There are many systems for romanising Russian. Most of them use kh for х (including those used by US/UK for Russian place names, names in Russian passports, road signs in Russia).

Wikipedia has a handy table: https://en.wikipedia.org/wiki/Romanization_of_Russian#Transl...

As to why it is that way, I don't know. Some closely related languages (Belarusian, Bulgarian) follow different conventions. For example, the national system in Belarus transliterates х as ch and г as h.

Hello, I'm Paolo Attivissimo, the poster of the original article. I am using the "Lunokhod" spelling because this is the spelling used by NASA and many other reference sources, including Anatoly Zak's RussianSpaceWeb http://www.russianspaceweb.com/spacecraft_planetary_lunar.ht...

Because х is romanised as kh.

Because 'h' and 'kh' usually denote different sounds, the latter encodes https://en.wikipedia.org/wiki/Voiceless_velar_fricative.