Is this an explanatory/appositive phrase, and do I need to separate it with a comma?

In the following sentence (forgive the obscure acronyms):

• To begin with, we search within three pixels of the predicted position to lock onto the target, using the WCS header in each FITS file to transform from astrometric into pixel coordinates.

I would say that the phrase beginning with "using the WCS header" is either appositive or explanatory. Is that correct?

I also feel it makes sense to put a comma before "using the WCS header," since I think it’s somewhat independent of the main clause (it explains how I do the action in the main clause). However, a language editor told me to remove the comma, leaving the following:

• To begin with, we search within three pixels of the predicted position to lock onto the target using the WCS header in each FITS file to transform from astrometric into pixel coordinates.

To me, the first way is better. It reads more like how I would speak out the sentence.