Misplaced Pages

#835164

118-476: The constellation consists of 66 active satellites in orbit, required for global coverage, and additional spare satellites to serve in case of failure. Satellites are placed in low Earth orbit at a height of approximately 781 kilometres (485 mi) and inclination of 86.4°. The nearly polar orbit and communication between satellites via Ka band inter-satellite links provide global service availability (including both poles , oceans and airways), regardless of

236-570: A domino effect known as Kessler syndrome . NASA's Orbital Debris Program tracks over 25,000 objects larger than 10 cm diameter in LEO, while the estimated number between 1 and 10 cm is 500,000, and the number of particles bigger than 1 mm exceeds 100 million. The particles travel at speeds up to 7.8 km/s (28,000 km/h; 17,500 mph), so even a small impact can severely damage a spacecraft. [REDACTED]  This article incorporates public domain material from websites or documents of

354-439: A gimbal , taking weeks instead of months or years. At its peak during the launch campaign in 1997 and 1998, Motorola produced a new satellite every 4.3 days, with the lead-time of a single satellite being 21 days. Over the years a number of Iridium satellites have ceased to work and are no longer in active service, some are partially functional and have remained in orbit whereas others have tumbled out of control or have reentered

472-473: A superconductor at temperatures below 0.14  K (−273.010 °C; −459.418 °F). Iridium's modulus of elasticity is the second-highest among the metals, being surpassed only by osmium . This, together with a high shear modulus and a very low figure for Poisson's ratio (the relationship of longitudinal to lateral strain ), indicate the high degree of stiffness and resistance to deformation that have rendered its fabrication into useful components

590-403: A 20.32 milliseconds period used for simplex messaging to devices such as pagers and to alert Iridium phones of an incoming call, followed by the four upstream slots and four downstream slots. This technique is known as time-division multiplexing . Small guard periods are used between time slots. Regardless of the modulation method being used, communication between mobile units and satellites

708-466: A 666 kilometres (414 mi) storage orbit. These can be boosted to the correct altitude and put into service in case of a satellite failure. After the Iridium company emerged from bankruptcy the new owners decided to launch seven new spares, which would have ensured two spare satellites were available in each plane. As of 2009, not every plane had a spare satellite; however, the satellites can be moved to

826-815: A February 15 statement, Iridium said that SpaceX pushed back the launch of its second batch of Iridium NEXT satellites from mid-April to mid-June 2017. This second launch, which occurred on June 25, 2017, delivered another ten Iridium NEXT satellites to low Earth orbit (LEO) on a SpaceX Falcon 9 rocket. A third launch, which occurred on October 9, 2017, delivered another ten satellites to LEO, as planned. The Iridium NEXT IV mission launched with ten satellites on December 23, 2017. The fifth mission, Iridium NEXT V, launched with ten satellites on March 30, 2018. The sixth launch on May 22, 2018, sent another 5 satellites into LEO. The penultimate Iridium NEXT launch occurred on July 25, 2018, launching another 10 Iridium NEXT satellites. The final ten NEXT satellites launched on January 11, 2019. Of

944-502: A custom backplane network. One processor was dedicated to each cross-link antenna ("HVARC"), and two processors ("SVARC"s) were dedicated to satellite control, one being a spare. Late in the project an extra processor ("SAC") was added to perform resource management and phone call processing. The cellular look down antenna had 48 spot beams arranged as 16 beams in three sectors. The four inter-satellite cross links on each satellite operated at 10 Mbit/s. Optical links could have supported

1062-637: A dedicated band segment from 1,618.725 to 1,626.5 MHz and shares with Globalstar a band segment from 1,617.775 to 1,618.725 MHz. These segments are part of the wider L band , adjacent to the Radio Astronomy Service (RAS) band segment from 1,610.6 to 1,613.8 MHz. The configuration of the Satellite concept was designated as Triangular Fixed, 80 Inch Main Mission Antenna, Light-weight (TF80L). The packaging design of

1180-543: A detailed account of the metal to the Royal Society , stating that he had seen no mention of it in any previous accounts of known minerals. Brownrigg also made note of platinum's extremely high melting point and refractory metal-like behaviour toward borax . Other chemists across Europe soon began studying platinum, including Andreas Sigismund Marggraf , Torbern Bergman , Jöns Jakob Berzelius , William Lewis , and Pierre Macquer . In 1752, Henrik Scheffer published

1298-446: A detailed scientific description of the metal, which he referred to as "white gold", including an account of how he succeeded in fusing platinum ore with the aid of arsenic . Scheffer described platinum as being less pliable than gold, but with similar resistance to corrosion . Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids ) to create soluble salts. They always observed

SECTION 10

#1732801086836

1416-409: A different plane if required. A move can take several weeks and consumes fuel which will shorten the satellite's expected service life. Significant orbital inclination changes are normally very fuel-intensive, but orbital perturbation analysis aids the process. The Earth's equatorial bulge causes the orbital right ascension of the ascending node (RAAN) to precess at a rate that depends mainly on

1534-582: A handheld phone to communicate with them, the Iridium satellites are closer to the Earth, in low Earth orbit , about 781 km (485 mi) above the surface. With an orbital period of about 100 minutes a satellite can only be in view of a phone for about 7 minutes, so the call is automatically "handed off" to another satellite when one passes beyond the local horizon. This requires a large number of satellites, carefully spaced out in polar orbits (see animated image of coverage) to ensure that at least one satellite

1652-416: A matter of great difficulty. Despite these limitations and iridium's high cost, a number of applications have developed where mechanical strength is an essential factor in some of the extremely severe conditions encountered in modern technology. The measured density of iridium is only slightly lower (by about 0.12%) than that of osmium, the densest metal known. Some ambiguity occurred regarding which of

