The belief is that the engineers and scientists of Nazi Germany were the first to consider the possibility of placing a (piloted) satellite in orbit for military reconnaissance purposes.
In 1946, the Rand Project report, which had studied the feasibility of satellites for the United States Army, suggested that satellites could be used effectively as observation platforms and several studies resulted from this report under a variety of guises.
These days, both the United States and the Union of Socialist Soviet Republics make extensive use of satellite based surveillance systems which provide an around the clock look at each others territory. Such surveillance is tolerated by both superpowers, if not willingly, by the fact that there is relatively little that can be done about it.
Obviously, details on the spacecraft used and the instrumentation on board of those spacecraft are quite scarce and patchy.
Identification Or Reconnaissance Satellites
Initially, the United States did identify its military satellites by name. However, starting in early 1962, the U.S. military authorities ceased to assign names to military satellites as a general practice. While it is relatively easy to identify a number of programs, in particular the communications, meteorological and navigational satellite programs, military photo reconnaissance satellites have proven difficult to accurately identify.
Although the satellites continued to be identified by an Ops number, it was clearly evident these number were either associated with an unknown identifier, perhaps a construction number, or they were used in purely random order. Other identification means have been Code numbers, assigned in random order, and code names.
Over time it has been possible to identify a number of programs through the disclosure of the launch vehicle as well as other information that became available through the literature. Also, some details of the earliest programs, such as Corona, have been unclassified recently.
Nevertheless, the classified nature of military surveillance satellites, and the occassionally conflicting information in the literature, makes the accurate compilation of tables of launch dates of each series difficult. The tables presented in this article may, therefore, differ from tables published elsewhere.
The development of a strategic satellite system for the United States began in early 1955 when the Air Force issued the specifications for Weapons System 117L which called for a rocket upper stage which was to be used as a bus for a number of applications packages.
The stage was to be carried into orbit on either a Thor or an Atlas missile and three roles were envisaged:
– Development of recovery techniques
– An operational early warning system
– An operational reconnaissance satellite system
In October of 1956, the WS-117L contract was awarded to Lockheed and gave birth to the Agena upper stage as the basis for the satellite systems. The Agena stage had a diameter of 1.52m and a length of 5.94m and was fitted with a Bell Hustler rocket motor. It had an in-orbit mass of 700kg and carried the payload in a conical forward section which included a 135kg re-entry capsule with a diameter of 84cm and a length of 68cm.
Once in orbit, the Agena stage would turn around and face backwards from the line of flight so that the re-entry capsule would be aligned for release and atmospheric re-entry.
The obvious choice for instrumentation was a television system, but in those days the resolution achieved by a television system was considered too poor. Kodak, Philco and the CBS Laboratories developed a film scanning technique as an alternative. With this technique, a photographic plate was exposed, developed on board, and scanned by an electronic instrument. The subsequent radio signal was transmitted to Earth. In addition, the film return option also considered which would provide a higher resolution image. The latter option required a reentry capsule.
The intention was to develop two separate families of reconnaissance satellites. One family was to fly in high altitude orbits for area survey, viewing large areas of the Earths surface, while another family was to fly in lower orbits to concentrate on close look reconnaissance, selectingspecific objects for detailed investigation.
area survey equipment were conducted but proved to be unsatisfactory due to the low resolution offered by imaging equipment. Not until the development of new and advanced equipment could effective area survey be introduced from the KH 9 series onwards.
The Corona program involved a range of different camera systems. The KH 1 and KH 2 cameras were developed by the Fairchild Camera and Instrument Corp. While the KH 3, KH 4, KH 4A and 4B cameras were developed by the Itek Corp. Of these, the KH 4A and KH 4B systems were essentially two KH 4 cameras stacked on top of one another.
The KH 1 camera had a resolution of 11.7m. This was improved to 7.3 on the KH 2, 3.5m on the KH 3, and 2.9m on the KH 4 cameras. The KH 4A and 4B cameras permitted the stereo images with a resolution of respectively 2.6m and 1.1m, respectively.
