RORSAT
Encyclopedia
Radar Ocean Reconnaissance SATellite or RORSAT is the western name given to the Soviet
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 Upravlyaemyj Sputnik Aktivnyj (Управляемый Спутник Активный) (US-A) satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

s. These satellites were launched between 1967 and 1988 to monitor NATO and merchant vessels using active radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

. RORSATs were launched under the cover name of Cosmos
Cosmos (satellite)
Kosmos is a designation given to a large number of satellites operated by the Soviet Union and subsequently Russia. Kosmos 1, the first spacecraft to be given a Kosmos designation, was launched on March 16, 1962....

 (Kosmos) satellites.

Because a return signal from a target illuminated by a radar transmitter diminishes as the inverse of the fourth power of the distance, for the surveillance radar to work effectively, RORSATs had to be placed in low earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...

. Had they used large solar panels for power, the orbit would have rapidly decayed due to drag through the upper atmosphere. Further, the satellite would have been useless in the shadow of earth. Hence the majority of RORSATs carried type BES-5 nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

s fuelled by uranium-235
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

. Normally the nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

 cores were ejected into high orbit (a so-called "disposal orbit") at the end of the mission, but there were several failure incidents, some of which resulted in radioactive material re-entering the Earth's atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

.

The Soviet RORSAT program was responsible for orbiting a total of 33 nuclear reactors, 31 of them BES-5 types with a capacity of providing about two kilowatts of power for the radar unit. In addition, in 1987 the Soviets launched two larger TOPAZ nuclear reactor
Topaz Nuclear Reactor
The TOPAZ nuclear reactor is a lightweight nuclear reactor developed for long term space use by the Soviet Union. Cooled by liquid metal, it uses a high-temperature moderator containing hydrogen and highly enriched fuel and produces electricity using a thermionic converter.-Nomenclature:In initial...

s (six kilowatts) in Kosmos satellites (Kosmos 1818 and Kosmos 1867) which were each capable of 6 months of operation. The high orbiting TOPAZ-containing satellites were the major source of orbital contamination for satellites that sensed gamma-rays for astronomical and security purposes, as radiothermal generators (RTGs) do not generate significant gamma radiation as compared with unshielded satellite fission reactors, and all of the BES-5-containing RORSATs orbited too low to cause positron-pollution in the magnetosphere. (The U.S. has launched only a single nuclear reactor into orbit-- the SNAP-10A
SNAP-10A
SNAP-10A was the first and so far only known launch of a U.S. nuclear reactor into space . The Systems Nuclear Auxiliary Power Program reactor was developed under the SNAPSHOT program overseen by the U.S...

 mission in 1965).

The last RORSAT was launched 14 March, 1988. The many problems with the program as well as economic problems in the USSR, apparently caused it to be cancelled by Mikhail Gorbachev
Mikhail Gorbachev
Mikhail Sergeyevich Gorbachev is a former Soviet statesman, having served as General Secretary of the Communist Party of the Soviet Union from 1985 until 1991, and as the last head of state of the USSR, having served from 1988 until its dissolution in 1991...

.

Notable incidents

  • RORSAT launch failure, April 25, 1973. Launch failed and the reactor fell into the Pacific Ocean north of Japan. Radiation was detected by U.S. air sampling airplanes.
  • Cosmos 367 (04564 / 1970-079A), 3 October 1970, failed 110 hours after start, moved to higher orbit.
  • Cosmos 954
    Cosmos 954
    Kosmos 954 was a Soviet Radar Ocean Reconnaissance Satellite with an onboard nuclear reactor. The satellite was launched on September 18, 1977 and was designed to track nuclear submarines...

    . The satellite failed to boost into a nuclear-safe storage orbit as planned. Nuclear materials re-entered the Earth's atmosphere on January 24, 1978 and left a trail of radioactive pollution over an estimated 124,000 km² of Canada
    Canada
    Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

    's Northwest Territories
    Northwest Territories
    The Northwest Territories is a federal territory of Canada.Located in northern Canada, the territory borders Canada's two other territories, Yukon to the west and Nunavut to the east, and three provinces: British Columbia to the southwest, and Alberta and Saskatchewan to the south...

    .

