In Focus: Approach Set on Space Radars

Feb. 1, 1984

Washington, D.C., December 28—Even though the Soviets have had a space-based military radar system, known as Rorsat, in operation for years, the US is still decades away from fielding an operational satellite constellation that can detect and track strategic and tactical targets on the oceans, in the air, and on land. But the Pentagon took an important, albeit tentative, step late in 1983 when Deputy Secretary of Defense Paul Thayer settled a long-festering dispute within the national security community over technological approaches to such a system.

OSD’s decision went in favor of a long-term technology program recommended by the blue-suit Air Force and some elements of the Navy, thereby terminating a short-term concept based on well-established technologies that had the support of some senior civilian Pentagon leaders and elements of the intelligence community. The latter approach centered on designs by MIT’s Lincoln Laboratory employing tried and true methods of building radars.

While this approach appears highly reliable and relatively risk-free — and is in use in a nonmilitary space system — it was judged to require excessive amounts of power, impose considerable weight penalties, and provide only limited performance. Also, this short-term concept would limit the radar satellites to low-orbit (below 1,000 km) operations, meaning both a relatively short lifespan because of “decaying orbits” and the need for very large numbers of satellites to provide global coverage.

The Lincoln Laboratory design was also thought to be confined mainly to the detection and tracking of surface ships, similar to the capabilities of the Soviet Rorsat system. While this system could have been expanded by moving toward much larger antennas and greater power levels than originally proposed, this was not deemed cost-effective, especially since the capability to deal with aircraft and cruise missiles would have been inadequate. Lastly, the Lincoln Laboratory concept was thought to be quite vulnerable to jamming.

By dropping the short-term solution, the Defense Department probably assured that advanced technologies relevant to future space-based radar systems will be pursed in a building-block fashion. The prospects are that these individual efforts will eventually coalesce into a high-performance, versatile system, but probably not before year 2000. Three fundamental elements of the long-term solution — as envisioned by the Defense Advanced Research Projects Agency (DARPA) and R&D elements of the three services — will continue to receive intensive attention.

The pivotal technology underlying the advanced space-based radar concept is known as the TR (for transmit and receive) module and opens the door to an advanced synthetic aperture phased-array radar. The idea behind this approach s to generate the radar signal right at the face of the antenna, divide it up between many thousands of small elements, and distribute it across the array. Between 50,000 to 90,000 of these tiny radar units would be arrayed over an area some thirty meters in diameter.

While solid-state TR modules are already in existence — both Raytheon and GE have produced working examples — they are prohibitively expensive. The first order of business, therefore, is to bring these devices down in price to affordable levels. This will require mass-production techniques patterned after the way the electronics industry turns out microchips. All services and DARPA are working toward this goal.

Development of an advanced onboard signal processor (AOSP) is another key element of crucial importance to a space-based radar system. The concern here is to come up with a very reliable and survivable on-board computer using gallium arsenide circuitry that can resist the electromagnetic pulse and other radiation effects produced by nuclear detonations. DARPA and other elements of the Defense Department have worked on the AOSP project for about five years and have made considerable progress.

The third technology challenge associated with an advanced space-based radar is a lightweight, highly efficient, on-board power and power distribution system. Relevant work here is being carried out by the air force Avionics Laboratory, with DARPA defraying the bulk of the cost.

If these technology programs can be brought to fruition and melded into a workable system, the consequences to both strategic and tactical warfare may well turn out to be revolutionary. As presently envisioned, such a system would operate at an altitude of about 5,000 kilometers and would be capable of detecting, tracking, and, when linked with a proper command and control system, targeting in near-real time a variety of bogeys extending from cruise missiles to aircraft and ships at sea. The individual satellites could be made to fit into the existing Space Shuttle by folding the arrays in the manner you would fold an umbrella.

For the moment, there is no definite assurance that such a system would be impervious to hostile jamming. On the other hand, experts associated with the program believe they have definitive notions for solving he problem. Confidence is already high that a phased-array radar can be made to resist side-lobe — as opposed to the main-beam — jamming simply by suppressing the side lobes. If this is so, the main problem is solved, because main-beam jamming is quite difficult to do.

Beyond that, in the case of solid-state, electronically agile radar designs, the beam moves across the face of the array rather than being fixed in the Center of the system, as is the case with conventional designs. As a result, the jammer would actually have to track the beam, which is quite difficult to do, especially since it is easier to move the radar beam than it is to track and jam it. Additionally, it may be possible to cope with main-beam jamming by “nulling” the antenna, meaning the selective use of narrow-band filters to reject — either in frequency or direction — specific jamming signals.

Assuming that a full-fledged constellation of US radar satellites will be deployed around the turn of the century, a central question from the military operator’s point of view is whether or not the system will be able to detect and track low-observable, “stealthy” targets, which by then will probably be commonplace. As in the case of jam-resistance, there is as yet no clear-cut answer. The difficulty in making predictions on this score stems in part from the circular nature of the assumptions about what advanced radars an “see,” the degree to which aircraft, remotely piloted vehicles, cruise missiles, and other air-breathing platforms can become “invisible,” and the point at which their radar returns become indistinguishable from natural background clutter.

