| Link Budget for Artemis II. Updated: 2026-07-09 12:20:28. See: https://www.sarcnet.org/files/link_budget.py |
|---|
| |
| 1. Constants: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 1.01 | c | 299792458 | m/s | Speed of light constant |
| 1.02 | k | 1.380e-23 | W/Hz/K | Boltzmann's constant |
| |
| 2. Artemis spacecraft data: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 2.01 | f | 2216509018 | Hz | Received Frequency of the Artemis downlink derived from the Bochum video |
| 2.02 | l = c/f | 0.13525 | m | Received Wavelength of the Artemis downlink derived from the Bochum video |
| |
| 3. AMSAT-DL Bochum 20m Radio Telescope data: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 3.01 | GTdB = 30.0-(2.3-(f/1e9))*(32.6-30.0)/(2.4-2.3) | 27.8 | dB/K | G/T for Bochum (dB) extrapolated for f from the AMSAT-DL website |
| 3.02 | GT = lin(GTdB) | 606.6 | /K | G/T for Bochum extrapolated for f from the AMSAT-DL website |
| |
| 4. Estimate the Artemis downlink Equivalent Isotropic Radiated Power (EIRP) derived from Bochum video data: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 4.01 | r | 184034000 | m | Range to Artemis derived from the Bochum video |
| 4.02 | PsdB | -80 | dB | The signal peak (dB) derived from the Bochum video |
| 4.03 | PndB | -95 | dB | The noise floor (dB) derived from the Bochum video |
| 4.04 | SNNRdB = PsdB - PndB | 15.0 | dB | Signal plus Noise to Noise Ratio (dB) derived from the Bochum video |
| 4.05 | SNNR = lin(SNNRdB) | 31.6 | | Signal plus Noise to Noise Ratio derived from the Bochum video |
| 4.06 | FSPL = (l/(4*pi*r))**2 | 3.4e-21 | | Free Space Path Loss derived from the Bochum video |
| 4.07 | FSPLdB = dB(FSPL) | -204.7 | | Free Space Path Loss (dB) derived from the Bochum video |
| 4.08 | B | 8000000 | Hz | Bandwidth of receiver derived from the Bochum video |
| 4.09 | Pt = 0.5*(SNNR-1)*k*B/(FSPL*GT) | 815 | W | Estimate of Artemis transmitted EIRP |
| 4.10 | PtdB = dB(Pt) | 29.1 | dBW | Estimate of Artemis transmitted EIRP (dBW) |
| |
| 5. System Dish calculations: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 5.01 | FD | 0.35 | | Focus to Diameter ratio of the dish |
| 5.02 | dt | 5 | degrees | Delta theta: Increment for all numerical integrations |
| 5.03 | d1 | 1.8 | m | Diameter of the dish reflector |
| 5.04 | d2 | 0.12 | m | Diameter of the feed antenna |
| 5.05 | e_mesh | 0.0018 | m | Mesh RMS surface error of the dish |
| 5.06 | a_mesh | 0.0030 | m | Mesh hole size of the dish |
| 5.07 | r_mesh | 0.0002 | m | Mesh wire radius (thickness / 2) of the dish |
| 5.08 | psi = dt*round(degrees(2*atan(1/(4*FD)))/dt) | 70 | degrees | Half-angle of Dish Rim at the focus point |
| 5.09 | theta_b = dt*round(degrees(2*atan(d2/d1/(4*FD)))/dt) | 5 | degrees | Half-angle of Feed Antenna at the focus point |
| 5.10 | cot_squared_psi_on_2 = (1/tan(radians(psi)/2))**2 | 2.040 | | cot squared psi on 2 |
| 5.11 | n_ill_numerator = 2*cot_squared_psi_on_2*integral(sqrt_p_tan_theta_on_2,0,psi,dt)**2 | 0.200 | | Illumination efficiency numerator |
| 5.12 | n_ill_denominator = integral(p_sin_theta,0,psi,dt) | 0.257 | | Illumination efficiency denominator |
| 5.13 | n_spill_numerator = integral(p_sin_theta,0,psi,dt) | 0.257 | | Spillover efficiency numerator |
