The Orlov-Schulman symmetries of the Manakov-Santini hierarchy

We construct the Orlov-Schulman symmetries for the Manakov-Santini (MS) hierarchy. We give an explicit proof of compatibility of additional symmetries with the basic flows of the MS hierarchy, and consider several simple examples, including the Galilean transformation and scalings. We also present a picture of the Orlov-Schulman symmetries in terms of the dressing scheme based on the Riemann-Hilbert problem.