Although Keyhole is often cited as the meaning of the acronym KH, it is suspected that the meaning of this military designation is different. (This suspicion is supported by the use by the U.S. Air Force of the letter K to designate aircraft cameras (such as KA-59 for a 1965 camera designed for medium altitude reconnaissance missions). The meaning of the letter H may be found in the apparent designations RH and VH and the associated designations VS and VU. The latter two are for non-satellite detection systems for surface and sub-surface nuclear explosions. Since the letters S and U have been used in other designation system to indicate surface and sub-surface, H may mean satellite borne.)
The first 38 satellites in the Corona program were identified as Discoverer. Subsequent satellites did not receive a name but have been referred to, as is common practice, by their KH system number followed by a serial number.
The satellites in the Corona series were launched by a Thor Agena launch vehicle and were placed in a polar orbit which allowed the recovery of the re-entry capsule over the Pacific Ocean (east of Hawaii) on the 17th or 18th orbit, after one day, or on the 32nd or 33rd orbit, on the second day, and so on. After ejection from the satellite, a small retro-rocket motor reduced the speed of the re-entry capsule to about 1400km/h. At an altitude of about 15km, the heatshield was jettisoned and the parachute deployed. The parachute and capsule were then captured mid-air by a trapeze-shaped device attached to, initially a Fairchild Packet aircraft and, later on, a Lockheed Hercules aircraft. Once winched inside the aircraft, the capsule was flown to the Hickam Air Force Base in Hawaii, with a different aircraft then flying the film to Washington where it was developed and interpreted.
The execution of the program proved to be far from easy. After an initial launch failure, the U.S. Air Force succeeded in placing Discoverer-1 in orbit. This satellite did not contain a re-entry capsule and was intended to test the tracking and acquisition facilities required in the recovery process. Unfortunately, tumbling of the spacecraft prevented accurate tracking. Discoverer-2 did contain a re-entry capsule which was, however, ejected too early in the flight to be effectively recovered. Instead of coming down over the Pacific Ocean near Hawaii, the capsule fell in the arctic regions of Norway and, although observed coming down, was never located.
Discoverer-3 and -4 were launch failures and did not achieve orbit. Discoverer-4 was fitted with a KH 1 camera system and was also known as mission 9001. The objective was to test the capsule recovery technique but insufficient second stage velocity prevented the satellite from reaching orbit.
Discoverer-5, on the other hand, did attain orbit, but was aligned in such a manner that the re-entry capsule was fired into the opposite direction and was lost.
The capsule of Discoverer-6 did eject but could not be tracked due to a failed radio beacon. This capsule eventually fell into the sea.
Discoverer-7 could not be stabilized in orbit and the capsule was not separated. Due to a malfunction of the Thor launch vehicle, Discoverer-8 was placed in an incorrect orbit and the capsule overshot the recovery area.
Discoverer-9 and -10 failed to orbit, the latter being destroyed on the launch pad by the range safety officer.
Discoverer-11, after having been successfully placed in the correct orbit, did eject the capsule and was lost when it fell into the ocean.
Some measure of success was finally achieved with Discoverer-13. Because of all the previous failures, this satellite had been fitted with special instruments to monitor the performance of the satellite and to obtain data that would be useful in future flights. The satellite also carried SCOTOP, an instrument to determine if the satellite was being tracked by the USSR. The capsule was ejected on the 17th orbit and came down successfully, 500km north west of Honolulu, although the recovery aircraft failed to pick it up. Instead it drifted in the ocean for three hours before it was recovered by a helicopter which was on stand-by. It has been suggested that Discoverer-14 was the first operational reconnaissance satellite which carried a modified version of the HYAC camera system, previously used in the WS416L balloon reconnaissance program. The target of the satellite was the Plesetsk cosmodrome, the existence of which had not been confirmed at that time.
