report of the action team on global navigation satellite systems (gnss)
report of the action team on global navigation satellite systems (gnss)
report of the action team on global navigation satellite systems (gnss)
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analyze <str<strong>on</strong>g>the</str<strong>on</strong>g> time signal from Global Positi<strong>on</strong>ing System Occultati<strong>on</strong> Sensors (GPSOS) asdescribed in paragraphs 238 to 241 below. 5238. Geometric determinati<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> locati<strong>on</strong> depend <strong>on</strong> inferences about <str<strong>on</strong>g>the</str<strong>on</strong>g> atmospherictemperature and moisture c<strong>on</strong>centrati<strong>on</strong>s. They provide valuable complementary informati<strong>on</strong> totropospheric infrared and microwave sounders about <str<strong>on</strong>g>the</str<strong>on</strong>g> tropopause and stratosphere. Raybending and changes in <str<strong>on</strong>g>the</str<strong>on</strong>g> phase and amplitude <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> transmitted signals allowing inference <str<strong>on</strong>g>of</str<strong>on</strong>g><str<strong>on</strong>g>the</str<strong>on</strong>g> upper atmosphere temperature pr<str<strong>on</strong>g>of</str<strong>on</strong>g>ile to <str<strong>on</strong>g>the</str<strong>on</strong>g> order <str<strong>on</strong>g>of</str<strong>on</strong>g> 1 deg K or better between altitudes <str<strong>on</strong>g>of</str<strong>on</strong>g> 8to 30 km in layers (with footprints ranging between 1 km x 30 km to 1 km x 200 km extent) withnear <strong>global</strong> coverage. The coverage would be expected to be evenly spread over <str<strong>on</strong>g>the</str<strong>on</strong>g> globe, exceptfor polar regi<strong>on</strong>s. The system measures upper atmospheric virtual temperature pr<str<strong>on</strong>g>of</str<strong>on</strong>g>iles; <str<strong>on</strong>g>the</str<strong>on</strong>g>refore,data from <str<strong>on</strong>g>the</str<strong>on</strong>g> lower atmosphere would require alternate data to separate vapour pressure andtemperature traces.239. The Global Positi<strong>on</strong>ing System Occultati<strong>on</strong> Sensor (GPSOS) will measure <str<strong>on</strong>g>the</str<strong>on</strong>g> refr<str<strong>on</strong>g>acti<strong>on</strong></str<strong>on</strong>g><str<strong>on</strong>g>of</str<strong>on</strong>g> radio-wave signals from <str<strong>on</strong>g>the</str<strong>on</strong>g> GPS c<strong>on</strong>stellati<strong>on</strong> and GLONASS. This uses occultati<strong>on</strong> between<str<strong>on</strong>g>the</str<strong>on</strong>g> c<strong>on</strong>stellati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> GPS <strong>satellite</strong> transmitters and receivers <strong>on</strong> LEO <strong>satellite</strong>s. The GPSOS willbe used operati<strong>on</strong>ally for spacecraft navigati<strong>on</strong>, characterizing <str<strong>on</strong>g>the</str<strong>on</strong>g> i<strong>on</strong>osphere, and experimentallyto determine tropospheric temperature and humidity. A similar system, GPSMET, flew in 1995.A GPS occultati<strong>on</strong> system was provided for launch <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> Oersted/Sunsat missi<strong>on</strong> and variati<strong>on</strong>swill also be included <strong>on</strong> CHAMP, SAC-C and GRACE, all scheduled to be launched before 2001.The Nati<strong>on</strong>al Oceanic and Atmospheric Administrati<strong>on</strong> (NOAA) was planning to manifest aGPSOS <strong>on</strong> all NPOESS platforms.240. The European Polar-orbiting Satellite (METOP), due to be launched in 2004, is expectedto