It is theoretically possible that ever-more-powerful radars proliferated to an extreme degree could detect targets with extremely small radar cross-sections. In practice, a host of economic and operational considerations militates against such an assumption. It is, nevertheless, tempting to suggest that, as the cost-effectiveness of new radar designs increases so will their ability to cope with many low-observable targets.

The ultimate fate of space-based radar systems may be influenced by the out come of this tug-of-war as well as by the role that will be assigned to them as part of the new strategic Defense Initiatives, referred to as “Star Wars” by the media.

Why NATO’s Conventional Forces Need Shoring Up

Gen. Bernard W. Rogers, the Supreme Allied Commander, Europe, and Commander in Chief of US European Command, recently counseled against decoupling NATO’s nuclear deterrence policies from its conventional warfare strategies on grounds that there is no enforceable “firebreak” between them. Talking to a group of defense analysts in Washington, D.C., General Rogers espoused continuation of the Alliance’s Flexible Response strategy, he opposed a “no first use” nuclear policy, and he strongly favored strengthening NATO’s conventional forces.

Treating nuclear and conventional deterrence as an integer, General Rodgers warned, however, that ACE’s (Allied Command Europe) deficiencies in conventional capability” strain the credibility of our deterrence because a potential aggressor knows that NATO’s escalation to nuclear weapons would invite at least as much devastation on us as we could inflict on him.” It follows, therefore, that a potential attacker might “doubt our resolve to make a drastic move to nuclear weapons rather than accept the outcome of a conventional battle.”

At the root of the problem, he said, is the fact that the gap between the military capabilities of the Warsaw Pact and NATO is widening, even through the Alliance’s conventional forces are getting stronger. As a result, “instead of possessing genuine flexibility for executing our strategy of Flexible Response, ACE’s current military posture will require us — if attacked conventionally — to escalate fairly quickly to the first use of nuclear weapons in order to halt the attack. This is [caused by] a lack of adequate sustainability: manpower, ammunition, and war reserve material to replace losses and expenditures on the battlefield.”

Backing up the last-resort character of nuclear forces must be the perception on the part of the Soviet Union that NATO has a “reasonable” chance of “frustrating conventional attack by conventional means.” Beyond this level of deterrence, “NATO’s nuclear weapons, coupled with the uncertainty of our first-use option, must continue as a critical source of deterrence for convincing a potential aggressor that the risks of any aggression outweigh any possible gains,” General Rogers contended.

While there are “no obvious indications that the Soviet Union intends to attack Western Europe, provided our deterrent posture remains credible,” it is imperative to thwart the “paramount Soviet goal” of dictating the fate of Western Europe “without having to fire a shot,” he pointed out. Political and economic intimidation is the menace likely to face Europe if the Soviets are not kept from achieving broadly superior military forces, according to General Rogers.

Rejecting the notion that Soviet intimidation of Western Europe is not in the cards, ACE’s commander pointed at a specific road map Moscow was following to create that option:

n First, to convince Western nations that they should forgo military improvements that might offend the Soviet Union.

n Second, to encourage the adoption of Western foreign policies that at least condone, if not support, Soviet actions and ambitions.

n Third, to promote Western governmental policies and popular attitudes supportive of Soviet aims, such as the securing of favorable financial and trade arrangements.

n And, finally, and encompassing all others, to split Western Europe from the United States politically and militarily.

Attainment of this set of objectives by the Soviets, General Rogers argued, “would severely erode the ability of Western European nations to deter overt aggression and would disintegrate our Alliance.” The symbiosis of nuclear and conventional capabilities affects deterrence of war as well as of intimidation, but takes on a different coloration in the case of the latter. The reason is that “conventional forces deter by conveying the prospect that an aggressor will be prevented physically from occupying defended territory. Obviously, this basis for deterrence is more reassuring than the first use of nuclear weapons, which would invite major retaliation on our territory. Even between nuclear powers, it is primarily the imbalance of conventional forces that can be exploited for intimidation and coercion because the threatened use of such forces is more credible than threatened use of nuclear weapons.”

General Rogers refuted claims that raising the nuclear threshold would signal a diminution in NATO’s will to escalate to nuclear weapons and, thereby, make conventional war more likely. “Improving our conventional forces by no means implies an inherent reduction in NATO’s resolve to resort to nuclear weapons, if necessary. Indeed, the resolve required to sacrifice [economically] in order to improve conventional forces testifies to the strength of our resolve to do whatever is necessary to protect ourselves.”

Lastly, he stressed that adequate deterrence requires that, at a minimum, “we have high confidence that our conventional forces are strong enough to protect our military means of escalation and to provide the time [needed to implement] our strategy of Flexible Response.”

Modernization of NATO’s conventional forces needs to be governed by a number of cardinal considerations, the most obvious of which is the principle of Forward Defense, according to General Rogers: “Adherence to Forward Defense is supported by military rationale as well as political needs….We should also keep in mind the complementary relationship between the requirement for holding the first echelon of attacking forces and….attacking the follow-on forces. Both missions are essential for ensuring Forward Defense.”

