Abstract
A low-cost underwater sound recorder has been developed and tested. It is designed to receive signals from sound sources that serve as navigation aids for RAFOS floats. This moored version of the RAFOS float (MAFOS) can monitor sound sources over many months and several hundred kilometers. It thus improves RAFOS navigation accuracy by enabling corrections for potential long-term clock drifts of the sound sources. MAFOS can also provide information on the local variation in the speed of sound due to natural hydrographic variability. In a first test, this usefulness has been proven and a warm, salty inhomogenity that traveled through a sound-source mooring array in the Iberian Basin has been observed.
