This is an obscure type of antenna, called sometimes cigar antenna, that works pretty much like Yagi - most of you will know it as (non-satellite) TV antenna - but instead of rods it has disks. It was used in Lunokhod 1 and 2, Soviet moon rovers launched in 1970 and 1973 respectively
you can think of these disks or rods or whatever as a kind of lens that makes signal stick to these elements - but only if it arrives from front. then all that signal falls on an actual radiating element in the back of antenna. this works only for some range of wavelengths - in general, the more volume this kind of antenna occupies, the bigger this range is