The International Space Station (ISS) Active Thermal Control System (ATCS) (Ref. 1,2) has changed over the past several years to address problems and to improve its assembly and operation on-orbit. This paper captures the ways in which the Internal (I) ATCS and External (E) ATCS have changed design characteristics and operations both for the system currently operating on-orbit and the new elements of the system that are about to be added and/or activated. The rationale for changes in ATCS design, assembly and operation will provide insights into the lessons learned during ATCS development.
The state of the assembly of the integrated ATCS will be presented to provide a status of the build-up of the system. The capabilities of the on-orbit system will be presented with a summary of the elements of the ISS ATCS that are functional on-orbit plus the plans for launch of remaining parts of the integrated ISS ATCS. The state of transition of the Early EATC system to the permanent EATC system and near term assembly processes leading to completion of EATC assembly will be addressed. The assembly operations planned for the Photovoltaic (PV) ATCS will be summarized with the changes that have been implemented in assembly planning.
The problems encountered will be reviewed with the resolution of the problems or the status of the resolution. Problems and resolutions summarized include IATC and Early EATC activation; the IATC coolant chemistry; and Quick Disconnect (QD) leakage and overpressurization.
Equipment added to flight manifests to gain data, the way equipment is operating versus initial plans and a summary of how the decisions are made to develop, verify, manifest and operate the equipment will be presented.