1770-604: A much greater bandwidth and a more aggressive growth path, but microwave cross links were chosen because their bandwidth was more than sufficient for the desired system. Nevertheless, a parallel optical cross link option was carried through a critical design review, and ended when the microwave cross links were shown to support the size, weight and power requirements allocated within the individual satellite's budget. Iridium Satellite LLC stated that their second generation satellites would also use microwave, not optical, inter-satellite communications links. Iridium's cross-links are unique in

1888-573: A new metal. Vauquelin treated the powder alternately with alkali and acids and obtained a volatile new oxide, which he believed to be of this new metal—which he named ptene , from the Greek word πτηνός ptēnós , " winged ". Tennant, who had the advantage of a much greater amount of residue, continued his research and identified the two previously undiscovered elements in the black residue, iridium and osmium . He obtained dark red crystals (probably of Na 2 [IrCl 6 ]· n H 2 O ) by

2006-528: A phenomenon called Iridium flares , whereby the satellite momentarily appeared as one of the brightest objects in the night sky and could be seen even during daylight. Newer Iridium satellites do not produce flares. The Iridium system was designed to be accessed by small handheld phones, the size of a cell phone. While "the weight of a typical cell phone in the early 1990s was 10.5 ounces" (300 grams) Advertising Age wrote in mid 1999 that "when its phone debuted, weighing 1 pound (453 grams) and costing $ 3,000, it

2124-491: A satellite into a LEO, and a satellite there needs less powerful amplifiers for successful transmission, LEO is used for many communication applications, such as the Iridium phone system . Some communication satellites use much higher geostationary orbits and move at the same angular velocity as the Earth as to appear stationary above one location on the planet. Unlike geosynchronous satellites , satellites in low orbit have

2242-460: A sequence of reactions with sodium hydroxide and hydrochloric acid . He named iridium after Iris ( Ἶρις ), the Greek winged goddess of the rainbow and the messenger of the Olympian gods , because many of the salts he obtained were strongly colored. Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804. British scientist John George Children

2360-460: A similar process since 1837 and had already presented fused iridium at a number of World Fairs . The first use of an alloy of iridium with ruthenium in thermocouples was made by Otto Feussner in 1933. These allowed for the measurement of high temperatures in air up to 2,000 °C (3,630 °F). In Munich , Germany in 1957 Rudolf Mössbauer , in what has been called one of the "landmark experiments in twentieth-century physics", discovered

2478-440: A single antenna may be utilized through a pass-through for both Iridium and GPS reception. The type of modulation used is normally DE- QPSK , although DE- BPSK is used on the uplink (mobile to satellite) for acquisition and synchronization. Each time slot is 8.28 milliseconds long and sits in a 90 milliseconds frame. Within each FDMA channel there are four TDMA time slots in each direction. The TDMA frame starts off with

SECTION 20

#1732801086836

2596-441: A small field of view and can only observe and communicate with a fraction of the Earth at a given time. This means that a large network (or constellation ) of satellites is required to provide continuous coverage. Satellites at lower altitudes of orbit are in the atmosphere and suffer from rapid orbital decay , requiring either periodic re-boosting to maintain stable orbits, or the launching of replacements for those that re-enter

2714-445: A small amount of a dark, insoluble residue. Joseph Louis Proust thought that the residue was graphite . The French chemists Victor Collet-Descotils , Antoine François, comte de Fourcroy , and Louis Nicolas Vauquelin also observed the black residue in 1803, but did not obtain enough for further experiments. In 1803 British scientist Smithson Tennant (1761–1815) analyzed the insoluble residue and concluded that it must contain

2832-433: A subset of LEO. These orbits, with low orbital inclination , allow rapid revisit times over low-latitude locations on Earth. Prograde equatorial LEOs also have lower delta-v launch requirements because they take advantage of the Earth's rotation. Other useful LEO orbits including polar orbits and Sun-synchronous orbits have a higher inclinations to the equator and provide coverage for higher latitudes on Earth. Some of

2950-640: A time-consuming process. During 2016, Iridium experienced in-orbit failures which could not be corrected with in-orbit spare satellites, thus only 64 of the 66 satellites required for seamless global coverage were in operation. This caused some service interruptions until the next-generation constellation was put into service. In 2017, Iridium began launching Iridium NEXT, a second-generation worldwide network of telecommunications satellites, consisting of 66 active satellites, with another nine in-orbit spares and six on-ground spares. These satellites incorporate features such as data transmission that were not emphasized in

3068-416: A total of 80 previously operating satellites are now defunct or no longer exist. At 16:56 UTC on February 10, 2009, Iridium 33 collided with the defunct Russian satellite Kosmos 2251 . This accidental collision was the first hypervelocity collision between two artificial satellites in low Earth orbit . Iridium 33 was in active service when the accident took place. It was one of the oldest satellites in

3186-539: Is Ir, which decays by isomeric transition with a half-life of 241 years, making it more stable than any of iridium's synthetic isotopes in their ground states. The least stable isomer is Ir with a half-life of only 2 μs. The isotope Ir was the first one of any element to be shown to present a Mössbauer effect . This renders it useful for Mössbauer spectroscopy for research in physics, chemistry, biochemistry , metallurgy , and mineralogy . Iridium forms compounds in oxidation states between −3 and +9, but

3304-589: Is a marine AIS ship-tracker receiver for Canadian company ExactEarth Ltd . In January 2020, the Iridium constellation was certified for use in the Global Maritime Distress and Safety System (GMDSS). The certification ended a monopoly on the provision of maritime distress services that had previously been held by Inmarsat since the system became operational in 1999. Iridium NEXT also provides data link to other satellites in space, enabling command and control of other space assets regardless of

3422-509: Is also found in secondary deposits, combined with platinum and other platinum group metals in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department of Colombia are still a source for platinum-group metals. As of 2003, world reserves have not been estimated. Iridium is found within marine organisms, sediments , and the water column. The abundance of iridium in seawater and organisms

