Nadir-viewing geometry is well-suited for sprite observation as it allows to simultaneously detect electromagnetic and particles emissions over the event. The downside is the loss of the vertical resolution making it harder for the determination of physical quantities like streamer altitudes. Ihaddadene and Celestin [JGR, 112, 1000-1014, 2017] have developed a method to estimate the streamer peak electric field and the altitude from N2 and N +2 sprite streamers optical emission: Lyman-Birge-Hopfield (LBH) (a1Πg → X1 Σ+g ) (∼ 100nm - 260 nm ), the first positif system 1P N2 (B3Πg → A3 Σ+u ) (∼ 650nm - 1070 nm ), the second positif system 2P N2 (C3Πu → B3Π+g ) (∼ 330nm - 450 nm ), and the first negative system of the N+ 2 ion (1N N + 2 ) (B2Σu → X2Σ+ g ) (∼ 390nm - 430nm ). The instrument MCP on board the TARANIS space mission is dedicated to the observation of sprites through optical emissions by means of 2 cameras and 4 photometers. The detection of optical emissions by the four photometers is performed over specific bands: PH1 (160nm - 260 nm for LBH), PH2 (337± 5nm for 2PN2 ), PH3 (762 ± 5nm for 1P N2 ), and the lightning light by PH4 (600 nm - 900nm ). In this work, we improve the Ihaddadene and Celestin's [2017] method taking into account the radiative transfer of sprite emissions through the Earth's atmosphere and the instrumental response of MCP.