The results of studying thin films and superlattices of rare-earth helimagnets Dy and Ho by neutron reflectometry are presented. It is shown that neutron reflectometry allows studying magnetic phase transitions in these nanostructures and obtain information about periodicity of magnetic helices in them. It is proposed to create a neutron reflectometer capable of conducting polarization analysis on a compact DARIA neutron source, optimized for studying long-period magnetic orderings in rare-earth helimagnets, and possible directions of this optimization are indicated.