During the late 1970s and early 1980s, photographic intelligence satellite operations assumed a fairly standard pattern. Two KH-11's, each with an operational life of about three years, would be in orbit at all times. As an old satellite exhausted its maneuvering fuel, it would be commanded to reenter the atmosphere, and a new satellite would be launched a week or two later. A KH-9 film-return satellite would be launched in late Spring each year, and operate until around the end of the year. And a KH-8 film-return satellite would be early Spring, and operate for a few months.
The United States continued operations of a pair of KH-11 photographic intelligence satellites through most of 1988. The sixth KH-11, launched in December 1984 remained in service through late 1995, surpassing by almost a year the previously demonstrated service life for this class of satellites. Given this longevity, it must be assumed that this spacecraft has been assigned secondary responsibilities since the launch in October 1987 of the seventh KH-11.
KH-11 /6 (1984-122A 15423) was launched on 4 December 1984, and surprisingly enough continued in operation through October of 1995, flying in a 98 degree inclination orbit of 335 kilometers by 758 kilometers. Although the unusual longevity of this satellite (prior KH-11s had demonstrated a typical lifetime of about three years) would suggest that this spacecraft had long since expired, in late July it maneuvered to raise its perigee by about 50 kilometers, postponing its natural decay until well into 1992. This spacecraft was initially in the morning sun-synchronous plane entered by KH-11 /8, but subsequently has drifted about 7 or 8 degrees out of alignment.
KH-11 /7 (1987-090A 18441) was launched on 26 October 1987 and maintained an orbit of about 300 kilometers by 1000 kilometers, with an inclination of 98 degrees, which resulted in 14.76 orbits per day.
KH-11 /8 (1988-099A 19625) was launched on 6 November 1988, and maintained an orbit of about 300 kilometers by 1000 kilometers, with an inclination of 98 degrees, which results in 14.76 orbits per day. These satellites were in sun-synchronous orbits, which repeat their ground tracks at four day intervals, and are synchronized to provide two day overlaps in coverage. The 1987 spacecraft was in the late, afternoon plane, and the 1988 spacecraft was in the early morning plane (which it initially shared with the 1984 spacecraft).