How did they make sure the rover landed/lands?

Question

Having read your comment, I give an example to explain what I had in mind by 'point of time being considered'.

The rover, Perseverance or Percy, started its voyage on 30 July '20. It landed on 18 Feb '21. Let's ask a question about a day inbetween these two days, say 1 Jan '21. Let us assume all planning or preparation was already done before the launch date, like finalising computer programmes etc. Today, which is after landing, we ask about Jan 1.

1) How did they make sure (before 30 July '20) that Percy lands/ would land/ landed (after 1 Jan '21, on 18 Feb '21) on flat terrain?

Or, should it be this?

2) On 1 Jan '21, how had they made sure, before 30 July '20, that Percy landed / would land/ lands on flat terrain on 18 Feb '21?

GPY · Accepted Answer

BulbulTadaThe rover, Perseverance or Percy, started its voyage on 30 July '20. It landed on 18 Feb '21. Let's ask a question about a day inbetween these two days, say 1 Jan '21. Let us assume all planning or preparation was already done before the launch date, like finalising computer programmes etc. Today, which is after landing, we ask about Jan 1.

What happened on Jan 1? How is Jan 1 relevant to anything?

To ask after landing about preparations before landing, you can say:

How did they make sure that Percy landed on flat terrain?
How did they make sure that Percy would land on flat terrain?

This is of course not specific that all planning or preparation was completed before the launch date, or any other date, except that by obvious implication it was completed before the landing concluded. You cannot specify such a "before" date using only tenses. You would need to explicitly state it.

How did they make sure the rover landed/lands?

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