In 1983, DOD began work on developing a national defense against ballistic missiles. Originally, the effort was known as the Strategic Defense Initiative (SDI) and was directed primarily at strategic missiles launched by the Soviet Union. By the early 1990s, however, the Cold War was winding down, and certain third world countries were posing a new threat, exemplified by the Scud missiles launched by Iraq in the Persian Gulf War of 1991. In response to the change in circumstances, the missile defense effort was redirected toward a more limited protection of U.S. territory, troops and allies from the more limited threat posed by third-world ballistic missiles. The new overall concept was called Global Protection Against Limited Strikes (GPALS), and the Strategic Defense Initiative was renamed Ballistic Missile Defense (BMD).

Included under the umbrella of SDI, and later BMD, were programs for surveillance systems to detect and track enemy missiles and for directed and kinetic energy weapons to destroy those missiles. Funding and direction for these programs came from OSD's Strategic Defense Initiative Organization (SDIO), later renamed the Ballistic Missile Defense Organization (BMDO). Space Division was involved in the earliest studies and continued to execute the major programs assigned to the Air Force. In August 1987, the Defense Acquisition Board selected three of SSD's programs for demonstration and validation: the Boost Surveillance and Tracking System, which would track enemy missiles in the early phase of their ballistic trajectory; the Space Surveillance and Tracking System, which would track them in the mid-course phase of their ballistic trajectory; and the Space-Based Interceptor, an orbiting, rocket-propelled weapon system that would destroy enemy missiles by impact. These systems were expected to become part of the first phase of a Strategic Defense System. As the overall concept for that system evolved, the three programs were affected in different ways.

Partially successful hover test of a laboratory model of the Space-Based Interceptor (SBI), conducted at the Air Force Astronautics Laboratory, Edwards AFB, California, in November 1988. This pre-prototype interceptor was demonstrated successfully in three series of SBI hover tests at the Astronautics Laboratory. The first series tested the interceptor's guidance and propulsion systems. The second series demonstrated the ability of the interceptor's integrated seeker assembly to lock on to a thrusting rocket plume and then shift its aimpoint from the hot, bright plume to the relatively cold, dim body of the rocket. This was a critical and previously unsatisfied requirement for any anti-ballistic-missile weapon system using infrared seekers. The last hover, the only one in the third series, took place in April 1992. It tested a vehicle that was partially miniaturized and much closer in weight to an operational interceptor. The hover accomplished almost all of its objectives despite an anomaly late in the test. The SBI pre-prototype interceptor became the pre-prototype for SDIO's preferred space-based weapon system, Brilliant Pebbles, which was terminated in 1994 for lack of funding.

The Space-Based Interceptor (SBI) system was to consist of groups of interceptors housed in orbiting modules with housekeeping and battle functions. In 1990, the SDIO decided to pursue an alternate system based on a weapons concept called Brilliant Pebbles--many highly autonomous interceptors floating independently in orbit. Development of Brilliant Pebbles was transferred from the BMDO to SMC in FY 1993. By that time, however, the program was being cut back, and it was terminated in 1994 as interest shifted away from defense against strategic missiles and toward defense against theater ballistic missiles launched by third-world countries. In August 1994, OSD approved a concept for a Boost Phase Interceptor (BPI) that would respond to the new threat. It endorsed a BPI technology demonstration led by the Air Force, and SMC was to manage the program and acquire the BPI missile. Congress appropriated funding for the BPI for 1995, but future funding support from the Air Force and BMDO appeared uncertain.

The SDIO's decision to replace the SBI system with a system using many highly autonomous interceptors affected the Boost Surveillance and Tracking System (BSTS) as well as SBI. Independent targeting capabilities to be incorporated into each autonomous interceptor reduced SDIO's requirements for separate systems of sensors such as BSTS, and management of BSTS was therefore transferred to the Air Force. As an Air Force program, the system would improve upon and replace the existing DSP system. It would detect and track enemy missiles but would not have to provide extremely accurate targeting information that would allow kinetic or directed energy weapons to shoot the missiles down.

After being transferred to the Air Force, BSTS was renamed the Advanced Warning System (AWS) and then the Follow-on Early Warning System (FEWS). In November 1993, the FEWS program was canceled and replaced with a cheaper alternative called the Alert Locate and Report Missiles (ALARM) program. Before the ALARM program could really get started, however, it was replaced in its turn by the Space-Based Infrared System (SBIRS). SBIRS was to be an integrated missile warning system that would support several missions--missile warning, missile defense, battlespace characterization, and technical intelligence--and it was to consolidate various infrared systems into a single architecture and employ constellations of different satellites in different orbits--geosynchronous, elliptical, and low earth. OSD approved the plan for SBIRS in November 1994 and soon approved the program's entry into the early phase of development. SMC awarded contracts in August 1995. The program's rapid first steps occurred through one of the earliest and most thorough applications of the Air Force's initiatives in streamlined acquisition reform.

Unlike BSTS, the Space Surveillance and Tracking System (SSTS) remained an SDI program, but it went through several restructurings and changes in concept. The program's flight experiments were canceled, and its planned constellation of satellites became smaller and cheaper. In July 1990, the SDIO renamed the program Brilliant Eyes, and Brilliant Eyes became a far simpler system as interest shifted from protection against Soviet strategic missiles toward protection against shorter range, third-world missiles. In FY 1995, funding for Brilliant Eyes was reduced, and the program's development efforts were cut back. However, plans called for SBIRS satellites in low earth orbit to use Brilliant Eyes technologies to track missiles in the middle portion of their trajectories.