Vertical Transmit-Vertical Receive Polarisation (VV)
"A mode of radar polarisation where the microwaves of the electric field are oriented in the vertical plane for both signal transmission and reception by means of a radar antenna. In this case, the plane of the electric field of the microwave energy is designated by the letter V (vertical) for both transmit and receive events, i.e. VV; this transmit-receive polarity is also called like-polarised as opposed to cross-polarised (horizontal transmit - vertical receive, HV). The amount of radar backscatter received at a particular linear polarisation state from a particular ground surface or object depends, in part, on the scattering mechanism and depolarisation effects involved. The transmit-receive acronym is often used in conjunction with the frequency band (wavelength) designation of a particular radar system, e.g. C-VV for C-band. Several satellite SAR designs have used single-band, horizontally like-polarised systems, for example the European ERS-1 and ERS-2 (C-VV)" (ESA, 2020).
European Space Agency. 2020. Earthnet online: Radar and SAR Glossary. https://earth.esa.int/handbooks/asar/CNTR5-2.html