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It is inevitable that the International Space Station (ISS) will play a significant role in the conduct of science in space. However, in order to provide this service to a wide and broad community and to perform it cost effectively, alternative concepts must be considered to complement NASA’s Institutional capability. Currently science payload forward and return data services must compete for higher priority ISS infrastructure support requirements. Furthermore, initial astronaut crews will be limited to a single shift. Much of their time and activities will be required to meet their physical needs (exercise, recreation, etc.), station maintenance, and station operations, leaving precious little time to actively conduct science payload operations. ISS construction plans include the provisioning of several truss mounted, space-hardened pallets, both zenith and nadir facing. The ISS pallets will provide a platform to conduct both earth and space sciences. Additionally, the same pallets can be used for life and material sciences, as astronauts could place and retrieve sealed canisters for long-term micro-gravity exposure. Thus the pallets provide great potential for enhancing ISS science return.
This significant addition to ISS payload capacity has the potential to exacerbate priorities and service contention factors within the exiting institution. In order to have it all, i.e., more science and less contention, the pallets must be data smart and operate autonomously so that NASA institutional services are not additionally taxed.
Specifically, the “Enhanced Science Capability on the International Space Station” concept involves placing data handling and spread spectrum X-band communications capabilities directly on ISS pallets. Spread spectrum techniques are considered as a means of discriminating between different pallets as well as to eliminate RFI. The data and RF systems, similar to that of “free flyers”, include a fully functional command and data handling system, providing, in part, science solid state recorders and instrument command management sub-systems. This, together with just one direct-to-ground based X-Band station co-located with a science payload operations center provides for a direct data path to ground, bypassing NASA institutions. The science center exists to receive user service requests, perform required constraint checks necessary for safe instrument operations, and to disseminate user science data. Payload commands can be up-linked directly or, if required, relayed through the existing NASA institution. The concept is modular for the downlink Earth terminals; in that multiple downlink X-band ground stations can be utilized throughout the world. This has applications for Earth science data direct to regional centers similar to those services provided by the EOS Terra spacecraft. However, for the purposes of this concept, just one downlink site was selected in order to define the worst-case data acquisition scenario necessary to ascertain concept feasibility.
The paper demonstrates that the concept is feasible and can lead to a design that significantly reduces operational dependency on the NASA institutions and astronauts while significantly increasing ISS science operational efficiency and access.
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