Search for SSA Sensors
Sensor(s) Details Click on a sensor from the map above to view its details
Cape Cod PAVE PAWS
Two PAVE PAWS (FPS-115) ballistic missile early warning radars are located on Cape Cod, Massachusetts (41.75˚E, 70.54˚W, oriented east), and at Beale Air Force Base in California (39,14˚N, 121.35˚W, oriented west). A third radar, the BMEWS (Ballistic Missile Early Warning System) radar at Clear, Alaska (64.30˚N, 149.19˚W, oriented north) appears to be essentially identical to the two PAVE PAWS and so is discussed with them. All three radars are collateral sensors in the SSN. PAVE PAWS radars in Georgia and Texas were deactivated in the mid-1980s and parts from these radars were used in building the Alaska radar.
The California radar has received upgrades that allowed it to be incorporated into the U.S. ground-based national missile defense system. These upgrades apparently did not involve hardware changes and are unlikely to have affected its space surveillance capabilities. The upgrading of the Alaska and Cape Cod radars currently is not scheduled to begin until at least 2016.
Each radar has two faces, covering a total azimuth of 240˚ per radar, with boresight elevations of 20˚, covering elevations from 3˚ to 85˚. The PAVE PAWS transmit/receive modules, which operate in the 420-450 MHz band, produce peak powers of about 330-340 W each.
Each face has a diameter of about 22.1 m and contains 1792 active T/R modules and 885 passive elements. The nominal peak power per face is usually stated as being 600 kW, with a corresponding average power of 150 kW. According to a Missile Defense Agency environmental impact statement, the radar’s peak power per face is 582.4 kW, the average power is 145.6 kW, and the antenna effective transmit gain is 37.92 dB (= 6,194), and the beam width is about 2.2˚. The maximum duty cycle of a face is 25%.
Search pulse lengths are 0.3, 5 (typical) and 8 ms with a chirp bandwidth of 0.1 MHz. Track pulse length are between 0.25 and 16 ms. (0.25, 0.5, 1, 2, 4, 8, and 16 ms.) with a 1 MHz bandwidth.
The PAVE PAWS radars appear to contribute to the SSN primarily or exclusively through detections (with follow-up tracking) made with radar fences while carrying out their primary missile warning mission.
While a PAVE PAWS face can operate at a duty cycle up to 25%, typically each face operates at an 18% duty cycle, and operating one face at 25% requires reducing the other face’s duty cycle to 11%. In normal operation, a duty factor of 11% per face is dedicated to a 120˚ wide surveillance fence, at elevation angles between 3˚ and 10˚, and the remaining 7% duty factor is used for tracking. During periods of very high tracking requirements, the total duty cycle of one face can be increased by 7% to 25%. However, the duty cycle of the other face must be reduced correspondingly (that is, down to as low as 11% total).
PAVE PAWS Performance Claims
The PAVE PAWS radars are about ten times less sensitive than the FPS-85. The radars are 5-10 dB less sensitive than the FPS-85 (it is unclear if this statement applies to the PAVE PAWS or BMEWS radar, or both)
 Donald J. Hoft, “Solid State Transmit/Receive Module for the PAVE PAWS phased array Radar,’’ in Edward D. Ostroff, Michael Borkowski, Harry Thomas, and James Curtis, Solid State Radar Transmitters (Artech; Dedham, Mass., 1985) pp. 246-249 (reprinted from Microwave Journal, October 1978); Michael T. Borkowski, “Solid State Transmitters,” in Merrill Skolnik, ed., Radar Handbook, 2nd. Ed. (McGraw-Hill: New York, 1990), pp. 5-3, 5-8, 5-25, and 5-26.
 U.S. Missile Defense Agency (MDA), Environmental Impact Statement, National Missile Defense System, Appendix H, Upgraded Early Warning Radars Analysis, July 1, 2000, p. H-1-7. Available at: (http://www.mda.mil/global/documents/pdf/env_gmd_eis_append_h.pdf)
 MDA, “Environmental Impact Statement,” p. H-1-8.
 Marvin N. Cohen, “Pulse Compression in Radar Systems,” in Jerry L. Eaves and Edward K. Reedy, eds. Principles of Modern Radar (Van Nostrand Reinhold: New York, 1987), p. 475.; F. Shackford, Technical Seminar, MIT Defense and Arms Control Studies Program.
 MDA, “Environmental Impact Statement,” pp. H-1-8, H-1-9.
 R. Sridharan and Antonio F. Pensa, “U.S. Space Surveillance Network Capabilities,” in C. Bruce Johnson, Timothy D. Maclay and Firooz A. Allahdadi, Image Intensifiers and Applications; and Characteristics and Consequences of Space Debris and Near Earth Objects, Proceedings of SPIE, Vol. 3434, July 1988, pp. 88-100.
 USAF Scientific Advisory Board, p. 9.
 “Pave Paws, BMEWS Radar Site Updates Will Broaden Missile Threat Coverage,” Aviation Week and Space Technology, December 9, 1985, pp. 52, 54.
 Ross Kerber, “Making (Radar) Waves, Boston Globe, July 2, 2001, p. C1.
 Cohen, “Pulse Compression in Radar Systems,”; F. Shackford, Technical Seminar.
This post originally was made by George Lewis and is used with permission.