3540-641: Is also obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper and nickel, noble metals such as silver, gold and the platinum group metals as well as selenium and tellurium settle to the bottom of the cell as anode mud , which forms the starting point for their extraction. Due to iridium's resistance to corrosion it has industrial applications. The main areas of use are electrodes for producing chlorine and other corrosive products, OLEDs , crucibles, catalysts (e.g. acetic acid ), and ignition tips for spark plugs. Resistance to heat and corrosion are

3658-543: Is always low-spin . Ir(III) and Ir(IV) generally form octahedral complexes . Polyhydride complexes are known for the +5 and +3 oxidation states. One example is IrH 5 (P Pr 3 ) 2 ( Pr = isopropyl ). The ternary hydride Mg 6 Ir 2 H 11 is believed to contain both the IrH 5 and the 18-electron IrH 4 anion. Iridium also forms oxyanions with oxidation states +4 and +5. K 2 IrO 3 and KIrO 3 can be prepared from

Iridium satellite constellation - Misplaced Pages Continue

3776-440: Is continually in view from every point on the Earth's surface. At least 66 satellites are required, in 6 polar orbits containing 11 satellites each, for seamless coverage. Orbital velocity of the satellites is approximately 27,000 km/h (17,000 mph). Satellites communicate with neighboring satellites via Ka band inter-satellite links. Each satellite can have four inter-satellite links: one each to neighbors fore and aft in

3894-695: Is done using a TDMA and FDMA based system using L-band spectrum between 1,616 and 1,626.5 MHz. Iridium exclusively controls 7.775 MHz of this and shares a further 0.95 MHz. In 1999, Iridium agreed to timeshare a portion of spectrum, allowing radio astronomers to observe hydroxyl emissions; the amount of shared spectrum was recently reduced from 2.625 MHz. External "hockey puck" type antennas used with Iridium handheld phones, data modems and SBD terminals are usually defined as 3  dB gain, 50  ohms impedance with RHCP (right hand circular polarization ) and 1.5:1 VSWR . As Iridium antennas function at frequencies very close to those of GPS ,

4012-556: Is found in gaseous [IrO 4 ] . Iridium does not form binary hydrides . Only one binary oxide is well-characterized: iridium dioxide , IrO 2 . It is a blue black solid that adopts the fluorite structure . A sesquioxide , Ir 2 O 3 , has been described as a blue-black powder, which is oxidized to IrO 2 by HNO 3 . The corresponding disulfides , diselenides , sesquisulfides , and sesquiselenides are known, as well as IrS 3 . Binary trihalides, IrX 3 , are known for all of

4130-454: Is intertwined with that of platinum and the other metals of the platinum group . The first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger as a description of an unknown noble metal found between Darién and Mexico, "which no fire nor any Spanish artifice has yet been able to liquefy ". From their first encounters with platinum,

4248-546: Is isolated. To separate the metals, they must first be brought into solution . Two methods for rendering Ir-containing ores soluble are (i) fusion of the solid with sodium peroxide followed by extraction of the resulting glass in aqua regia and (ii) extraction of the solid with a mixture of chlorine with hydrochloric acid . From soluble extracts, iridium is separated by precipitating solid ammonium hexachloroiridate ( (NH 4 ) 2 IrCl 6 ) or by extracting IrCl 6 with organic amines. The first method

4366-406: Is often used as a starting material for the synthesis of other Ir(III) compounds. Another compound used as a starting material is potassium hexachloroiridate(III), K 3 IrCl 6 . Organoiridium compounds contain iridium– carbon bonds. Early studies identified the very stable tetrairidium dodecacarbonyl , Ir 4 (CO) 12 . In this compound, each of the iridium atoms is bonded to

4484-496: Is only slightly less than on the Earth's surface. This is because the distance to LEO from the Earth's surface is much less than the Earth's radius. However, an object in orbit is in a permanent free fall around Earth, because in orbit the gravitational force and the centrifugal force balance each other out. As a result, spacecraft in orbit continue to stay in orbit, and people inside or outside such craft continuously experience weightlessness . Objects in LEO orbit Earth between

4602-482: Is performed at 25  kilobaud . Low Earth orbit A low Earth orbit ( LEO ) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, peaking in number at an altitude around 800 km (500 mi), while the farthest in LEO, before medium Earth orbit (MEO), have an altitude of 2,000 kilometers, about one-third of

4720-461: Is relatively common in meteorites , with concentrations of 0.5 ppm or more. The overall concentration of iridium on Earth is thought to be much higher than what is observed in crustal rocks, but because of the density and siderophilic ("iron-loving") character of iridium, it descended below the crust and into Earth's core when the planet was still molten . Iridium is found in nature as an uncombined element or in natural alloys , especially

4838-666: Is relatively low, as it does not readily form chloride complexes . The abundance in organisms is about 20 parts per trillion, or about five orders of magnitude less than in sedimentary rocks at the Cretaceous–Paleogene (K–T) boundary . The concentration of iridium in seawater and marine sediment is sensitive to marine oxygenation , seawater temperature, and various geological and biological processes. Iridium in sediments can come from cosmic dust , volcanoes, precipitation from seawater, microbial processes, or hydrothermal vents , and its abundance can be strongly indicative of

Iridium satellite constellation - Misplaced Pages Continue

4956-413: Is similar to the procedure Tennant and Wollaston used for their original separation. The second method can be planned as continuous liquid–liquid extraction and is therefore more suitable for industrial scale production. In either case, the product, an iridium chloride salt, is reduced with hydrogen, yielding the metal as a powder or sponge , which is amenable to powder metallurgy techniques. Iridium

5074-404: Is sufficient to cover the entire Earth surface at every moment. The Iridium satellite constellation was conceived in the early 1990s as a way to reach high Earth latitudes with reliable satellite communication services. Early calculations showed that 77 satellites would be needed, hence the name Iridium, after the metal with atomic number 77 . It turned out that just 66 were required to complete

