The Iridium satellite constellation provides L-band sound and data coverage to satellite phones, pagers and transceivers integrated throughout the Earth's surface. Iridium Communications owns and operates constellations, in addition to selling equipment and access to its services. It was originally conceived by Bary Bertiger, Raymond J. Leopold and Ken Peterson in late 1987 (and protected by a patent by Motorola on their behalf in 1988) and later developed by Motorola on a fixed price contract from July 29, 1993 to November 1, 1998, when the system becomes operational and commercially available.
The constellation consists of 66 active satellites in orbit, required for global coverage, and additional backup satellites to serve in case of failure. The satellite is in low Earth orbit at an altitude of about 485 mi (781 km) and a slope of 86.4 °. The speed of the satellite orbit is about 17,000 mph (27,000 km/h). Satellites communicate with neighboring satellites via inter-satellite links K a . Each satellite can have 4 inter-satellite links: one to each of the front and back neighbors in the same orbital plane, and each for satellites on neighboring planes to either side. The satellites orbit from the poles to the same pole with an orbital period of about 100 minutes. This design means that there is excellent satellite visibility and service coverage especially in the North and South poles. Over-the-pole orbital designs produce "connections" in which satellites on the plane spin opposite next to each other traveling in opposite directions. Cross-seam inter-hand links must occur very quickly and overcome the large Doppler shift; therefore, Iridium supports the relationship between satellites only between satellites orbiting in the same direction. The 66 active satellite constellations have 6 separate orbits 30 Â °, with 11 satellites on each aircraft (excluding spare parts). The original concept is to have 77 satellites, which are the origin of the name Iridium, being elements with atomic number 77 and satellites generating the Bohr model image of electrons orbiting around Earth as their nuclei. This reduces 6 planes enough to cover the entire surface of the Earth at any time.
Due to the Iridium satellite reflective antenna shape, the satellite focuses sunlight on a small area of ​​the Earth's surface incidentally. This produces an effect called Iridium flares, where satellites momentarily appear as one of the brightest objects in the night sky and can be seen even during the day.
Video Iridium satellite constellation
History
The constellation of the Iridium satellite was conceived in the early 1990s, as a way of reaching high latitudes of Earth with reliable satellite communications services. Initial calculations showed that 77 satellites would be needed, hence the name Iridium after the metal with atomic number 77. It turned out that only 66 were required to complete the planet's blanket coverage with a communications service.
The first generation constellation was developed by Iridium SSC, and financed by Motorola. Satellite deployed in 1997-2002. "The drawback of the Iridium concept is that the constellation requires all of its satellites to be in orbit before commercial services can begin - resulting in high initial outlay."
Iridium SSC uses a globally diverse armored fleet to get 77 of their satellites into orbit, including launch vehicles (LVs) from the United States, Russia and China. 60 was launched to orbit at twelve LV II Delta carrying five satellites each; 21 on three Proton-K/DM2 LVs with each of seven, 2 on one Rokot/Briz-KM LV carrying two; and 12 on six LV Chang Zheng 2C/SD carrying two each. The total set up cost for the first generation fleet is about US $ 5 billion .
The first test call was made over the network in 1998, and full global coverage was completed in 2002. However, even though the system met its technical requirements, it did not work in the market. Market demand is insufficient for the product at the price point offered from Iridium as set by its parent company, Motorola. The company failed to earn enough revenue to service the debt associated with building the constellation and bankrupt Iridium, the biggest bankruptcy in US history at the time.
The constellation continued after the bankruptcy of the original Iridium company. A new entity appears to operate satellites and develop different pricing and deployment strategies, offering communications services to customer niche markets that require reliable service of this type in the region of the planet that is not covered by traditional geosynchronous orbital communications satellite services. Users include journalists, explorers, and military units.
No new satellites were launched from 2002 to 2017 to fill the constellation, although the original satellites based on the LM-700A model have been projected to have a design life of only 8 years.
