159897 APOGEE Abundances from spectra with SNR<150

TSN reduces label scatter relative to visit-level ASPCAP for S/N<60 visits. It reproduces the ASPCAP scale with residual scatters of sigma~19K in Teff, sigma~0.06dex in logg, and sigma~0.03dex in Fe/H. TSN tightens intra-cluster abundance dispersions, recovers cleaner chemical sequences in inner-disk and bulge and satellite samples, and improves C/N-based age precision for APOKASC giants from 1.70 to 1.49Gyr. By learning survey-specific noise patterns from repeated observations, TSN demonstrates how empirical paired learning can extend the chemical reach of existing spectroscopic data, providing a template that is applicable to other multi-visit surveys.