5192-510: Is used for deep-water pipes because of its corrosion resistance. Iridium is used for multi-pored spinnerets , through which a plastic polymer melt is extruded to form fibers, such as rayon . Osmium–iridium is used for compass bearings and for balances. Because of their resistance to arc erosion, iridium alloys are used by some manufacturers for the centre electrodes of spark plugs , and iridium-based spark plugs are particularly used in aviation. Iridium compounds are used as catalysts in

5310-435: Is white, resembling platinum, but with a slight yellowish cast. Because of its hardness, brittleness, and very high melting point , solid iridium is difficult to machine, form, or work; thus powder metallurgy is commonly employed instead. It is the only metal to maintain good mechanical properties in air at temperatures above 1,600 °C (2,910 °F). It has the 10th highest boiling point among all elements and becomes

5428-649: The Alvarez hypothesis , is now widely accepted to explain the extinction of the non-avian dinosaurs. A large buried impact crater structure with an estimated age of about 66 million years was later identified under what is now the Yucatán Peninsula (the Chicxulub crater ). Dewey M. McLean and others argue that the iridium may have been of volcanic origin instead, because Earth's core is rich in iridium, and active volcanoes such as Piton de la Fournaise , in

5546-461: The Cativa process for carbonylation of methanol to produce acetic acid . Iridium complexes are often active for asymmetric hydrogenation both by traditional hydrogenation . and transfer hydrogenation . This property is the basis of the industrial route to the chiral herbicide (S)-metolachlor . As practiced by Syngenta on the scale of 10,000 tons/year, the complex [Ir(COD)Cl] 2 in

5664-512: The National Aeronautics and Space Administration . Iridium Iridium is a chemical element ; it has symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group , it is considered the second-densest naturally occurring metal (after osmium ) with a density of 22.56 g/cm (0.815 lb/cu in) as defined by experimental X-ray crystallography . Ir and Ir are

5782-637: The mass extinctions , such as the Cretaceous extinction , can be identified by anomalously high concentrations of iridium in sediment, and these can be linked to major asteroid impacts . The Cretaceous–Paleogene boundary of 66 million years ago, marking the temporal border between the Cretaceous and Paleogene periods of geological time , was identified by a thin stratum of iridium-rich clay . A team led by Luis Alvarez proposed in 1980 an extraterrestrial origin for this iridium, attributing it to an asteroid or comet impact. Their theory, known as

5900-460: The period and inclination . A spare Iridium satellite in the lower storage orbit has a shorter period so its RAAN moves westward more quickly than the satellites in the standard orbit. Iridium simply waits until the desired RAAN (i.e., the desired orbital plane) is reached and then raises the spare satellite to the standard altitude, fixing its orbital plane with respect to the constellation. Although this saves substantial amounts of fuel, it can be

6018-589: The r-process (rapid neutron capture) in neutron star mergers and possibly rare types of supernovae. Iridium is one of the nine least abundant stable elements in Earth's crust , having an average mass fraction of 0.001  ppm in crustal rock; gold is 4 times more abundant, platinum is 10 times more abundant, silver and mercury are 80 times more abundant. Osmium , tellurium , ruthenium , rhodium and rhenium are about as abundant as iridium. In contrast to its low abundance in crustal rock, iridium

SECTION 50

#1732801086836

6136-402: The radius of Earth and near the beginning of the inner Van Allen radiation belt . The term LEO region is used for the area of space below an altitude of 2,000 km (1,200 mi) (about one-third of Earth's radius). Objects in orbits that pass through this zone, even if they have an apogee further out or are sub-orbital , are carefully tracked since they present a collision risk to

6254-459: The 99 built satellites were launched between 1997 and 2002. Four satellites were kept on the ground as spares. The 95 satellites were launched over twenty-two missions (nine missions in 1997, ten in 1998, one in 1999 and two in 2002). One extra mission on Chang Zheng was a payload test and did not carry any actual satellites. ^ Iridium satellite number changed over time following failure and replacement. Spare satellites are usually held in

6372-424: The Greek word iris (rainbow), refers to the various colors of its compounds. Iridium is one of the rarest elements in Earth's crust , with an estimated annual production of only 6,800 kilograms (15,000 lb) in 2023. The dominant uses of iridium are the metal itself and its alloys, as in high-performance spark plugs , crucibles for recrystallization of semiconductors at high temperatures, and electrodes for

6490-718: The Iridium NEXT satellites. All the Iridium NEXT launches have taken place using a Falcon 9 rocket launch from Vandenberg Air Force Base in California. Deployment of the constellation began in January 2017, with the launch of the first ten Iridium NEXT satellites. Most recently, on January 11, 2019, SpaceX launched an additional ten satellites, bringing the number of upgraded satellites in orbit to 75. The satellites each contained seven Motorola/ Freescale PowerPC 603E processors running at roughly 200 MHz, connected by

6608-498: The LEO region but are not in a LEO orbit because they re-enter the atmosphere . The distinction between LEO orbits and the LEO region is especially important for analysis of possible collisions between objects which may not themselves be in LEO but could collide with satellites or debris in LEO orbits. The mean orbital velocity needed to maintain a stable low Earth orbit is about 7.8 km/s (4.8 mi/s), which translates to 28,000 km/h (17,000 mph). However, this depends on

6726-552: The Spanish generally saw the metal as a kind of impurity in gold, and it was treated as such. It was often simply thrown away, and there was an official decree forbidding the adulteration of gold with platinum impurities. In 1735, Antonio de Ulloa and Jorge Juan y Santacilia saw Native Americans mining platinum while the Spaniards were travelling through Colombia and Peru for eight years. Ulloa and Juan found mines with

6844-463: The United States, Russia, and China. 60 were launched to orbit on twelve Delta II rocket carrying five satellites each; 21 on three Proton-K/DM2 rocket with seven each, two on one Rokot/Briz-KM rocket carrying two; and 12 on six Long March 2C/SD rocket carrying two each. The total setup cost for the first-generation fleet was approximately US$ 5 billion . The first test telephone call