fly a GPS Radio occultati<strong>on</strong> Atmospheric Sounder (GRAS). GRAS will provide “all wea<str<strong>on</strong>g>the</str<strong>on</strong>g>r”temperature pr<str<strong>on</strong>g>of</str<strong>on</strong>g>iles with high vertical resoluti<strong>on</strong> in <str<strong>on</strong>g>the</str<strong>on</strong>g> upper troposphere and stratosphere, andhumidity pr<str<strong>on</strong>g>of</str<strong>on</strong>g>iles in <str<strong>on</strong>g>the</str<strong>on</strong>g> lower troposphere.241. A promising research GPS system is COSMIC (C<strong>on</strong>stellati<strong>on</strong> Observing System forMeteorology, I<strong>on</strong>osphere and Climate). The Nati<strong>on</strong>al Space Program Office (NSPO) in <str<strong>on</strong>g>the</str<strong>on</strong>g>People’s Republic <str<strong>on</strong>g>of</str<strong>on</strong>g> China, <str<strong>on</strong>g>the</str<strong>on</strong>g> University Corporati<strong>on</strong> for Atmospheric Research (UCAR), <str<strong>on</strong>g>the</str<strong>on</strong>g>Jet Propulsi<strong>on</strong> Laboratory (JPL), <str<strong>on</strong>g>the</str<strong>on</strong>g> Naval Research Laboratory (NRL), <str<strong>on</strong>g>the</str<strong>on</strong>g> University <str<strong>on</strong>g>of</str<strong>on</strong>g> Texasat Austin, <str<strong>on</strong>g>the</str<strong>on</strong>g> University <str<strong>on</strong>g>of</str<strong>on</strong>g> Ariz<strong>on</strong>a, Florida State University and o<str<strong>on</strong>g>the</str<strong>on</strong>g>r partners in <str<strong>on</strong>g>the</str<strong>on</strong>g> universitycommunity are developing COSMIC, a project for wea<str<strong>on</strong>g>the</str<strong>on</strong>g>r and climate research, climatem<strong>on</strong>itoring, space wea<str<strong>on</strong>g>the</str<strong>on</strong>g>r, and geodetic science. COSMIC was planning to launch eight LEO<strong>satellite</strong>s in 2002, with each COSMIC <strong>satellite</strong> retrieving about 500 daily pr<str<strong>on</strong>g>of</str<strong>on</strong>g>iles <str<strong>on</strong>g>of</str<strong>on</strong>g> keyi<strong>on</strong>ospheric and atmospheric properties from <str<strong>on</strong>g>the</str<strong>on</strong>g> tracked GPS radio-signals as <str<strong>on</strong>g>the</str<strong>on</strong>g>y are occultedbehind <str<strong>on</strong>g>the</str<strong>on</strong>g> Earth limb. The c<strong>on</strong>stellati<strong>on</strong> will provide frequent <strong>global</strong> snapshots <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g>atmosphere and i<strong>on</strong>osphere with about 4000 daily soundings (See web site,http://www.cosmic.ucar.edu/cosmic/index.html).D. Internati<strong>on</strong>al organizati<strong>on</strong>sEuropean Group <str<strong>on</strong>g>of</str<strong>on</strong>g> Institutes <str<strong>on</strong>g>of</str<strong>on</strong>g> Navigati<strong>on</strong>242. The European Group <str<strong>on</strong>g>of</str<strong>on</strong>g> Institutes <str<strong>on</strong>g>of</str<strong>on</strong>g> Navigati<strong>on</strong> (EUGIN) is an internati<strong>on</strong>al associati<strong>on</strong>,with scientific and educati<strong>on</strong>al purposes. More precisely, <str<strong>on</strong>g>the</str<strong>on</strong>g> objectives <str<strong>on</strong>g>of</str<strong>on</strong>g> EUGIN are:5 The descripti<strong>on</strong> is an excerpt from <str<strong>on</strong>g>the</str<strong>on</strong>g> World Wea<str<strong>on</strong>g>the</str<strong>on</strong>g>r Watch, Technical Report No. 20, ObservingSystems Technologies and <str<strong>on</strong>g>the</str<strong>on</strong>g>ir Use in <str<strong>on</strong>g>the</str<strong>on</strong>g> Next Decade, WMO/TD No. 1040.44