Air University Review, November-December 1968
During the last fifteen years the military forces of the world have witnessed a technological explosion that is having a profound impact on concepts, weapons, and the balance of power between nations. Nowhere is this impact more apparent than in Aerospace Defense Command (ADC).
The term “aerospace” emphasizes the continuity of the air/space medium which forms the operating environment of today’s Air Force. Both physically and conceptually, the extension of military systems beyond the lower atmosphere has turned out to be natural and evolutionary.
Although new spacecraft are evolutionary in concept, their performance is a radical departure from the past. Strategic offensive vehicles can now deliver nuclear warheads anywhere in the world using ballistic trajectories. Simultaneously, dramatic advances have been made in the coverage and responsiveness of support satellites for surveillance, communications, weather, navigation, command and control, mapping, scientific research, and exploration.
Because strategic offensive space systems are inherently capable of operating anywhere, any time, and in any weather, the necessity for effective space defense weapons is both obvious and urgent. The purpose of this article is to detail the urgency of the aerospace defense problem, discuss the basic concepts involved, review our current capabilities, and describe operational requirements for space defense systems.
deterrence in the space age
For nearly two decades our national defense strategy has been based on deterrence of war through overwhelming strength. In the event general war occurs, the goal is to defeat the enemy as quickly as possible. In the past, the capabilities of our strategic and defensive forces have deterred general war through a number of major crises. How effective will these forces be in the space age?
Lieutenant General Arthur C. Agan, Commander of the Aerospace Defense Command, has pointed out that deterrence is a state of mind—the opponents mind. If the opponent does not fear the effect of a counterstrike (e.g., through his development of a new countermeasure or weapon), he is not deterred. Deterrence can also fail through miscalculation of relative strength, triggering of general war by a third power, or by an irrational or accidental act.
When manned bombers were the only threat to national survival, we could expect several hours of tactical warning. In addition, we could expect strategic warning from the intelligence community because of the unavoidable overt activity inherent in an intercontinental bomber raid.
With the introduction of intercontinental ballistic missiles (ICBM), the time in flight was greatly reduced. Additionally, with weapons deployed in silos, elimination of crew communications, and perpetual launch readiness, overt indications of preparations have been greatly suppressed. The result has been a marked reduction in both tactical and strategic warning time. Thus, the prospects of an aggressor’s achieving surprise attack have been significantly enhanced.
Another factor jeopardizing our deterrent posture is the rapidly increasing
size and maturity of the Soviet ballistic missile force. Former Secretary of
Defense Robert S. McNamara recently testified that the Russians are expected to
attain ICBM parity with the
The Soviet emphasis on military space systems provides small assurance that our deterrent posture will improve in the l970s, since their development time table has often put them one step ahead of us in space. The Soviets orbited the first satellite, the first living creature, the first man, the first woman, and the first multiman space vehicle. More recently, they achieved the first unmanned orbital rendezvous and docking as well as the first soft interplanetary landing on Venus.
The demonstrated space accomplishments of the U.S.S.R., together with their avowed intention of ruling the world, leave no room for complacency. Regardless of our intent and desire to use space for peaceful purposes, the fact remains that the Soviets are deeply committed to their space program and that it is conducted under military management.
In statements to the Senate Armed Services Committee in 1968, Secretary McNamara noted that the U.S.S.R. has intensively tested a fractional orbit bombardment system (FOBS) and is now deploying an antiballistic missile (ABM) defense system The first of these Systems may be aimed at neutralizing our manned bomber force through surprise attack; the second may be intended to provide an ICBM defense function, which General Agan has identified as a vital military requirement.
basic concepts and requirements
Experience has shown that space defense concepts evolve naturally and logically from air doctrine. Specifically, space defense must adhere to the principle of defense in depth, with the goal of making the battle as remote as possible. We cannot, however, just extrapolate from past experience. The unique characteristics of space demand that we do our technological and operational homework carefully in developing specific requirements for weapon and support systems.
