1.) "Last week, I found out that NASA stands for 'National Aeronautics and Space Administration.'"
2.) "Last week, I found out that NASA stood for 'National Aeronautics and Space Administration.'"
Both versions #1 and #2 are acceptable. It's up to you (or your editor) as to which one you want to use. The second version happens to use a backshifted preterite ("stood") in the subordinate clause.
To explain backshifting, it might be easier to use an example.
Assume that Kim has blue eyes, and that Tom knows that. And then Tom tells me,
Then I can tell you,
- "Tom told me that Kim had blue eyes."
which has backshifting. Or I can choose to not use backshifting,
- "Tom told me that Kim has blue eyes."
Both versions are fine. Note that Kim's eye color is assumed to be a permanent sort of thing.
The above examples used sentences that involved indirect reported speech. Though those are the types of examples often used to demonstrate the use of backshifting, backshifting also happens often in other types of construction: constructions where the matrix clause is headed by a past-tense verb form or when the time of the matrix clause situation is the past.
For an example that could use backshifting but that doesn't involving indirect reported speech:
"Last week, Tom found out that Kim had blue eyes." -- (backshifted)
"Last week, Tom found out that Kim has blue eyes." -- (not backshifted)
both of the above versions are fine.
Sometimes, depending on the purpose of the sentence, there can be a preference for either the non-backshifted version or for the backshifted version. Sometimes the non-backshifted version might be considered to be "much more widely appropriate" than the backshifted version. Sometimes the backshifted version is obligatory.
Note that the examples I've used are either borrowed from or related to the examples used in the 2005 textbook by Huddleston and Pullum, A Student's Introduction to English Grammar, pages 47-8.
From that textbook, on page 48, is the excerpt:
Although indirect reported speech represents the most obvious case, backshift also happens quite generally in constructions where one clause is embedded within a larger one containing a preterite verb: . . .
There's a common misconception that a present-tense verb being used in its timeless sense (or other related uses) cannot be backshifted. That is untrue, as backshifting is still generally available. For instance, in the older 1985 reference grammar by Quirk et al., A Comprehensive Grammar of the English Language, section 14.31, page 1027:
Here are other examples where present forms may be retained in indirect speech:
- Their teacher had told them that the earth moves around the sun. -- 
. . .
In all these sentences, past forms may also be used, by optional application of the backshift rule. Sentence  has the simple present in its timeless use, . . .
And so, according to Quirk et al., the following backshifted version (to correspond to ) is also acceptable:
- Their teacher had told them that the earth moved around the sun.