corona, luminous envelope surrounding the sun, outside the chromosphere. Its density is less than one billionth that of the earth's atmosphere. The corona is visible only at the time of totality during a total eclipse of the sun. It then appears as a halo of light with an irregular outer edge, often with streamers radiating from the sun's surface and contrasting with the dark lunar disk that it borders. It is divided into the inner corona, a ring of pale-yellow light against which crimson prominences are outlined, and the outer corona, a pearly white halo that extends far out into space. The corona consists of ionized gas at a temperature of 1 million°C;. By means of the coronagraph, the innermost part of the corona can be studied and photographed in full daylight. Although the visible corona extends a few solar radii above the sun, because of its high temperature it produces a continual flow of electrically charged particles called the solar wind that move outward through the solar system.

Corona, city (1990 pop. 76,095), Riverside co., S Calif.; inc. 1896. The city developed as a primary citrus fruit producer and shipping center. There is also light manufacturing. The name Corona ("circle") was derived from the 3 mi (5 km) circular drive around the city that was once used for car racing. State prisons for men and women are nearby. Cleveland National Forest and hot springs lie in the vicinity.

A corona is a type of plasma "atmosphere" of the Sun or other celestial body, extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. The Latin root of the word corona means crown.

The high temperature of the corona gives it unusual spectral features, which led some to suggest, in the 19th century, that it contained a previously unknown element, "coronium". These spectral features have since been traced to highly ionized Iron (Fe(XIV)) which indicates a plasma temperature in excess of 10⁶ kelvin.

The corona is divided into three parts. The K-corona (K for continuum) interfaces directly with the chromosphere and is created by sunlight scattering off electrons. The E-corona (E for emission) contains abundant calcium and iron. The F-corona (F for Fraunhofer) is created by sunlight bouncing off dust particles.

Physical features

The Sun's corona is much hotter (by a factor of nearly 200) than the visible surface of the Sun: the photosphere's average temperature is 5800 kelvin compared to the corona's one to three million kelvin. The corona is 10⁻¹² as dense as the photosphere, however, and so produces about one-millionth as much visible light. The corona is separated from the photosphere by the relatively shallow chromosphere. The exact mechanism by which the corona is heated is still the subject of some debate, but likely possibilities include induction by the Sun's magnetic field and sonic pressure waves from below (the latter being less probable now that coronae are known to be present in early-type, highly magnetic stars). The outer edges of the Sun's corona are constantly being transported away due to open magnetic flux generating the solar wind.

The Corona is not always evenly distributed across the surface of the sun. During periods of quiet, the corona is more or less confined to the equatorial regions, with coronal holes covering the polar regions. However during the Sun's active periods, the corona is evenly distributed over the equatorial and polar regions, though it is most prominent in areas with sunspot activity. The solar cycle spans approximately 11 years, from solar minimum to solar maximum, where the solar magnetic field is continually wound up (due to a differential rotation at the solar equator; the equator rotates quicker than the poles). Sunspot activity will be more pronounced at solar maximum where the magnetic field is twisted to a maximum. Associated with sunspots are coronal loops, loops of magnetic flux, upwelling from the solar interior. The magnetic flux pushes the hotter photosphere aside, exposing the cooler plasma below, thus creating the dark (when compared to the solar disk) spots.

Coronal Loops

Coronal loops are the basic structures of the magnetic solar corona. These loops are the closed-magnetic flux cousins of the open-magnetic flux that can be found in coronal hole (polar) regions and the solar wind. Loops of magnetic flux well up from the solar body and fill with hot solar plasma. Due to the heightened magnetic activity in these coronal loop regions, coronal loops can often be the precursor to solar flares and Coronal Mass Ejections (CMEs). Solar plasma feeding these structures are heated from under 6000K to well over 1×10⁶K from the photosphere, through the transition region, and into the corona. Often, the solar plasma will fill these loops from one foot point and drain from the other (siphon flow due to a pressure difference, or asymmetric flow due to some other driver). This is known as chromospheric evaporation and chromosperic condensation respectively. There may also be symmetric flow from both loop foot points, causing a buildup of mass in the loop structure. The plasma may cool in this region creating dark filaments in the solar disk or prominences off the limb. Coronal loops may have lifetimes in the order of seconds (in the case of flare events), minutes, hours or days. Usually coronal loops lasting for long periods of time are known as steady state or quiescent coronal loops, where there is a balance in loop energy sources and sinks (example).

Coronal loops have become very important when trying to understand the current coronal heating problem. Coronal loops are highly radiating sources of plasma and therefore easy to observe by instruments such as TRACE, they are highly observable laboratories to study phenomena such as solar oscillations, wave activity and nanoflares. However, it remains difficult to find a solution to the coronal heating problem as these structures are being observed remotely, where many ambiguities are present (i.e. radiation contributions along the LOS). In-situ measurements are required before a definitive answer can be arrived at, but due to the high plasma temperatures in the corona, in-situ measurements are impossible (at least for the time-being).

