Two approaches for Ni Atomic Layer Deposition on glass substrates have been studied for spacecraft optical applications. The first strategy is to first deposit a NiO thin film and then reduce the metal oxide film using noble gas under high temperature. NiCp2 and O3 as the precursors were chosen due to the low-temperature required for deposition and high growth rate. An alternative pathway was to deposit a Ru metallic film as the adsorption layer, using Ru(DMBD)(CO)3 and H2O, then deposit the Ni metallic film on the Ru film using Ni(DAD)2 and tert-butylamine. The reaction mechanisms for both processes were developed. The ideal theoretical growth rates of these ALD processes were calculated as 2.40 Å/cycle for NiO, 2.19 Å/cycle for Ru and 2.04 Å/cycle for Ni metallic film.