APPLESOSS: A Producer of ProfiLEs for SOSS. Application to the NIRISS SOSS Mode

TL;DR

This paper introduces APPLESOSS, a method for generating accurate spatial profiles for the NIRISS SOSS mode, improving spectral extraction and contamination separation for exoplanet observations with JWST.

Contribution

APPLESOSS provides high-fidelity spatial profiles for SOSS spectra, enhancing the accuracy of spectral extraction and contamination decontamination in JWST data analysis.

Findings

APPLESOSS profiles closely match true spatial profiles.

Order contamination effects are minimal for relative measurements.

Atmospheric parameters are reliably retrieved from contaminated spectra.

Abstract

The SOSS mode of the NIRISS instrument is poised to be one of the workhorse modes for exoplanet atmosphere observations with the newly launched James Webb Space Telescope. One of the challenges of the SOSS mode, however, is the physical overlap of the first two diffraction orders of the G700XD grism on the detector. Recently, the ATOCA algorithm was developed and implemented as an option in the official JWST pipeline, as a method to extract SOSS spectra by decontaminating the detector -- that is, separating the first and second orders. Here, we present APPLESOSS (A Producer of ProfiLEs for SOSS), which generates the spatial profiles for each diffraction order upon which ATOCA relies. We validate APPLESOSS using simulated SOSS time series observations of WASP-52\,b, and compare it to ATOCA extractions using two other spatial profiles (a best and worst case scenario on-sky), as well as a simple box extraction performed without taking into account the order contamination. We demonstrate that APPLESOSS profiles retain a high degree of fidelity to the true underlying spatial profiles, and therefore yield accurate extracted spectra. We further confirm that the effects of the order contamination for relative measurements (e.g., exoplanet transmission or emission observations) is small -- the transmission spectrum obtained from each of our four tests, including the contaminated box extraction, is consistent at the $\sim$1$\sigma$ level with the atmosphere model input into our noiseless simulations. We further confirm via a retrieval analysis that the atmosphere parameters (metallicity and C/O) obtained from each transmission spectrum are consistent with the true underlying values.