If you have crafted a subject line that is compelling and mitigates any potential trust issues, then it is up to the invitation to convert them from prospect to survey respondent. Opening the invitation is the job of the subject and from lines. Getting the prospect to move forward and click on the survey link is the job of the invitation copy.
Personalization is the place to start. When it is possible to include the individual’s first name, by all means do so. We are social creatures....