In this contribution, we describe the status of the development of a precision-spectroscopic experiment aimed at measuring transitions to states of high principal quantum number n of the hydrogen atom (H). These states form series (called Rydberg series) which converge for n → ∞ to the ionization threshold of H. The ionization energy of H can thus be determined directly by measuring the frequencies of transitions to high-n states and extrapolating the Rydberg series to n → ∞.