Template:SLBM-FSS-7
Responding to contract proposals for an interim missile launch detection system, AVCO Corporation's plan to modify existing FPS-26 height finder radars at six prime SAGE System radar sites and to install a new one near Laredo AFB, Texas was approved in July 1965. Radars were to be located at the following sites:
| SAGE ID | Location | State | Equipment | 14th MWS | Notes |
|---|---|---|---|---|---|
| Moorestown AFS | NJ | Prototype FPS-49 | Det 1 | ||
| Z-37 | Point Arena AFS | CA | Not Modified | Replaced by Mill Valley AFS | |
| Z-38 | Mill Valley AFS | CA | Modified FPS-26 | Det 3 | Replaced Point Arena AFS |
| Z-65 | Charleston AFS | ME | Modified FPS-26 | Det 6 | |
| Z-76 | Mount Laguna AFS | CA | Modified FPS-26 | Det 4 | |
| Z-l00 | Mount Hebo AFS | OR | Modified FPS-26 | Det 2 | |
| Z-115 | Fort Fisher AFS | NC | Modified FPS-26 | Det 5 | |
| Z-129 | MacDill AFB | FL | Modified FPS-26 | Det 7 | |
| Z-230 | Laredo AFS | TX | New FSS-7 | Det 8 |
It was expected that the Avco 474N Submarine Launched Ballistic Missile (SLBM) Detection and Warning System would be operational by the end of 1967. The system included GSQ-89 data processing equipment and the modified radars were called FSS-7's. The radars provided seaward coverage of about 750 nm and with three basic modes of operation: search, acquisition, and track.
In operation, a warning and impact message was generated for transmission to the central processor at the Cheyenne Mountain 425L System Complex within 50 seconds from the initial detection of a missile. The Cheyenne Mountain Complex then relayed 474N data to SAC, the National Military Command Center (NMCC), and the Alternate NMCC over BMEWS circuits. At maximum detection range, this provided approximately 7 to 10 minutes of warning.