NASA's Earth Observing System (EOS) Program will place a series of unmanned polar-orbiting spacecraft in low-earth orbit to support a variety of scientific and Earth-observation missions. The EOS AM Spacecraft has two instruments requiring an advanced heat transport system for thermal accommodation. The need for advanced heat transport is primarily due to the relatively high power and tight temperature control requirements for these instruments, compounded by the dense instrument layout on the Spacecraft nadir deck which must accommodate restrictive instrument thermal and science fields-of-view. Advanced heat transport is recommended for those instruments that must have their waste heat collected and transported a significant distance to the cold side of the Spacecraft for rejection to space via a body-mounted radiator. Capillary Pumped Heat Transport Systems (CPHTS) using Capillary Pumped Loop (CPL) technology have been selected for accommodating the two EOS AM instruments requiring advanced heat transport. This paper describes the design approach taken to define the three CPHTSs used for thermal control of the two EOS AM set instruments, ASTER and MOPITT.