Extended Data Fig. 1: Comparison of the (x, y) positions of NIRISS orders 1 and 2 across the detector as modelled from different reduction pipelines.

a,c, Each pipeline traces the curvature of orders 1 and 2 using different methods. We show the best-fit trace for order 1 in panel a and order 2 in panel b. We highlight zoomed-in regions to further examine differences. We note that iraclis uses the JWST-provided spectral trace. There is generally good agreement between the traces across the entire detector (<1 pixel deviations), with the strongest deviations towards the ends of each trace (for example, x pixel position <500 for orders 1 and 2). This demonstrates the reliability of order spectral traces across all pipelines. b,d, We provide an example spatial profile along the column for order 1 (b) and order 2 (d) at x = 1,250. (https://github.com/afeinstein20/wasp39b_niriss_paper/blob/main/scripts/edfigure1.py).