Low-resolution spectroscopy () in the new system is expected to be much improved because of long-exposure stability, slit rotation capability, and diffraction-limited, Nyquist-sampled PSFs in all bands. Repeated, reliable co-adds will make it possible to raise SNR and track night sky line variation. The current slit is 100 m wide, which represents 24 mas at the detector in the spectral direction. The diffraction-limited disk is currently truncated by the slit in and bands.
Figure 8 shows the minimum amount of exposure time needed to no longer be limited by the detector noise and background noise.
Minimum exposure time required at each wavelength for sky background and dark current to equal read noise (background limited) and for source flux to equal 2sky flux (source limited).
Limiting magnitudes in the bands for spectroscopy with the ShARCS 8 subaperture (the initial configuration) and ShARCS 16 setup are shown in Figure 9
Magnitude limits (SNR=5) versus wavelength for point source spectroscopy with ShARCS 8 and ShARCS 16 configurations.