Forecast Rotation Sensitivity of Future Polarisation Surveys: A Scaling Estimate Calibrated to a Published Uncertainty

This paper examines how precisely future polarisation surveys could measure a uniform rotation angle, estimated by scaling from a published uncertainty rather than by running a full instrument simulation, and where that scaling estimate should not be trusted. The calculation is performed from stated assumptions and published polarisation measurements, using the deposited script so that every quoted number can be reproduced. The headline outputs are: sigma plancklike deg = 0.110; sigma at 2uK = 0.0043; sigma at 1uK = 0.0018. The treatment separates what the published measurements supply from what a theoretical framework must additionally provide; where a required quantity is not supplied, that absence is reported plainly as a negative result rather than replaced by an assumed value. The study is computed from stated assumptions and published inputs; it is not a new measurement. SIMULATED, NOT MEASURED in the sense that all derived quantities are calculated, not observed.