Second generation
The second generation Iridium-NEXT satellite began deploying into the constellation in January 2017. Iridium Communications, the Iridium SSC replacement company, has ordered a total of 81 new satellites built by Thales Alenia Space and Orbital ATK, which includes a number of land parts.
In August 2008, Iridium selected two companies - Lockheed Martin and Thales Alenia Space - to participate in the final phase of procuring the next generation of satellite constellations.
In 2009, the original plan was to launch a new satellite in 2014.
The draft was completed in 2010, and Iridium stated that the existing satellite constellation will remain in operation until Iridium NEXT is fully operational, with many satellites expected to remain operational by the 2020s, while NEXT satellites will increase bandwidth. The new system must be backward compatible with the current system. In June 2010, the contract winner was announced as Thales Alenia Space, in a deal worth $ 2.1 billion borne by the Compagnie FranÃÆ'§aise d'Assurance pour le Commerce Extée © rieur. Iridium also stated that they would spend about $ 800 million to launch satellites and improve some basic facilities.
SpaceX has been tasked to launch all of the Iridium NEXT satellites. All the Iridium NEXT launches have been performed using the Falcon 9 rocket launch from Vandenberg Air Force Base in California. The dispersal of the constellation began in January 2017, with the launch of the first 10 Iridium NEXT satellites. More recently, in May 2018, SpaceX launched five additional satellites, bringing the number of satellites upgraded to 55.
Maps Iridium satellite constellation
Description
The original Iridium constellation
Each satellite contains seven Motorola/Freescale PowerPC 603E processors running at approximately 200 MHz, connected by a special backplane network. One processor is dedicated to each cross-link antenna ("HVARC"), and two processors ("SVARC" s) are dedicated to satellite control, which is a backup. The final project of an extra processor ("SAC") is added to perform resource management and call processing of the phone.
Mobile viewing antennas have 48 beam spots arranged as 16 blocks in three sectors. Four cross-links between satellites on each satellite operate at 10 Mbit/s. Optical links can support much larger bandwidth and more aggressive growth paths, but microwave cross link is selected because their bandwidth is more than adequate for the desired system. Nevertheless, parallel cross-parallel parallel options are carried out through critical design review, and ends when a microwave connection is shown to support the size, weight and power requirements allocated in individual satellite budgets. Iridium Satellite LLC has stated that their second generation satellites will also use microwave, not optical, intercellular communication links. Such cross-links are unique in the satellite phone industry, as other providers do not deliver data between satellites; Globalstar and Inmarsat both use transponders without cross links.
The original design as envisaged in the 1960s was a static "stupid satellite" with a set of control messages and time trigger for all orbits to be uploaded as satellites passed through the poles. It was found that this design lacks sufficient bandwidth in a space-based backhaul to upload every satellite quickly and reliably above the poles. In addition, fixed and static scheduling will make over 90% of satellite links paused at any time. Therefore, the design was removed in favor of designs that perform dynamic control routing and channel selection at the end of the project, resulting in a one year delay in system delivery.
Each satellite can support up to 1100 concurrent phone calls at 2400 bit/s and weigh about 1,500 pounds (680 kg). The Iridium system currently operates in the bands 1618.85 to 1626.5 MHz, part of a wider L-band, adjacent to the 1610.6-1613.8 MHz Radio Astronomy Service (RAS) band.
The configuration configuration of Satellites is defined as Fixed Triangular, 80 Inch Main Mission Antenna, Light-weight (TF80L). The design of the spacecraft is managed by the Lockheed Bus Spacecraft team; it was the first commercial satellite bus designed at the Sunnyvale Space Systems Division in California. The TF80L configuration is considered a non-conventional innovative approach for developing satellite designs that can be assembled and tested in five days. The TF80L design configuration also plays a role in solving the fundamental design issues simultaneously involving the optimization of the thermal environment of the communication load and the performance of the main RF antenna antenna, while achieving the highest loading packaging charge for each of the three major launch vehicle providers.
