# Juno RF power output

What is the RF Power Output from Juno into its Parabolic dish, and the RF radiated out from the dish and the eventual power received say at the dish in Canberra which obviously then would need to be amplified immensely.

tl;dr: Juno's transmitter, about 28W, power out of the antenna, about 80% of that. Power received, about 1 to 2E-16 Watts by a 70 meter dish antenna. There are three 70 meter DSN dishes; one each in Canberra, Madrid, and the Goldstone complex in California.

From Spaceflight101's excellent writeup Juno Spacecraft Information:

Juno’s Communication System works as both, a science instrument and communication subsystem. The High Gain Antenna of the spacecraft supports X-Band communications with Earth for command uplink and science data & telemetry downlink. The subsystem also pro­vides for dual-band (X- and Ka-band) Doppler tracking for gravity science at Jupiter. (emphasis added)

After clicking through several menus I found https://www.missionjuno.swri.edu/spacecraft/juno-spacecraft#group_communication

The five different antennae that comprise Juno's communication system

HIGH-GAIN ANTENNA (HGA) The high-gain antenna (named for the gain achieved though its narrowly focused beam, sits on top of the electronics vault. This 2.5-meter (8-foot) -wide, saucer-shaped radio antenna is Juno’s main communications link with Earth. It will be the primary antenna used during Juno’s time at Jupiter. The HGA has the strongest signal of the spacecraft’s five antennas, which enables Juno to transmit data at a much higher rate than the others. The antenna will transmit less power than a 40-watt light bulb, yet this will be sufficient to carry all the results from the scientific instruments, plus information about the spacecraft’s health and safety. Juno’s HGA is protected from heat produced by the sun’s harsh light with insulating blankets when it is in the inner solar system. (emphasis added)

If you would like to try to do the link budget calculation yourself, you can follow the calculation that I did for Voyager in this answer.

However it's easier to look at Table 3-4 Juno Cruise HGA X-band downlink DCT starting on page 44 of the DESCANSO Design and Performance Summary Series Article 16m Juno Telecommunications by Ryan Mukai, David Hansen, Anthony Mittskus, Jim Taylor, and Monika Danos.

In short, using Watts = 10^((dBm-30)/10), the nominal transmitter power of 44.5 dBm would be about 28 Watts, not quite the "40 Watt light bulb" mentioned above. The circuit loss is only -0.9 dB is about a 20% loss. The antenna gain is 44.7 dBi (the "i" means relative to a theoretical isotropic antenna) or about half that of Voyager's high gain antenna (48 dBi).

After a nominal path loss ("space loss") of -248 dB and a DSN receiving dish antenna gain of +68 dB, the received power is about -129 dBm, or about 1.3E-13 mW or 1.3E-16 Watts.

By a very happy coincidence, NASA's Deep Space Network's DSN Now is showing both transmitting and receiving signals to/from Juno right now as I am writing this! This is possible because uplink and downlink are on different X-band frequencies; downlink: 8.3 to 8.6 GHz, uplink: 7.1 to 7.2 GHz. Juno's X-band diplexer is discussed here and a summary is shown below.

2.23E-19 kW is 2.23E-16 W, very close to the nominal values in the table.

DSS-14 is the huge 70 meter dish at DSN's Goldstone complex. You can read more about DSS-14 (or see more pictures) and about deep space communications and science within Stack Exchange here and here.

                                          Design   Fav   Adv   Mean   Var
Link Parameter                     Unit   Value    Tol   Tol   Value
-----------------------------------------------------------------------------------------------
TRANSMITTER PARAMETERS
1. S/C transmitter power           dBm    44.40   0.30  0.00   44.50 0.0050
2. S/C Xmit circuit loss           dB     -0.90   0.10 -0.10   -0.90 0.0033
3. S/C Antenna Gain                dBi    44.70   0.50 -0.50   44.70 0.0417
4. Degrees-off-boresight DOFF loss dB      0.93  -0.00 -0.00    0.93 0.0000
5. S/C transmit pointing loss      dB      0.00   0.00  0.00    0.00 0.0000
6. EIRP (1+2+3-4+5)                dBm    87.37   0.67 -0.67   87.37 0.0500
-----------------------------------------------------------------------------------------------
PATH PARAMETERS
7. Space loss                      dB   -284.46   0.00  0.00 -284.46 0.0000
8. Atmospheric attenuation         dB     -0.06   0.00  0.00   -0.06 0.0000
-----------------------------------------------------------------------------------------------
9. DSN antenna gain                dBi    68.26   0.10 -0.20   68.22 0.0039
10. DSN antenna pointing loss      dB     -0.10   0.10 -0.10   -0.10 0.0033
11. Polarization loss              dB     -0.05   0.10 -0.10   -0.05 0.0033
-----------------------------------------------------------------------------------------------
TOTAL POWER SUMMARY
12. Tot Rcvd Pwr (6+7+8+9+10+11)   dBm  -129.08  -0.74  0.74 -129.08 0.0606


Further interesting information:

13. SNT due to Antenna-MW          K      16.33  -1.00  2.00   16.67 0.3889
14. SNT due to Atmosphere          K       3.68   0.00  0.00   3.68  0.0000
15. SNT due to Cosmic Backgnd      K       2.69   0.00  0.00   2.69  0.0000
16. SNT due to the Sun             K       0.00   0.00  0.00   0.00  0.0000
17. SNT due to other Hot Bodies    K       0.00   0.00  0.00   0.00  0.0000
18. SNT (13+14+15+16+17)           K      22.70  -1.00  2.00   23.03 0.3889
19. Noise Spectral Density         dBm/Hz -185.04 -0.20 0.37 -184.98 0.0136
20. Received Pt/N0 (12-19)         dB-Hz  55.90   0.82 -0.82   55.90 0.0741
21. Received Pt/N0, mean-2 Sigma   dB-Hz  55.36   0.00  0.00   55.36 0.0000
22. Required Pt/N0                 dB-Hz  51.80   0.00  0.00   51.80 0.0000
23. Pt/N0 Margin (20–22)           dB      4.10   0.82 -0.82   4.10  0.0741
24. Pt/N0 Margin, mean-2sig (21–22)dB      3.55   0.00 -0.00   3.55  0.0000