On the 17th orbit on August 19, 1960, the capsule was successfully recovered by an aircraft during parachute descent.
On the Discoverer-15 flight, the capsule ejected successfully but could not be recovered.
The flight of Discoverer-16 saw the introduction of the Agena B upper stage, which had an improved performance, as well as the KH 2 camera system. While this flight failed to orbit, subsequent flights met with some success. The re-entry capsule was successfully recovered on the Discoverer-17 and -18. While Discoverer-19 did not carry a re-entry capsule, it did test infra-red equipment for the Midas program.
Discoverer-20 was the first to carry the KH 5 camera system. The KH 5 camera system was used in the Argon program and was a geodetic mapping camera with a resolution of 134.7m used by the U.S. Army to obtain data for pin pointing strategic targets. In addition to the normal payload, the satellite carried samples of silicon test material to determine the effect of space radiation on solar cells, external flashing lights for optical tracking as well as a precision tracking beacon experiment for further evaluation of the Transit Doppler shift navigation system. Due to a system malfunction the capsule was not released.
Discoverer-21 did not carry a camera system and capsule for recovery as the primary objective was to test changing the satellites orbit by restarting the Agena engine. This was successfully achieved. In addition the satellite carried infrared imaging sensors for the Midas program as well as other reconnaissance equipment.
Discoverer-22 and -24 failed to orbit the re-entry capsule ejected by Discoverer-23 was not recovered.
In addition to being fitted with a KH 2 camera system, Discoverer-25 also carried:
Three GeigerMueller tubes to monitor cosmic rays
Ion density gauges
Micrometeorite density gauges
Instruments to count and measure micrometeorite impact
Samples of gold, bismuth, iron, titanium, cadmium, magnesium, nickel and yttrium
After the 33rd orbit, on June 18, 1961, the capsule was successfully recovered.
Discoverer-26, another satellite fitted with a KH 2 camera system, also carried instruments to measure the density and effects of ions and micrometeorites and included an impact detector and a tuned piezoelectric crystal erosion gauge.
The capsule, which was recovered on July 7, 1961 after 32 orbits, contained samples of silicon, iron, bismuth, yttrium, magnesium, nickel, lead and uranium which were studied for the impact of space radiation on these materials. It also contained infrared sensors and photographic equipment for use on board of future Midas and Samos type spacecraft.
The Discoverer-27 and -28 flights failed to orbit.
The KH 3 camera system was first used on Discoverer-29. The satellite also tested an electron spectrometer, a galactic RF detector and an Xray counter for the Vela Hotel program. In addition, emulsions, biological samples (including two types of viruses and embryonic chicken hearts) were carried in the capsule, which was recovered after 33 orbits. The re-entry capsule was successfully recovered on the Discoverer-30, while Discoverer-31 carried a re-entry capsule which was not ejected.
Discoverer-32 carried, in addition to the KH 3 camera system samples of yttrium, gold, iron, magnesium, titanium and nickel to test their shielding properties; an electron and ion density gauge; a NoraAlloe beacon transmitter; a Secor experiment; an erosion gauge; and seed corn to evaluate the genetic effects of radiation. The capsule was recovered after 18 orbits on October 14, 1961.
Discoverer-33 was another failure, followed by Discoverer-34, which carried a re-entry capsule which was not ejected, and Discoverer-35 and -36, for which the re-entry capsules were successfully recovered. The Discoverer-36 launch also carried the Oscar-1 amateur radio satellite as a secondary payload. A few other launches in the series also carried secondary payloads, usually referred to as Hitchhikers. Discoverer-37 was a launch failure.
The early Satellite and Missile Observation System (Samos) satellites may be a considered as an experimental series of military reconnaissance satellites equipped with a CBS/Kodak imaging system. Using the Agena satellite bus and upper stage, the satellites were intended for area survey reconnaissance. Also known as Sentry, the satellites were initially placed in relatively high orbits of 250 to 700km, but it was soon found the area survey approach did not provide satisfactory results. The program was terminated during 1962. The satellites had a mass of about 1860kg.
