Granat
Encyclopedia
The International Astrophysical Observatory "GRANAT" (usually known as Granat; ), was a Soviet
(later Russia
n) space observatory
developed in collaboration with France
, Denmark
and Bulgaria
. It was launched on 1 December 1989 aboard a Proton rocket and placed in a highly eccentric
four-day orbit
, of which three were devoted to observations. It operated for almost nine years.
In September 1994, after nearly five years of directed observations, the gas supply for its attitude control
was exhausted and the observatory was placed in a non-directed survey mode. Transmissions finally ceased on 27 November 1998.
With seven different instruments on board, Granat was designed to observe the universe at energies ranging from X-ray
to gamma ray
. Its main instrument, SIGMA, was capable of imaging both hard X-ray and soft gamma-ray sources. The PHEBUS instrument was meant to study gamma-ray bursts and other transient X-Ray sources. Other experiments such as ART-P were intended to image X-Ray sources in the 35 to 100 keV range. One instrument, WATCH, was designed to monitor the sky continuously and alert the other instruments to new or interesting X-Ray sources. The ART-S spectrometer covered the X-ray energy range while the KONUS-B and TOURNESOL experiments covered both the X-ray and gamma ray spectrum.
-class spacecraft produced by the Lavochkin Scientific Production Association
. It was similar to the Astron
observatory which was functional from 1983 to 1989; for this reason, the spacecraft was originally known as the Astron 2. It weighed 4.4 metric ton
s and carried almost 2.3 metric tons of international scientific instrumentation. Granat stood 6.5 m tall and had a total span of 8.5 m across its solar arrays. The power made available to the scientific instruments was approximately 400 W
.
The spacecraft was launched on 1 December 1989 aboard a Proton rocket from the Baikonur Cosmodrome
in Kazakh SSR
. It was placed in a highly eccentric
98-hour orbit with an initial apogee/perigee
of 200,000 km/2,000 km respectively and an inclination of 51.5 degrees. This meant that solar and lunar perturbations would significantly increase the orbits inclination while reducing its eccentricity, such that the orbit had become near-circular by the time Granat completed its directed observations in September 1994. (By 1991, the perigee had increased to 20,000 km; by September 1994, the apogee/perigee was 59,025 km144,550 km at an inclination of 86.7 degrees.)
Three days out of the four-day orbit were devoted to observations. After over nine years in orbit, the observatory finally reentered
the Earth's atmosphere on May 25, 1999.
was a collaboration between CESR
(Toulouse) and CEA
(Saclay). It covered the energy range 35–1300 keV, with an effective area of 800 cm2 and a maximum sensitivity field of view of ~5°×5°. The maximum angular resolution
was 15 arcmin. The energy resolution was 8% at 511 keV. Its imaging capabilities were derived from the association of a coded mask and a position sensitive detector based on the Anger camera principle.
The ART-P X-ray telescope was the responsibility of the IKI
in Moscow
. The instrument covered the energy range 4 to 60 keV for imaging and 4 to 100 keV for spectroscopy and timing. There were four identical modules of the ART-P telescope, each consisting of a position sensitive multi-wire proportional counter (MWPC)
together with a URA coded mask. Each module had an effective area of approximately 600 cm², producing a field of view
of 1.8° by 1.8°. The angular resolution was 5 arcmin
; temporal and energy resolutions were 3.9 ms
and 22% at 6 keV, respectively. The instrument achieved a sensitivity of 0.001 of the Crab nebula
source (= 1 "mCrab") in an eight-hour exposure. The maximum time resolution was 4 ms.
MWPCs, making an effective area of 2,400 cm² at 10 keV and 800 cm² at 100 keV. The time resolution was 200 microsecond
s.
to record high energy transient events in the range 100 keV to 100 MeV. It consisted of two independent detectors and their associated electronics
. Each detector consisted of a bismuth germinate (BGO) crystal 78 mm in diameter
by 120 mm thick, surrounded by a plastic anti-coincidence jacket. The two detectors were arranged on the spacecraft so as to observe 4π
steradian
s. The burst mode was triggered when the count rate in the 0.1 to 1.5 MeV energy range exceeded the background level by 8 sigma
in either 0.25 or 1.0 seconds. There were 116 energy channels.