The first mock-up spaceship of this design was built in a garage workshop in Santa Clara, California for the PDR/CDR Bus as a proof-of-concept model. This first prototype paved the way for the design and construction of the first engineering model. This design is the largest constellation base of satellites placed in low Earth orbit. After ten successful years in orbital performance, the Iridium team celebrated the equivalent of 1,000 years of cumulative orbital performance in 2008. One of the Iridium satellite engineering models is housed at a permanent exhibit at the Smithsonian Air and Space Museum in Washington DC..
Launch campaign
Ninety-five of the 99 built satellites were launched between 1997 and 2002. Three satellites are stored on the ground as spare parts.
95 satellites launched over twenty-two missions (nine missions in 1997, ten in 1998, one in 1999 and two in 2002). An additional mission to Chang Zheng is a load test and does not carry the actual satellite.
^ Iridium satellite numbers change over time after failure and replacement.
In-orbit Spares
Usually the backup satellite is stored in 414 km (666 km) of storage orbit. This can be upgraded to the correct height and put into service in the event of a satellite failure. After the Iridium company emerged from bankruptcy, the new owner decided to launch seven new spare parts, which will ensure two spare satellites are available in each aircraft. As of 2009, not every plane has a backup satellite; However, satellites can be moved to different planes if needed. A step can take several weeks and consume fuel that will shorten the expected service life of the satellite.
Changes in significant orbital tendencies are usually very fuel intensive, but an orbital disturbance analysis helps the process. The Earth's equatorial alignment causes the right orbital rise of the ascending node (RAAN) to be prain at a rate that is highly dependent on period and slope. The Iridium satellite has a slope of 86.4 Â °, which places each satellite in a prograde orbit (inclination & lt; 90 Â °). This led to their equestrian crossing to continue pushing westward.
Iridium's reserve satellites in lower storage orbits have shorter periods so that RAAN moves westward faster than satellites in standard orbits. Iridium only waits until the desired RAAN (that is, the desired orbital plane) is reached and then raises the reserve satellites to standard heights, improving its orbital plane in relation to the constellation. While this saves a lot of fuel, it can be a time consuming process.
By mid 2016, Iridium had experienced a failure in an orbit that could not be corrected with a spare satellite in orbit, so only 64 of 66 satellites were required for unlimited global coverage in operation. Therefore, service interruptions can be observed, especially around the equator region where satellite footprints are most widespread and at least there is overlap.
Next-generation constellations
In 2017, Iridium began launching Iridium NEXT , the second generation telecommunication network worldwide, consisting of 66 active satellites, with nine spare parts in orbit and six spare parts on land. These satellites will combine features such as data transmission that is not emphasized in the original design. The constellation will provide up to 128 kbit/dt of L-band data rates to mobile terminals, up to 1.5 Mbit/dt to the Pilot Iridium sea terminal, and high-speed K a service -band up to 8 Mbit/sec for fixed/transportable terminals. Future terminals and services are expected to be commercially available by the end of 2018. However, the proposed use of Iridium from the next generation of satellites has raised concerns that service will disrupt GPS devices.
The satellite will combine a secondary charge for Aireon, the recipient of a space-qualified ADS-B data receiver. This is for use by air traffic control and, through FlightAware, for use by airlines. A tertiary payload on 58 satellites is a marine AIS ship tracker receiver.
Iridium can also be used to provide data links to other satellites in space, allowing commands and controls from other space assets regardless of the earth station and gate positions.
Launch campaign
Iridium Communications uses launch vehicles from various sources, including the Falcon 9 from SpaceX.
In June 2010, Iridium signed the largest commercial rocket launch agreement at the time, a contract worth 492 million US dollars with SpaceX to launch 70 Iridium NEXT satellites on seven Falcon 9 rockets from 2015 to 2017 through Vandenberg Air Force Base. The last two satellites are scheduled to be orbited by a launch of the ISC Kosmotras Dnepr. The technical problems and consequential demands of Iridium insurance delayed the launch of the first pair of Iridium NEXT satellites until April 2016.