Transients

Generated by solar flares or large solar prominences, "coronal transients" (also called coronal mass ejections) are sometimes released. These are enormous loops of coronal material traveling outward from the Sun at over a million kilometers per hour, containing roughly 10 times the energy of the solar flare or prominence that triggered them. Some larger ejections can propel hundreds of millions of tons of material in to space at roughly at 1.5 million kilometers an hour.

Other stars

Stars other than the Sun have coronae, which can be detected using X-ray telescopes. Some stellar coronae, particularly in young stars, are much more luminous than the Sun's.

Coronal heating problem

The coronal heating problem in solar physics relates to the question of why the temperature of the Sun's corona is millions of kelvin higher than that of the surface. The high temperatures require energy to be carried from the solar interior to the corona by non-thermal processes, because the second law of thermodynamics prevents heat from flowing directly from the solar photosphere, or surface, at about 5800 kelvin, to the much hotter corona at about 1 to 3 MK (parts of the corona can even reach 10 MK). The amount of power required to heat the solar corona can easily be calculated. It is about 1 kilowatt for every square meter of surface area on the Sun, or 1/40000 of the amount of light energy that escapes the Sun.

This thin region of temperature increase from the chromosphere to the corona is known as the transition region and can range from tens to hundreds of kilometers thick. An analogy of this would be a light bulb heating the air surrounding it hotter than its glass surface. The second law of thermodynamics would be broken. So, what mechanism is heating the tenuous coronal plasma to these temperatures?

Many coronal heating theories have been proposed, but two theories have remained as the most likely candidates, wave heating and magnetic reconnection (or nanoflares). Through most of the past 50 years, neither theory has been able to account for the extreme coronal temperatures. Most solar physicists now believe that some combination of the two theories can probably explain coronal heating, although the details are not yet complete.

The NASA mission Solar Probe + is intended to approach the sun to a distance of approximately 9.5 solar radii in order to investigate coronal heating and the origin of the solar wind.

Competing heating mechanisms

Heating Models
Hydrodynamic	Magnetic
No magnetic field Slow rotating stars	DC (reconnection)	AC (waves)
	B-field stresses Reconnection events Flares Uniform heating rates	Photospheric foot point shuffling MHD wave propagation High Alfvén wave flux Non-uniform heating rates
Not our Sun!	Competing theories

Wave heating theory

The wave heating theory, proposed in 1949 by Evry Schatzman, proposes that waves carry energy from the solar interior to the solar chromosphere and corona. The Sun is made of plasma rather than ordinary gas, so it supports several types of waves analogous to sound waves in air. The most important types of wave are magneto-acoustic waves and Alfvén waves. Magneto-acoustic waves are sound waves that have been modified by the presence of a magnetic field, and Alfvén waves are similar to ULF radio waves that have been modified by interaction with matter in the plasma. Both types of waves can be launched by the turbulence of granulation and super granulation at the solar photosphere, and both types of waves can carry energy for some distance through the solar atmosphere before turning into shock waves that dissipate their energy as heat.

One problem with wave heating is delivery of the heat to the appropriate place. Magneto-acoustic waves cannot carry sufficient energy upward through the chromosphere to the corona, both because of the low pressure present in the chromosphere and because they tend to be reflected back to the photosphere. Alfvén waves can carry enough energy, but do not dissipate that energy rapidly enough once they enter the corona. Waves in plasmas are notoriously difficult to understand and describe analytically, but computer simulations, carried out by Thomas Bogdan and colleagues in 2003, seem to show that Alfvén waves can transmute into other wave modes at the base of the corona, providing a pathway that can carry large amounts of energy from the photosphere into the corona and then dissipate it as heat.

Another problem with wave heating has been the complete absence, until the late 1990s, of any direct evidence of waves propagating through the solar corona. The first direct observation of waves propagating into and through the solar corona was made in 1997 with the SOHO space-borne solar observatory, the first platform capable of observing the Sun in the extreme ultraviolet for long periods of time with stable photometry. Those were magneto-acoustic waves with a frequency of about 1 millihertz (mHz, corresponding to a 1,000 second wave period), that carry only about 10% of the energy required to heat the corona. Many observations exist of localized wave phenomena, such as Alfvén waves launched by solar flares, but those events are transient and cannot explain the uniform coronal heat.

It is not yet known exactly how much wave energy is available to heat the corona. Results published in 2004 using data from the TRACE spacecraft seem to indicate that there are waves in the solar atmosphere at frequencies as high as 100 mHz (10 second period). Measurements of the temperature of different ions in the solar wind with the UVCS instrument aboard SOHO give strong indirect evidence that there are waves at frequencies as high as 200 Hz, well into the range of human hearing. These waves are very difficult to detect under normal circumstances, but evidence collected during solar eclipses by teams from Williams College suggest the presences of such waves in the 1–10 Hz range.