Inasmuch as the extrapolation process implies development of future values from past experience, a brief review of aerospace defense history will be useful to an understanding of ADC’s future in space.
When ADC came into being in March 1946, its Commander, Lieutenant General George E. Stratemeyer, had assigned four understrength fighter squadrons and one radar unit in training status, equipped with World War II sets. During the war scare associated with Communist seizure of power in Czechoslovakia (1948), the Air Force ordered ADC to establish air defenses in the northeastern and northwestern sections of the U.S. (one warning radar in each) and in Alaska (four warning radars).
From this modest beginning, the conventional bomber threat was met by radars and interceptors sited near the most densely populated sections. As more equipment became available, the system was deployed more extensively. Since the range of the interceptors exceeded that of the radars, it was seldom possible to complete an intercept using one station. This led to the development of control centers linked by telephone and teletype.
A new generation of air defense systems was triggered in 1953 when the
U.S.S.R. successfully detonated a hydrogen bomb and began producing jet
bombers. The decreased warning time, increased range, and seriousness of the
threat demanded the development of early-warning systems, more sophisticated
radars, a semiautomatic ground environment (SAGE) for battle management and
advanced all-weather jet interceptors employing guided missiles. To provide
warning time and to remote the air battle, radars were deployed to forward
sites. In this way the Pinetree line, mid-Canada
line, and distant early-warning (Dew) line came into being. The sea franks were covered by radar aircraft, picket ships, and
When fully deployed, these defenses against the manned bomber provided
virtually continuous radar coverage throughout the continental
anti-ICBM defense
Development of the nuclear-armed ICBM in the 1950s had a major impact on our defense capability. Its trajectory enabled the weapon to fly over the existing active defense system and strike with little warning. Even with the best conceivable radars then under development, the maximum warning time was only 15-20 minutes.
The initial response to this threat was the deployment of the Ballistic
Missile Early Warning System (BMEWS) to accomplish detection and
identification. This system, which consists of three large radar sites in
Detection by the two systems is accomplished by formation of electronic fences (detection fans) which detect re-entry vehicles at ranges from several hundred to several thousand miles, thus providing from 5 to 20 minutes’ warning. The identification function for a ballistic target is straightforward and consists of computing launch point, impact point, and time of impact.
To date BMEWS has proven effective and reliable. Additionally, by using supplementary technology, we have increased both the warning time and credibility. One such system uses over-the-horizon (OTH) techniques. Disturbances in the ionosphere created by missiles passing through it can be detected by transmitting high-frequency radio signals across potential launch sites to receivers. Analysis of these signals then provides detection data with a significant increase in warning time as well as preventing the attacker from using global-range ballistic missiles (GRBM) to make an “end run”, around EMEWS.
Studies of anti-ICBM (AICBM) systems to accomplish the intercept and destruction functions fall into three major categories. In the first category are the boost-phase intercept systems, which attack the ICBM booster. During launch, the system is moving at relatively slow speeds, is vulnerable to nonnuclear kill, and is relatively easy to locate by use of passive infrared sensors. The aim here is to destroy the weapon prior to deployment of multiple independent-target re-entry vehicles (MIRV) or swarms of decoys. To engage the ICBM at maximum range seems to be as sound a concept for space defense as it has been for air defense. This approach, however, involves formidable development problems in space-based sensors, homing interceptors, and automated command and control.
In the second category are the midcourse-phase intercept systems, which attack the ICBM re-entry vehicle during the relatively long (20-25 minutes) exoatmospheric part of the trajectory. During this phase, ground-based multiple-object tracking radars could make meaningful predictions and direct ground-based interceptors for a nuclear kill. This approach employs the principle of defense in depth but requires a sophisticated discrimination system to sort out the real warhead vehicles from decoys, chaff, satellites, and orbiting debris.
