KH-9 Hexagon

KH-9 without MCS [NRO]

KH-9 with MCS [NRO]

KH-9 (Keyhole-9), also known as Hexagon or inofficially as "Big Bird", was a large reconnaissance satellite to replace the earlier KH-4B Corona satellites. In contrast to earlier models, it was not based on the Agena stage, but on a new maneuverable bus called SCS (Satellite Control Section). It featured four return capsules for a much increased lifetime. The McDonnell Douglas manufactured Mk.8 return capsules were of a similar type as in the earlier Corona satellites and were designed to deorbit a film capsule from space with mid-air recovery of the returning capsule by a specially equipped aircraft.

The camera system was built by Perkin-Elmer and consisted of two large panoramic cameras for area surveillance.

12 of the 20 satellites featured also a mapping Camera System (MCS) mounted on the forward end with an own smaller Mk.5 return capsule. It was present on missions KH-9 5 to KH-9 16.

The lifetime of the satellites increased from 40 days in the beginning to up to 275 days during the final missions.

Secondary Payloads

Some satellites carried secondary payloads mounted on the satellite:

• KH-9 12 carried the STP S75-1 payload
• KH-9 14 carried the STP S76-1 (NAVPAC 01) payload and the STP S77-2 (S3-4) payload
• KH-9 17 carried the STP S81-1 (SEEP) payload
• KH-9 19 carried the STP S85-1 (HVP-III) payload
• KH-9 20 carried the STP S86-1 (RADC 801), GPSPAC 3 and RDBS payloads