Magnetic reconnection theory

The Magnetic reconnection theory relies on the solar magnetic field to induce electric currents in the solar corona. The currents then collapse suddenly, releasing energy as heat and wave energy in the corona. This process is called "reconnection" because of the peculiar way that magnetic fields behave in a plasma (or any electrically conductive fluid such as mercury or seawater). In a plasma, magnetic field lines are normally tied to individual pieces of matter, so that the topology of the magnetic field remains the same: if a particular north and south magnetic pole are connected by a single field line, then even if the plasma is stirred or if the magnets are moved around, that field line will continue to connect those particular poles. The connection is maintained by electric currents that are induced in the plasma. Under certain conditions, the electric currents can collapse, allowing the magnetic field to "reconnect" to other magnetic poles and release heat and wave energy in the process.

Magnetic reconnection is hypothesized to be the mechanism behind solar flares, the largest explosions in our solar system. Furthermore, the surface of Sun is covered with millions of small magnetized regions 50–1,000 km across. These small magnetic poles are buffeted and churned by the constant granulation. The magnetic field in the solar corona must undergo nearly constant reconnection to match the motion of this "magnetic carpet", so the energy released by the reconnection is a natural candidate for the coronal heat, perhaps as a series of "microflares" that individually provide very little energy but together account for the required energy.

The idea that micro flares might heat the corona was put forward by Eugene Parker in the 1980s but is still controversial. In particular, ultraviolet telescopes such as TRACE and SOHO/EIT can observe individual micro-flares as small brightenings in extreme ultraviolet light, but there seem to be too few of these small events to account for the energy released into the corona. The additional energy not accounted for could be made up by wave energy, or by gradual magnetic reconnection that releases energy more smoothly than micro-flares and therefore doesn't appear well in the TRACE data. Variations on the micro flare hypothesis use other mechanisms to stress the magnetic field or to release the energy, and are a subject of active research in 2005.

References

External links

• Coronal heating problem at Innovation Reports
• NASA/GSFC description of the coronal heating problem
• FAQ about coronal heating
• Solar and Heliospheric Observatory, including near-real-time images of the solar corona
• Sun|trek website An educational resource for teachers and students about the Sun and its effect on the Earth

Corona was the name of a series of US military reconnaissance satellites operated under a CIA program run by the Directorate of Science & Technology with substantial assistance from the US Air Force, used for photographic surveillance of the Soviet Union, China and other areas from June 1959 until May 1972. The project name is sometimes given as CORONA, but it is a codeword, not an acronym.

The project was accelerated after the U-2 incident in May 1960.

The satellites were designated KH-1, KH-2, KH-3, KH-4, KH-4A and KH-4B. KH stood for Key Hole or Keyhole (Code number 1010) , and the incrementing number indicated changes in the surveillance instrumentation, such as the change from single-panoramic to double-panoramic cameras. The KH naming system was first used in 1962 with KH-4 and the earlier numbers were retroactively applied. There were 144 Corona satellites launched, of which 102 returned usable imagery.

Technology

The Corona satellites used 31,500 ft (9,600 m) of special 70 mm film with a 24 inch (0.6 m) focal length lens. Initially orbiting at 165 to 460 km, the cameras could resolve images on the ground down to 7.5 m. The two KH-4 systems improved the resolution to 2.75 m and 1.8 m respectively and used a lower altitude pass.

Ironically, the name Corona was more fitting than its originators had ever imagined. The initial missions of the program suffered from many technical problems, among them, mysterious fogging and bright streaks were seen on the returned film of some missions, only to disappear on the next mission. Eventually it was determined by a collaborative team of scientists and engineers from the project and from academia, (among them: Luis Alvarez, Sidney Beldner, Malvin Ruderman, and Sidney Drell) that electrostatic discharges (called corona discharge) caused by rubber components of the camera, were exposing the film. Recommended corrective actions solving the problem included better grounding of spacecraft components and outgassing testing of parts before launch. These practices are still used on practically all US reconnaissance satellites today.

Discoverer

The initial Corona launches were obscured as part of a space technology program called Discoverer, the first test launches for which were in early 1959. The first launch with a camera was June 1959 as Discoverer 4, which was a 750 kg satellite launched by a Thor-Agena rocket. The satellites returned film canisters to Earth in capsules, called "buckets", which were recovered in mid-air by a specially equipped aircraft during their parachute descent (they were designed to float in water for a short period of time, and then sink, if the mid-air recovery failed). The first camera-fitted Discoverer missions failed to return usable film, but following repeated recovery tests on August 18, 1960 with Discoverer 14, a bucket was successfully retrieved two days later by a C-119.

