# Telecommunication Systems for Small Satellites Operating at High Frequencies: A Review
## 2 Asteria
### Operations  
Spacecraft deployment from the ISS occurred nominally at 12:25:01 UTC on 20 November 2017. Because ASTERIA was deployed by itself, the identification by the JSpOC (Joint Special Operations Command) was relatively quick, and a TLE (Two Line Element) set was available within 12 h of deployment. The acquisition for ASTERIA was particularly challenging due to the following aspects [1]: \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **ASTERIA Antenna** \\ \hline Frequency & 2.0–2.11 GHz (receive) 2.2–2.3 GHz (transmit) \\ Peak gain & 7 dBi \\ Half-power beamwidth & 70 deg \\ Power handling & 10 W \\ Impedance & 50 Ohm \\ Polarization & RHCP \\ Temperature Range & \(-\)40 deg C to \(+\)85 deg C \\ \hline \hline \end{tabular}
\end{table} 
Table 1: ASTERIA antenna’s characteristics. Figure 3: ASTERIA radio, courtesy of Vulcan Wireless Inc.  
Figure 2: ASTERIA antenna, courtesy of Vulcan Wireless Inc.  
1 ASTERIA was relying on only one ground station. 2 The MSU station has a very small beamwidth, as a result of having such a large dish (21 m). 3 The ASTERIA antennas are regulated by a switch, so there is no omnidirectional coverage of the spacecraft. 4 The radio does not support a beacon mode, and it needs to receive an uplink signal before it can activate the downlink. 5 The radio was on a duty cycle for which it was on for 30 min and off for 10 min, due to power consumption constraints. As a result of all these challenges, acquisition was deemed a difficult task and the operations team was planning to dedicate several passes just to acquire the signal. Luckily, the system worked even better than expected and the signal from ASTERIA was acquired at the very first available opportunity, which was the second time that the spacecraft was in visibility with the ground station from the moment of deployment. The team later realized from telemetry post-processing that the duty cycle had the radio off during the first visibility opportunity. Following first acquisition, the operations team performed radio checkout operations which entails ensuring the health of the telecom subsystem by monitoring the key telemetry parameters and the spectrum, and performed a switch to high data rates to verify functionality in every configuration. The key telecommunication telemetry parameters provided in the ASTERIA real-time telemetry (with values updated every 28 s) are the following: antenna selection (1 or 2 depending on which particular antenna the spacecraft is using to communicate), radio temperature of the Memory Signal Processor (flight allowable temperature range is \(-25\) to 60 deg C), radio lock (1 if the radio is locked, zero otherwise), radio oscillator temperature (the flight allowable range for this sensor is \(-25\) to 60 deg C), and radio voltage of the power amplifier (normal range is between 3 and 5 V). Examples of the values can be found in [1]. For the first few passes, telemetry was nominal, so that the operation activity lead allowed us to command the spacecraft to transition into high data rate modes. It took a couple of passes to perform this operation, as the rotation of the spacecraft was affecting the antenna gain and the link performance. Finally, at the second trial, the change of data rates was successful. Operations in the following days were focused on troubleshooting some issues identified during these early operations. Specifically:  
1. The spectrum was shifting in frequency faster than expected due to both Doppler and spacecraft rotation. 2. Downlink Eb/N0 was lower than expected due to 1. The high level of uplink power was saturating the ASTERIA receiver. 2. The rotation of the spacecraft was affecting the antenna pointing. 3. Though not known at the beginning of the operations, the LNA at the ground station was failing. This failure was discovered during the extended mission phase. Replacing the LNA resulted in a 3 dB increase in the received Eb/N0). The fixes implemented were the following:  
1.