Washington Observations

« The White House and the Defense Department settled a turf fight within the Pentagon over who would run the new Strategic Defense Initiatives (previously known as the “Star Wars” or Defense Against Ballistic Missiles) organization and the amount of funds allocated to it in the FY ’85 Defense budget. The SDI office will report directly to the Deputy Secretary of Defense and will have direct oversight over five functional program elements involving the individual services and agencies of the Defense Department. These program elements comprise surveillance, systems survivability, directed-energy weapons, conventional ballistic missile defenses, and battle management. Specific details about the SDI organization are to be worked out within a thirty-day period. SDI funding was set at $2.3 billion, or $560 million more than assigned to these functions in FY ’84.

« The President’s pending decision concerning the nation’s long-term space goals is likely to allow for the ultimate creation of a lunar base that could serve both national-security as well as nonmilitary scientific and other purposes. If there is a commitment to a manned space station, it will probably serve as a stepping-stone to a lunar base. Such a step would not constitute a US attempt to claim sovereignty over that site or the moon as a whole.

« Technical difficulties have caused a number of delays in testing the F-15-launched US ASAT in its first space-flight. At this writing, a test launch is reportedly imminent, but is limited to an attempt to aim the anti-satellite weapon against an imaginary point in space. Congressionally imposed strictures and the Administration’s concern about the political sensitivity of a full-up test against an actual satellite account for the compromise of a “point in space” intercept attempt.

Meanwhile, DARPA Director Dr. Robert Cooper told Congress that the US needs to carry out full operational tests of ASAT and place enough ASATs into operation to deny the Soviets the option of targeting grounds and sea-based targets with space-based sensors on a real-time basis. The Soviets, he said, are moving toward such a capability. He cited in this context a number of Soviet satellite systems, including Rorsat, Eorsat, and the USSR’s counterpart to this country’s Navstar Global Positioning System, Glonas.

Dr. Cooper stressed that the confluence of two technologies — the ability to perform real-time targeting by means of surveillance satellites and the advent of sophisticated “smart” weapons in the manner of the Assault Breaker concept — presage broad and revolutionary capabilities on the part of both the US and the soviet Union for real-time targeting by space-based sensors. The size of some receivers of data from the GPS network has shrunk to that of a pack of cigarettes, according to the DARPA Director. Space-based laser designators, he told Congress, could be used to “paint” targets on the surface of the oceans, on land, or even in the air and space, and to guide weapons against them. The effectiveness of such an approach could be compounded by the use of “stealthy” delivery systems coupled with medium-and long-range delivery systems.

Dr. Cooper told Congress that stealth, meaning low-observable characteristics encompassing radar, infrared, visual, sound, and others, represents the most revolutionary military aeronautics technology since the jet engine and the swept sing. The payoff of stealthy platforms, linked to real-time targeting from space and effective standoff weapons, is the ability to shoot at an opponent “from the dark.” In the view of some defense scientists, the survivability of stealthy air vehicles may eventually be threatened by ground-based air defenses employing laser and other directed-energy technologies. Defensive weapons of this type operate with the speed of light. Since even the stealthiest penetrators become “visible” to the eye as they approach in daylight, they might become vulnerable to rapidly reacting laser or particle-beam weapons.

« Complementary research by elements of the Defense Department and NASA has bolstered the long-term prospects for supersonic, and eventually hypersonic, vehicles and boost-glide weapons. NASA Administrator James M. Beggs recently told Congress that “long-range cruise missiles utilizing supersonic-combustion ramjets (scramjets) and high-density hydrocarbon fuels may be the first generation of operational hypersonic vehicles, followed later by very-high-altitude Mach 5-7 cruise airplanes used for strategic reconnaissance. There is also renewed interest in a hypersonic maneuvering airplane capable of sustained operation both in the atmosphere and in low orbit. It would utilize a combination of scramjet and rocket propulsion to match the trans-atmospheric envelope and would probably have horizontal takeoff as well as landing capability.”

In the same vein, DARPA reported that high-life-to-drag-ratio hypersonic vehicles could be operational in the late 1990s. Over a shorter term, the payoffs from supersonic cruise and maneuver, when combined with advanced beyond-visual-range missiles and stealth technologies, could provide the next US fighter design with “favorable combat exchanges of ten to one or more, far in excess of F-15 and F-16 capability,” according to Defense Department analyses.

« Teal Ruby, a potentially revolutionary space-based infrared sensor that detects air-breathing vehicles against the “clutter” of the earth’s surface, is to be launched, presumably by the Shuttle, from Vandenberg AFB, Calif., either late in 1985 or early in 1986, according to DARPA. Teal Ruby is thought to be a highly promising tool for detecting stealthy aircraft.

« Defense Department officials registered surprise over delay sin the first launch of the Soviet Union’s new heavy-lift launch vehicle that has been sitting on its launch pad at the Tyuratam complex for several months. The vehicle is thought to be capable of launching payloads in a range of between 300,000 and 400,000 pounds into low earth orbits. DARPA Director Cooper told Congress last yea about the theoretical threat that such a system might be used in violation of the Outer Space Treaty to place heavy nuclear weapons into space and de-orbit tem on command.