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38-479: One of the main tasks of the telescope is the optical support of orbital X-ray observatories: INTEGRAL observatory and Spektr-RG . 36°49′30″N 30°20′10″E  /  36.82500°N 30.33611°E  / 36.82500; 30.33611 This article about a specific observatory, telescope or astronomical instrument is a stub . You can help Misplaced Pages by expanding it . INTEGRAL The INTErnational Gamma-Ray Astrophysics Laboratory ( INTEGRAL )

76-431: A fast radio burst. By 2018, approximately 5,600 scientific papers had been published, averaging one every 29 hours since the launch. Reaction wheel A reaction wheel ( RW ) is an electric motor attached to a flywheel , which, when its rotation speed is changed, causes a counter-rotation proportionately through conservation of angular momentum . A reaction wheel can rotate only around its center of mass ; it

114-416: A higher altitude. The failure of one or more reaction wheels can cause a spacecraft to lose its ability to maintain attitude (orientation) and thus potentially cause a mission failure. Recent studies conclude that these failures can be correlated with space weather effects. These events probably caused failures by inducing electrostatic discharge in the steel ball bearings of Ithaco wheels, compromising

152-419: A mechanical system of Stirling coolers to about 80K. IBIS and SPI use active detectors to detect and veto charged particles that lead to background radiation. The SPI ACS (AntiCoincidence Shield) consists of a BGO scintillator blocks surrounding the camera and aperture, detecting all charged particles, and photons exceeding an energy of about 75 keV, that would hit the instrument from directions different from

190-844: A proprietary period of up to one year. INTEGRAL was launched from the Russian Baikonur spaceport, in Kazakhstan . The 2002 launch aboard a Proton -DM2 rocket achieved a 3-day elliptical orbit with an apogee of nearly 160,000 km and a perigee of above 2,000 km, hence mostly beyond radiation belts which would otherwise lead to high instrumental backgrounds from charged-particle activation. The spacecraft and instruments are controlled from ESOC in Darmstadt , Germany, ESA's control centre, through ground stations in Belgium ( Redu ) and California ( Goldstone ). 2015: Fuel usage

228-467: A radiation monitor, INTEGRAL Radiation Environment Monitor ( IREM ), to note the orbital background for calibration purposes. IREM has an electron and a proton channel, though radiation up to cosmic rays can be sensed. Should the background exceed a preset threshold, IREM can shut down the instruments. INTEGRAL contributes to multi-messenger astronomy, detecting gamma rays from the first merger of two neutron stars observed in gravitational waves, and from

266-419: A reaction wheel failed on Swift in 17 years. Swift resumed science operations on February 17, 2022. A control moment gyroscope (CMG) is a related but different type of attitude actuator, generally consisting of a momentum wheel mounted in a one-axis or two-axis gimbal . When mounted to a rigid spacecraft, applying a constant torque to the wheel using one of the gimbal motors causes the spacecraft to develop

304-435: A spacecraft's attitude . For this reason, reaction wheels are often used to aim spacecraft carrying cameras or telescopes. Over time, reaction wheels may build up enough stored momentum to exceed the maximum speed of the wheel, called saturation. However, slowing down the wheels imparts a torque causing undesired rotation. Designers therefore supplement reaction wheel systems with other attitude control mechanisms to cancel out

342-420: A telescope pointed at a star. A reaction wheel is sometimes operated at a constant (or near-constant) rotation speed, to provide a satellite with a large amount of stored angular momentum . Doing so alters the spacecraft's rotational dynamics so that disturbance torques perpendicular to one axis of the satellite (the axis parallel to the wheel's spin axis) do not result directly in spacecraft angular motion about

380-492: A three axis configuration. Changes in speed (in either direction) are controlled electronically by computer. The strength of the materials used in a reaction wheel determine the speed at which the wheel would come apart, and therefore how much angular momentum it can store. Since the reaction wheel is a small fraction of the spacecraft's total mass, easily controlled, temporary changes in its speed result in small changes in angle. The wheels therefore permit very precise changes in