6962-541: The altitude above ground can vary by as much as 30 km (19 mi) (especially for polar orbits ) due to the oblateness of Earth's spheroid figure and local topography . While definitions based on altitude are inherently ambiguous, most of them fall within the range specified by an orbit period of 128 minutes because, according to Kepler's third law , this corresponds to a semi-major axis of 8,413 km (5,228 mi). For circular orbits, this in turn corresponds to an altitude of 2,042 km (1,269 mi) above

7080-434: The area requiring treatment. Specific treatments include high-dose-rate prostate brachytherapy, biliary duct brachytherapy, and intracavitary cervix brachytherapy. Iridium-192 is normally produced by neutron activation of isotope iridium-191 in natural-abundance iridium metal. Iridium complexes are key components of white OLEDs . Similar complexes are used in photocatalysis . An alloy of 90% platinum and 10% iridium

7198-542: The atmosphere. Iridium 21, 27, 20, 11, 46, 71, 44, 14, 79, 69 and 85 all suffered from issues before entering operational service soon after their launch. By 2018, of these eleven, Iridium 27, 79 and 85 have decayed out of orbit; Iridium 11, 14, 20 and 21 were renamed to Iridium 911, 914, 920 and 921 respectively since replacements of the same name were launched. From 2017, several first-generation Iridium satellites have been deliberately de-orbited after being replaced by operational Iridium NEXT satellites. As of January 2023,

SECTION 60

#1732801086836

7316-433: The atmosphere. The effects of adding such quantities of vaporized metals to Earth's stratosphere are potentially of concern but currently unknown. The LEO environment is becoming congested with space debris because of the frequency of object launches. This has caused growing concern in recent years, since collisions at orbital velocities can be dangerous or deadly. Collisions can produce additional space debris, creating

7434-715: The bases for several uses of iridium and its alloys. Owing to its high melting point, hardness, and corrosion resistance , iridium is used to make crucibles. Such crucibles are used in the Czochralski process to produce oxide single-crystals (such as sapphires ) for use in computer memory devices and in solid state lasers. The crystals, such as gadolinium gallium garnet and yttrium gallium garnet, are grown by melting pre-sintered charges of mixed oxides under oxidizing conditions at temperatures up to 2,100 °C (3,810 °F). Certain long-life aircraft engine parts are made of an iridium alloy, and an iridium– titanium alloy

7552-422: The blanket coverage of the planet with communication services. The first-generation constellation was developed by Iridium SSC , and financed by Motorola . The satellites were deployed in 1997–2002. All the satellites needed to be in orbit before commercial service could begin. Iridium SSC employed a globally diverse fleet of rockets to get their 77 satellites into orbit, including launch vehicles (LVs) from

7670-539: The communications payload thermal environment and RF main mission antenna performance, while achieving the highest payload fairing packaging for each of the three main launch vehicle providers. The first spacecraft mock-up of this design was built in the garage workshop in Santa Clara, California for the Bus PDR/CDR as a proof-of-concept model. This first prototype paved the way for the design and construction of

7788-462: The constellation, having been launched in 1997. The satellites collided at a relative speed of roughly 35,000 km/h (22,000 miles per hour) This collision created over 2000 large space debris fragments that could be hazardous to other satellites. Iridium moved one of its in-orbit spares, Iridium 91 (formerly known as Iridium 90), to replace the destroyed satellite, completing the move on March 4, 2009. Communication between satellites and handsets

7906-525: The debt associated with building out the constellation and Iridium went bankrupt , one of the largest bankruptcies in US history at the time. The constellation continued operation following the bankruptcy of the original Iridium corporation. A new entity emerged to operate the satellites and developed a different product placement and pricing strategy, offering communication services to a niche market of customers who required reliable services of this type in areas of

8024-455: The denser part of the atmosphere and below the inner Van Allen radiation belt . They encounter atmospheric drag from gases in the thermosphere (approximately 80–600 km above the surface) or exosphere (approximately 600 km or 400 mi and higher), depending on orbit height. Satellites in orbits that reach altitudes below 300 km (190 mi) decay quickly due to atmospheric drag. Equatorial low Earth orbits ( ELEO ) are

8142-499: The entire launch sequence for the 75-satellite constellation. It launched and successfully deployed 10 satellites with SpaceX on January 14, 2017, delayed due to weather from January 9, 2017, and the first of those new satellites took over the duties of an old satellite on March 11, 2017. At the time of the launch of the first batch, the second flight of ten satellites was planned to launch only three months later in April 2017. However, in

8260-403: The exact altitude of the orbit. Calculated for a circular orbit of 200 km (120 mi) the orbital velocity is 7.79 km/s (4.84 mi/s), but for a higher 1,500 km (930 mi) orbit the velocity is reduced to 7.12 km/s (4.42 mi/s). The launch vehicle's delta-v needed to achieve low Earth orbit starts around 9.4 km/s (5.8 mi/s). The pull of gravity in LEO

8378-413: The exception of Ir, which decays by electron capture . Synthetic isotopes heavier than 191 decay by β decay , although Ir also has a minor electron capture decay path. All known isotopes of iridium were discovered between 1934 and 2008, with the most recent discoveries being Ir. At least 32 metastable isomers have been characterized, ranging in mass number from 164 to 197. The most stable of these

8496-405: The existing constellation in January 2017. Iridium Communications , the successor company to Iridium SSC, has ordered a total of 81 new satellites being built by Thales Alenia Space and Orbital ATK : 66 operational units, nine on-orbit spares, and six ground spares. In August 2008, Iridium selected two companies — Lockheed Martin and Thales Alenia Space — to participate in the final phase of

8614-400: The field of satellite communications, and the manufacturer generated several hundred patents protecting the technology in the system. Satellite manufacturing initiatives were also instrumental in the technical success of the system. Motorola made a key hire of the engineer who set up the automated factory for Apple 's Macintosh . He created the technology necessary to mass-produce satellites on

