A brake temperature sensing system for an aircraft including a sensor apparatus and an interrogation apparatus. The sensor apparatus includes a temperature sensor for attachment to a brake disc of an aircraft brake, and a relay for attachment to the brake. The temperature sensor is configured to wirelessly transmit a measurement signal containing information relating to a temperature of the brake disc, responsive to receiving a wireless interrogation signal. The relay is configured to receive an interrogation signal from the interrogation apparatus; wirelessly transmit the interrogation signal to the temperature sensor; receive the wireless measurement signal from the temperature sensor; and transmit the received measurement signal. The interrogation apparatus comprises a controller configured to generate an interrogation signal; and a transceiver configured to transmit the generated interrogation signal to the sensor apparatus; and receive the measurement signal transmitted by the sensor apparatus.