GPS World, March 2018

SYSTEM SYSTEMS SYS OF Policy and System Developments GPS Galileo GLONASS BeiDou Accuracy from LEO Birds Improves FIGURE 1 OCXO timing result with base station BeiDous Long March Air Force Issues GPS III Follow on Contract T he U S Air Force Space Command released its request for proposals to build 22 new GPS III satellites called the GPS III Follow On Phase 2 contract The contract will be awarded to a single bidder and has an estimated dollar value of 10 billion including all options Phase 2 is planned as a single predominantly fixed price incentivetype contract awarded via full and open competition for production of 22 GPS III satellites Deadline for proposals is April 16 Delivery of the first satellite is to be in 2026 Phase 1 contracts awarded in May 2016 to Boeing Northrop Grumman and Lockheed Martin builder of the first 10 GPS III satellites determined that viable low risk high confidence sources exist to conduct a full and open competition for Phase 2 the production of 22 GPS III SVs space vehicles starting in the FY19 timeframe 8 GPS WORLD WWW GPSWORLD COM MARCH 2018 O n Feb 12 BeiDou 3 28 and 29 were launched into medium Earth orbits following the launch of a pair of BeiDou satellites on Jan 11 The satellites form part of a third phase of BeiDou deployment taking BeiDou coverage from regional to covering the countries along the Belt and Road initiative by the end of 2018 and global by 2020 Stay up to date with GPS Worlds Upcoming GNSS Satellite Launches table at gpsworld com upcoming R esults from new tests of the Satellite Time and Location STL service using equipment configurations with a differential source and with a more accurate OCXO clock show timing accuracy of 160 nanoseconds The STL service uses a signal from the low Earth orbit LEO Iridium constellation In 2016 Satelles demonstrated sub microsecond timing using a stand alone TCXO based receiver see Innovation Navigation from LEO July 2017 GPS World New testing employed three different configurations of equipment services and environment including a Stanford Research Systems SRS rubidium vapor frequency reference based on the PRS10 module and a Satelles Evaluation Kit EVK2 STL receiver comprising a Maxim RF chip Xylinx Spartan 3 FPGA TI dual core DSP chip and internal OCXO oven controlled crystal oscillator or external clock Parameters and equipment for the three tests are 1 Optimal Outdoor antenna Rubidium clock powered on for months prior to data collection receiver configured in static mode with a known location and high quality antenna 2 Sub optimal Indoor antenna Rubidium clock powered on six hours prior to data collection receiver configured in static mode with an unknown location and low quality antenna 3 Three independent receivers collecting data receiver on board OCXO indoor antenna receiver configured in static mode with an unknown location low quality antenna Tests performed 10 days with no local reference station running 10 days with local reference station 20 kilometers away from test receivers providing timing corrections to STL ground segment See FIGURE 1 and gpsworld com STLimproves for more extensive test results The 66 satellite Iridium LEO constellation transmits overlapping spot beams which provide location specific data that changes every few seconds