• Document: VELOX-CI: Advanced Application of GPS for Radio Occultation and Satellite Attitude Determination
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VELOX-CI: Advanced Application of GPS for Radio Occultation and Satellite Attitude Determination Yung-Fu Tsai, Guo Xiong Lee and Kay Soon Low Satellite Research Centre (SaRC) School of Electrical and Electronic Engineering 30/09/2015 1 1 Satellite Programs @SaRC 2015 2016 2015 2014 2014 2011 2013 2 VELOX-CI Mission objectives  Radio occultation for climate study  GPS based attitude determination  Star tracker algorithm PDR CDR FRR EQM FM APR 2013 AUG 2014 Sep 2015 PDR : Preliminary Design Review CDR : Critical Design Review FRR : Flight Readiness Review 5 3 Radio Occultation Principle • GPS measurement in atmosphere  Doppler shift  Ray bending angle  Profile of index of refraction (function of atmospheric density)  Temperature & humidity profile, characteristics of the ionosphere GPS GPS LEO Clear LOS LEO With Bending ࢜ ࢜ GPS ࢻ LEO ࢜ Earth 4 4 GPS RO Activities in Space • CHAMP (CHAllenging Minisatellite Payload) – Since 2000~2009 – Near polar orbit – Earth's gravity and magnetic field study / atmospheric limb sounding • GRACE (Gravity Recovery And Climate Experiment) CHAMP GRACE – Since 2002 – Near circular polar orbit – Gravity field variations study / GPS occultation • FORMOSAT-3/COSMIC – Since 2006 (6 satellite constellation) – Inclination 72 deg circular orbit – GPS occultation experiment / tiny ionosphere photometer FORMOSAT-3/ COSMIC • Metop, TerraSAR-X, KOMPSat-5, COSMIC-2, etc. CubeSat-Sized • CANX-2: First radio occultation experiment using a CubeSat – University of Calgary and Toronto – Launched in April 2008 • PSSC-2: First successful occultation profiles on a CubeSat – United States Air Force – Launched in July 2011 • Spire Lemur2, MIT MicroMAS, etc. 5 5 Near Equatorial Orbit GPS RO Experiment • Satellite orbit at 550 km altitude, 9 degree inclination • 600 Onlyprofiles per day 450 profiles percould be obtained day could be obtained (under house-keeping mode) • Distributed uniformly around tropical region 80 80 60 60 40 40 (deg) (deg) 20 20 Latitude Latitude 00 -20 -20 North -40 -40 -60 -60 -80 -80 -150 -150 -100 -50 0 50 100 150 Longitude East (deg) Longitude (deg) 6 6 Ground-based Collaboration • International GNSS Service (IGS Network) – Collect high

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