These were the result of two years' worth of studies based on high-resolution photography of the lunar surface by the five uncrewed probes of the Lunar Orbiter program and information about surface conditions provided by the Surveyor program.
ðiːz wɜː ðə ɹɪzˈʌlt ʌv tˈuː jˈɪɹz wˈɜːθ ʌv stˈʌdiz bˈeɪst ˌɔn hˈaɪɹˌɛzəlˈuːʃən fətˈɑːɡɹəfi ʌvðə lˈuːnɚ sˈɜːfɪs baɪ ðə fˈaɪv ʌŋkɹˈuːd pɹˈoʊbz ʌvðə lˈuːnɚɹ ˈɔːɹbɪɾɚ pɹˈoʊɡɹæm ænd ˌɪnfɚmˈeɪʃən ɐbˌaʊt sˈɜːfɪs kəndˈɪʃənz pɹəvˈaɪdᵻd baɪ ðə sɚvˈeɪɚ pɹˈoʊɡɹæm.