ES Link (uplink: code instructions)

Attenuations	-267.9dB
TX antenna gain	69.8 dBi
Transmit power	4kW [1]
	36 dBW
RX antenna gain	40.7 dBi
Received power	-130.2 dBW
Noise power	-152 dBW
System noise temp.	150 K
CNR	21.8 dB

ES Link (downlink: seismic data)

Attenuations	-227.9 dB
TX antenna gain	42.0 dBi
Transmit power	200 W
	23.0 dBW
RX antenna gain	71.0 dBi
Received power	-141.9 dBW
Noise power	-152 dBW
System noise temp.	150 K
CNR	10.1 dB

As mentioned before, the ES link operates in X-band, where the uplink is at 7.3 GHz and the downlink is at 8.4 GHz. For the free-space pathloss, the average distance between Venus and Earth is considered, which is 1.5 AU (atmospheric unit) or 224,000,000 km. Using these values, the attenuation is calculated as

The satellite antenna has 1.3 meters of diameter with efficiency 0.6. The DSN antenna has 34 meters diameter with efficiency 0.7. The antenna gain G of the appropriate antenna is calculated as

where

• : the efficiency
• : the area of the antenna.

Moreover, The thermal noise power is calculated as

where k is the Boltzmann's constant, B is the bandwidth. To achieve as high CNR as possible, we employ a BPSK modulation and the half-rate turbocode. A raised-cosine filterwith roll-off factor 0.5 is used as the pulse to achieve a RF bandwidth of 300kHz.

SV Link (uplink: VIRGILs to Satellite)

EIRP	277 MW / 84.4 dBW
Dish antenna gain	30 dBi
RX gain	40.7 dBi
SNR	-48.5 dB [2]

SV Link (downlink: Satellite to VIRGILs)

TX power	23.0 dBW
TX gain	40.7 dBi
SNR	-47.8 dB [2]

As discussed before, the link between the orbiter and VIRGILs operate at 7.3 GHz to achieve the maximum SNR. The SNRs for uplink and downlink are estimated from Figs. 1-2, which shows the measured SNRs vs. the wavelength. Assuming the satellite is directly above the antennas, the incident angle of 0-degree is assumed here.

IV Links (VIRGILs to VIRGILs)

EIRP	24kW / 43.8dBW
RX gain	85dB
Attenuation (10km)	-11dB
Received power	18.8dBW
Noise power	-144.5dBW
System noise temp.	150K
Atm. noise temp.	740K [2]

Recall that the attenuation over the Venusian atmosphere increases with the frequency. Hence, we chose the lower frequency spectrum to mitigate the pathloss of the signal between two VIRGILs. For calculation, the average distance between two VIRGILs at 10 km is assumed. The temperature of the Venusian atmosphere is found from Fig. 1.