418-692: Is SPI , the SPectrometer of INTEGRAL. It was conceived and assembled by the French Space Agency CNES , with PI institutes in Toulouse/France and Garching/Germany. It observes radiation between 20 keV and 8 MeV . SPI has a coded mask of hexagonal tungsten tiles, above a detector plane of 19 germanium crystals (also packed hexagonally). The high energy resolution of 2 keV at 1 MeV is capable to resolve all candidate gamma-ray lines. The Ge crystals are actively cooled with

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456-1126: Is a space telescope for observing gamma rays of energies up to 8 MeV. It was launched by the European Space Agency (ESA) into Earth orbit in 2002, and is designed to provide imaging and spectroscopy of cosmic sources. In the MeV energy range, it is the most sensitive gamma ray observatory in space. It is sensitive to higher energy photons than X-ray instruments such as NuSTAR , the Neil Gehrels Swift Observatory , XMM-Newton , and lower than other gamma-ray instruments such Fermi and HESS . Photons in INTEGRAL's energy range are emitted by relativistic and supra-thermal particles in violent sources, radioactivity from unstable isotopes produced during nucleosynthesis , X-ray binaries , and astronomical transients of all types, including gamma-ray bursts . The spacecraft's instruments have very wide fields of view , which

494-574: Is achieved by coded masks casting a shadowgram onto pixelised cameras; the tungsten masks were provided by the University of Valencia, Spain. The INTEGRAL imager, IBIS (Imager on-Board the INTEGRAL Satellite) observes from 15 keV (hard X-rays) to 10 MeV (gamma rays). Angular resolution is 12 arcmin, enabling a bright source to be located to better than 1 arcmin. A 95 x 95 mask of rectangular tungsten tiles sits 3.2 meters above

532-458: Is much lower than predictions. INTEGRAL has far exceeded its 2+3-year planned lifetime, and is set to enter Earth atmosphere in 2029 as a definite end of the mission. Its orbit was adjusted in Jan/Feb 2015 to cause such a safe (southern) reentry (due to lunar/solar perturbations, predicted for 2029), using half the remaining fuel then. In July 2020 INTEGRAL put itself in safe-mode, and it seemed

570-424: Is not capable of moving from one place to another ( translational force ). Reaction wheels are used primarily by spacecraft for three-axis attitude control , and do not require rockets or external applicators of torque , which reduces the mass fraction needed for fuel. They provide a high pointing accuracy, and are particularly useful when the spacecraft must be rotated by very small amounts, such as keeping

608-501: Is particularly useful for detecting gamma-ray emission from transient sources as they can continuously monitor large parts of the sky. INTEGRAL is an ESA mission with additional contributions from European member states including Italy, France, Germany, and Spain. Cooperation partners are the Russian Space Agency with IKI (military CP Command Punkt KW) and NASA . As of June 2023, INTEGRAL continues to operate despite

646-517: Is via a star tracker , multiple Sun sensors (ESM), and multiple momentum wheels . The dual solar arrays, spanning 16 meters when deployed and producing 2.4 kW at beginning of life (BoL), are backed up by dual nickel-cadmium battery sets. The instrument structure ("payload module") is also composite. A rigid base supports the detector assemblies, and an H-shaped structure holds the coded masks approximately 4 meters above their detectors. The payload module can be built and tested independently from

684-616: The aperture. A thin layer of plastic scintillator behind the tungsten tiles serves as additional charged-particle detector within the aperture. The large effective area of the ACS turned out to be useful as an instrument in its own right. Its all-sky coverage and sensitivity make it a natural gamma-ray burst detector, and a valued component of the IPN (InterPlanetary Network). Dual JEM-X units provide additional information on sources at soft and hard X-rays, from 3 to 35 keV. Aside from broadening