The third category of AICBM systems consists of re-entry-phase intercept systems. During atmospheric re-entry, objects with low ballistic coefficients (lightweight decoys, chaff, etc.) will he slowed down so that the heavier re-entry vehicles can be identified by multiple-object tracking radars. Kill would then be effected by terminal defense interceptors. Inherent in such systems is vulnerability to saturation attack and engagement of the threat at minimum range. Terminal defense systems have traditionally been the province of the Army.
The problem of developing an active AICBM system has been a matter of prime concern to the Secretary of Defense and the service secretaries. The most advanced system, Sentinel, is aimed at the 1970 Chinese ICBM threat and is projected to become operational in the early 1970s.
In summary, defense against the ICBM/ SLBM threat consists of an alerting system (OTH), two warning systems (BMEWS and SLBMD&WS), and Sentinel.
space defense systems
The necessity for a capability to detect and track satellites was triggered by the launch of Sputnik I in 1957. It was essential to maintain a detailed catalog of orbiting objects in order to be able to detect new satellite launches as they occurred. This led to the establishment of the SPACETRACK system in 1958.
It was determined almost immediately that maintaining a meaningful satellite
catalog was a major effort resembling the complexity and operation of a SAGE
center. Observations from remote tracking radars are processed on a 24-hour
basis by centralized digital computers assigned to the
The air defense system catalogs air traffic through a tracking radar complex with overlapping, redundant coverage. These trackers, with a maximum range of several hundred miles, are supplemented with gap-filler sensors, which routinely acquire and follow maneuvering targets via hand-off procedures throughout their flights.
In contrast, the SPACETRACK system has only four sites capable of tracking satellites up to 2000 miles away. This means that a satellite is under direct observation for only a few minutes at most. Moreover, there is no hand-off capability, and penetration of the next SPACETRACK coverage may not occur for several hours.
The accuracy required to predict penetrations of SPACETRACK coverage gives rise to requirements for precision observations, complex mathematical models, extensive communication and computation facilities, and sophisticated equipment, operations, and technical evaluations. In particular, the narrow beams of our trackers give them only meager capability to acquire space targets. Thus, supplementary detection radars (available at only two sites) or computations based on known orbital elements (unavailable for new launches) are required, to align the trackers to the proper azimuth and elevation at the appropriate time for lock-on. Since several of the 1300 objects currently in orbit may penetrate simultaneously, a complicated system of tasking priorities must be maintained.
To supplement this meager system, consisting of a lash-up of old radars and HF-microwave-cable communications links, there are several cooperating and contributing tracking radars (belonging to missile test ranges) and the SPASUR (space surveillance) facility (a satellite detection fence belonging to the Navy). An additional capability has recently been realized from the BMEWS system, which now contributes one-third of our satellite observations. However, BMEWS siting and equipment were designed for ConUS-targeted missiles on north-south trajectories, and the BMEWS orbital data are limited in both precision and coverage at present.
The identification element in space defense also differs substantially from that in air or missile defense. Satellites are unique targets in that they reappear periodically and predictably. Thus, satellite identification is practically synonymous with prediction.
The first action by both BMEWS and SPACETRACK detection radars is to see if fan penetrations can be correlated with a known satellite. At the present time, the 1300 known objects in orbit make some 400-500 fan penetrations per hour. If a penetration is out of tolerance or if a new object appears, it is automatically handled as an unknown. If a new object cannot be correlated with a friendly launch, then it is considered potentially hostile.
Unlike missiles and aircraft, an unfriendly satellite that overflies the ConUS is not necessarily hostile. Therefore, identification of nationality is not sufficient. Like customs at a port of entry, the investigation must be extended to include inspection. Our capability to do this from the earth’s surface is rather limited and consists of radar signature analysis and orbit parameter studies.
future developments
Our capabilities with respect to the ICBM/SLBM threat are incomplete. In particular, current missile defense is limited to detection and identification only of a massive U.S.S.R. attack on the NORAD-defended area. Thus, as we enter the era of space defense, it is apparent that our national strategy of “deter or win” depends primarily on the ability of our strategic forces to survive and react.