KH 4 Series
The first KH 4 camera system was carried on Discoverer-38. The capsule was recovered after 65 orbits. The satellite also carried samples of silicon, iron, bismuth, gold, magnesium, nickel and titanium which were exposed to radiation, as well as magnetometers, two total energy detectors and a radio scintillator. Following the flight of Discoverer-38, further U.S. military flights were classified and were no longer named.
KH 6 Series
The KH 6 Lanyard camera system had a resolution of 60cm and was specifically developed for the surveillance of suspected missile sites near Leningrad, in the USSR. Five satellites were built but only three were orbited and only one was successful.
KH 6-2carried also instrumentation for the detection of auroral electrons.
KH 7 Series
The KH 7 military reconnaissance satellites were based on the Discoverer series of satellites and carried the KH 7 camera system. Also known as Gambit, this system had a resolution of 45cm. Several of the satellites in this series, which were launched by the Atlas Agena D, ejected capsules or Hitchhiker secondary satellites.
KH 4A Series
The KH 4A series of satellites carried the KH 4A close look camera system which had a resolution of 2.5m. The systems was essentially two KH 4 cameras stacked on top of one another. Launched by a Thor Agena B, several of the satellites also carried emulsion and dosimetry film and other auxiliary experiments.
KH 8 Series
The KH 8 series was the third generation of close look military reconnaissance satellites. They were based on the Agena upper stage and had a mass of about 3000kg. The KH 8 multispectral camera was developed by Itek Corp.
KH 4B Series
The next series carried the KH 4B camera system was based on the KH 4A system and had a resolution of 1.10m. These satellites were launched by a Thor Agena D launch vehicle.
KH 9 Series
The KH 9, or Low Altitude Surveillance Platform (LASP), more commonly known as Big Bird, was originally developed as a back-up to the cancelled Manned Orbiting Laboratory (MOL) project (also referred to as KH 10). The KH 9, which has also been referred to as Code 612, Code 467 or Hexagon, was built by Lockheed. The satellites had a length of 15m and a diameter of 3m with an estimated mass of 13000kg. They were placed in a sun-synchronous orbit with an altitude from 160 to 260km.
The KH 9 satellites combined the close look and area survey requirements in a single spacecraft. For the close-look function, the satellites carried a Perkin Elmer camera with a resolution of 30cm, sufficient to distinguish between civilian and military personnel. The film with the images was processed on board and was returned to the surface in a return film capsule, which was recovered over the Pacific Ocean. As many as six such capsule were carried. To perform area surveys, KH 9 carried an Eastman Kodak camera system with a film scanner, data of which was sent back to the ground station by means of radio. Other instrumentation that was included, not necessarily on all flights, were a multi-spectral scanning system and side looking radar.
The KH 9 series also carried one or more Hitchhiker sub-satellites which served a number of purposes, including electronic data gathering and miscellaneous scientific and technology objectives. These sub-satellites, sometimes referred to as P11 were octagonal in shape with a diameter of about 90 cm. It is believed the KH 9 satellites had limited maneuvering capability through the propulsion systems of the Agena upper stage. At the end of the mission, the satellites were de-orbited.
Beyond KH 9
The designation KH 10 was assigned to an operational development of the U.S. Manned Orbiting Laboratory (MOL). MOL was cancelled in June 1969, along the KH 10. Subsequently, KH 11 and KH 12 reconnaissance satellites were placed in orbit, as well as reconnaissance satellites operating with other names. Some of these may still be operational today.
About the author
Jos Heyman is the Managing Director of Tiros Space Information, a Western Australian consultancy specializing in the dissemination of information on the scientific exploration and commercial application of space for use by educational as well as commercial organisations. An accountant by profession, Jos is the editor of the TSI News Bulletin and is also a regular contributor to the British Interplanetary Societys Spaceflight journal.