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? 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, they are not known as HEOs for nothing!... they are far away!

HEO - Tracking: Link Budget Range Dependence System Divergence ≈ good collimation required!

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

Daylight - Tracking: “The 3 Buddies” Laserbeam Pointing Telescope Pointing (Mount Model) Receiver Field of View 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.

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

CONT05 CAMPAIGN PASS SEGMENTS CUMULATIVE DATA YIELD SINCE 01-SEP-2005 Station PAD WAVE GPS35 GPS36 GLONASS87 GLONASS89 GLONASS95 TOTAL Maidanak Simeiz Riga Mcdonald Observ Yarragadee Greenbelt Monument Peak Changchun Tanegashima Hartebeesthoek Zimmerwald Zimmerwald Mt Stromlo Riyadh Graz Herstmonceux Wettzell