It is very clear that the nation which first deploys a cost-effective space defense system will enjoy a military advantage. It is therefore mandatory that our planners and developers exploit technological advances in accordance with sound operational requirements. Based on our experience in aerospace defense, these requirements can be stated explicitly as follows:
(a) Detection systems. Our present capability to detect missile and space launches is limited to alerting information from the OTH system and actual penetration of BMEWS, SLBMD&WS, and SPACETRACK detection fans. Fractional orbit bombardment system, multiple orbit bombardment system (MOBS), and global-range ballistic missiles can approach the ConUS on trajectories that avoid most of this coverage.
What is urgently needed, I believe, is the capability to detect launches on a global basis. By observing launches as they leave the silos and pads, rather than during apogee of the ballistic phase as we do now, we can double the warning time available. This, of course, assumes the existence of automated, high-data-rate, redundant communications — preferably via satellites.
These characteristics can only be met by using a space-based sensor system. The technology for such a system appears to be attainable. If sufficiently sensitive, it could also observe FOBS/MOBS deboost maneuvers.
(b)Tracking systems. The number of satellites in orbit is expected to increase exponentially so that the orbit population in the 1970s will approach 3000. In order to avoid saturation, second-generation SPACETRACK sensors with multiple-object tracking are mandatory. Hand-off capability is vital for tracking spacecraft that possess significant maneuverability. Therefore, a global distribution of precision tracking sites is necessary. These characteristics are best met by ground-based, phased-array tracking and detection radars, currently in test at Eglin AFB.
(c) Identification/inspection systems. Currently there are over 50 Soviet payloads in orbit. As the number, size, and versatility of these payloads increase, it will become increasingly important to assess the capability and intent of those spacecraft which will make repeated crossings of the ConUS. When available and cost-effective, an inspection capability using sounding rockets or co-orbital satellites should be deployed.
It is encouraging to note that most of these operational requirements have been under study since 1960. But during this same period there has been much more progress by both the free and Communist worlds in production and deployment of strategic offensive missile and support satellite systems. The inevitable result has been to escalate the arena of general war from the theater limitations of yesteryear to the global dimensions of space.
Recognition of space as today’s front line of defense demands commensurate emphasis on studies of defenses for every space weapon we can foresee, designs to counter every space weapon we find the enemy testing, and deployment of defense weapons against the existing space threat just as rapidly as cost-effective systems become available. We must be prepared, since the price of technological and operational surprise in the space age can be disaster. We can, and must, expend the effort to deter or win.
Fourteenth Aerospace Force
Bibliography
Agan, Major General Arthur C. “Aerospace Defense,” Air University Quarterly Review, XII, 3-4(Winter-Spring 1960-61), 89-103.
Clark, Evert. “FOBS Game,” Astronautics and Aeronautics, VI, 1 (January 1968), 6-7.
Le May, General Curtis E. “The Present Pattern,” Air University Quarterly Review, XII, 3-4 (Winter-Spring 1960-61), 25-39.
McNamara, Robert S. “Threat/Counterthreat: The Strategic Forces,” Journal of the Armed Forces, CV, 24 (10 February 1968), 27.
___________.”Final Military Posture Statement,” Senate Armed Forces Committee, 1 February 1968.
Schriever, General Bernard A. “The Space
Challenge,”
White, General Thomas D. “The Aerospace and Military Operations,”
Major General Oris
Baker Johnson (B. S., Northwestern Louisiana State College) is Commander,
9th Aerospace Defense Division, Aerospace Defense Command, Ent AFB,
Disclaimer
The conclusions and opinions expressed in this
document are those of the author cultivated in the freedom of expression,
academic environment of
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