Direct Observational Analysis of the Cosmic Microwave Background Angular Power Spectrum from Planck Data

This work presents a direct observational analysis of the Cosmic Microwave Background (CMB) angular power spectrum using the publicly available Planck SMICA full-sky temperature dataset. The CMB temperature field defined on the celestial sphere is decomposed into spherical harmonic modes and the corresponding angular power spectrum CℓC_\ellCℓ is computed directly from the observational map. The procedure is entirely observational and avoids cosmological parameter fitting, theoretical priors, or model-dependent statistical reconstructions. The resulting spectrum reproduces the characteristic acoustic peak structure observed in Planck measurements while providing a transparent and reproducible computational framework. Particular attention is devoted to the large angular scale regime (ℓ