An alternative program named SAMOS included several satellite types that used a different method, taking an image on film, developing the film on board the spacecraft, and then scanning the image and transmitting it to the ground. The Samos E-1 and E-2 satellite programs used this technology, but it was not able to take many pictures and relay them to the ground each day. Later Samos programs, such as the E-5 and the E-6, used the film-return approach, but neither one was successful.

At least two Discoverer launches were used to test satellites for the Missile Defense Alarm System, an early missile-launch-detection program that used infrared cameras to detect the heat signature of rockets launching to orbit.

The Corona film-return capsule was later adapted for the KH-7 GAMBIT satellite, which took higher resolution photos.

Discoverer 13 was the first satellite that landed and was recovered on August 11, 1960. The last launch under the Discoverer name was Discoverer 38 on 27 February 1962; with a successful midair recovery of the capsule on the 65th orbit (13th recovery, 9th in midair). After that, the launches were entirely secret. The last Corona launch was on May 25, 1972. The project was abandoned after a Soviet submarine was detected waiting below a Corona mid-air retrieval zone. The best sequence of Corona launches was from 1966 to 1971, when there were 32 consecutive launch-and-film-recoveries.

Corona launches

Source: USGS

Time period	No.	Nickname	Resolution	Notes	Number
Jun 1959– Sep 1960	KH-1	"Corona", C	7.5 m	First series of US imaging spy satellites. Each satellite carried a single panoramic camera and a single return vehicle.	10 systems; 1 recovery.
Oct 1960– Oct 1961	KH-2	Corona′, C′,(C-prime)*	7.5 m	Single panoramic camera and a single return vehicle.	7 systems; 4 recoveries.
Aug 1961– Jan 1962	KH-3	Corona‴, C‴,(C-triple-prime)*	7.5 m	Single panoramic camera and a single return vehicle.	9 systems; 5 recoveries.
Feb 1962- Dec 1963	KH-4	Corona-M, Mural	7.5 m	Film return. Two panoramic cameras.	26 systems; 20 recoveries.
Aug 1963- Oct 1969	KH-4A	Corona J-1	2.75 m	Film return with two reentry vehicles and two panoramic cameras. Large volume of imagery.	52 systems; 94 recoveries.
Sep 1967- May 1972	KH-4B	Corona J-3	1.8 m	Film return with two reentry vehicles and two panoramic cameras.	17 systems; 32 recoveries.
Feb 1961- Aug 1964	KH-5	Argon	140 m	Low-resolution mapping missions; single frame camera.	12 systems; 5 recoveries.
Mar 1963- July 1963	KH-6	Lanyard	1.8 m	Experimental camera in a short-lived program.	3 systems; 2 recoveries.

^*(The stray "quote marks" are the original designations of the first three generations of cameras, as described in Perry's history.)

Declassification

Corona was officially secret until 1992. On February 22, 1995, the imagery acquired by the Corona and two contemporary programs (Argon and Lanyard) was declassified. Review of "obsolete broad-area film-return systems other than Corona" mandated by the order led to the 2002 declassification of the imagery from KH-7 and the KH-9 low-resolution camera system.

The declassified imagery has since been used by a team of scientists from the Australian National University to locate and explore ancient habitation sites, pottery factories, megalithic tombs, and Palaeolithic remains in northern Syria.