, were in operation on the Granat observatory. The instruments could localize bright sources in the 6 to 180 keV range to within 0.5° using a Rotation Modulation Collimator
. Taken together, the instruments' three fields of view covered approximately 75% of the sky. The energy resolution was 30% FWHM
at 60 keV. During quiet periods, count rates in two energy bands (6 to 15 and 15 to 180 keV) were accumulated for 4, 8, or 16 seconds, depending on onboard computer memory availability. During a burst or transient event, count rates were accumulated with a time resolution
of 1 second per 36 energy channels.
in St. Petersburg
, consisted of seven detectors distributed around the spacecraft that responded to photon
s of 10 keV to 8 MeV energy. They consisted of NaI
(Tl) scintillator crystals 200 mm in diameter by 50 mm thick behind a Be
entrance window. The side surfaces were protected by a 5 mm thick lead layer. The burst detection threshold was 500 to 50 microjoule
s per square meter (5 × 10 to 5 × 10 erg/cm²), depending on the burst spectrum and rise time
. Spectra
were taken in two 31-channel pulse height analyzer
s (PHAs), of which the first eight were measured with 1/16 s time resolution and the remaining with variable time resolutions depending on the count rate. The range of resolutions covered 0.25 to 8 s.
The KONUS-B instrument operated from 11 December 1989 until 20 February 1990. Over that period, the "on" time for the experiment was 27 days. Some 60 solar flares and 19 cosmic gamma-ray bursts were detected.
s. The proportional counters detected photons between 2 keV and 20 MeV in a 6° by 6° field of view. The visible detectors had a field of view of 5° by 5°. The instrument was designed to look for optical counterparts of high-energy burst sources, as well as performing spectral analysis
of the high-energy events.
, broad-band observations of black hole
candidates, and X-ray novae
. After 1994, the observatory was switched to survey mode and carried out a sensitive all-sky survey in the 40 to 200 keV energy band.
Some of the highlights included:
, two problems arose for the project. The first was geopolitical in nature: the main spacecraft control center was located at the Yevpatoria facility in the Crimea
region. This control center was significant in the Soviet space program, being one of only two in the country equipped with a 70 m dish antenna. With the breakup of the Union, the Crimea region, although mostly populated by ethnic Russians, found itself part of the newly independent Ukraine
and the center was put under Ukrainian national control, prompting new political hurdles.
The main and most urgent problem, however, was in finding funds to support the continued operation of the spacecraft amid the spending crunch in post-Soviet Russia. The French space agency
, having already contributed significantly to the project (both scientifically and financially), took upon itself to fund the continuing operations directly.
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....
(later Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n) space observatory
Space observatory
A space observatory is any instrument in outer space which is used for observation of distant planets, galaxies, and other outer space objects...
developed in collaboration with France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
and Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...
. It was launched on 1 December 1989 aboard a Proton rocket and placed in a highly eccentric
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
four-day orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
, of which three were devoted to observations. It operated for almost nine years.
In September 1994, after nearly five years of directed observations, the gas supply for its attitude control
Attitude dynamics and control
Spacecraft flight dynamics is the science of space vehicle performance, stability, and control. It requires analysis of the six degrees of freedom of the vehicle's flight, which are similar to those of aircraft: translation in three dimensional axes; and its orientation about the vehicle's center...
was exhausted and the observatory was placed in a non-directed survey mode. Transmissions finally ceased on 27 November 1998.
With seven different instruments on board, Granat was designed to observe the universe at energies ranging from X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
to gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
. Its main instrument, SIGMA, was capable of imaging both hard X-ray and soft gamma-ray sources. The PHEBUS instrument was meant to study gamma-ray bursts and other transient X-Ray sources. Other experiments such as ART-P were intended to image X-Ray sources in the 35 to 100 keV range. One instrument, WATCH, was designed to monitor the sky continuously and alert the other instruments to new or interesting X-Ray sources. The ART-S spectrometer covered the X-ray energy range while the KONUS-B and TOURNESOL experiments covered both the X-ray and gamma ray spectrum.
