UK-based Surrey Satellite Technology Limited (SSTL) announced this week that their exactView-1 satellite was successfully launched into a sun-synchronous polar orbit on Sunday. The tiny 100kg exactView-1 satellite is being touted as the “highest detection performance commercial Automatic Identification System (AIS) satellite ever built” and was lifted to an orbit of 800km, where it will provide near real-time AIS data on the location, speed, and routes of ships traveling throughout the world’s oceans.
AIS tracks vessel movements in near real-time and updates every two minutes when near shore stations. Terrestrial AIS transponders, using frequencies near 150 MHz, can’t reach ships in the open ocean. Small polar orbiting satellites, however, can pick up those AIS signals mid-ocean, then relay them to base stations located near the North and South poles.
Canada’s exactEarth will provide worldwide maritime traffic information in near real-time. According to its website, the organization, which is co-owned by COM DEV International and HISDESAT uses microsatellites to collect ship-monitoring data and delivers that information to customers all over the globe.
It is the fifth deployed satellite in the exactView vessel monitoring satellite constellation, which will consist of six polar orbiting satellites designed to provide an hourly update of global vessel positions (pdf).
“AIS is currently deployed on more than 80,000 vessels globally, however AIS base station receivers are mostly based on land and can only track ships moving up to 50 nautical miles off the coast,” SSTL said in a previous statement announcing the spacecraft’s launch date.
Orbcomm is the exclusive licensee for AIS data collected by VesselSat1. AIS data is used for ship tracking and other maritime navigational and safety efforts.
Orbcomm launched six AIS-equipped satellites in 2008. But the AIS satellites ceased functioning “toward the end of the fourth quarter 2010.” As part of its settlement with OHB Technology of Bremen, Germany, OHB and its Luxspace affiliate built the two dedicated AIS spacecraft for Orbcomm, following the failure of their six “Quick Launch” satellites. The U.S. Coast Guard gave Orbcomm an initial AIS contract, but that ended in late 2010 when the last of Orcomm’s six AIS-equipped satellites failed in orbit.
Orbcomm’s 27 current-generation satellites operate for the most part in an 825-kilometer orbit inclined 45 degrees relative to the equator. The second generation will be placed into a 52 degree inclination, an orbit that gives better coverage of northern latitudes to enhance Orbcomm’s AIS maritime coverage.
Globalstar plans to integrate the 24 new second-generation satellites with the eight first-generation satellites that were launched in 2007, to form a 32 satellite constellation. Sierra Nevada Space Systems of Louisville, Colo., is building the 18 2nd generation satellites under a $130 million contract that includes options to build up to 30 more.
The ESA also contracted with OHB for an AIS satellite constellation using technology from Kongsberg Seatex and others. Kongsberg Satellite Services (KSAT) is a world leading commercial satellite centre. The company currently operates Svalbard Satellite Station (SvalSat) at 78°15´N 15°80´E., (near the North Pole) and TrollSat 72°S 2°E (near the South Pole). Satellite store/dump facilities are provided in direct mode for satellites passing over the station. Data processing and distribution to any site in the world is provided.
ExactEarth AIS satellites pass over Norway’s Svalbard Earth Station every 90 to 100 minutes. AIS tracks vessel movements in near real-time and updates every two minutes or so when near shore stations.
Canada’s Com Dev claims their patented technology for “message de-collision” is superior to what Orbcomm uses. Com Dev’s technology is based on bypassing on-board processing on the satellites in favor of sending down raw message data to ground terminals. These terminals then separate hundreds of thousands of ship messages — up to 1.5 million per day per satellite — and deliver them to coastal authorities.
Their COM DEV core technology is said to enable ExactEarth to filter out all but a very specific VHF portion of the signals dedicated to AIS. To achieve global AIS coverage with a latency of about 10 minutes about 30 satellites are required.
COM DEV has calculated that only three satellites are needed to provide a six hour “revisit time”. According to CEO John Keating, “If you put three satellites in polar orbits that takes 100 minutes to complete, 120 degrees apart from one another, then [due to the earth’s rotation] you can see any point on earth within six hours – you may be over the poles once every 30 minutes, but you are everywhere over the equator once every six hours.”
ExactEarth AIS satellites pass over Norway’s Svalbard Earth Station every 90 to 100 minutes.
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