SAGE III ISS Operations: A Two-Year Perspective on Operating on the ISS

The Stratospheric Aerosol and Gas Experiment III (SAGE III) was delivered to the International Space Station (ISS) on 23 February 2017. The SAGE III payload was robotically installed on Ex-PRESS Logistics Carrier-4 (ELC-4) on the S3 Truss and began acquiring science measurements on 17 March 2017. The SAGE III telescope and instrument assembly employs the methods of solar occultation and lunar occultation to retrieve near-global vertical profiles of atmospheric ozone, water vapor, nitrogen dioxide, multiwavelength aerosol extinctions, and other gaseous species and atmospheric state parameters. The activities on the ISS contribute to a dynamic operational environment. The attitude changes, EVAs, and the arrival and departure of vehicles require continual consideration when operating. After operating for two years, the SAGE III payload has planned over 20,000 occultation events and acquired approximately 17,000. A significant number of the missed events were because of visiting vehicles blocking the field of view. Using instrument data from these blocked events, the SAGE III team has mapped the structure of the ISS from the perspective of the instrument. Error Correction and Detection (EDAC) methods are necessary to preserve the functionality of the instrument software. On SAGE III the Hexapod Electrical Unit (HEU), which controls the orientation of the telescope, reports whenever an EDAC occurs. By analyzing the EDAC messages in the HEU telemetry, information concerning the orbital environment of the ISS can be obtained. To be presented is a summary of operational considerations when working on ISS along with how instrument data can be used to map the structural and electromagnetic environment of ISS.