8732-549: The first engineering models. This design was the basis of the largest constellation of satellites deployed in low Earth orbit . After ten years of successful on-orbit performance, the Iridium team celebrated the equivalent of 1,000 cumulative years of on-orbit performance in 2008. One of the engineering Iridium satellite models was placed on permanent exhibit in the National Air and Space Museum in Washington, D.C. 95 of

8850-647: The first generation of Starlink satellites used polar orbits which provide coverage everywhere on Earth. Later Starlink constellations orbit at a lower inclination and provide more coverage for populated areas. Higher orbits include medium Earth orbit (MEO), sometimes called intermediate circular orbit (ICO), and further above, geostationary orbit (GEO). Orbits higher than low orbit can lead to early failure of electronic components due to intense radiation and charge accumulation. In 2017, " very low Earth orbits " ( VLEO ) began to be seen in regulatory filings. These orbits, below about 450 km (280 mi), require

8968-754: The former structures. The largest known primary reserves are in the Bushveld igneous complex in South Africa, (near the largest known impact structure, the Vredefort impact structure ) though the large copper– nickel deposits near Norilsk in Russia, and the Sudbury Basin (also an impact crater) in Canada are also significant sources of iridium. Smaller reserves are found in the United States. Iridium

9086-499: The halogens. For oxidation states +4 and above, only the tetrafluoride , pentafluoride and hexafluoride are known. Iridium hexafluoride, IrF 6 , is a volatile yellow solid, composed of octahedral molecules. It decomposes in water and is reduced to IrF 4 . Iridium pentafluoride is also a strong oxidant, but it is a tetramer , Ir 4 F 20 , formed by four corner-sharing octahedra. Iridium has extensive coordination chemistry . Iridium in its complexes

9204-461: The heat-affected zone cracks, but it can be made more ductile by addition of small quantities of titanium and zirconium (0.2% of each apparently works well). The Vickers hardness of pure platinum is 56 HV, whereas platinum with 50% of iridium can reach over 500 HV. Iridium is the most corrosion-resistant metal known. It is not attacked by acids , including aqua regia , but it can be dissolved in concentrated hydrochloric acid in

9322-525: The impact of a massive extraterrestrial object caused the extinction of non-avian dinosaurs and many other species 66 million years ago , now known to be produced by the impact that formed the Chicxulub crater . Similarly, an iridium anomaly in core samples from the Pacific Ocean suggested the Eltanin impact of about 2.5 million years ago. A member of the platinum group metals, iridium

9440-487: The iridium– osmium alloys osmiridium (osmium-rich) and iridosmium (iridium-rich). In nickel and copper deposits, the platinum group metals occur as sulfides , tellurides , antimonides , and arsenides . In all of these compounds, platinum can be exchanged with a small amount of iridium or osmium. As with all of the platinum group metals, iridium can be found naturally in alloys with raw nickel or raw copper . A number of iridium-dominant minerals , with iridium as

9558-521: The island of Réunion , are still releasing iridium. Worldwide production of iridium was about 7,300 kilograms (16,100 lb) in 2018. The price is high and varying (see table). Illustrative factors that affect the price include oversupply of Ir crucibles and changes in LED technology. Platinum metals occur together as dilute ores. Iridium is one of the rarer platinum metals: for every 190 tonnes of platinum obtained from ores, only 7.5 tonnes of iridium

9676-514: The launch of the first pair of Iridium NEXT satellites until April 2016. Iridium NEXT launch plans originally included launch of satellites on both Ukrainian Dnepr launch vehicles and SpaceX Falcon 9 launch vehicles, with the initial satellites launching on Dnepr in April 2016; however, in February 2016, Iridium announced a change. Due to an extended slowdown in obtaining the requisite launch licenses from Russian authorities, Iridium revamped

9794-476: The many LEO satellites. No human spaceflights other than the lunar missions of the Apollo program (1968-1972) and the 2024 Polaris Dawn have taken place beyond LEO. All space stations to date have operated geocentric within LEO. A wide variety of sources define LEO in terms of altitude . The altitude of an object in an elliptic orbit can vary significantly along the orbit. Even for circular orbits ,

9912-455: The mean radius of Earth, which is consistent with some of the upper altitude limits in some LEO definitions. The LEO region is defined by some sources as a region in space that LEO orbits occupy. Some highly elliptical orbits may pass through the LEO region near their lowest altitude (or perigee ) but are not in a LEO orbit because their highest altitude (or apogee ) exceeds 2,000 km (1,243 mi). Sub-orbital objects can also reach

10030-424: The metal limited the possibilities for handling iridium. John Isaac Hawkins was looking to obtain a fine and hard point for fountain pen nibs , and in 1834 managed to create an iridium-pointed gold pen. In 1880, John Holland and William Lofland Dudley were able to melt iridium by adding phosphorus and patented the process in the United States; British company Johnson Matthey later stated they had been using

10148-413: The most common oxidation states are +1, +2, +3, and +4. Well-characterized compounds containing iridium in the +6 oxidation state include IrF 6 and the oxides Sr 2 MgIrO 6 and Sr 2 CaIrO 6 . iridium(VIII) oxide ( IrO 4 ) was generated under matrix isolation conditions at 6 K in argon . The highest oxidation state (+9), which is also the highest recorded for any element,

10266-456: The only two naturally occurring isotopes of iridium, as well as the only stable isotopes ; the latter is the more abundant. It is one of the most corrosion -resistant metals, even at temperatures as high as 2,000 °C (3,630 °F). Iridium was discovered in 1803 in the acid-insoluble residues of platinum ores by the English chemist Smithson Tennant . The name iridium , derived from

10384-540: The original design. The next-generation terminals and service became commercially available in 2018. One of the Iridium NEXT services is Iridium Certus, a globally available satellite broadband, which is capable of up to 704 kbit/s of bandwidth across maritime, aviation, land mobile, government, and IoT applications. The NEXT satellites incorporate a secondary payload for Aireon , a space-qualified ADS-B data receiver for use by air traffic control and, via FlightAware , by airlines. A tertiary payload on 58 satellites

