  Infrastructures are not inherently durable or fragile, yet all are fragile
over the long term. Durability requires care and maintenance of individual
components and the links between them. Astronomy is an ideal domain in which to
study knowledge infrastructures, due to its long history, transparency, and
accumulation of observational data over a period of centuries. Research
reported here draws upon a long-term study of scientific data practices to ask
questions about the durability and fragility of infrastructures for data in
astronomy. Methods include interviews, ethnography, and document analysis. As
astronomy has become a digital science, the community has invested in shared
instruments, data standards, digital archives, metadata and discovery services,
and other relatively durable infrastructure components. Several features of
data practices in astronomy contribute to the fragility of that infrastructure.
These include different archiving practices between ground- and space-based
missions, between sky surveys and investigator-led projects, and between
observational and simulated data. Infrastructure components are tightly
coupled, based on international agreements. However, the durability of these
infrastructures relies on much invisible work - cataloging, metadata, and other
labor conducted by information professionals. Continual investments in care and
maintenance of the human and technical components of these infrastructures are
necessary for sustainability.
