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HEO - Daylight Tracking

HEO - Daylight Tracking. Some things to consider. What makes daylight so special?. Day: Background noise level is higher Night: Rangegate, FOV... who cares?. What makes HEOs so special?. ... they are not known as HEOs for nothing! ... they are far away!.

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HEO - Daylight Tracking

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  1. HEO - Daylight Tracking Some things to consider...

  2. What makes daylight so special? • Day: Background noise level is higher • Night: Rangegate, FOV... who cares?

  3. What makes HEOs so special? ... they are not known as HEOs for nothing! ... they are far away! The array measures 239 millimeters in length, 194 millimeters in width, and 37 millimeters in height and weighs 1.27 kilograms. At normal light incident angle, the aperature of an individual cube corner is a rectilinear hexagon equivalent in area to a circle 28.6 millimeters in diameter. 1. Degnan, J.J., Pavlis, E.C., "Laser Ranging to GPS Satellites with Centimeter Accuracy", GPS World, 9, 1994

  4. HEO - Tracking: Link Budget Range Dependence good collimation required! System Divergence ≈ http://www.wettzell.ifag.de/publ-cgi-bin/linkbudget.py

  5. HEO - Tracking: Pointing • Collimation reduces the spatial Coverage • The further the Target is away, the more it hurts • Because of a worse SNR, scanning also takes a lot longer • All this adds to Observer Frustration - Result: NO PASSES

  6. Daylight - Tracking: “The 3 Buddies” Receiver Field of View Laserbeam Pointing Telescope Pointing (Mount Model) • The Receiver FOV is limited: Background Light! • The Pointing defines the Tracking Offsets • If the Cross Section between FOV and Laser reduces to 0 --> no Returns • The further the Satellite is away, the more the 3 Buddies separate --> the worse it gets.

  7. Daylight - Tracking: “Secondaries” • The Receiver FOV wants to be small - reduces Amount of Background Light • Narrow Spectral Filtering is less important than common Lore tells us... • The Rangegate wants to be short - NO Problem for current Predictions • Observer Motivation (Big Issue)! - Noone loves frustrating Jobs

  8. CONT05 CAMPAIGN PASS SEGMENTS CUMULATIVE DATA YIELD SINCE 01-SEP-2005 Station PAD WAVE GPS35 GPS36 GLONASS87 GLONASS89 GLONASS95 TOTAL --------------- ----- ----- ----- ----- --------- --------- --------- ----- Maidanak 1864 5320 5 5 3 13 Simeiz 1873 5320 1 4 5 Riga 1884 5320 1 1 Mcdonald Observ 7080 5320 8 8 11 3 4 34 Yarragadee 7090 5320 39 2 53 35 51 180 Greenbelt 7105 5320 1 1 10 5 17 Monument Peak 7110 5320 14 11 14 14 18 71 Changchun 7237 5320 2 1 3 Tanegashima 7358 5320 2 2 Hartebeesthoek 7501 5320 17 36 53 Zimmerwald 7810 4230 9 16 16 19 16 76 Zimmerwald 7810 8460 7 13 15 20 15 70 Mt Stromlo 7825 5320 2 7 11 6 26 Riyadh 7832 5320 19 17 9 11 56 Graz 7839 5320 6 7 13 10 7 43 Herstmonceux 7840 5320 6 8 8 8 30 Wettzell 8834 5320 4 3 15 11 17 50 ----- ----- --------- --------- --------- ----- 109 84 187 199 151 730

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