Continental U.S. receiving and processing center for early warning satellites is located
at Buckley Airfield, CO.
The four domes at Buckley (above) house reception antennas. Similar facility is situated
near Woomera, Australia.
Air Force, industry to focus on vulnerability of current satellite
system improvements, tracking and hardware design
By Barry Miller
Los Angeles-U, S.is taking steps to reduce the vulnerability of its satellite based
ballistic missile early warning system to hostile action and to improve the quality of
tracking data it now gathers on foreign ballistic missile launches.
The satellite warning system, or Defense Support Program (DSP) (AW&ST
July l5, p.45), is an indispensable part of the early warning network that alerts North
American Aerospace Defense Command, Strategic Air Command and the National Military
Command System to enemy intercontinental or submarine-launched ballistic missile attack
against the U. S. (AW&ST May 14, 1973, p. .17; Sept, 20.. 1971, p. 18).
Air Force efforts to strengthen the system are essentially twofold:
existing system and reduce its vulnerability to counteraction.
satellite missile warning system design.
To insure viability of the satellite warning system in the future, USAF's
Space and Missile Systems Organization (SAMSO) is expected to kick off a series of
parallel industry studies shortly after the first of the year. These studies will
investigate whether a new satellite design is necessary or whether the existing
design-which incorporates at least decade-old technology-can be adapted to satisfy future
needs. The studies also are likely to explore the possibility of adding more missions,
such as tracking objects in space, to the system's basic mission of detecting and
providing initial tracking information on ballistic missile launches. Competitors for
these studies are likely to include TRW Systems, Lockheed Missiles & Space, Rockwell
International, Hughes Aircraft and Grumman Aerospace.
SAMSO will soon initiate an effort in "proliferated ground
stations" for the early warning satellite system with selection of a contractor to
develop a simplified processing station (AW&:.ST July 22, p. 17) over the next two
years. The sim- plified processing station will be a special-purpose transportable data
readout center intended to enhance satellite system survivability by reducing dependence
on the system's two existing fixed-site data receiving and processing centers. Small
simplified processing station centers could be deployed in airborne command display launch
warning data transmitted directly over two data links from the synchronously orbiting
warning satellites. The data are derived from the satellites' infrared charged-particle
and radiation sensors that detect missile firings shortly after liftoff. At present, the
information is data linked in real time from the satellites to either of two similar
ground facilities, one operated by SAMSO's Detachment 2 near Woomera, Australia, and the other
at SAMSO's Aerospace Data Facility, Buck:ley Airfield (Air National Guard), Colo., where
data are processed and correlated with other intelligence information by dual IBM 360-75J
The small processing station will be comprised of two units-a satellite
communications module and a data processing equipment unit. The communications module will
receive data from the satellites, route them to the processing unit before transmission in
near real time to dedicated users. Competitors for the development are two teams
incorporating the four existing early warning satellite associate contractors, TRW
Systems, IBM Corp., Aerojet Electrosystems and Philco-Ford, IBM is head company in a
team including TRW Systems and Radiation, Inc, Aerojet heads a second team that includes
Philco-Ford and Control Data Corp.
USAF's intent With a multiplicity of transportable centers is to make the
critical ground centers less vulnerable by having more of them and making them more
elusive targets, The centers would provide an airborne alternative in the event one of the
ground centers were lost and could give USAF airborne command posts a capability roughly
equivalent to what is now at Buckley without having to operate through Norad. The
proliferated sites would enable the Navy to use data the Defense Support program can give
it to help speed response to surface-to-surface missile threats. The transportable centers
could relieve dependence of command authorities on or or both of the existing ground
stations, particularly the politically controversial site in Australia (AW&ST Apr. 30,
The satellites, which, are identified as code 647, are highly vulnerable to
attack, lacking even the simple self-protective measures of decoy dispensing and orbital
change that SAMSO is in the early stages of investigating for future satellites. USAF does
plan to protect the 647 satellite's sensitive optics from probing laser beams that an
enemy could direct at them. Martin Marietta is developing for USAF a passive warning
device, probably a silicon detector located within the satellites' giant Schmitt telescope.
The warning detector either could alert USAF or trigger a protective shutter when laser
energy penetrates into the 3-ft.-dia. telescope. Unprotected optical mechanisms are
especially sensitive to detection, identification and even damage when illuminated by
optical energy m the technique known as retro-reflection.
The Air Force also will flight test a simple impact alerting device, built by
Westinghouse for the 647 satellites, which give USAF an independent alarm when the
satellite is struck by foreign bodies.
