No signals have come from the lander after it made the final descent.
I would say the sentence from the BBC is not quite grammatical, because I understand "after it made the final descent" to refer to the period of time following its descent, which time is in the past; it does not extend to the present.
The word after in after it made does not function like an
after operator in a data query language:
select * from employees where dateHired after 20120101.
which would include employees hired today.
The time phrases in a present perfect construction cannot exclude the present.
I would have written:
No signals have come from the lander since it made the final descent.
P.S. But if the speaker understands after to be perfectly synonymous with since, the BBC sentence will strike the speaker's ear as grammatical.