If we can demonstrate that social media accurately captures a population’s sentiment, it could be a more affordable, accessible and timely alternative to what are otherwise expensive and logistically challenging surveys. 

各位老师好，以上内容来自2019下半年翻译资格考试二级笔译综合题，请问to和what做什么成分？Otherwise在这里是什么意思？

谢谢！