RPI passive wave measurement capturing voltage spectral density of the radio emissions in space as a function of frequency, typically between 3 and 1009 kHz. This operating frequency range was selected by the RPI team to provide optimal temporal resolution of the wave observations. Commonly used in the analysis of noise generators, spectral density is a frequency-dependent characteristic that describes how much power is generated by the emission source in a 1 Hz bandwidth. The original description of emissions was done in terms of thermal noise measurements, though the same approach also applies to non-thermal emissions such as AKR. CDF_DS_PT5M stores calibrated data from all three RPI antennas X, Y, and Z individually and a combined X+Y antenna channel. The data are presented as the Voltage Spectral Density (VSD), which is the root of power spectral density, measured in [V/root-Hz] units. Note that conversion of antenna voltage to electric field strength depends on the effective length of the receive antenna, and such conversion is not performed here. (See spase://SMWG/Instrument/IMAGE/RPI for a time history of the lengths of the three mutually orthogonal RPI dipole antennas.) RPI is capable of detecting input radio emissions above its noise floor of 5 nV/root-Hz, which is determined by the internal white noise of the RPI antenna pre-amplifiers. The VSD in RPI spectrogram data is presented in dB relative to 1 V/root-Hz (logarithmic scale), units of dB(V/root-Hz). The RPI instrument noise floor is 5 nV/root-Hz = -166 dB(V/root-Hz) at the receiver input. Software suggested by the science team for CDF file visualization: (1) Plotting tool at the CDAWeb portal, (2) For analysis beyond static image inspection, including color scale optimization, zooming, text export, alternative data representations in physical units, detailed frequency and time information, overlaid model fpe and fce graphs, and EPS quality figures, use BinBrowser software at UML, http://ulcar.uml.edu/rpi.html