This question appears in Mumbai University > Satellite Communication and Network subject

Marks: 5 M

Year: May 2015

An isotropic antenna is a type of antenna that radiates equally in all directions. Typically, it is used for emergency-mode TT&C (telemetry, tracking and command).

Radiation pattern from an Isotropic antenna

Such an antenna is necessary if the satellite loses Earth pointing, and the (focused) communications antennas are thus no longer pointing at the Earth. In such a circumstance, an isotropic antenna (which would actually be a quasi-isotropic, omnidirectional antenna) may be the only way of getting commands to the satellite in order to recover control and re-establish Earth pointing.

Since the communication is only through antennas, it is essential to consider even the worst-case scenarios so as to recover control over the satellite. Hence, an isotropic antenna is always needed on board a satellite with continuous power supply which will be automatically triggered once the satellite loses connection.