USAF is pleased with the performance and capability of its 647 satellites,
despite nagging software problems that have sweled program costs. Commenting on the
program, Air Force Secretary John L. Monucas observed: "We have developed satellites
which can detect and track intercontinental ballistic missiles and submarine-launched
ballistic missiles, almost from the moment they are fired. In addition these warning
satellites have the capability to detect nuclear explosions above the ground and
ultimately will replace current satellites [Vela satellites] which monitor the atmospheric
nuclear test ban treaty" (AW&ST Feb. l8, p. 9).
More than 1,000 ballistic missile launches by the Soviet Union, China, France
and the U. S. have been observed by 647 satellites since the first one was orbited in
1971. These include firings of the Soviet SSX-J8 and SSX-19 ballistic missile and the
submarine-launched SS- N-8 missile. The satellites' launch observation have corrected
mistaken intelligence estimates of the performance of the Soviet weapon systems.
The ability of the satellites to provide even coarse tracking
information and to predict the missile's impact area was a surprise fallout from the
program, since the spacecraft were designed and optimized for detection, not tracking, The
satellites infrared sensor detects energy emitted by a missile's booster during the early
powered stages of flight, typically spotting a Soviet missile launch within 90 sec.
liftoff. USAF has taken two steps to void the relatively high probability of false alarms
created by the sensor erroneousy identifying forest fires, blast furnaces or natural
phenomena as missile launches. It can command the threshold levels of each of the hundreds
of infrared detectors in the satellite sensor to be triggered above minimum levels and has
configured logic in an onboard processor to reject as spurious events phenomena of low
interest. In addition, the sensor must mate a series of "detections" on
successive scans to confirm a missile launch, thereby discriminating a genuine missile
trajectory from a comparatively static hot spot like the large California brush fire a 647
satellite observed in the summer of 1973 or a spurious phenomenon like reflections of
solar energy off cloud edges. The multiple hits effectively define a velocity vector that
supplies an immediate indication of the corridor through which the missile will
travel and forecasts the target area.
As the missile speeds toward its target after burnout, the
intensity of the infrared energy emitted in the short wavelengths monitored by the
satellite declines sharply, causing the satellite to lose missile track in midcourse, but
before any decoys are dispensed. The Air Force is relying on other tracking sensors, such
as airborne and ground tracking radar's, like its three BMEWS sites and eight sea-launched
missile detection sites, to pick up missile targets after handoff from track data supplied
by the 647.
Studies were conducted by TRW Systems and Philco-Ford several years ago on a
low earth orbit midcourse satellite surveillance system using long
wavelength infrared detectors, like mercury cadmium telluride, to track missiles after
burnout. for high confidence trajectory information to be fed into ballistic missile
defenses.. Long wavelength infrared detectors can detect relatively cold bodies, such as a
burned out booster or reentry vehicles, against cold sky backgrounds at long ranges
because of the relatively high intensity of energy emitted over the 8 to l4 micron band.
But these efforts have been stalled because long wavelength detectors require cryogenic
cooling at low temperatures (77K) and complicated plumbing that lacks sufficient assurance
of long-term, trouble-free operation demanded by reliable military satellite operations.
Now USAF is going to take another look at midcourse surveillance in its space
track augmentation activity to determine whether it can more effectively hand off 647
information. A USAF West Coast study group has recommended new efforts in this direction.
Visible light sensors may prove to be one of the more attractive alternatives for
midcourse tracking, but they are cloud limited.
Observers attribute successful 647 operation in large measure to the choice
in such a complex system design of simple, proved technology wherever possible. For
infrared detectors, for example, Aerojet Electrosystems resorted to lead sulfide cells,
one of the oldest and better known infrared detector materials. These detectors provide
good sensitivity at comparatively elevated temperature of 193K, which permitted Aerojet,
designer of the satellite's optical telescope, to rely on passive, space radiative
cooling. This avoided the expense and mechanical pitfalls of active cooling, Aerojet has
earned substantial incentive fees from the Air Force over a three-year period for the
performance of the infrared telescope in orbit. Similarly, TW Systems, the spacecraft
designer and fabricator, also has received incentive awards for its performance.
The 647 satellite consists of a 10-ft-long, 9-ft-dia. cylinder section
supporting an infrared telescope. Weight of the satellite, which is orbited by a Titan 3C
booster, is over 2,000 lb. In its equatorial orbit, the spacecraft is oriented so the
telescope points toward the earth. The vehicle spins about its cylindrical axis at a rate
of about 5-7 rpm. The telescope line of sight is offset from the satellite's spin axis so
that the telescope field of view turns about the satellite spin axis, generating a
constant conical scanning of the infrared detector array and effectively enlarge the
telescope field of view. A 400- ft.-lb Sperry Flight Systems momentum wheel about 24 in.
in dia., housed in the supporting cylindrical section, spins at a constant speed counter
to the spin direction of the satellite to remove any moment accumulated during the
satellite spin. A pair of visual star sensors helps maintain proper satellite orientation.