Launches

Mission No.	Cover Name	Launch Date	NSSDC ID No.	Alt. Name	Camera	Notes
R&D	Discoverer	21 Jan 1959	1959-E01	1959-E01	none	Mission Failed. Failed to achieve orbit
R&D	Discoverer 1	28 Feb 1959	1959-002A	1959 BET	none	First object in polar orbit
R&D	Discoverer 2	13 Apr 1959	1959-003A	1959 GAM	none	First three-axis stabilized satellite; capsule recovery failed
R&D	Discoverer 3	03 Jun 1959	DISCOV3	1959-F02	none	Failed to orbit
9001	Discoverer 4	25 Jun 1959	DISC4	1959-U01	KH-1	Mission failed. Failed to achieve orbit.
9002	Discoverer 5	13 Aug 1959	1959-005A	1959 EPS 1	KH-1	Mission failed. Power supply failure. No recovery.
9003	Discoverer 6	19 Aug 1959	1959-006A	1959 ZET	KH-1	Mission failed. Retro rockets malfunctioned negating recovery.
9004	Discoverer 7	07 Nov 1959	1959-010A	1959 KAP	KH-1	Mission failed. Failed to achieve orbit.
9005	Discoverer 8	20 Nov 1959	1959-011A	1959 LAM	KH-1	Mission failed. Eccentric orbit negating recovery.
9006	Discoverer 9	04 Feb 1960	DiSC9	1960-F01	KH-1	Mission failed. Failed to achieve orbit.
9007	Discoverer 10	19 Feb 1960	DISC10	1960-F02	KH-1	Mission failed. Destroyed just after launch due to erratic attitude.
9008	Discoverer 11	15 Apr 1960	1960-004A	1960 DEL	KH-1	Mission failed. Attitude control system malfunctioned.
R&D	Discoverer 12	29 Jun 1960	DISC12	1960-F08	none	Failed to orbit
R&D	Discoverer 13	10 Aug 1960	1960-008A	1960 THE	none	Tested capsule recovery system; first successful capture.
9009		18 Aug 1960	1960-010A	1960 KAP	KH-1	First successful recovery of IMINT from space. Cameras operated satisfactorily.
9010	Discoverer 15	13 Sep 1960	1960-012A	1960 MU	KH-1	Mission failed. Attained orbit successfully. Capsule sank prior to retrieval.
9011	Discoverer 16	26 Oct 1960	1960-F15	1960-F15	KH-2	Mission failed. Satellite failed to separate from booster. Failed to achieve orbit.
9012	Discoverer 17	12 Nov 1960	1960-015A	1960 OMI	KH-2	Mission failed. Obtained orbit successfully. Film separated before any camera operation leaving only 1.7 ft of film in capsule.
9013	Discoverer 18	07 Dec 1960	1960-018A	1960 SIG	KH-2	First successful mission employing KH-2 camera system.
RM-1	Discoverer 19	20 Dec 1960	1960-019A	1960 TAU	none	Test of Midas missile-detection system
9014A	Discoverer 20	17 Feb 1961	1961-005A	1961 EPS 1	KH-5	See KH-5
RM-2	Discoverer 21	18 Feb 1961	1961-006A	1961 ZET	none	Test of restartable rocket engine
9015	Discoverer 22	30 Mar 1961	DISC22	1961-F02	KH-2	Mission failed. Second stage failed to obtain orbital velocity.
9016A	Discoverer 23	08 Apr 1961	1961-011A	1961 LAM 1	KH-5	See KH-5
9018A	Discoverer 24	16 Jun 1961	DISC24	1961-F05	KH-5	See KH-5
9017	Discoverer 25	16 Jun 1961	1961-014A	1961 XI 1	KH-2	Capsule recovered from water on orbit 32. Streaks throughout film.
9019	Discoverer 26	07 Jun 1961	1961-016A	1961 PI	KH-2	Main camera malfunctioned on pass 22.
9020A	Discoverer 27	21 Jun 1961	DISC27	1961-F07	KH-5	See KH-5
9021	Discoverer 28	03 Aug 1961	DISC28	1961-F08	KH-2	Mission failed. No orbit. Satellite guidance system failed.
9022	Discoverer 30	12 Sep 1961	1961-024A	1961 OME 1	KH-3	Best mission to date. Same out-of-focus condition as in 9023.
9023	Discoverer 29	30 Aug 1961	1961-023A	1961 PSI	KH-3	First use of KH-3 camera system. All frames out of focus.
9024	Discoverer 31	17 Sep 1961	1961-026A	1961 A BET	KH-3	Mission failed. Power failure and loss of control gas on orbit 33. Capsule was not recovered.
9025	Discoverer 32	13 Oct 1961	1961-027A	1961 A GAM 1	KH-3	Capsule recovered on orbit 18. 96% of film out of focus.
9026	Discoverer 33	23 Oct 1961	DISC33	1961-F10	KH-3	Mission failed. Satellite failed to separate from Thor booster. No orbit.
9027	Discoverer 34	05 Nov 1961	1961-029A	1961 A EPS 1	KH-3	Mission failed. Improper launch angle resulted in extreme orbit. Gas valve failed
