DSP 5, 6, 7 (Phase 2)

DSP 5 [USAF]

The next block of DSP satellites was known as "Phase II." There were three satellites in this series, Flights 5 through 7, launched between 1975 and 1977. This main upgrade from the "DSP Phase I" block of satellites provided increased on-orbit design lifetime from 1.25 to 2.0 years, increasing the weight of the Phase II from 907 kg to 1043 kg, and the solar panel output from 400 to 480 Watts. This block used the same basic spacecraft, but other packages were added. The same basic sensor was still used (2000 PbS detectors) providing BTH coverage. An experimental Above-the-Horizon (ATH) array sensor was flown on Flight 6. Phase II satellites can be distinguished from DSP Phase I satellites by the two electronic packages (located 180 degrees apart) on the rim of the satellite conical section. The prime launch vehicle was still the reliable Titan-3(23)C along with a Transtage.