Spacecraft
Granat was a three-axis-stabilized spacecraft and the last of the VeneraVenera
The Venera series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus...
-class spacecraft produced by the Lavochkin Scientific Production Association
Lavochkin
NPO Lavochkin is a Russian aerospace company. It is a major player in the Russian space program, being the developer and manufacturer of the Fregat upper stage, as well as interplanetary probes such as Phobos Grunt...
. It was similar to the Astron
Astron (spacecraft)
Astron was a Soviet spacecraft launched on 23 March 1983 at 12:45:06 UTC, using Proton launcher, which was designed to fulfill an astrophysics mission. It was based on the Venera spacecraft design and was operational for six years as the largest ultraviolet space telescope during its lifetime...
observatory which was functional from 1983 to 1989; for this reason, the spacecraft was originally known as the Astron 2. It weighed 4.4 metric ton
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s and carried almost 2.3 metric tons of international scientific instrumentation. Granat stood 6.5 m tall and had a total span of 8.5 m across its solar arrays. The power made available to the scientific instruments was approximately 400 W
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
.
Launch and orbit
Baikonur Cosmodrome
The Baikonur Cosmodrome , also called Tyuratam, is the world's first and largest operational space launch facility. It is located in the desert steppe of Kazakhstan, about east of the Aral Sea, north of the Syr Darya river, near Tyuratam railway station, at 90 meters above sea level...
in Kazakh SSR
Kazakh SSR
The Kazakh Soviet Socialist Republic , also known as the Kazakh SSR for short, was one of republics that made up the Soviet Union.At in area, it was the second largest constituent republic in the USSR, after the Russian SFSR. Its capital was Alma-Ata . Today it is the independent state of...
. It was placed in a highly eccentric
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
98-hour orbit with an initial apogee/perigee
Perigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...
of 200,000 km/2,000 km respectively and an inclination of 51.5 degrees. This meant that solar and lunar perturbations would significantly increase the orbits inclination while reducing its eccentricity, such that the orbit had become near-circular by the time Granat completed its directed observations in September 1994. (By 1991, the perigee had increased to 20,000 km; by September 1994, the apogee/perigee was 59,025 km144,550 km at an inclination of 86.7 degrees.)
Three days out of the four-day orbit were devoted to observations. After over nine years in orbit, the observatory finally reentered
Atmospheric reentry
Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...
the Earth's atmosphere on May 25, 1999.
| Date | Perigee Perigee Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"... (km) | Apogee (km) | Arg.perigee (deg) | Inc. Inclination Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit... (deg) | Long.asc.node Longitude of the ascending node The longitude of the ascending node is one of the orbital elements used to specify the orbit of an object in space. It is the angle from a reference direction, called the origin of longitude, to the direction of the ascending node, measured in a reference plane... (deg) |
|---|---|---|---|---|---|
| December 1, 1989 | 285 | 51.5 | 20.0 | ||
| December 1, 1991 | 311.9 | 82.6 | 320.3 | ||
| December 1, 1994 | 343.0 | 86.5 | 306.9 | ||
| December 1, 1996 | 9.6 | 93.4 | 302.2 |
SIGMA
The hard X-ray and low-energy gamma-ray SIGMA telescopeTelescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
was a collaboration between CESR
Centre d'Etude Spatiale des Rayonnements
The Centre d'Etude Spatiale des Rayonnements is a French laboratory of space astrophysics. It is located in Toulouse. The centers main areas of investigation are: space plasmas, planetology, the high energy universe, the cold Universe....
(Toulouse) and CEA
Commissariat à l'Énergie Atomique
The Commissariat à l'énergie atomique et aux énergies alternatives or CEA, is a French “public establishment related to industrial and commercial activities” whose mission is to develop all applications of nuclear power, both civilian and military...