10502-586: The other three, forming a tetrahedral cluster. The discovery of Vaska's complex ( IrCl(CO)[P(C 6 H 5 ) 3 ] 2 ) opened the door for oxidative addition reactions, a process fundamental to useful reactions. For example, Crabtree's catalyst , a homogeneous catalyst for hydrogenation reactions. Iridium complexes played a pivotal role in the development of Carbon–hydrogen bond activation (C–H activation), which promises to allow functionalization of hydrocarbons , which are traditionally regarded as unreactive . The discovery of iridium

10620-485: The planet not covered by traditional geosynchronous orbit communication satellite services. Users include journalists , explorers, and military units. No new satellites were launched 2002–2017 to replenish the constellation, even though the original satellites based on the LM-700A model had been projected to have a design life of only 8 years. The second-generation Iridium-NEXT satellites began to be deployed into

10738-446: The position of ground stations and gateways. In 1999, The New York Times quoted a wireless market analyst, regarding people having "one number that they could carry with them anywhere" as "expensive... There never was a viable market." Due to the shape of the original Iridium satellites' reflective antennas, the first generation satellites focused sunlight on a small area of the Earth surface in an incidental manner. This resulted in

10856-521: The position of ground stations and gateways. In June 2010, Iridium signed the largest commercial rocket-launch deal ever at that time, a US$ 492 million contract with SpaceX to launch 70 Iridium NEXT satellites on seven Falcon 9 rockets from 2015 to 2017 via SpaceX leased launch facility at Vandenberg Air Force Base . The final two satellites were originally slated to be orbited by a single launch of an ISC Kosmotras Dnepr . Technical issues and consequential demands from Iridium's insurance delayed

10974-412: The presence of Josiphos ligands . The radioisotope iridium-192 is one of the two most important sources of energy for use in industrial γ-radiography for non-destructive testing of metals. Additionally, Ir is used as a source of gamma radiation for the treatment of cancer using brachytherapy , a form of radiotherapy where a sealed radioactive source is placed inside or next to

11092-548: The presence of sodium perchlorate. In the presence of oxygen , it reacts with cyanide salts. Traditional oxidants also react, including the halogens and oxygen at higher temperatures. Iridium also reacts directly with sulfur at atmospheric pressure to yield iridium disulfide . Iridium has two naturally occurring stable isotopes , Ir and Ir, with natural abundances of 37.3% and 62.7%, respectively. At least 37 radioisotopes have also been synthesized, ranging in mass number from 164 to 202. Ir , which falls between

11210-504: The procurement of the next-generation satellite constellation. As of 2009, the original plan had been to begin launching new satellites in 2014. The design was complete by 2010, and Iridium stated that the existing constellation of satellites would remain operational until Iridium NEXT is fully operational, with many satellites expected to remain in service until the 2020s, while the NEXT satellites would have improved bandwidth. The new system

11328-425: The production of chlorine in the chloralkali process . Important compounds of iridium are chlorides and iodides in industrial catalysis . Iridium is a component of some OLEDs . Iridium is found in meteorites in much higher abundance than in the Earth's crust. For this reason, the unusually high abundance of iridium in the clay layer at the Cretaceous–Paleogene boundary gave rise to the Alvarez hypothesis that

11446-510: The purification of iridium and used as precursors for most other iridium compounds, as well as in the preparation of anode coatings. The IrCl 6 ion has an intense dark brown color, and can be readily reduced to the lighter-colored IrCl 6 and vice versa. Iridium trichloride , IrCl 3 , which can be obtained in anhydrous form from direct oxidation of iridium powder by chlorine at 650 °C, or in hydrated form by dissolving Ir 2 O 3 in hydrochloric acid ,

11564-407: The reaction of potassium oxide or potassium superoxide with iridium at high temperatures. Such solids are not soluble in conventional solvents. Just like many elements, iridium forms important chloride complexes. Hexachloroiridic (IV) acid, H 2 IrCl 6 , and its ammonium salt are common iridium compounds from both industrial and preparative perspectives. They are intermediates in

11682-525: The report in 1748, Ulloa did not continue to investigate the new metal. In 1758, he was sent to superintend mercury mining operations in Huancavelica . In 1741, Charles Wood , a British metallurgist , found various samples of Colombian platinum in Jamaica, which he sent to William Brownrigg for further investigation. In 1750, after studying the platinum sent to him by Wood, Brownrigg presented

11800-592: The resonant and recoil -free emission and absorption of gamma rays by atoms in a solid metal sample containing only Ir. This phenomenon, known as the Mössbauer effect resulted in the awarding of the Nobel Prize in Physics in 1961, at the age 32, just three years after he published his discovery. Along with many elements having atomic weights higher than that of iron, iridium is only naturally formed by

11918-488: The same direction. The constellation of 66 active satellites has six orbital planes spaced 30° apart, with 11 satellites in each plane (not counting spares). The original concept was to have 77 satellites, which is where the name Iridium came from; the element iridium has the atomic number 77, and the satellites evoked the Bohr model image of electrons orbiting around the Earth as its nucleus. This reduced set of six planes

12036-708: The same orbital plane, and one each to satellites in neighboring planes to either side. The satellites orbit from pole to same pole with an orbital period of roughly 100 minutes. This design means that there is excellent satellite visibility and service coverage especially at the North and South poles. The over-the-pole orbital design produces "seams" where satellites in counter-rotating planes next to one another are traveling in opposite directions. Cross-seam inter-satellite link hand-offs would have to happen very rapidly and cope with large Doppler shifts ; therefore, Iridium supports inter-satellite links only between satellites orbiting in

