GPS Block IIFとは 意味・読み方・使い方

GPS Block IIF, or GPS IIF is an interim class of GPS satellite, which will be used to keep the Navstar Global Positioning System operational until the Block IIIA satellites become operational. They are being built by Boeing, and will be operated by the United States Air Force following their launch by United Launch Alliance, using Evolved Expendable Launch Vehicles. They will be the final component of the Block II GPS constellation to be launched. The spacecraft have a mass of 1,630 kilograms (3,600 lb) and a design life of 12 years. Like earlier GPS satellites, Block IIF spacecraft operate in semi-synchronous medium Earth orbits, with an altitude of approximately 20,460 kilometres (12,710 mi), and an orbital period of twelve hours.