Accommodations for external payloads on the International Space Station

Abstract

The design of the International Space Station (ISS) includes payload locations that are external to the pressurized environment. These external or attached payload accommodation locations will allow direct access to the space environment at the ISS orbit and direct viewing of the earth and space. NASA sponsored payloads will have access to several different types of standard external locations, the S3/P3 Truss Sites, the Columbus Exposed Payload Facility (EPF), and the Japanese Experiment Module Exposed Facility (JEM-EF). In addition, the Russians will have an external payload capability on their Science Power Platform. As the ISS Program develops, it may also be possible to locate external payloads at non-standard locations similar to the handrail-attached payloads that were flown during the MIR Program. Each external site will have different power and data handling capabilities, however they all share one common trait. The sum of the capabilities of all sites is greater than the total resources available to external payloads. Each of these resources must be scheduled and shared with other payloads. Thus, although a site may be physically capable of providing 3000 watts of power, it may be limited to a lower amount and there may be times when a payload is required to power down to minimum levels.