# K/Ka-Band Very High Data-Rate Receivers: A Viable Solution for Future Moon Exploration Missions
## 3 Mission Scenario  
Future Moon explorations will be characterized by quite complex mission scenarios, as many different vehicles and spacecrafts will be involved [2]. Preliminary plans from the major space agencies foresee the usage of a LOP-G in cislunar orbit, the adoption of a small- to medium-size constellation of space vehicles or LRS around the Moon, and lunar surface elements (LSEs) such as rovers, landers and so on. All these vehicles should be able to communicate with each other and with the ground stations on the Earth. Finally, for the LRS, cubesats could be adopted, which calls for further constraints due to the well-known limitations of these platforms with respect to size, mass and power consumption. After the basic considerations of the previous section, a more in-depth mission scenario is considered here. All the simulations were performed with STK, [9]. In creating the scenario, only the case of a direct communication between Earth and Moon was considered (i.e., no repeaters and no transponders), since this is the most critical situation (greater link distance, presence of the Earth atmosphere). Three ground stations were assumed on the Earth (with the transmitters), namely:  
* ESRIN (Lat. 41.83 \({}^{\circ}\) N, Lon. 12.68\({}^{\circ}\) E),
* New Norcia (Lat. 31.04 \({}^{\circ}\) S, Lon. 116.19\({}^{\circ}\) E),
* Guiana Space Center (Lat. 5.23 \({}^{\circ}\) N, Lon. 52.77\({}^{\circ}\) W),  
The receiver, instead, was on a base located near the South pole of the Moon (Lat. 66.41 \({}^{\circ}\) S, Lon. 9.82 \({}^{\circ}\) W). The disposition of these ground stations guarantees a full coverage of the Moon. The receiver, on the other hand, has been positioned on the face of the Moon visible from the Earth. For realistic simulations, the Earth atmosphere model was included. The analysis considered also the motion of the celestial bodies and their influence on the communication. Each ground station is equipped with a 10 m parabolic antenna and, according to Table 2, transmits a power of 100 W in the K-band at 22.85 GHz. A data stream of 100 Mbit/s modulates the carrier with a quadrature phase shift keying (QPSK) constellation, so that the resulting signal bandwidth is of about 50 MHz. To improve the environment simulation, some models were included in the scenario, like: (i) the ITU-R P.618, to model the total propagation losses; (ii) the ITU-R P.676-9, to model the atmospheric absorption due to gases [14]. Regarding the receiver, likewise the transmitters, a parabolic antenna with the same efficiency is assumed but, in this case, with a 50 cm diameter (see Table 1). The receiver noise figure is \(F_{RX}=3\) dB and the corresponding system noise temperature is modeled according to (6). Finally, STK computes the antenna noise temperature using Sun, atmospheric and cosmic background noise models. Depending on the modulation scheme used in the transmission, the demodulator can be selected automatically by the software and is useful for bit error rate (BER) estimations. The computations were performed on a time interval of one month, from the first of January 2025 to the first of February of the same year. As it is understandable, depending on the ground station position and calculation time, the results may vary significantly. Thus, two case studies are considered onwards. The first one is when only two ground stations are visible from the Moon, namely: ESRIN and New Norcia. In the second case, instead, all three ground stations are in visibility to the Moon base. Figure 2 reports Moon-centered and Earth-centered visuals in two different days: 1 January 2025 (first case of study) and 17 January 2025 (second case of study). The main results are quoted in Table 3 for the two different situations. Here \(C/N\) is the carrier-to-noise ratio and \(E_{b}/N_{0}\) is the energy per bit to noise power spectral density ratio (\(\frac{E_{b}}{N_{0}}=\frac{C}{N}\frac{B}{f_{b}}\)  
Figure 2: Distances and angles.