The Simons Observatory (SO) is a new cosmic microwave background (CMB) experiment planned for construction on Cerro Toco in Chile, set to begin observations in the early 2020s. The experiment aims to measure the temperature and polarization anisotropy of the CMB in six frequency bands: 27, 39, 93, 145, 225, and 280 GHz. The initial configuration will include three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. The key science goals include characterizing primordial perturbations, measuring the number of relativistic species and the mass of neutrinos, testing for deviations from a cosmological constant, improving understanding of galaxy evolution, and constraining the duration of reionization. The small aperture telescopes will map approximately 10% of the sky to a white noise level of 2 μK-arcmin in the 93 and 145 GHz bands, aiming to measure the primordial tensor-to-scalar ratio r at a target level of σ(r)=0.003. The large aperture telescope will map approximately 40% of the sky at arcminute angular resolution to an expected white noise level of 6 μK-arcmin in the 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope (LSST) sky region. The experiment will provide a legacy catalog of 16,000 galaxy clusters and over 20,000 extragalactic sources. The SO will have a 6-meter primary mirror and three 0.5-meter refracting telescopes, with new optical designs providing larger focal planes. The experiment will be located in the Atacama Desert at an altitude of 5,200 meters, sharing the same site as ACT, Simons Array, and CLASS. The site is also planned for the future CMB-S4 experiment. The SO will cover a sky region overlapping many astronomical surveys, including LSST, DES, DESI, and Euclid. The experiment will use a baseline model for instrument performance, including detector noise, frequency bands, and angular resolution. The results of this process will inform the optimization of experimental design choices, including aperture sizes, angular resolutions, and frequency bands. The SO will use a combination of foreground cleaning methods and component separation techniques to remove foreground emissions. The experiment will provide insights into cosmological parameters, including the Hubble constant, neutrino mass, and dark matter interactions. The SO will also study the thermal and kinematic Sunyaev-Zel'dovich effects, and the polarization signature of primordial gravitational waves. The experiment will use a combination of foreground cleaning methods and component separation techniques to remove foreground emissions.The Simons Observatory (SO) is a new cosmic microwave background (CMB) experiment planned for construction on Cerro Toco in Chile, set to begin observations in the early 2020s. The experiment aims to measure the temperature and polarization anisotropy of the CMB in six frequency bands: 27, 39, 93, 145, 225, and 280 GHz. The initial configuration will include three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. The key science goals include characterizing primordial perturbations, measuring the number of relativistic species and the mass of neutrinos, testing for deviations from a cosmological constant, improving understanding of galaxy evolution, and constraining the duration of reionization. The small aperture telescopes will map approximately 10% of the sky to a white noise level of 2 μK-arcmin in the 93 and 145 GHz bands, aiming to measure the primordial tensor-to-scalar ratio r at a target level of σ(r)=0.003. The large aperture telescope will map approximately 40% of the sky at arcminute angular resolution to an expected white noise level of 6 μK-arcmin in the 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope (LSST) sky region. The experiment will provide a legacy catalog of 16,000 galaxy clusters and over 20,000 extragalactic sources. The SO will have a 6-meter primary mirror and three 0.5-meter refracting telescopes, with new optical designs providing larger focal planes. The experiment will be located in the Atacama Desert at an altitude of 5,200 meters, sharing the same site as ACT, Simons Array, and CLASS. The site is also planned for the future CMB-S4 experiment. The SO will cover a sky region overlapping many astronomical surveys, including LSST, DES, DESI, and Euclid. The experiment will use a baseline model for instrument performance, including detector noise, frequency bands, and angular resolution. The results of this process will inform the optimization of experimental design choices, including aperture sizes, angular resolutions, and frequency bands. The SO will use a combination of foreground cleaning methods and component separation techniques to remove foreground emissions. The experiment will provide insights into cosmological parameters, including the Hubble constant, neutrino mass, and dark matter interactions. The SO will also study the thermal and kinematic Sunyaev-Zel'dovich effects, and the polarization signature of primordial gravitational waves. The experiment will use a combination of foreground cleaning methods and component separation techniques to remove foreground emissions.