The surface data at iss2 sounding site stopped around 16z. The culprit turns out to have been a bad system time on the DSM, causing samples to get dropped as too different from absolute time on the data manager. I don't know what caused the DSM system time to jump so far off, but I've adjusted the chrony configuration to correct even large offsets. Surface data have been restored, and if this happens again, one thing to try is to restart chrony on the dsm. See ISS-562 for details.