(Saclay). It covered the energy range 35–1300 keV, with an effective area of 800 cm2 and a maximum sensitivity field of view of ~5°×5°. The maximum angular resolution
Angular resolution
Angular resolution, or spatial resolution, describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object...
was 15 arcmin. The energy resolution was 8% at 511 keV. Its imaging capabilities were derived from the association of a coded mask and a position sensitive detector based on the Anger camera principle.
ART-P
Russian Space Research Institute
The Russian Space Research Institute is the leading organization of the Russian Academy of Sciences on space exploration to benefit fundamental science....
in Moscow
Moscow
Moscow is the capital, the most populous city, and the most populous federal subject of Russia. The city is a major political, economic, cultural, scientific, religious, financial, educational, and transportation centre of Russia and the continent...
. The instrument covered the energy range 4 to 60 keV for imaging and 4 to 100 keV for spectroscopy and timing. There were four identical modules of the ART-P telescope, each consisting of a position sensitive multi-wire proportional counter (MWPC)
Wire chamber
A multi-wire chamber is a detector for particles of ionizing radiation which is an advancement of the concept of the Geiger counter and the proportional counter....
together with a URA coded mask. Each module had an effective area of approximately 600 cm², producing a field of view
Field of view
The field of view is the extent of the observable world that is seen at any given moment....
of 1.8° by 1.8°. The angular resolution was 5 arcmin
Minute of arc
A minute of arc, arcminute, or minute of angle , is a unit of angular measurement equal to one sixtieth of one degree. In turn, a second of arc or arcsecond is one sixtieth of one minute of arc....
; temporal and energy resolutions were 3.9 ms
Millisecond
A millisecond is a thousandth of a second.10 milliseconds are called a centisecond....
and 22% at 6 keV, respectively. The instrument achieved a sensitivity of 0.001 of the Crab nebula
Crab Nebula
The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus...
source (= 1 "mCrab") in an eight-hour exposure. The maximum time resolution was 4 ms.
ART-S
The ART-S X-ray spectrometer, also built by the IKI, covered the energy range 3 to 100 keV. Its field of view was 2° by 2°. The instrument consisted of four detectors based on spectroscopicSpectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...
MWPCs, making an effective area of 2,400 cm² at 10 keV and 800 cm² at 100 keV. The time resolution was 200 microsecond
Microsecond
A microsecond is an SI unit of time equal to one millionth of a second. Its symbol is µs.A microsecond is equal to 1000 nanoseconds or 1/1000 millisecond...
s.
PHEBUS
The PHEBUS experiment was designed by CESR (Toulouse)Centre d'Etude Spatiale des Rayonnements
The Centre d'Etude Spatiale des Rayonnements is a French laboratory of space astrophysics. It is located in Toulouse. The centers main areas of investigation are: space plasmas, planetology, the high energy universe, the cold Universe....
to record high energy transient events in the range 100 keV to 100 MeV. It consisted of two independent detectors and their associated electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
. Each detector consisted of a bismuth germinate (BGO) crystal 78 mm in diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
by 120 mm thick, surrounded by a plastic anti-coincidence jacket. The two detectors were arranged on the spacecraft so as to observe 4π
Pi
' is a mathematical constant that is the ratio of any circle's circumference to its diameter. is approximately equal to 3.14. Many formulae in mathematics, science, and engineering involve , which makes it one of the most important mathematical constants...
steradian
Steradian
The steradian is the SI unit of solid angle. It is used to describe two-dimensional angular spans in three-dimensional space, analogous to the way in which the radian describes angles in a plane...
s. The burst mode was triggered when the count rate in the 0.1 to 1.5 MeV energy range exceeded the background level by 8 sigma
Sigma
Sigma is the eighteenth letter of the Greek alphabet, and carries the 'S' sound. In the system of Greek numerals it has a value of 200. When used at the end of a word, and the word is not all upper case, the final form is used, e.g...
in either 0.25 or 1.0 seconds. There were 116 energy channels.
WATCH
Starting in January 1990, four WATCH instruments, designed by the Danish Space Research InstituteDanish Space Research Institute
Danish Space Research Institute was the space agency of Denmark from 1966 to 2005. It was a Danish sector research institute formed in 1966 under the Danish Ministry for Education and Research, later the Danish Ministry of Science Technology and Innovation...
