The RFS instrument is a two-channel digital receiver and spectrometer, at the terminals of four 2-m monopole electric antennas (V1 to V4) mounted near the front of the spacecraft close to the extremities of the heat shield diagonals, so that the two corresponding linear dipoles are of 7-m tip-to-tip length, perpendicular to the axis of the spacecaft.

The RFS is the highest-frequency component of the PSP FIELDS suite, with a bandwidth of 10 kHz to 19.2 MHz.

This frequency range is subdivided into the Low Frequency Range, LFR, from about 10 kHz to 2.4 MHz, and High Frequency Range, HFR, about 1.6 kHz to 19.2 MHz. The primary science of the LFR consists of in situ quasi-thermal noise, QTN, spectrum measurements.