FIG. 4.

Simulated JWST observations of the three simulated planets from Fig. 2. Synthetic JWST/NIRISS and JWST/NIRSPEC observations (simulations performed by Drake Deming; Schwieterman et al., 2016a,b) of an O₂-rich water loss atmosphere (Top), a self-consistent M dwarf Earth (Middle), and the CO₂-rich atmosphere (Bottom). These results are for 10 transits, corresponding to about 65 h of JWST time for each object and instrument. The observed points are in black, and to improve the S/N the wavelength resolution has been degraded by coadding the 2048 resolution elements of the detector down to 32 columns. Photon-limited noise was used in the simulations, assuming on-orbit instrument performance and exoplanet-tailored observing techniques will ultimately be able to achieve this. The intensity of the star backlighting the planet's atmosphere begins to drop at longer wavelengths, so the photon-limited S/N will decrease, resulting in larger error bars. Note that the features seen here with the assumed photon-limited noise are of the order of 2–8 ppm, which is below the instrument systematic errors assumed prelaunch (Greene et al., 2016). These observations will therefore be extremely challenging and will depend ultimately on on-orbit performance of the JWST science instruments and excellent knowledge of instrument systematics and how to ameliorate them. (Credit: J. Lustig-Yaeger, D. Deming, E. Schwieterman)