DOW JONES NEWSWIRES Northrop Grumman Corp.'s (NOC) fourth-quarter earnings rose 46% amid a year-earlier debt-retirement charge and improved operating margins. However, the defense company reported weaker sales across its business segments and a sharply lower backlog. For the year, the company projected per-share earnings of $6.40 to $6.70 on sales of $24.7 billion to $25.4 billion, below recent estimates of analysts polled by Thomson Reuters of $6.80 and $26.17 billion, respectively. Northrop and other defense companies are facing challenges amid uncertainty over military budgets in the U.S. and abroad. Northrop Grumman reported a profit of $548 million, or $2.09 a share, up from $376 million, or $1.27 a share, a year earlier. Excluding pension-related adjustments and a prior-year debt retirement charge, earnings from continuing operations were up at $1.85 from $1.51. Revenue decreased 5.7% to $6.51 billion amid tight defense spending and moves to reduce volume in noncore businesses. Analysts polled by Thomson Reuters most recently projected earnings of $1.67 on revenue of $6.67 billion. Operating margin rose to 11.9% from 10.9%. Aerospace systems sales declined 4.1%, though operating income edged up 0.9% amid stronger margins. Electronics systems segment sales edged down 0.3% and operating profit fell 5.9% as margins weakened. Total backlog at year's end was $39.5 billion, compared with $64.2 billion a year earlier. Shares closed Tuesday at $58.05 and were inactive premarket. The stock is down roughly 9% in the past year. -By Tess Stynes, Dow Jones Newswires; 212-416-2481; Tess.Stynes@dowjones.com