9028	Discoverer 35	15 Nov 1961	1961-030A	1961 A ZET 1	KH-3	All cameras operated satisfactorily. Grainy emulsion noted.
9029	Discoverer 36	12 Dec 1961	1961-032A	1961 A KAP 1	KH-3	Best mission to date.
9030	Discoverer 37	13 Jan 1962	DISC37	1962-F01	KH-3	Mission failed. No orbit.
9031	Discoverer 38	27 Feb 1962	1962-005A	1962 EPS 1	KH-4	First mission of the KH-4 series. Much of film slightly out of focus.
9032	Discoverer 39	18 Apr 1962	1962-011A	1962 LAM 1	KH-4	Best mission to date.
9033	FTV 1125	28 Apr 1962	1962-017A	1962 RHO 1	KH-4	Mission failed. Parachute ejector squibs holding parachute container cover failed to fire. No recovery.
9034A	FTV 1126	15 May 1962	1962-018A	1962 SIG 1	KH-5	See KH-5
9035	FTV 1128	30 May 1962	1962-021A	1962 PHI 1	KH-4	Slight corona static on film.
9036	FTV 1127	02 Jun 1962	1962-022A	1962 CHI 1	KH-4	Mission failed. During air catch
9037	FTV 1129	23 Jun 1962	1962-026A	1962 A BET	KH-4	Corona static occurs on some film.
9038	FTV 1151	28 Jun 1962	1962-027A	1962 A GAM	KH-4	Severe corona static.
9039	FTV 1130	21 Jun 1962	1962-031A	1962 A ETA	KH-4	Aborted after 6 photo passes. Heavy corona and radiation fog.
9040	FTV 1131	28 Jun 1962	1962-032A	1962 A THE	KH-4	No filters on slave horizon cameras. Heavy corona and radiation fog.
9041	FTV 1152	02 Aug 1962	1962-034A	1962 A KAP 1	KH-4	Severe corona and radiation fog.
9042A	FTV 1132	01 Sep 1962	1962-044A	1962 A UPS	KH-5	See KH-5
9043	FTV 1133	17 Sep 1962	1962-046A	1962 A CHI	KH-4	Capping shutter malfunction
9044	FTV 1153	29 Aug 1962	1962-042A	1962 A SIG	KH-4	Erratic vehicle attitude. Radiation fog minimal.
9045	FTV 1154	29 Sep 1962	1962-050A	1962 B BET	KH-4	First use of stellar camera
9046A	FTV 1134	09 Oct 1962	19762-053A	1962 B EPS	KH-5	See KH-5
9047	FTV 1136	05 Nov 1962	1962-063A	1962 B OMI	KH-4	Camera door malfunctioned
9048	FTV 1135	24 Nov 1962	1962-065A	1962 B RHO	KH-4	Some film exposed through base.
9049	FTV 1155	04 Dec 1962	1962-066A	1962 B SIG	KH-4	Mission failed. During air catch chute tore
9050	FTV 1156	14 Dec 1962	1962-069A	1962 B PHI	KH-4	Best mission to date.
9051	OPS 0048	07 Jan 1963	1963-002A	1963-002A	KH-4	Erratic vehicle attitude. Frame ephemeris not created.
9052	OPS 0583	28 Feb 1963	1963-F02	1963-F02	KH-4	Mission failed. Destroyed by range safety officer
9053	OPS 0720	01 Apr 1963	1963-007A	1963-007A	KH-4	Best imagery to date.
9054	OPS 0954	12 Jun 1963	1963-019A	1963-019A	KH-4	Some imagery seriously affected by corona.
9055A	OPS 1008	26 Apr 1963	1963-F07	1963-F07	KH-5	See KH-5
9056	OPS 0999	26 Jun 1963	1963-025A	1963-025A	KH-4	Experimental camera carried. Film affected by light leaks.
9057	OPS 1266	18 Jun 1963	1963-029A	1963-029A	KH-4	Best mission to date.
9058A	OPS 1561	29 Aug 1963	1963-035A	1963-035A	KH-5	See KH-5
9059A	OPS 2437	29 Oct 1963	1963-042A	1963-042A	KH-5	See KH-5
9060	OPS 2268	09 Nov 1963	1963-F14	1963-F14	KH-4	Mission failed. No orbit.
9061	OPS 2260	27 Nov 1963	1963-048A	1963-048A	KH-4	Mission failed. Return capsule separated from satellite but remained in orbit.
9062	OPS 1388	21 Dec 1963	1963-055A	1963-055A	KH-4	Corona static fogged much of film.
9065A	OPS 2739	21 Aug 1964	1964-048A	1964-048A	KH-5	See KH-5
9066A	OPS 3236	13 Jun 1964	1964-030A	1964-030A	KH-5	See KH-5
1001	OPS 1419	24 Aug 1963	1963-034A	1963-034A	KH-4A	First mission of KH-4A. Some film was fogged. Two buckets but 1001-2 was never recovered.
1002	OPS 1353	23 Sep 1963	1963-037A	1963-037A	KH-4A	Severe light leaks
1003	OPS 3467	24 Mar 1964	1964-F04	1964-F04	KH-4A	Mission failed. Guidance system failed. No orbit.
1004	OPS 3444	15 Feb 1964	1964-008A	1964-008A	KH-4A	Main cameras operated satisfactorily. Minor degradations due to static and light leaks.
1005	OPS 2921	27 Apr 1964	1964-022A	1964-022A	KH-4A	Mission failed. Recovery vehicle impacted in Venezuela.
1006	OPS 3483	04 Jun 1964	1964-027A	1964-027A	KH-4A	Highest quality imagery attained to date from the KH-4 system.