12154-456: The satellite telephone industry as other providers do not relay data between satellites; Globalstar and Inmarsat both use a transponder without cross-links. The original design as envisioned in the 1960s was that of a completely static "dumb satellite" with a set of control messages and time-triggers for an entire orbit that would be uploaded as the satellite passed over the poles. It was found that this design did not have enough bandwidth in

12272-478: The six additional spare satellites five have been launched on 20 May 2023 while the last one, Iridium 101, is still on the ground. ^ Iridium satellite number could change over time following failure and replacement. Iridium 127 had to be re-designated as Iridium 100 before launch due to a ground software issue. The main patents on the Iridium system, U.S. Patents 5,410,728: "Satellite cellular telephone and data communication system" , and 5,604,920, are in

12390-411: The source. It tends to associate with other ferrous metals in manganese nodules . Iridium is one of the characteristic elements of extraterrestrial rocks, and, along with osmium, can be used as a tracer element for meteoritic material in sediment. For example, core samples from the Pacific Ocean with elevated iridium levels suggested the Eltanin impact of about 2.5 million years ago. Some of

12508-564: The space-based backhaul to upload each satellite quickly and reliably over the poles. Moreover, fixed, static scheduling would have left more than 90% of the satellite links idle at all times. Therefore, the design was scrapped in favour of a design that performed dynamic control of routing and channel selection late in the project, resulting in a one-year delay in system delivery. Each satellite can support up to 1,100 concurrent phone calls at 2,400 bit/s and weighs about 680 kilograms (1,500 lb). The Iridium System presently operates within

12626-547: The spacecraft was managed by Lockheed Bus Spacecraft team; it was the first commercial satellite bus designed at the Sunnyvale Space Systems Division in California. The TF80L configuration was considered a non-conventional, innovative approach to developing a satellite design that could be assembled and tested in five days. The TF80L design configuration was also instrumental in simultaneously solving fundamental design problems involving optimization of

12744-406: The species-forming element, are known. They are exceedingly rare and often represent the iridium analogues of the above-given ones. The examples are irarsite and cuproiridsite, to mention some. Within Earth's crust, iridium is found at highest concentrations in three types of geologic structure: igneous deposits (crustal intrusions from below), impact craters , and deposits reworked from one of

12862-440: The two elements was denser, due to the small size of the difference in density and difficulties in measuring it accurately, but, with increased accuracy in factors used for calculating density, X-ray crystallographic data yielded densities of 22.56 g/cm (0.815 lb/cu in) for iridium and 22.59 g/cm (0.816 lb/cu in) for osmium. Iridium is extremely brittle, to the point of being hard to weld because

12980-536: The two stable isotopes, is the most stable radioisotope , with a half-life of 73.827 days, and finds application in brachytherapy and in industrial radiography , particularly for nondestructive testing of welds in steel in the oil and gas industries; iridium-192 sources have been involved in a number of radiological accidents. Three other isotopes have half-lives of at least a day— Ir, Ir, and Ir. Isotopes with masses below 191 decay by some combination of β decay , α decay , and (rare) proton emission , with

13098-412: The use of novel technologies for orbit raising because they operate in orbits that would ordinarily decay too soon to be economically useful. A low Earth orbit requires the lowest amount of energy for satellite placement. It provides high bandwidth and low communication latency . Satellites and space stations in LEO are more accessible for crew and servicing. Since it requires less energy to place

13216-451: The whitish metal nuggets and took them home to Spain. Ulloa returned to Spain and established the first mineralogy lab in Spain and was the first to systematically study platinum, which was in 1748. His historical account of the expedition included a description of platinum as being neither separable nor calcinable . Ulloa also anticipated the discovery of platinum mines. After publishing

13334-518: Was made over the network in 1998, and full global coverage was complete by 2002. However, although the system met its technical requirements, it was not a success in the market. Poor reception from inside buildings, bulky and expensive handsets, and competition with the conventional cellular phone contributed to its failure. Insufficient market demand existed for the product at the price points on offer from Iridium as set by its parent company Motorola. The company failed to earn revenue sufficient to service

13452-469: Was redefined in terms of the Planck constant . Iridium–osmium alloys were used in fountain pen nib tips . The first major use of iridium was in 1834 in nibs mounted on gold. Starting in 1944, the famous Parker 51 fountain pen was fitted with a nib tipped by a ruthenium and iridium alloy (with 3.8% iridium). The tip material in modern fountain pens is still conventionally called "iridium", although there

13570-661: Was the first to melt a sample of iridium in 1813 with the aid of "the greatest galvanic battery that has ever been constructed" (at that time). The first to obtain high-purity iridium was Robert Hare in 1842. He found it had a density of around 21.8 g/cm (0.79 lb/cu in) and noted the metal is nearly immalleable and very hard. The first melting in appreciable quantity was done by Henri Sainte-Claire Deville and Jules Henri Debray in 1860. They required burning more than 300 litres (79 US gal) of pure O 2 and H 2 gas for each 1 kilogram (2.2 lb) of iridium. These extreme difficulties in melting

13688-418: Was to be backward-compatible with the current system. In June 2010, the winner of the contract was announced as Thales Alenia Space, in a $ 2.1 billion deal underwritten by Compagnie Française d'Assurance pour le Commerce Extérieur . Iridium additionally stated that it expected to spend about $ 800 million to launch the satellites and upgrade some ground facilities. SpaceX was contracted to launch all

13806-560: Was used in 1889 to construct the International Prototype Meter and kilogram mass, kept by the International Bureau of Weights and Measures near Paris. The meter bar was replaced as the definition of the fundamental unit of length in 1960 by a line in the atomic spectrum of krypton , but the kilogram prototype remained the international standard of mass until 20 May 2019 , when the kilogram

13924-414: Was viewed as both unwieldly and expensive." An omnidirectional antenna was intended to be small enough to be mounted on the planned phone, but the low handset battery power was insufficient for contact with a satellite in geostationary orbit , 35,785 km (22,236 mi) above the Earth; the normal orbit of communications satellites , in which the satellite appears stationary in the sky. In order for

#835164