Lomb-Scargle periodograms for SSO/Io (top, red) and SSO/Europa (bottom, blue). The five highest peaks are marked by black crosses in both cases. For SSO/Europa, the most significant peak is around 50–55 days and the next highest four are at ~1 day and were determined to be aliases. The results for SSO/Io are less clear due to large gaps and much less data. The most significant peaks are found at 23.0, 54.0, and 4.3 days. The peak around 54 days could correspond to the one detected for SSO/Europa, but the other two are not present in SSO/Europa’s periodogram.