722-523: The detectors. The detector system contains a forward plane of 128 x 128 Cadmium-Telluride tiles (ISGRI- Integral Soft Gamma-Ray Imager), backed by a 64 x 64 plane of Caesium-Iodide tiles (PICsIT- Pixellated Caesium-Iodide Telescope). ISGRI is sensitive up to 1 MeV, while PICsIT extends to 10 MeV. Both are surrounded by passive shields of tungsten and lead. IBIS was provided by PI institutes in Rome/Italy and Paris/France. The spectrometer aboard INTEGRAL

760-403: The effects of vacuum on lubricants . The lubricating compound was found to be in 'excellent condition'. In 2002, during Servicing Mission 3B ( STS-109 ), astronauts from the shuttle Columbia replaced another reaction wheel. Neither of these wheels had failed and Hubble was designed with four redundant wheels, and maintained pointing ability so long as three were functional. In 2004, during

798-648: The end of 2024, which will be followed by a two-year post-operations phase and further monitoring of the spacecraft until its estimated reentry in February 2029. Also in March 2023, a new software based safe mode was tested that would use reaction wheels (rather than the failed thrusters). The spacecraft body ("service module") is a copy of the XMM-Newton body. This saved development costs and simplified integration with infrastructure and ground facilities. An adapter

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836-474: The failed reaction wheels, while the Kepler team considered alternative uses for Kepler that do not require the extreme accuracy in its orientation needed by the original mission. On May 16, 2014, NASA extended the Kepler mission to a new mission named K2 , which uses Kepler differently, but allows it to continue searching for exoplanets . On October 30, 2018, NASA announced the end of the Kepler mission after it

874-408: The loss of its thrusters through the use of its reaction wheels and solar radiation pressure . Radiation more energetic than optical light, such as ultraviolet, X-rays , and gamma rays , cannot penetrate Earth's atmosphere, and direct observations must be made from space. INTEGRAL is an observatory, scientists can propose for observing time of their desired target regions, data are public after

912-659: The mission of the Hayabusa spacecraft, an X-axis reaction wheel failed. The Y-axis wheel failed in 2005, causing the craft to rely on chemical thrusters to maintain attitude control. From July 2012 to May 11, 2013, two out of the four reaction wheels in the Kepler space telescope failed. This loss severely affected Kepler 's ability to maintain a sufficiently precise orientation to continue its original mission. On August 15, 2013, engineers concluded that Kepler's reaction wheels cannot be recovered and that planet-searching using

950-419: The momentum wheel's axis to be parallel to the orbit-normal vector, this satellite is in a "pitch momentum bias" configuration. For three-axis control, reaction wheels must be mounted along at least three directions, with extra wheels providing redundancy to the attitude control system. A redundant mounting configuration could consist of four wheels along tetrahedral axes, or a spare wheel carried in addition to

988-449: The next most efficient practice is to use high-efficiency attitude jets such as ion thrusters . Beresheet was launched on a Falcon 9 rocket on 22 February 2019 1:45 UTC, with the goal of landing on the Moon . Beresheet uses the low-energy transfer technique to save fuel. Since its fourth maneuver in its elliptical orbit, to prevent shakes when the amount of liquid fuel ran low, there

1026-480: The reaction wheels during the three-year journey to Ceres. The loss of the reaction wheels limited the camera observations on the approach to Ceres. On the evening of Tuesday, January 18, 2022, a possible failure of one of the Swift Observatory 's reaction wheels caused the mission control team to power off the suspected wheel, putting the observatory in safe mode as a precaution. This was the first time

1064-422: The same axis as the disturbance torque; instead, they result in (generally smaller) angular motion ( precession ) of that spacecraft axis about a perpendicular axis. This has the effect of tending to stabilize that spacecraft axis to point in a nearly-fixed direction, allowing for a less-complicated attitude control system. Satellites using this "momentum-bias" stabilization approach include SCISAT-1 ; by orienting

