# Telecommunication Systems for Small Satellites Operating at High Frequencies: A Review
## 3 MarCO
### Hardware Characteristics  
The main component of the telecommunication system for the MarCO mission is the Iris radio. Originally designed at JPL for the NSPIRE (Interplanetary NanoSpacecraft Pathfinder In Relevant Environment) mission [4], the Iris radio aims to be a CubeSat compatible radio to support not only telecommunication but also navigation functionalities for interplanetary CubeSat and small satellite missions. Iris has a modular design with interchangeable boards to allow interoperability at different frequencies. For the MarCO mission, the Iris radio (Figure 5) was composed of five slices: a power slice, an FPGA slice for the major digital signal processing functions, a transmitting slice at the X-Band, a receiving slice at X-Band and a receiving slice at UHF. Iris radio is a software defined radio which allows flexibility in the selection of the central frequency which is again important due to the fact that in many of the CubeSat missions the development schedule is such that the frequency license application is filed concurrently with the development of the telecommunication system. The Iris radio at X-band is compatible with both the Near Earth and Deep Space frequency ranges (8400-8500 MHz for downlink, 7145-7235 MHz for uplink), and it performs multiple navigation functions: ranging, Doppler, and Delta-Differential One-way Ranging (DDOR). It can operate in both non-coherent and coherent modes with a turn-around ratio of 880/749. The noise factor of the receiver is variable depending on the environmental conditions but it does not exceed 5 dB. In downlink, it allows for either subcarrier or direct carrier BPSK modulation with multiple encoding options: Reed Solomon (255,223), convolutional (K = 7, r = 1/2), Turbo \(\frac{1}{2}\), Turbo 1/3 and Turbo 1/6. Downlink data rates range from a minimum of 62.5 bps to a maximum of 256 kbps. The uplink signal from DSN is uncoded PCM/PSK/PM and it ranges from a minimum of 62.5 bps to 2 kbps. The radio weighs approximately 1200 g [4] and consumes up to 30 W of power in full duplex mode (including the SSPA power). The UHF slice allows receiving functionalities in the 390-405 MHz band. The X-Band antennas (Figures 6 and 7, Table 2) used for the MarCO mission are: low gain patch antennas, medium gain patch antenna arrays, and a high gain antenna. The LGA (both transmit and receive) consist of dual-edge-fed circularly polarized patch antennas. The two RHCP patch antennas are printed on RT Duroid 5880 [6]. In terms of performance, the antennas are designed to operate in the entire Near Earth and Deep Space frequency ranges, with a peak gain of 6 dBi and a 3 dB beamwidth of approximately 60\({}^{\circ}\). The MGA antennas consist of \(2\times 1\) patch arrays and they are used to slightly increase the gain (especially for operations around) while still maintaining the beamwidth wide enough to minimize the need for fine pointing. Furthermore, these antennas are designed for the entire X-Band  
Figure 5: IRIS radio [5]. range and they provide a peak gain of approximately 9 dBi with a 3 dB beamwidth of 20\({}^{\circ}\). The mass of the LGA and MGA is approximately 15 g each. The high gain antenna (Figure 7) [7] is designed based on the reflectarray technology which uses, instead of a more traditional deployable parabola, a flat, reflecting surface that rely on a simple  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **X-Band HGA** & **X-Band MGA** & **X-Band LGA** & **UHF** \\ \hline \multirow{3}{*}{Frequency} & 7.14–7.23 GHz & 7.14–7.23 GHz & 7.14–7.23 GHz & \multirow{3}{*}{401 MHz (receive)} \\  & (receive) 8.4–8.5 GHz (transmit) & GHz (transmit) & GHz (transmit) & \\ \hline Peak gain & 29.2 dBi & 9 dBi & 6 dBi & 2.5 dBi \\ \hline Half-power \multirow{3}{*}{Frequency} & \multirow{3}{*}{5.5 deg} & \multirow{3}{*}{20 deg} & \multirow{3}{*}{60 deg} & \multirow{3}{*}{60 deg} \\  & & & & \\ \cline{1-1  
mechanical deployment with spring-loaded hinges. The fully deployed antennas surface for the MarCO HGA is \(59.7\times 33.5\) cm.