PLASMA IS THE MOST ABUNDANT MATTER IN THE UNIVERSE AND THE MEDIUM OF SPACE WEATHER IT PLAYS A VITAL ROLE IN THE INTERPLANETARY ENVIRONMENT OF THE SOLAR SYSTEM AND ITS INTERACTIONS WITH PLANETS. THE INTERACTIONS OF THE SOLAR WIND AND UV RADIATION WITH BODIES IN THE SOLAR SYSTEM CREATE THE: 1) MAGNETOSPHERES AROUND THE PLANETS WITH GLOBAL MAGNETIC FIELDS; 2) THE IONOSPHERES OF THE PLANETS WITH SIGNIFICANT ATMOSPHERES; AND 3) THE CHARGED SURFACES AND PLASMA WAKES OF AIRLESS BODIES. BECAUSE OF THE CRITICAL ROLE THAT PLASMA PLAYS IN DETERMINING HOW THE SOLAR SYSTEM WORKS AND EVOLVES IT IS OF FUNDAMENTAL INTEREST IN MANY SPACECRAFT (SC) MISSIONS. OVER THE PAST 50 YEARS LANGMUIR PROBES HAVE BEEN THE BEST AND MOST FREQUENTLY USED INSTRUMENTS FOR IN-SITU MEASUREMENTS TO DETERMINE THE SPACE PLASMA CHARACTERISTICS. LANGMUIR PROBES WORK BY INSERTING A CONDUCTING ELECTRODE (THE GEOMETRIES ARE USUALLY SPHERES CYLINDERS OR PLANES) IN A PLASMA AND SWEEPING A VOLTAGE RANGE ACROSS IT. THE AMOUNT OF CURRENT DRAWN BY THE PROBE I.E. THE CURRENT-VOLTAGE (I-V) CURVE IS THEN INTERPRETED TO YIELD THE POTENTIAL TEMPERATURE AND DENSITY OF THE PLASMA. HOWEVER EVEN AFTER DECADES OF USE THERE ARE STILL CHALLENGES IN THE ANALYSIS AND INTERPRETATION OF LANGMUIR PROBE MEASUREMENTS. FOR EXAMPLE DUE TO AMBIENT PLASMA INTERACTIONS WITH THE SC AND PROBES THEMSELVES A LOCAL PLASMA ENVIRONMENT IS CREATED AROUND THE PROBES THAT IS DIFFERENT FROM THE TRUE AMBIENT PLASMA. THESE LOCAL PLASMA ENVIRONMENTS ARE OFTEN INHOMOGENEOUS AND/OR ANISOTROPIC WHICH ARE DIFFICULT FOR TRADITIONAL LANGMUIR PROBES TO IDENTIFY AND REMOVE THEIR EFFECTS ON THE PROBE MEASUREMENTS. AS A RESULT THIS CAN INTRODUCE LARGE ERRORS IN THE DERIVED PLASMA PARAMETERS. THIS PROPOSAL IS TO CONSTRUCT AND CALIBRATE A DOUBLE HEMISPHERICAL LANGMUIR PROBE (DHP) WHICH CONSISTS OF TWO CONDUCTING HEMISPHERES ELECTRICALLY ISOLATED FROM EACH OTHER AND SWEPT SIMULTANEOUSLY WITH SAME BIASES. BY LOOKING AT THE DIFFERENCE IN THE IV CURVES BETWEEN THE TWO HEMISPHERES ANISOTROPIES AND INHOMOGENEITIES IN THE ENVIRONMENT AROUND THE PROBE CAN BE IDENTIFIED AND THEN REMOVED OR MINIMIZED FROM THE PROBE MEASUREMENTS. THE DHP WILL INCREASE THE CAPABILITY AND ACCURACY FOR SPACE PLASMA MEASUREMENTS IN A VARIETY OF DIFFICULT SPACE ENVIRONMENTS: I) LOW-DENSITY PLASMAS; II) HIGH-SURFACE-EMISSION ENVIRONMENTS DUE TO PHOTO AND/OR SECONDARY ELECTRON PRODUCTION FROM PROBE AND THE SC; III) FLOWING PLASMAS; AND IV) DUST-RICH ENVIRONMENTS. THE DHP ADDRESSES THE SCIENCE GOALS OF NASA'S 2014 SCIENCE MISSION DIRECTORATE (SMD) SCIENCE PLAN: "1) UNDERSTAND THE SUN AND ITS INTERACTIONS WITH THE EARTH AND THE SOLAR SYSTEM INCLUDING SPACE WEATHER; 2) EXPLORE AND OBSERVE THE OBJECTS IN THE SOLAR SYSTEM TO UNDERSTAND HOW THEY FORMED AND EVOLVE; 3) ADVANCE THE UNDERSTANDING OF HOW THE CHEMICAL AND PHYSICAL PROCESSES IN OUR SOLAR SYSTEM OPERATE INTERACT AND EVOLVE." ADDITIONALLY THE DHP ADDRESSES NASA'S SPACE TECHNOLOGY ROADMAP OF TA 08 "SCIENCE INSTRUMENTS OBSERVATORIES AND SENSOR SYSTEMS'' SPECIFICALLY THE TECHNOLOGY AREA BREAKDOWN STRUCTURE (TABS) ELEMENT 8.3.1 "FIELD AND PARTICLE DETECTORS'' AND MORE GENERALLY THE TABS ELEMENT 8.3.3 "IN-SITU (OTHER)."