1007	OPS 3754	19 Jun 1964	1964-032A	1964-032A	KH-4A	Out-of-focus area on some film.
1008	OPS 3491	10 Jun 1964	1964-037A	1964-037A	KH-4A	Cameras operated satisfactorily
1009	OPS 3042	05 Aug 1964	1964-043A	1964-043A	KH-4A	Cameras operated successfully.
1010	OPS 3497	14 Sep 1964	1964-056A	1964-056A	KH-4A	Small out of focus areas on both cameras at random times throughout the mission.
1011	OPS 3333	05 Oct 1964	1964-061A	1964-061A	KH-4A	Primary mode of recovery failed on second portion of the mission (1011-2). Small out of focus areas present at random on both cameras.
1012	OPS 3559	17 Oct 1964	1964-067A	1964-067A	KH-4A	Vehicle attitude became erratic on the second portion of the mission necessitating an early recovery.
1013	OPS 5434	02 Nov 1964	1964-071A	1964-071A	KH-4A	Program anomaly occurred immediately after launch when both cameras operated for 417 frames. Main cameras ceased operation on rev 52D of first portion of mission negating second portion. About 65 % of aft camera film is out of focus.
1014	OPS 3360	18 Nov 1964	1964-075A	1964-075A	KH-4A	Cameras operated successfully.
1015	OPS 3358	19 Dec 1964	1964-085A	1964-085A	KH-4A	Discrepancies in planned and actual coverage due to telemetry problems during the first 6 revolutions. Small out-of-focus areas on film from aft camera.
1016	OPS 3928	15 Jan 1965	1965-002A	1965-002A	KH-4A	Smearing of highly reflective images due to reflections within camera.
1017	OPS 4782	25 Feb 1965	1965-013A	1965-013A	KH-4A	Capping shutter malfunction occurred during last 5 passes of mission.
1018	OPS 4803	25 Mar 1965	1965-026A	1965-026A	KH-4A	Cameras operated successfully. First KH-4A reconnaissance system to be launched into a retrograde orbit.
1019	OPS 5023	29 Apr 1965	1965-033A	1965-033A	KH-4A	Cameras operated successfully. Malfunction in recovery mode on 1019-2 negated recovery.
1020	OPS 8425	09 Jun 1965	1965-045A	1965-045A	KH-4A	All cameras operated satisfactorily. Erratic attitude caused an early recovery after the second day of 1020-2.
1021	OPS 8431	18 May 1965	1965-037A	1965-037A	KH-4A	Aft camera ceased operation on pass 102.
1022	OPS 5543	19 Jun 1965	1965-057A	1965-057A	KH-4A	All cameras operated satisfactorily.
1023	OPS 7208	17 Aug 1965	1965-067A	1965-067A	KH-4A	Program anomaly caused the fore camera to cease operation during revolutions 103-132.
1024	OPS 7221	22 Sep 1965	1965-074A	1965-074A	KH-4A	All cameras operated satisfactorily. Cameras not operated on passes 88D-93D.
1025	OPS 5325	05 Oct 1965	1965-079A	1965-079A	KH-4A	Main cameras operated satisfactorily.
1026	OPS 2155	28 Oct 1965	1965-086A	1965-086A	KH-4A	All cameras operated satisfactorily.
1027	OPS 7249	09 Dec 1965	1965-102A	1965-102A	KH-4A	Erratic attitude necessitated recovery after two days of operation. All cameras operated satisfactorily.
1028	OPS 4639	24 Dec 1965	1965-110A	1965-110A	KH-4A	Cameras operated satisfactorily.
1029	OPS 7291	02 Feb 1966	1966-007A	1966-007A	KH-4A	Both panoramic cameras were operational throughout.
1030	OPS 3488	09 Mar 1966	1966-018A	1966-018A	KH-4A	All cameras operated satisfactorily.
1031	OPS 1612	07 Apr 1966	1966-029A	1966-029A	KH-4A	The aft-looking camera malfunctioned after the recovery of bucket 1. No material was received in bucket 2 (1031-2).
1032	OPS 1508	03 May 1966	1966-F05A	1966-F05	KH-4A	Mission failed. Vehicle failed to achieve orbit.
1033	OPS 1778	24 May 1966	1966-042A	1966-042A	KH-4A	The stellar camera shutter of bucket 2 remained open for approximately 200 frames.
1034	OPS 1599	21 Jun 1966	1966-055A	1966-055A	KH-4A	Failure of velocity altitude programmer produced poor imagery after revolution 5.
1035	OPS 1703	20 Sep 1966	1966-085A	1966-085A	KH-4A	All cameras operated satisfactorily. First mission flown with pan geometry modification.
1036	OPS 1545	09 Aug 1966	1966-072A	1966-072A	KH-4A	All cameras operated satisfactorily.
