Dielectric Property Measurements to Support Interpretation of Cassini Radar Data
Abstract
Radar observations are useful for constraining surface and near-surface compositions and illuminating geologic processes on Solar System bodies. The interpretation of Cassini radiometric and radar data at 13.78 GHz (2.2 cm) of Titan and other Saturnian icy satellites is aided by laboratory measurements of the dielectric properties of relevant materials. However, existing dielectric measurements of candidate surface materials at microwave frequencies and low temperatures is sparse. We have set up a microwave cavity and cryogenic system to measure the complex dielectric properties of liquid hydrocarbons relevant to Titan, specifically methane, ethane and their mixtures to support the interpretation of spacecraft instrument and telescope radar observations. To perform these measurements, we excite and detect the TM020 mode in a custom-built cavity with small metal loop antennas powered by a Vector Network Analyzer. The hydrocarbon samples are condensed into a cylindrical quartz tube that is axially oriented in the cavity. Frequency sweeps through a resonance are performed with an empty cavity, an empty quartz tube inserted into the cavity, and with a sample-filled quartz tube in the cavity. These sweeps are fit by a Lorentzian line shape, from which we obtain the resonant frequency, f, and quality factor, Q, for each experimental arrangement. We then derive dielectric constants and loss tangents for our samples near 13.78 GHz using a new technique ideally suited for measuring liquid samples. We will present temperature-dependent, dielectric property measurements for liquid methane and ethane. The full interpretation of the radar and radiometry observations of Saturn’s icy satellites depends critically on understanding the dielectric properties of potential surface materials. By investigating relevant liquids and solids we will improve constrains on lake depths, volumes and compositions, which are important to understand Titan’s carbon/organic cycle and inevitably the evolution of its environment.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #44
- Pub Date:
- October 2012
- Bibcode:
- 2012DPS....4431215J