Electrodynamic-tether fault measurement using time-domain reflectometry

The use of time-domain reflectometry (TDR) has been proposed to determine fault position and/or density along electrodynamic tether (EDT) systems. Future EDT missions are desired to be long duration (from several months to years); hence, these missions can expect possibly significant performance degradation due to breaches in tether insulating material caused by hazards such as micrometeoroids. A TDR system provides one possible method for measuring EDT fault build-up as a function of time, allowing researchers to understand and model the degradation characteristics and to design EDT systems to survive expected levels, In addition, including a TDR system as part of long-duration EDT missions would facilitate real-time tracking of the expected performance degradation and health state of the tether. The TDR technique has long been an effective tool for deter-mining the location of loads and faults along common transmission lines (TLs) such as coaxial cables. Also sometimes known as pulse reflectometry, TDR works by sending an impulse down a TL and recording the reflected energy as a function of time. Measurement of the reflected TDR waveform provides insight into the physical structure of the TL and any loads, i.e., faults, along its length. In addition, the delay between launched and reflected signals determines the location of the load or fault.