Aided by strong program performance, stock buybacks and the ability to keep revenues level amid constrained federal spending, Northrop Grumman [NOC] yesterday posted solid second quarter earnings and the company raised its financial guidance for 2013. The results are similar to its peers in the defense industry, that is higher earnings despite flat to somewhat down sales, and no significant impacts so far from an ongoing budget sequester that defense company executives seem to all believe presents more hazards to…