Program: GN-2009B-Q-101

We propose moderate resolution 1.9-4.2~$\mu$m grism spectroscopy with NIRI of {\it Spitzer} identified protostars in the Orion molecular cloud complex. Orion contains the richest collection of protostars within 500 pc and is the premiere region for studying protostellar evolution in different environments - from crowded clusters to isolation. This study will be part of a larger comprehensive program to measure detailed properties of protostars in the Orion molecular clouds using the {\it Spitzer}, {\it Hubble}, and Herschel Space Telescopes. Using radiative transfer models, we will use these data to determine the fundamental protostellar properties such as gas infall rate, rotation rate, outflow cavity angle, and we will trace the flow of gas from the protostellar envelope to the central protostar. NIRI will provide information on the 3~$\mu$m ice feature, hydrogen lines created by accretion onto the central protostar, and photospheric features from the central protostar.