THE QUANTITATIVE STUDY OF SPACE PLASMA ELECTRODYNAMICS REQUIRES THE ACCURATE MEASUREMENT OF IN SITU ELECTRIC FIELDS. IN ORDER TO OPTIMIZE THE ACCURACY OF THE DOUBLE PROBE METHOD FOR BOTH DC AND AC FIELD MEASUREMENTS A VARIETY OF SENSOR AND ANTENNA GEOMETRIES AND BIASING SCHEMES HAVE BEEN USED ON PAST AND PRESENT MISSIONS. THESE MECHANICAL DESIGNS AND OPERATIONAL TECHNIQUES SERVE TO REDUCE OFFSETS AND ATTENUATION DUE TO THE NEARBY SPACECRAFT STRUCTURE OR THE E FIELD ANTENNA STRUCTURE ITSELF BUT HAVE UNEXPECTEDLY BEEN THE SOURCE OF EITHER ANOMALOUS RESPONSE E.G. UNEXPECTED VOLTAGE GAIN OR OUTRIGHT OSCILLATIONS RENDERING THE MEASUREMENTS AMBIGUOUS AT BEST AND UNUSABLE AT WORST. EXAMPLES OF THIS IN THE RECENT PAST INCLUDE THE BEHAVIOR OF THE POLAR-EFI DEMETER-ICE CNOFS-VEFI AND POSSIBLY VAN ALLEN PROBES EFW-AXBS HINDERING THE ANALYSIS OF THE FLUCTUATIONS RESPONSIBLE FOR THE BULK OF GEOEFFECTIVE WAVE-PARTICLE INTERACTIONS AND DEGRADING THE MEASUREMENT OF QUASI-DC E-FIELDS WITH INTENSE BACKGROUND NOISE AND NONLINEAR OFFSETS TO SENSOR POTENTIALS. WHILE THEORETICAL ANALYSES EXIST FOR THE RELEVANT ANTENNA-PLASMA INTERACTIONS IN SITU OBSERVATIONS PROVIDE ONLY CIRCUMSTANTIAL EVIDENCE FOR THEIR VALIDITY. RECENT SUCCESSFUL MEASUREMENTS OF THE RELEVANT SENSOR-PLASMA INTERACTIONS IN THE LABORATORY SETTING POINT THE WAY TO A CONCLUSIVE TEST OF THAT THEORETICAL ANALYSIS A WAY FORWARD TO AVOID THE PITFALLS FOUND IN EARLIER DESIGNS AND A PROCESS TO PROVE OUT NEW MORE AMBITIOUS DESIGNS FOR AC E-FIELD ANTENNAS BEFORE LAUNCH. LIEFSI THE LABORATORY INVESTIGATION OF E FIELD SENSOR INSTABILITIES ADDRESSES THIS GOLDEN OPPORTUNITY TO SIGNIFICANTLY IMPROVE OUR PRACTICAL KNOWLEDGE OF ELECTRIC FIELD SENSOR DESIGN AND TO SUPPORT THE INVESTIGATION OF FUNDAMENTAL PLASMA PROCESSES THAT CONTRIBUTE TO ALL ASPECTS OF SPACE PHYSICS. SUCH AN EFFORT WHEN SUCCESSFUL SHALL DIRECTLY SUPPORT PROGRESS ON ALL THREE OF THE NASA HELIOSPHERIC RESEARCH PLAN (HRP) AND DECADAL SURVEY (DS) GOALS OF EXPLORATION ADVANCEMENT AND DEVELOPMENT BY ENABLING THE DESIGN FABRICATION AND OPERATION OF MORE ROBUST AND CAPABLE ELECTRIC SENSORS THROUGHOUT HELIOSPACE. THE RESULTS OF THE LIEFSI EFFORT DO NOT SUPPORT A PARTICULAR INSTRUMENT OR DESIGN EFFORT BUT SHALL SIGNIFICANTLY INCREASE THE CHANCE OF SUCCESS OF ALL SUBSEQUENT EFFORTS BY THE COMMUNITY. ITS RESULTS SHALL PROVIDE A CLEARER UNDERSTANDING OF THE MECHANISMS BY WHICH THESE SENSOR INSTABILITIES OCCUR THEIR PARAMETRIC DEPENDENCE ON PLASMA CONDITIONS AND SENSOR DIMENSIONS AND GEOMETRY ALLOWING FOR MORE CERTAIN DESIGN OF E-FIELD SENSORS ON FUTURE MISSIONS AND ENHANCED SCIENCE RETURN FROM SUCH MEASUREMENTS.