, were in operation on the Granat observatory. The instruments could localize bright sources in the 6 to 180 keV range to within 0.5° using a Rotation Modulation Collimator
Collimator
A collimator is a device that narrows a beam of particles or waves. To "narrow" can mean either to cause the directions of motion to become more aligned in a specific direction or to cause the spatial cross section of the beam to become smaller.- Optical collimators :In optics, a collimator may...
. Taken together, the instruments' three fields of view covered approximately 75% of the sky. The energy resolution was 30% FWHM
Full width at half maximum
Full width at half maximum is an expression of the extent of a function, given by the difference between the two extreme values of the independent variable at which the dependent variable is equal to half of its maximum value....
at 60 keV. During quiet periods, count rates in two energy bands (6 to 15 and 15 to 180 keV) were accumulated for 4, 8, or 16 seconds, depending on onboard computer memory availability. During a burst or transient event, count rates were accumulated with a time resolution
Temporal resolution
Temporal resolution refers to the precision of a measurement with respect to time. Often there is a tradeoff between temporal resolution of a measurement and its spatial resolution. This trade-off can be attributed to the finite speed of light and the fact that it takes a certain period of time...
of 1 second per 36 energy channels.
KONUS-B
The KONUS-B instrument, designed by the Ioffe Physico-Technical InstituteIoffe Physico-Technical Institute
Ioffe Physical-Technical Institute of the Russian Academy of Sciences is one of Russia's largest research centers specialized in physics and technology. The institute was established in 1918 in Petrograd and run for several decades by Abram Fedorovich Ioffe...
in St. Petersburg
Saint Petersburg
Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...
, consisted of seven detectors distributed around the spacecraft that responded to photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s of 10 keV to 8 MeV energy. They consisted of NaI
Sodium iodide
Sodium iodide is a white, crystalline salt with chemical formula NaI used in radiation detection, treatment of iodine deficiency, and as a reactant in the Finkelstein reaction.-Uses:Sodium iodide is commonly used to treat and prevent iodine deficiency....
(Tl) scintillator crystals 200 mm in diameter by 50 mm thick behind a Be
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
entrance window. The side surfaces were protected by a 5 mm thick lead layer. The burst detection threshold was 500 to 50 microjoule
Microjoule
Microjoule is a team that builds ultra-efficient vehicles. It is composed of students and advisors at Lycée La Joliverie in St Sébastien sur Loire, France. The team has broken the world record for most efficient gasoline-powered vehicle three times:...
s per square meter (5 × 10 to 5 × 10 erg/cm²), depending on the burst spectrum and rise time
Rise time
In electronics, when describing a voltage or current step function, rise time refers to the time required for a signal to change from a specified low value to a specified high value...
. Spectra
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
were taken in two 31-channel pulse height analyzer
Pulse height analyzer
A Pulse Height Analyzer is an instrument used in nuclear and elementary particle physics research which accepts electronic pulses of varying heights from particle and event detectors, digitizes the pulse heights, and saves the number of pulses of each height in registers or channels for later...
s (PHAs), of which the first eight were measured with 1/16 s time resolution and the remaining with variable time resolutions depending on the count rate. The range of resolutions covered 0.25 to 8 s.
The KONUS-B instrument operated from 11 December 1989 until 20 February 1990. Over that period, the "on" time for the experiment was 27 days. Some 60 solar flares and 19 cosmic gamma-ray bursts were detected.
TOURNESOL
The French TOURNESOL instrument consisted of four proportional counters and two optical detectorPhotodetector
Photosensors or photodetectors are sensors of light or other electromagnetic energy. There are several varieties:*Active pixel sensors are image sensors consisting of an integrated circuit that contains an array of pixel sensors, each pixel containing a both a light sensor and an active amplifier...
s. The proportional counters detected photons between 2 keV and 20 MeV in a 6° by 6° field of view. The visible detectors had a field of view of 5° by 5°. The instrument was designed to look for optical counterparts of high-energy burst sources, as well as performing spectral analysis
Spectral analysis
Spectral analysis or Spectrum analysis may refer to:* Spectrum analysis in chemistry and physics, a method of analyzing the chemical properties of matter from bands in their visible spectrum...
of the high-energy events.
