t the Sun's magnetic field becomes warped and creates 'bubbles' at the edge of the solar system [6]. The design of the Voyager on-board telecommunications system needed to take into account the path loss experienced by a signal travelling over 15 billion km. Depending on the frequency of operation this path loss is in the order of 1030 times, or 300 dB. Strong antennas on-board the crafts as well as on the Earth ensure a highly directional line of sight is maintained between the transmitter and receiver, and signal power is collected as much Broadband Telecommunications Technologies and Management Table 4.2 Link budget calculation parameters for the downlink of Voyager 2's telemetry system 1. Transmission power 40.9 dBm 2. Probe antenna gain 48.1 dB 3. Path loss (7.3 X 109 km) in the 8 GHz band 308.2 dB 4. Receiver antenna gain 73.7 dB 5. Receiver noise power -170.6 dBm 6. Signal suppression -6.2 dB 7. Received SNR = (1+2-3+4-5+6) 18.9 dB as possible. Nevertheless, the received signal is very weak, and its ratio to noise at the receiver is very small. Nevertheless this signal power is enough SO that information and con- trol command transfer still takes place between the probe and the Earth. Over the years stronger antennas have been deployed to improve the link budget of this telecommunica- tions link [7]. The link budget calculation parameters of a probe at present are listed in Table 4.2. Such a calculation gives insight on how communications with the probe may be car- ried out and the range at which the probe may be controlled. Furthermore, as will be described below, link budget analysis can be used to calculate the maximum possible transmission rate on the link, or channel capacity. This limit determines the amount of information that may be transmitted back to Earth and therefore the specification of sensors and other devices on-board the probe. Case Study Questions What factors decided the type of sensors to be used on-board the Voyager probes? How did NASA engineers decide on the information telecommunic