。
On that same day, Apollo 11 successfully landed on the moon.
Literal
Same day [to-に] Apollo 11 [subject-が] moon-surface landing [to-に] succeeded.
同日に ('on the same day') references a previously mentioned date. アポロ１１号 ('Apollo 11') uses 号 as the numbering counter for vehicles/missions. 月面着陸 (げつめんちゃくりく, 'lunar surface landing') is a compound: 月面 ('moon surface') + 着陸 ('landing'). 成功した ('succeeded') completes the factual statement. A historic milestone sentence.