| 5.14 | n_spill_denominator = integral(p_sin_theta,0,180, dt) | 0.267 | | Spillover efficiency denominator |
| 5.15 | n_block_numerator = integral(sqrt_p_tan_theta_on_2,theta_b,psi,dt)**2 | 0.048 | | Blocking efficiency numerator |
| 5.16 | n_block_denominator = integral(sqrt_p_tan_theta_on_2,0,psi,dt)**2 | 0.049 | | Blocking efficiency denominator |
| 5.17 | n_ill = n_ill_numerator/n_ill_denominator | 0.779 | | Illumination efficiency of the dish |
| 5.18 | n_spill = n_spill_numerator/n_spill_denominator | 0.965 | | Spillover efficiency of the dish |
| 5.19 | n_block = n_block_numerator/n_block_denominator | 0.983 | | Blocking efficiency of the dish |
| 5.20 | n_ruze = exp(-(4*pi*e_mesh/l)**2) | 0.972 | | Ruze efficiency of the dish |
| 5.21 | n_mesh = 1-((2*a_mesh/l)*log(a_mesh/(2*pi*r_mesh)))**2 | 0.999 | | Mesh efficiency of the dish |
| 5.22 | n = n_ill*n_spill*n_block*n_ruze*n_mesh | 0.72 | | Aperture efficiency of the dish |
| 5.23 | A = n*pi*(d1**2)/4 | 1.83 | m^2 | Effective area of the dish |
| |
| 6. System Gains and Noise Figures: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 6.01 | GlnadB | 15.0 | dB | LNA Gain (dB) |
| 6.02 | Glna = lin(GlnadB) | 31.6 | | LNA Gain |
| 6.03 | NFlnadB | 0.35 | dB | LNA Noise Figure (dB) from TQP3M9037 datasheet |
| 6.04 | NFlna = lin(NFlnadB) | 1.08 | | LNA Noise Figure from TQP3M9037 datasheet |
| 6.05 | GfildB | -0.37 | dB | Filter Gain (dB) |
| 6.06 | Gfil = lin(GfildB) | 0.92 | | Filter Gain |
| 6.07 | NFsdrdB | 3.00 | dB | SDR Noise Figure (dB) from AD9363 datasheet |
| 6.08 | NFsdr = lin(NFsdrdB) | 2.00 | | SDR Noise Figure from AD9363 datasheet |
| |
| 7. System Noise Temperatures: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 7.01 | T0 | 290.0 | K | Standard reference temperature |
| 7.02 | Ts | 36.0 | K | Sky Noise Temperature from ITU-R P.372-14 (Worst case) |
| 7.03 | Tg = T0 | 290.0 | K | Ground Noise Temperature from ITU-R P.372-14 (Worst case) |
| 7.04 | Tlna = T0*(NFlna-1) | 24.3 | K | LNA Noise Temperature |
| 7.05 | Tfil = T0*((1/Gfil)-1) | 26.1 | K | Filter Noise Temperature |
| 7.06 | Tsdr = T0*(NFsdr-1) | 288.6 | K | SDR Noise Temperature |
| 7.07 | Tr = Tlna + Tfil/Glna + Tsdr/(Glna*Gfil) | 35.1 | K | Receiver Noise Temperature |
| 7.08 | Ta = (n_spill*Ts)+((1-n_spill)*Tg) | 45.0 | K | Antenna Noise Temperature |
| 7.09 | Tsys = Ta + Tr | 80.1 | K | System Noise Temperature |
| 7.10 | TsysdB = dB(Tsys) | 19.0 | dB/K | System Noise Temperature (dB/K) |
| |
| 8. System Figure of Merit: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 8.01 | GdB = dB(4*pi*A/(l**2)) | 31.0 | dB | Gain of the dish (dB) |
| 8.02 | G = lin(GdB) | 1253.9 | | Gain of the dish |
| 8.03 | GT = G/Tsys | 15.7 | /K | G/T of the system |
| 8.04 | GTdB = GdB-TsysdB | 11.9 | dB/K | G/T of the system (dB/K) |
| |
| 9. Estimate the SNNR of the Artemis downlink from the Moon: |
|---|
| |
| Line | Parameter | Value | Units | Comments |
| 9.01 | r | 405696000 | m | Max range to moon |
| 9.02 | FSPL = (l/(4*pi*r))**2 | 7.0e-22 | | Free Space Path Loss |
| 9.03 | FSPLdB = dB(FSPL) | -211.5 | | Free Space Path Loss |
| 9.04 | B | 4000000 | Hz | Bandwidth of receiver |
| 9.05 | SNNR = 2*(Pt*FSPL*GT/(k*B))+1 | 1.3 | | SNNR |
| 9.06 | SNNRdB = dB(SNNR) | 1.22 | dB | SNNR (dB) |