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

2. 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

3. 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%

4. 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

5. 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)
Bit Rate (dBHz) 90
SNR (Eb/No)
24,67

6. 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

7. 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!

8. 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

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