and ALCOR
The Advanced Research Project Agency (ARPA) Long Range Tracking=
and=20
Identification Radar (ALTAIR) and the ARPA Lincoln C Band Observab=
le=20
Radar (ALCOR) are on the island of Kwajalein in the western Pacifi=
c. =20
Operated by the Army, they are primarily used for ABM testing in=20
support of the Western Space and Missile Center (WSMC). They supp=
ort=20
space surveillance missions when possible. ALCOR is a near Earth=20
tracking radar, and is the only other radar besides Haystack that =
can=20
provide wideband Space Object Identification. ALTAIR is a near ea=
rth=20
and deep space tracking radar. Because of its nearness to the=20
equator, ALTAIR alone can track one third of the objects in the=20
geosynchronous belt.
=20
Kaena Point
Kaena Point is a tracking radar located on Oahu, Hawaii. It is=
=20
part of the Western Test Range and reports to the Western Space an=
d=20
Missile Center. When not being used for test support, it supports=
the=20
Space Surveillance Center with very accurate satellite tracking da=
ta.
=20
Advance Research Program Agency (ARPA) Maui Optical Station (AMOS)
AMOS is a similar to the GEODSS type optical sensor except that=
it=20
has a deformable mirror to compensate for atmospheric disturbance,=
=20
thereby creating clearer, sharper imagery. Operation is limited t=
o=20
nighttime only. Clouds and bright lights further restrict viewing=
=20
opportunities. It is collocated with the GEODSS and MOTIF sensors=
on=20
Maui. Its primary mission is to support research and development.
=20
=20