The Iridium NEXT launch plan initially included satellite launches at both the Dnepr Ukraine launch vehicle and launch vehicle SpaceX Falcon 9, with an initial satellite launch at Dnepr in April 2016; However, in February 2016, Iridium announced the changes. Due to the extended slowdown in obtaining the necessary launch licenses from the Russian authorities, Iridium overhauled 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 the new satellites took over the old satellite assignment on March 11, 2017.
At the launch of the first batch, the second flight of 10 is planned to be launched just 3 months later, in April 2017. However, in a Feb. 15 statement, Iridium said that SpaceX pushed back the launch of the second batch of the NEXT Iridium Satellite from mid-April to mid-June 2017 This second launch, which occurred on June 25, 2017, sent ten other Iridium NEXT satellites into low Earth orbit (LEO) on the SpaceX Falcon 9 rocket. The third launch, which occurred on October 9, 2017 sent another 10 satellites, as planned for LEO. SpaceX targets the next five Iridium NEXTs launched approximately every two months thereafter. Iridium NEXT IV was launched with ten additional satellites on December 23, 2017. Iridium NEXT V was launched with ten additional satellites on March 30, 2018.
75 of the 81 satellites built have or will be launched between 2017 and 2018. 6 satellites will be stored on the ground as spare parts.
^ Iridium satellite numbers may change over time after failure and replacement.
Patents and Manufactures
Major patents on the Iridium system, US Patent 5,410,728: "Cellular and satellite data communications systems", and 5.604.920, are in the field of satellite communications, and manufacturers produce several hundred patents protecting the technology inside system. Satellite-making initiatives also play a role in the technical success of the system. Motorola made major recruits from engineers who set up automated factories for Apple's Macintosh. He created the technology necessary to mass-produce satellites on dreadlocks, taking weeks, not months or years and at record low construction costs of only US $ 5 million per satellite. At its peak during launch campaigns in 1997 and 1998, Motorola generated new satellites every 4.3 days, with the primary time from one satellite to 21 days.
Satellite dies
Over the years a number of Iridium satellites have stopped working and are no longer in active service, some functioning well and remain in orbit while others fall out of control or have reentered the atmosphere.
Iridium 21, 27, 20, 11, 24, 71, 44, 14, 79, 69 and 85 all suffered problems before entering service operations immediately after their launch in 1997. By 2018, from this eleven, Iridium 21, 27, 79 and 85 have decayed from orbit; Iridium 11, 14, 20 and 21 were renamed Iridium 911, 914, 920 and 921 because the same renaming was launched.
Starting in 2017, some of the first generation Iridium satellites were deliberately dide-orbited after being replaced by the operational Iridium NEXT satellite.
Iridium 33 collision
At 16:56 UTC on February 10, 2009, Iridium 33 collided with the deadly Russian satellite Kosmos 2251. This unintentional collision is the first hypervelocity collision between two artificial satellites in low Earth orbit. Iridium 33 was in active service when the accident occurred. It is one of the oldest satellites in the constellation, launched in 1997. The satellite collides at a relative speed of about 35,000 km/h (22,000 miles per hour) This collision creates a large amount of space debris that can be harmful to other satellites.
Iridium moved one of its in-orbit spares, Iridium 91 (formerly known as Iridium 90), to replace the crushed satellite, complete the movement on March 4, 2009.
See also
- Mobile satellite service
- Satellite phone
- Globalstar
- Globalsat Group
- Intersputnik
- Intelsat
- Inmarsat
- OneWeb
- O3b Networks
- Orbcomm
- Radiotelephone
- SES Broadband for Maritime
- Thuraya
References
External links
- Company website Iridium Satellite LLC
- Iridium satellite tracking
- Iridium satellite phone descriptions
- Media related to Iridium flare on Wikimedia Commons
Source of the article : Wikipedia
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