Three methods that we are using to make in situ measurements of complex permittivity over a broad frequency range are discussed along with some test results. The methods would appear to be suitable not only for experiments in simulated space environments, but also for outer space, in “space dielectrometers” suitably instrumented for terrestrial readout and data reduction. At low frequencies (1 kHz), a planar capacitor technique is used with conventional null method and capacitance bridge. At microwave frequencies (9 GHz), a vacuum TE⁰¹ⁿ resonant cavity is used. At millimeter wavelengths (35 GHz), a dielectric rod technique is employed.