As the body primarily responsible for coordinating international research on the role of the stratosphere in climate, the WCRP’s SPARC core project is a major user of stratospheric CDRs, and since its inception has made substantial efforts to improve the characterization and understanding of stratospheric CDRs for scientific use. This included the establishment of its ad hoc limb profiling group, several of whom are contributors to this SPIN proposal. This study is therefore designed to serve the needs of, and feed into, the various SPARC activities directly concerned with the evaluation and production of stratospheric CDRs, as this ensures a high level of scientific quality and is the most direct route to international acceptance of the new data sets. At the same time, this connection allows the consortium to take full advantage of the work already done in SPARC, to obtain maximum scientific return from the financial investment. Accordingly, all members of the consortium team are currently involved in one or more of these SPARC activities, in many cases in a leadership role. This close connection to the satellite-based CDR developer and user communities has resulted in the retrieval algorithms and analyses to be used within this study being internationally recognised state-of-the-art. The objectives of SPIN can only be achieved by building on the retrieval algorithm developments made in the research groups comprising this consortium who are responsible for the successful development of the relevant level 1 and level 2 data products and their characterisation and calibration over the past two decades. The state-of-the-art approaches described in this proposal build on the research undertaken by the retrieval teams and data analysis experts working together in this consortium.