CAY link Station for VSOP-2 Satellite down-link budget and Status Centro Astronómico de Yebes, Observatorio Astronómico Nacional (IGN)

CAY Link budget Considerations Transmission parameters – Space craft (antenna, transmiter). As Given. Rain and atmospheric gas attenuation On site measurements and models Reception parameters Link station upgraded Cooled receiver Other aspects Availability of the link strongly affected by radome Wind 100% Rain 0% during rain

Rain attenuation link VSOP-2 14m antenna CAY Worst measured case. Rain attenuation link VSOP-2 14m antenna CAY Frequency (GHz) 37,44 Operational frequency k 0,27 function of the fr α 0,98 R(mm/h) 14,00 precipitable water p(%) 1,00 % of time hs 951,00 station altitude φ(º) 40,00 station latitude ρ applicable for φ≥20º hr (m) 3735,59 0º isotherm θ(rad) 0,79 antenna elevation Ls 3939,57 effective rain length rp 0,89 related with homogeneity of rain Aoo1 (dB) 12,64 Rain exceeded attenuation t=0,01% At p(%) 1,52 applicable for 0,001<p<1%

Atmospheric attenuation (H2O, O2) Gas Attenuation link VSOP-12 14m antenna CAY r 7,50 vapour water density (gr/m^3) f 37,44 link frequency go 0,03 dB/km gw 0,07 ho 3,83 1GHz<f<56,7GHz hw 1,66 f<350GHz Ag 0,35 dB

Satellite Link Budget Spread Sheet VSOP-2 at 14m in CAY at Ka band Down-link budget Satellite Link Budget Spread Sheet VSOP-2 at 14m in CAY at Ka band   Link frequency (GHz) 37,44 Link wavelenght (m) 0,008 Satellite range (km) 30000 Space Craft Transmitter power (dBW) 13,01 Tx Antenna diameter (m) 0,80 Tx Antenna efficiency 0,65 Gain Tx Antenna (dB) 48,06 Pointing Loss (dB) 0,20 Polarization+Cable loss (dB) 5,50 Medium Path loss (dB) 213,45 Rain loss (dB) 1,52 H2O,O2 loss (dB) 0,35 Earth Station   Rx Antenna diameter (m) 13,72 Rx Antenna efficiency 0,65 Rx antenna surface efficiency 0,90 Gain Rx Antenna (dB) 72,29 Pointing loss 0,50 Feed,optics and polarization loss 1,00 Radome losses 3,00 Gain Sum (dB)=Ptx+Gtx+Grx-Lt -92,17 Boltzman´s constant (dBW/K*Hz) -228,60 System Noise (K) 150,00 Noise PSD (dB/Hz) -206,84 Bit Rate (bits/sec) 1000000000 Bit Rate (dBHz) 90 SNR (Eb/No) 24,67

Down-link budget SNR=24.67 dB 14,37 10,30 Margin Calculation (dB) 8   Required ideal SNR (dB) 8 Spacecarft modulator (dB) 1 Earth Station demodulator (dB) 1,30 Required SNR (dB) 10,30 Margin (dB) 14,37

Down-link budget (37,44GHz) p=1%, θ=45º M=14,37dB p=1%, θ=10º M=11,8dB p=0,1%, θ=45º M=11dB p=0,1%, θ=10º M=2,9dB p=0,01%, θ=45º M=3,27dB p=0,01%, θ=10º M=-18dB Radome under rain = + Attenuation+ Tsys probably NO LINK during rain >3 dB Tsys increase >2 dB Losses increase But windy days exceed rainy days!

Down-link budget (26GHz) p=1%, θ=45º M=11,9dB p=1%, θ=10º M=10,5dB p=0,1%, θ=45º M=10,1dB p=0,1%, θ=10º M=5,7dB p=0,01%, θ=45º M=5,9dB p=0,01%, θ=10º M=-5,7dB

A POSSIBLE ROADMAP FOR YEBES Mechanical upgrade study 2007 Link station common design 2007 High speed connection (>1 Gbps) 2008 Mechanical actuations 2008-2009 Servo upgrade and replacements Reflector improvement Radome repair VLBI & up-down link equipment 2009-2010