1037	OPS 1866	08 Nov 1966	1966-102A	1966-102A	KH-4A	Second pan geometry mission. Higher than normal base plus fog encountered on both main camera records.
1038	OPS 1664	14 Jan 1967	1967-002A	1967-002A	KH-4A	Fair image quality.
1039	OPS 4750	22 Feb 1967	1967-015A	1967-015A	KH-4A	Normal KH-4 mission. Light from horizon camera on both main camera records during 1039-1.
1040	OPS 4779	30 Mar 1967	1967-029A	1967-029A	KH-4A	Satellite flown nose first
1041	OPS 4696	09 May 1967	1967-043A	1967-043A	KH-4A	Due to the failure of the booster cut-off switch
1042	OPS 3559	16 Jun 1967	1967-062A	1967-062A	KH-4A	Small out-of-focus area in forward camera of 1042-1.
1043	OPS 4827	07 Aug 1967	1967-076A	1967-076A	KH-4A	Forward camera film came out of the rails on pass 230D. Film degraded past this point.
1044	OPS 0562	02 Nov 1967	1967-109A	1967-109A	KH-4A	All cameras operated fine.
1045	OPS 2243	24 Jan 1968	1968-008A	1968-008A	KH-4A	All cameras operated satisfactorily.
1046	OPS 4849	14 Mar 1968	1968-020A	1968-020A	KH-4A	Image quality good for 1046-1 and fair for 1046-2.
1047	OPS 5343	20 Jun 1968	1968-052A	1968-052A	KH-4A	Out-of-focus imagery is present on both main camera records.
1048	OPS 0165	18 Sep 1968	1968-078A	1968-078A	KH-4A	Film in the forward camera separated and camera failed on mission 1048-2
1049	OPS 4740	12 Dec 1968	1968-112A	1968-112A	KH-4A	Degraded film
1050	OPS 3722	19 Mar 1969	1969-026A	1969-026A	KH-4A	Due to abnormal rotational rates after revolution 22
1051	OPS 1101	02 May 1969	1969-041A	1969-041A	KH-4A	Imagery of both pan camera records is soft and lacks crispness and edge sharpness.
1052	OPS 3531	22 Sep 1969	1969-079A	1969-079A	KH-4A	Last of the KH-4A missions
1101	OPS 5089	15 Sep 1967	1967-087A	1967-087A	KH-4B	First mission of the KH-4B series. Best film to date.
1102	OPS 1001	09 Dec 1967	1967-122A	1967-122A	KH-4B	Noticeable image smear for forward camera
1103	OPS 1419	01 May 1968	1968-039A	1968-039B	KH-4B	Out-of-focus imagery is present on both main camera records.
1104	OPS 5955	07 Aug 1968	1968-065A	1968-065A	KH-4B	Best imagery to date on any KH-4 systems. Bicolor and color infrared experiments were conducted on this mission.
1105	OPS 1315	03 Nov 1968	1968-098A	1968-098A	KH-4B	Image quality is variable and displays areas of soft focus and image smear.
1106	OPS 3890	05 Feb 1969	1969-010A	1969-010A	KH-4B	The best image quality to date.
1107	OPS 3654	24 Jun 1969	1969-063A	1969-063A	KH-4B	Forward camera failed on pass 1 and remained inoperative throughout the rest of the mission.
1108	OPS 6617	04 Dec 1969	1969-105A	1969-105A	KH-4B	Cameras operated satisfactorily and the mission carried 811 ft of aerial color film added to the end of the film supply.
1109	OPS 0440	04 Mar 1970	1970-016A	1970-016A	KH-4B	Cameras operated satisfactorily but the overall image quality of both the forward and aft records is variable.
1110	OPS 4720	20 May 1970	1970-040A	1970-040A	KH-4B	The overall image quality is less than that provided by recent missions and 2
1111	OPS 4324	23 Jun 1970	1970-054A	1970-054A	KH-4B	The overall image quality is good.
1112	OPS 4992	18 Nov 1970	1970-098A	1970-098A	KH-4B	The forward camera failed on pass 104 and remained inoperative throughout the rest of the mission.
1113	OPS 3297	17 Feb 1971	1971-F01A	1971-F01	KH-4B	Mission failed due to failure of Thor booster. Destroyed shortly after launch.
1114	OPS 5300	24 Mar 1971	1971-022A	1971-022A	KH-4B	The overall image quality is good and comparable to the best of past missions. On-board program failed after pass 235
1115	OPS 5454	10 Sep 1971	1971-076A	1971-076A	KH-4B	Overall image quality is good.
1116	OPS 5640	19 Mar 1972	1972-032A	1972-032A	KH-4B	Very successful mission and image quality was good.
1117	OPS 6371	25 May 1972	1972-039A	1972-039A	KH-4B	Last KH-4B mission. Very successful mission

See also

• KH-5-ARGON,