  • Cosmos 1402
    Cosmos 1402
    Kosmos 1402 was a Soviet spy satellite that failed to achieve its correct orbit. Normally, such satellites burn up harmlessly in the Earth's atmosphere upon re-entry. However, Kosmos 1402 was nuclear powered. A similar satellite, Kosmos 954, crashed in Canada's Northwest Territories in...

    . Failed to boost into storage orbit in late 1982. The reactor core was separated from the remainder of the spacecraft and was the last piece of the satellite to return to Earth, landing in the South Atlantic Ocean on February 7, 1983.

  • Cosmos 1900. The primary system failed to eject the reactor core into storage orbit, but the backup managed to push it into an orbit 80 km (49.7 mi) below its intended altitude.

Other concerns

Although most nuclear cores were successfully ejected into high orbits, their orbits will still decay after several hundred years.

RORSATs were a major source of space debris
Space debris
Space debris, also known as orbital debris, space junk, and space waste, is the collection of objects in orbit around Earth that were created by humans but no longer serve any useful purpose. These objects consist of everything from spent rocket stages and defunct satellites to erosion, explosion...

 in low Earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...

. During 16 reactor core ejections, approximately 128 kg of NaK
NaK
NaK, or sodium-potassium alloy, an alloy, of potassium , and sodium , is usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water and may catch fire when exposed to air, so must be handled with special precautions...

-78 (a fusible alloy
Fusible alloy
A fusible alloy is a metal alloy capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys....

 eutectic of 22 and 78 % w/w
Percentage solution
"Percentage solution" is an ambiguous term which is used to describe a solution with the unit "%". It may refer to:* Mass fraction if mass/mass is meant...

 sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 and potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

 respectively) escaped from the primary coolant systems of the BUK reactors. The smaller droplets have already decayed/reentered, but larger droplets (up to 5.5 cm in diameter) are still in orbit. Since the metal coolant was exposed to neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...

 radiation it contains some radioactive argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...

-39, with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of 269 years. The risk of surface contamination is low, as the droplets will burn up completely in the upper atmosphere on re-entry and the argon, a chemically inert gas, will dissipate. The major risk is impact with operational satellites.

American radar satellites

The United States National Reconnaissance Office
National Reconnaissance Office
The National Reconnaissance Office , located in Chantilly, Virginia, is one of the 16 U.S. intelligence agencies. It designs, builds, and operates the spy satellites of the United States government.-Mission:...

 operates a series of terrain-mapping radar satellites known as Lacrosse
Lacrosse (satellite)
For the 2009 Lunar Impactor Mission designed to crash into the moon, see LCROSS.Lacrosse and Onyx are the code names for the United States' National Reconnaissance Office terrestrial radar imaging reconnaissance satellite. While not officially confirmed by the NRO or anybody in the U.S...

. These do not have a maritime capability, but the U.S. Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

 and Space Command
United States Space Command
The United States Space Command was a Unified Combatant Command of the United States Department of Defense, created in 1985 to help institutionalize the use of outer space by the United States Armed Forces. The Commander in Chief of U.S...

 are developing a satellite constellation known as Space-Based Radar
Space-Based Radar
Space-based radar refers to space-borne radar systems that may have any of a variety of purposes. A number of earth-observing radar satellites, such as RadarSat, have employed synthetic aperture radar to obtain terrain and land-cover information about the Earth.Space-Based Radar is a proposed...

 (or SBR). SBR will fulfill the maritime function of RORSATs, as well as have the ability to track aircraft and potentially ground-based vehicles.

German radar satellites

Germany currently is developing the SAR Lupe radar satellite program, which consists of five identical satellites. Three satellites were launched between December 2006 and November 2007. Others followed in 2008.

Israeli radar satellites

Israel launched TecSar
TecSAR
TecSAR, also known as TechSAR, Polaris and Ofek-8, is an Israeli reconnaissance satellite, equipped with synthetic aperture radar developed by Elta Systems...

, a synthetic aperture radar satellite, in 2008 using an Indian rocket. This is the first small and lightweight radar satellite in operation.

See also

  • SNAP-10A
    SNAP-10A
    SNAP-10A was the first and so far only known launch of a U.S. nuclear reactor into space . The Systems Nuclear Auxiliary Power Program reactor was developed under the SNAPSHOT program overseen by the U.S...

    , an experimental nuclear reactor launched into orbit by the United States

External links

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