GNSS-R Group Delay Altimetry and Ionospheric Delay Uncertainty

Based on the analysis conducted in [23], the ionospheric delay constitutes a significant component within the error budget associated with GNSS-R ocean surface altimetry retrievals. At elevation angles above 60◦, the uncorrected ionospheric delay can reach ~15 m during daytime and ~7 at nighttime. The ionospheric group delay bias propagates to an altimetric bias based on the relation between the height offset Δ*<sup>h</sup>* and the signal path Δ*p*. Consequently, when considering only the ionospheric altimetric error, where *E* is the elevation angle, it can be expressed as:

$$
\Delta h\_{iono} = \frac{\Delta\_{p\_{ions}}}{2 \ast \sin E} \tag{4}
$$

Assuming a relative uncertainty of 30% for the ionospheric delay bias, as established in [20], we introduce normally distributed random errors with a respective standard deviation *δiono* = N 0, 0.32 ).
