  Quantum memories promise to enable global quantum repeater networks. For
field applications, alkali metal vapors constitute an exceptional storage
platform, as neither cryogenics, nor strong magnetic fields are required. We
demonstrate a technologically simple, in principle satellite-suited quantum
memory based on electromagnetically induced transparency on the cesium D1 line,
and focus on the trade-off between end-to-end efficiency and signal-to-noise
ratio, both being key parameters in applications. For coherent pulses
containing one photon on average, we achieve storage and retrieval with
end-to-end efficiencies of $\eta_{e2e} = 13(2)\%$, which correspond to internal
memory efficiencies of $\eta_{mem} = 33(1)\%$. Simultaneously, we achieve a
noise level corresponding to $\mu_1 = 0.07(2)$ signal photons. This noise is
dominated by spontaneous Raman scattering, with contributions from
fluorescence. Four wave mixing noise is negligible, allowing for further
minimization of the total noise level.