1102-461: The service module, reducing cost. Alenia Spazio (now Thales Alenia Space Italia) was the spacecraft prime contractor. Four instruments with large fields-of-view are co-aligned on this platform, to study targets across such a wide energy range of almost two orders of magnitude in energy (other astronomy instruments in X-rays or optical cover much smaller ranges of factors of a few at most). Imaging

1140-569: The smoothness of the mechanism. Two servicing missions to the Hubble Space Telescope have replaced a reaction wheel. In February 1997, the Second Servicing Mission ( STS-82 ) replaced one after 'electrical anomalies', rather than any mechanical problem. Study of the returned mechanism provided a rare opportunity to study equipment that had undergone long-term service (seven years) in space, particularly for

1178-484: The spectral coverage, imaging is more precise due to the shorter wavelength. Detectors are gas scintillators ( xenon plus methane ) in a microstrip layout, below a mask of hexagonal tiles. INTEGRAL includes an Optical Monitor ( OMC ) instrument, sensitive from 500 to 580 nm . It acts as both a framing aid, and can note the activity and state of some brighter targets, e.g. it had been useful to monitor supernova light over months from SN2014J. The spacecraft also includes

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1216-447: The thrusters had failed. Since then alternative algorithms to slew and unload the reaction wheels have been developed and tested. In September 2021 a single event upset triggered a sequence of events that put INTEGRAL into an uncontrolled tumbling state, considered to be a 'mission critical anomaly'. The operations team used the reaction wheels to recover attitude control. In March 2023, INTEGRAL science operations were extended to

1254-450: The torque caused by "desaturating" the reaction wheels. Typically designers use " reaction control systems "; arrays of small chemical rocket engines that fire as the wheels slow down to counter the torque the wheels are imparting on the spacecraft as they slow down. More fuel efficient methods for reaction wheel desaturation have been developed over time. By reducing the amount of fuel the spacecraft needs to be launched with, they increase

1292-446: The transit method (measuring changes in star brightness caused by orbiting planets) could not continue. Although the failed reaction wheels still function, they are experiencing friction exceeding acceptable levels, and consequently hindering the ability of the telescope to properly orient itself. The Kepler telescope was returned to its "point rest state", a stable configuration that uses small amounts of thruster fuel to compensate for

1330-470: The useful payload that can be delivered to orbit. These methods include magnetorquers (better known as torque rods), which transfer angular momentum to the Earth through its planetary magnetic field requiring only electrical power and no fuel. They are however limited to areas of space with a sufficiently large magnetic field (such as in low Earth orbit). In the absence of a sufficiently strong magnetic field,

1368-414: Was a need to use a reaction wheel. The James Webb Space Telescope has six reaction wheels built by Rockwell Collins Deutschland. LightSail 2 was launched on 25 June 2019, focused around the concept of a solar sail . LightSail 2 uses a reaction wheel system to change orientation by very small amounts, allowing it to receive different amounts of momentum from the light across the sail, resulting in

1406-517: Was determined that the fuel supply had been exhausted. The NASA space probe Dawn had excess friction in one reaction wheel in June 2010. It was originally scheduled to depart Vesta and begin its two-and-a-half-year journey to Ceres on August 26, 2012; however, a problem with another of the spacecraft's reaction wheels forced Dawn to briefly delay its departure from Vesta's gravity until September 5, 2012, and it planned to use thruster jets instead of

1444-486: Was necessary to mate with the different launch vehicle, though. However, the denser instruments used for gamma rays and hard X-rays make INTEGRAL the heaviest scientific payload ever flown by ESA. The body is constructed largely of composites. Propulsion is by a hydrazine monopropellant system, containing 544 kg of fuel in four exposed tanks. The titanium tanks were charged with gas to 24 bar (2.4  MPa ) at 30 °C, and have tank diaphragms. Attitude control

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