Science results
Over the initial four years of directed observations, Granat observed many galactic and extra-galactic X-ray sources with emphasis on the deep imaging and spectroscopy of the galactic centerGalactic Center
The Galactic Center is the rotational center of the Milky Way galaxy. It is located at a distance of 8.33±0.35 kpc from the Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest...
, broad-band observations of black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
candidates, and X-ray novae
Soft X-ray transient
Soft X-ray transients are composed of some type of compact object and some type of "normal", low mass star . These objects show changing levels of low-energy, or "soft", X-ray emission, probably produced somehow by variable transfer of mass from the normal star to the compact object...
. After 1994, the observatory was switched to survey mode and carried out a sensitive all-sky survey in the 40 to 200 keV energy band.
Some of the highlights included:
- A very deep imaging (more than 5 million seconds duration) of the galactic center region.
- Discovery of electronElectronThe electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
-positronPositronThe positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...
annihilation lines from the galactic microquasar 1E1740-294 and the X-ray Nova MuscaeGRS 1124-683The gamma-ray and X-ray source GRS 1124-683, discovered by the Granat mission and Ginga, is a system containing a black hole candidate. The system also goes by the name X-ray Nova Muscae 1991 or GU Mus...
. - Study of spectra and time variability of black hole candidates.
- Across eight years of observations, Granat discovered some twenty new X-ray sources, i.e. candidate black holeBlack holeA black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
s and neutron starNeutron starA neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
s. Consequently, their designations begin with "GRS" meaning "GRANAT source". Examples are GRS 1915+105GRS 1915+105GRS 1915+105 or V1487 Aquilae is an X-ray binary star system which features a regular star and a black hole. It was discovered on August 15, 1992 by the WATCH all-sky monitor aboard Granat. "GRS" stands for "GRANAT source", "1915" is the right ascension and "105" is declination in units of 0.1...
(the first microquasar discovered in our galaxyMilky WayThe Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
) and GRS 1124-683GRS 1124-683The gamma-ray and X-ray source GRS 1124-683, discovered by the Granat mission and Ginga, is a system containing a black hole candidate. The system also goes by the name X-ray Nova Muscae 1991 or GU Mus...
.
Impact of the dissolution of the Soviet Union
After the end of the Soviet UnionSoviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
, two problems arose for the project. The first was geopolitical in nature: the main spacecraft control center was located at the Yevpatoria facility in the Crimea
Crimea
Crimea , or the Autonomous Republic of Crimea , is a sub-national unit, an autonomous republic, of Ukraine. It is located on the northern coast of the Black Sea, occupying a peninsula of the same name...
region. This control center was significant in the Soviet space program, being one of only two in the country equipped with a 70 m dish antenna. With the breakup of the Union, the Crimea region, although mostly populated by ethnic Russians, found itself part of the newly independent Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
and the center was put under Ukrainian national control, prompting new political hurdles.
The main and most urgent problem, however, was in finding funds to support the continued operation of the spacecraft amid the spending crunch in post-Soviet Russia. The French space agency
CNES
The is the French government space agency . Established under President Charles de Gaulle in 1961, its headquarters are located in central Paris and it is under the supervision of the French Ministries of Defence and Research...
, having already contributed significantly to the project (both scientifically and financially), took upon itself to fund the continuing operations directly.
See also
- AstronAstron (spacecraft)Astron was a Soviet spacecraft launched on 23 March 1983 at 12:45:06 UTC, using Proton launcher, which was designed to fulfill an astrophysics mission. It was based on the Venera spacecraft design and was operational for six years as the largest ultraviolet space telescope during its lifetime...
, a previous space observatory based on the VeneraVeneraThe Venera series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus...
spacecraft.
External links
- Official GRANAT Observatory homepages: English Russian
- Encyclopedia Astronautica: On This Day
- Global Telescope Network: Granat
- Gunter's Space Page: Granat (Astron 2)