This Standard specifies star sensor performances as part of a space project. The Standard covers all aspects of performances, including nomenclature, definitions, and performance requirements for the performance specification of star sensors. The Standard focuses on: " performance specifications (including the impact of temperature, radiation and straylight environments); " robustness (ability to maintain functionalities under non nominal environmental conditions). Other specification types, for example mass and power, housekeeping data and data structures, are outside the scope of this Standard. This Standard also proposes a standard core of functional interfaces defined by unit suppliers and avionics primes in the context of Space AVionics Open Interface aRchitecture (SAVOIR) initiative. When viewed from the perspective of a specific project context, the requirements defined in this Standard should be tailored to match the genuine requirements of a particular profile and circumstances of a project. This standard may be tailored for the specific characteristics and constraints of a space project in conformance with ECSS-S-ST-00.