P78-1 or Solwind was a

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...

launched aboard an Atlas F rocket from

Vandenberg Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in Key West, Florida * Vandenberg Sp ...

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

on February 24, 1979. The satellite's mission was extended by several weeks, so that it operated until it was destroyed in orbit on September 13, 1985, to test the

ASM-135 ASAT The ASM-135 ASAT is an air-launched anti-satellite multistage missile that was developed by Ling-Temco-Vought's LTV Aerospace division. The ASM-135 was carried exclusively by United States Air Force (USAF) F-15 Eagle fighter aircraft. Developm ...

anti-satellite missile.

Construction and payload

The satellite's

Orbiting Solar Observatory The Orbiting Solar Observatory (abbreviated OSO) Program was the name of a series of American space telescopes primarily intended to study the Sun, though they also included important non-solar experiments. Eight were launched successfully int ...

(OSO) platform included a solar-oriented sail and a rotating wheel section.

Ball Aerospace Ball Aerospace & Technologies Corp. is an American manufacturer of spacecraft, components and instruments for national defense, civil space and commercial space applications. The company is a wholly owned subsidiary of Ball Corporation ( NYSE: BA ...

was the primary contractor for design and construction, and provided the

attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...

and determination computer programs. The P78-1 carried a

gamma-ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically sh ...

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...

, a white-light

coronagraph A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved. Most coronagraphs are intended to view t ...

, an extreme-

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

imager, an

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

, a high-latitude particle spectrometer, an

aerosol An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of anthropogen ...

monitor, and an

monitor. The X-ray monitor, designated NRL-608 or XMON, was a collaboration between the

Naval Research Laboratory The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps. It was founded in 1923 and conducts basic scientific research, applied research, technologic ...

and

Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...

. The white-light

and the ultraviolet imager were combined in a single package, designated NRL-401 or SOLWIND, which was built by the

. The coronagraph was the flight spare of the white-light coronagraph on the

OSO-7 OSO 7 or Orbiting Solar Observatory 7 (NSSDC ID: 1971-083A), before launch known as OSO H is the seventh in the series of American Orbiting Solar Observatory satellites launched by NASA between 1962 and 1975. OSO 7 was launched from Cape Kennedy ...

satellite. The ultraviolet imager used a CCD imager, one of the first uses of a CCD in space.

Discovery of comets

P78-1 was the first satellite in space to discover a comet in general and a

sungrazing comet A sungrazing comet is a comet that passes extremely close to the Sun at perihelion – sometimes within a few thousand kilometres of the Sun's surface. Although small sungrazers can completely evaporate during such a close approach to the Sun, ...

in particular. In total, 9 sungrazing comets, all belonging to the Kreutz group, were discovered on images taken by the Solwind coronagraph: Apart from these yet another comet C/1984 R1 (SOLWIND) was found by Rainer Kracht, a German amateur astronomer, on 23 July 2005 in Solwind's images of 17 Sep 1984. Its

perihelion distance An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

of 0.1051 AU was at least ten times larger than that of the previously found true sungrazers.

Destruction

By 1985, the satellite's batteries were degrading. This caused more and more frequent "under-voltage cutoffs", a condition where the satellite detected a low main bus voltage and automatically shut down all non-vital systems. In addition, the last of the three tape recorders failed in the spring of 1985, so data collection could only occur while the spacecraft was in contact with a ground station. A normal contact lasted only about 15 minutes, so this was a serious impediment. Special arrangements could be made to string several contacts together. As a result of these failures, an ever-increasing amount of time and network resources were spent reconfiguring the satellite for normal operation. Data collection from the few remaining payloads was severely limited. Because of the additional burden on the

Air Force Satellite Control Network The Satellite Control Network (SCN), operated by the United States Space Force's Space Delta 6, provides support for the operation, control, and maintenance of a variety of United States Department of Defense and some non-DoD satellites. This i ...

(e.g., extra support and antenna time at the tracking stations), discussions were already underway to terminate the mission. This led to the satellite being chosen as a test target for an

anti-satellite missile. The mission was extended for several weeks solely to support the test. During this final phase, the satellite was often allowed to remain in the under-voltage condition for several days at a time. On September 13, 1985, the satellite was destroyed in orbit at 20:43 UTC at with an altitude of by an

launched from a

US Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Sig ...

F-15 Eagle The McDonnell Douglas F-15 Eagle is an American Twinjet, twin-engine, all-weather Air combat manoeuvring#Tactics, tactical fighter aircraft designed by McDonnell Douglas (now part of Boeing). Following reviews of proposals, the United States ...

fighter aircraft Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...

. The test resulted in 285 cataloged pieces of

orbital debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) are defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict space ...

. 1 piece of debris remained in orbit to at least May 2004, but had deorbited by 2008. The last piece of debris, COSPAR 1979-017GX, SATCAT 16564, deorbited 9 May 2004 according to SATCAT. The test outraged some scientists because although five of P78-1's instruments had failed at the time of the test, two instruments remained in operation, and the satellite was what one solar

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

called "the backbone of coronal research through the last seven years".

Gallery

File:ASM-135 ASAT 5.jpg, F-15A ''Celestial Eagle'' launching the ASAT missile that destroyed the P78-1

References

External links