KH-9 Hexagon

KH-9 (BYEMAN codename HEXAGON), commonly known as Big Bird, was a series of photographic reconnaissance satellites launched by the United States between 1971 and 1986. Of twenty launch attempts by the National Reconnaissance Office, all but one were successful. Photographic film aboard Big Bird was sent back to Earth in recoverable film return capsules for processing and interpretation. The best ground resolution achieved by the main cameras was better than 0.6 meters.

They are also officially known as the Broad Coverage Photo Reconnaissance satellites (Code 467), built by Lockheed Corporation for the National Reconnaissance Office.

The KH-9 was declassified in September 2011 and an example was put on public display on September 17, 2011.

On January 26, 2012 the National Museum of the United States Air Force put a KH-9 on public display along with its predecessors the KH-7 and KH-8.

Development
The KH-9 was originally conceived in the early 1960s as a replacement for the Corona search satellites. The goal was to search large areas of the earth with a medium resolution camera. The KH-9 carried two main cameras, although a mapping camera was also carried on several missions. The photographic film from the cameras was sent to recoverable re-entry vehicles and returned to earth, where the capsules were caught in mid-air by an aircraft. Four re-entry vehicles were carried on most missions, with a fifth added for missions that included a mapping camera.

Between September 1966 and July 1967, the contractors for the Hexagon subsystems were selected. LMSC was awarded the contract for the Satellite Basic Assembly (SBA), Perkin Elmer for the primary Sensor Subsystem (SS), McDonnell for the Reentry Vehicle (RV), RCA Astro-Electronics Division for the Film Take Up system, and Itek for the Stellar Index camera (SI). Integration and ground-testing of Satellite Vehicle 1 (SV-1) was completed in May 1971, and it was subsequently shipped to Vandenberg Air Force Base in a 70 ft container. Ultimately, four generations ("blocks") of KH-9 Hexagon reconnaissance satellites were developed. KH9-7 (1207) was the first to fly a Block-II panoramic camera and SBA. Block-III (vehicles 13 to 18) included upgrades to electrical distribution and batteries. Two added tanks with ullage control for the Orbit Adjust System (OAS) and new thrusters for the Reaction Control System (RCS) served to increase KH-9's operational lifetime. In addition the nitrogen supply for the film transport system and the camera vessel was increased. Block-IV was equipped with an extended command system using plated wire memory. In the mid 1970s, over 1000 people in the Danbury, Connecticut area worked on the secret project.

A reentry vehicle from the first Hexagon satellite sank to 16,000 feet below the Pacific Ocean after its parachute failed. The USS Trieste II (DSV-1) retrieved its payload in April 1972 after a lengthy search but the film disintegrated due to the nine months underwater, leaving no usable photographs.

Over the duration of the program the lifetime of the individual satellites increased steadily. The final KH-9 operated for up to 275 days. Different versions of the satellite varied in mass; most weighed 11,400 kg or 13,300 kg.

Main camera


The main camera system was designed to take stereo images, with a forward looking camera on the port side, and an aft looking camera on the starboard side. The camera optical layout is a f/3.0 folded Wright Camera, with a focal length of 60 in. The system aperture is defined by a 20 in diameter aspheric corrector plate, which corrects the spherical aberration of the Wright design. In each of the cameras the ground image passes through the corrector plate to a 45 degree angle flat mirror, which reflects the light to a 0.91 m diameter concave main mirror. The main mirror directs the light through an opening in the flat mirror and through a four-element lens system onto the film platen. The cameras could scan contiguous areas up to 120 degree wide, and achieved a ground resolution better than 2 ft during the later phase of the project.

Mapping imagery
Missions 1205 through 1216 carried a "mapping camera" (also known as a "frame camera") that used 9 inch film and had a moderately low resolution of initially 30 ft, which improved to 20 ft on later missions (somewhat better than LANDSAT). Intended for mapmaking, photos this camera took cover essentially the entire Earth with at least some images between 1973 and 1980. Almost all the imagery from this camera, amounting to 29,000 images, each covering 3400 square km, was declassified in 2002 as a result of Executive order 12951, the same order which declassified CORONA, and copies of the films were transferred to the U.S. Geological Survey's Earth Resources Observation Systems office. Images from the mapping camera covering the state of Israel and all imagery from the KH-9's other cameras remain classified.

The KH-9 was never a backup project for the KH-10 Manned Orbital Laboratory. It was developed solely as a replacement for the Corona search system.

High-altitude atmospheric density
Missions 1205 to 1207 carried Doppler beacons to help map the atmospheric density at high altitudes in an effort to understand the effect on ephemeris predictions. The measurements of the atmospheric density were released through NASA.

ELINT subsatellites
Missions 1203, 1207, 1208, 1209, and 1212 to 1219 included Ferret ELINT subsatellites, which were launched into a higher orbit to catalogue Soviet air defence radars, eavesdrop on voice communications, and tape missile and satellite telemetry. Missions 1210 to 1212 also included scientific subsatellites.

KH-9 missions
(NSSDC ID Numbers: See COSPAR)

Cost
The total cost of the 20  flight KH-9 program from FY1966 to FY1986 was US$3.262 billion in respective year dollars.

Specifications
Data source: The Encyclopedia of US Spacecraft and NSSDC
 * Launch vehicle: Titan IIID/34D
 * Total weight: 11400 kg, with mapping camera 13300 kg
 * Reentry weight: 5330 kg
 * Max. diameter (main body): 3.05 m
 * Length (with mapping camera): 16.21 m
 * Orbit: elliptical, 100 miles by 150 miles
 * Scanners: television, radio, and high resolution camera

Gallery
 File:HEXAGON 11.png|The RCS system of a KH-9, showing the propellant tanks. File:HEXAGON 12.png|A KH-9 in scaffolding, being prepared for launch. File:HEXAGON Film being despooled.png|A technician despools one of the re-entry modules which contained the film used by the cameras. File:HEXAGON Factory to Launch sequence.png|A diagram showing the assembly, testing and launch preparations of a KH-9. File:HEXAGON Forward section with mapping camera.png|The forward section of a KH-9. File:HEXAGON Re-entry vehicle.png|A KH-9 re-entry module hanging from its parachute, ready to be retrieved. File:HEXAGON Reaction Control Module.png|Another view of the KH-9's RCS system. File:HEXAGON satellite vehicle transporter.png|A KH-9 being transported by truck in a special canister. File:HEXAGON Shroud and Base in Acoustic Chamber.png|The shroud and base of a KH-9 undergo vibration tests in an acoustic chamber. File:KH-9 HEXAGON satellite 2.jpg|This painting of a KH-9 shows the two different camera types that the satellite carried. File:KH-9 HEXAGON satellite.jpg|Basic specifications and diagram of the KH-9. File:KH9 Hexagon integration.png|A KH-9 being raised vertically during its assembly. File:KH9 HEXAGON profile.png|This diagram shows the various sections of the KH-9 and their dimensions. 