The satellite's Schmidt telescope combine the simplicity, ease of alignment
and mounting of a spherical reflector with the diffraction limited performance and
image quality of a parabolic reflector. Energy is collected through an aspheric
corrector lens located at the center of curvature of a spherical mirror, or reflector at
the base of the telescope.
Infrared energy is reflected from the mirror onto a spherically shaped
detector array the focal surface of the assembly, midway between the reflector and the
corrected optics. Each of the many lead sulfide detector cells, covered by a narrow-band
spectral filter that peaks response at 2.7 microns, subtends an angle corresponding to an
area on earth from this altitude of less than 2 naut. mi. square. The two-dimensional
detector array is supplied by Electronics Corp. of America. Cambridge, Mass. Santa Barbara
Research Center is the second source.
Electrical outputs from each cell are signal conditioned, amplified and
digitized for transmission over data link to ground terminals. The spacecraft's
electronics located behind the reflector, compress data supplied by the infrared detector
channels and several hundred channels of data from other spacecraft systems and sensors to
more effectively use available communications bandwidth. The infrared sensor data
transmitted to earth include identification of the individual detector, and a digital
voltage corresponding to infrared intensity and time/frame number. The airborne processor
is supplied by Radiation, Inc., Melbourne, Fla.
The satellite's nuclear radiation detectors include proton counters and
X-ray gauges mounted on two of the four solar cell pedals that generate additional power
to supplement that or body-mounted solar cells on the main cylinder section. Several
radiation detectors view the earth from locations next to the infrared telescope and
parallel to the spin axis.
A complete operational 647 satellite system is comprised of three
satellites. One would be situated, as it now is, over the Indian Ocean area from which it
can monitor Soviet and Chinese launch activity .Two are stationed over the Western
Hemisphere to warn of submarine-launched ballistic missiles fired against the continental
U. S. Two are necessary in the event one is blinded by solar phenomena. Natural
interference with satellite operations is not as debilitating over the Eurasian land mass
because U. S. warning capability from that quarter is supplemented by other warning
Data from the satellites are processed on earth in near real time, generating
warning times measured in minutes. Data also are stored on magnetic tape and subsequently
sent to Aerojet in Azusa, Calif., where a vast library of information or: missile launch
and reentry phenomenology has now accumulated.
Aerospace Corp., a major participant in the Defense Support Program,
indicates it has assisted the Air Force from program inception, contributing to system
conceptual design, and performing the general, systems engineering associated with the
development, fabrication, installation and operation of the system." Besides its
infrared payload role, Aerojet had overall software responsibility for the first center in
Australia, with IBM assisting it and supplying the preprocessor for its dual computers.
IBM later got main responsibility for writing and implementing software for the second
center at Buckley. System Development Corp., Santa Monica, Calif., works directly for USAF
with responsibility for software management and consolidation of software documentation.
Defense Support Program officials have advised the Navy, which is seeking
ways of enhancing task force survivability, that the 647 satellites can provide essential
warning data on Soviet.surface-to-surface missile threats.
Successful performance of the initial group of 647 satellites appears to be
making it difficult for organizations working on the program to sustain their continuing
early warning efforts. A backlog of completed satellites, perhaps three or four in number,
has been accumulated and will be held in reserve as replenishments for satellites now in
orbit for a longer period than had originally been planned because of unexpectedly lengthy
mean mission-duration times. USAF has ordered a total of 13 647 satellites. The consequent
stretch in launch schedule and diminution in inventory planning is being felt by TRW
Systems, Aerojet and other groups on the program.
USAF has launched a total of four 647 satellites, the first of which failed
to achieve the desired orbit. The most recent 647 satellite was orbited on board a Titan
3C booster from the Eastern Test Range last year (AW&ST June l8, 1973., p. 17).
For the current fiscal year, Air Force had requested $77.1 million for the
Defense Support Program. .'The major portion of this request," Lt. Gen. William
John Evans, USAF's deputy chief of staff for research and development, told the House
Armed Services committee, "will be used to procure a DSP [the 13th] satellite, to
provide continued technical support, and to complete the survivability retrofit of three
In addition to its concern about improving midcourse tracking of ICBMs, USAF
would like to acquire positive missile launch warning information earlier. One way of
doing this would be to shorten the present time needed to initially detect a missile
launch to well below the 90 sec. or less now required. Such a move would impose a heavy
burden on system processing and may begin to push against the natural limitations of
infrared technology to detect phenomena partially or wholly obscured by atmospheric
Published by Aviation Week & Space
Technology December 2, 1974