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Satellite Communications. Chris Webster NSF Users Workshop 2007 NCAR - EOL. Reasons / Motivation. Safety situational awareness Remote real-time instrument monitoring Remote real-time science Remote real-time instrument control Project coordination Troubleshooting. History.
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Satellite Communications Chris Webster NSF Users Workshop 2007 NCAR - EOL
Reasons / Motivation • Safety situational awareness • Remote real-time instrument monitoring • Remote real-time science • Remote real-time instrument control • Project coordination • Troubleshooting
History • 2002, Iridium first used on the P3 for IHOP • Small data feed including A/C track. • 2003, BAMEX – P3 • Chat introduced • 2005, RAINEX - P3 • Images sent to plane were requested. • We learned a lot. • 2005, HIAPER – INMARSAT • 2007, C-130 Upgraded to INMARSAT
Existing EOL Uses • Driftsonde (Iridium) • Instrument Control & Data Retrieval • ISFF (GOES Motosat) • Summary Data Retrieval • ISS / GAUS (Motosat) • Instrument Control & Data Retrieval • Aircraft (INMARSAT & Iridium) • Chat, Two-way data, Trouble Shooting
Options • GOES • Iridium • Capabilities / Limitations / Cost • GlobalStar • Motosat / Direcway - Consumer • INMARSAT 3 • Capabilities / Limitations / Cost • High Bandwidth Line of Site Options Exist • Commercial KU Band / TDRSS S Band • Commercial Remote Internet • Ground Dish (get photo from PASE).
Iridium • Capabilities • True Global/Polar Coverage • 2800 baud per modem. • Pros • Compact • Multiple units can be ganged. • NASA DC-8 gangs 8 Iridiums. • Limitations • Low bandwidth • Thrashes and disconnects when too much traffic. • Cost • $1,500 per unit/modem (not including installation). • 7 cents per KB
INMARSAT 3 • Capabilities • 64Kbps (per modem), there are two on each aircraft. • Upcoming INMARSAT 4 • 4 times the bandwidth • Fewer coverage holes • Pros • Good bandwidth • Limitations • Not Polar (~76 degrees Latitude). • Other “holes” exist in the globe. • Cost • $300K per unit • 5.7 cents per KB • GV, 1 second data is about $270 / hour using MPDS mode.
Problems Encountered • Incomplete Global Coverage (some) • Dropped connections and cycling connections • Extraneous Traffic • Chat “away tracking” overhead • “Phone home” traffic • Microsoft automatic updates • Short time-out before redialing • Satellite Handoff • Security (Firewall necessary)
Drop-outs are a fact of life • Aircraft Shadow • GV tail wing shadows antenna on 10 degree bank turn (away from satellite). • C130 conformal antenna shadow flying to/from a satellite. • Satellite Handoff • 1 minute for INMARSAT to redial. • Holes in Satellite Coverage (INMARSAT).
Applications • Internet Relay Chat (IRC) • Data Feed from aircraft • Into SQL database available to anyone for real-time ground processing/display. • Generic file transfer • Google Earth tracks with satellite overlays • onboard and on ground.
What do you want? • Communication (chat) • Current weather products up to aircraft • Situational awareness (onboard and ground). • Aircraft Guidance / Coordination • Instrument monitoring • Are there unsatisfied needs? • Instrument Control • Short transmission lag
Questions • How can we connect with the other SATCOM communities (e.g. Marine, Polar Research, Earth Sciences, Oil, Security, Transportation, HAM)?