  Scientific open-source software (OSS) has greatly benefited research
communities through its transparent and collaborative nature. Given its
critical role in scientific research, ensuring the sustainability of such
software has become vital. Earlier studies have proposed sustainability
strategies for conventional scientific software and open-source communities.
However, it remains unclear whether these solutions can be easily adapted to
the integrated framework of scientific OSS and its larger ecosystem. This study
examines the challenges and opportunities to enhance the sustainability of
scientific OSS in the context of interdisciplinary collaboration, open-source
community, and multi-project ecosystem. We conducted a case study on a
widely-used software ecosystem in the astrophysics domain, the Astropy Project,
using a mixed-methods design approach. This approach includes an interview with
core contributors regarding their participation in an interdisciplinary team, a
survey of disengaged contributors about their motivations for contribution,
reasons for disengagement, and suggestions for sustaining the communities, and
finally, an analysis of cross-referenced issues and pull requests to understand
best practices for collaboration on the ecosystem level. Our study reveals the
implications of major challenges for sustaining scientific OSS and proposes
concrete suggestions for tackling these challenges.
