Xichang, China — A French-Chinese satellite blasted off Saturday on a hunt for the mightiest explosions in the universe, in a notable example of cooperation between a Western power and the Asian giant. Developed by engineers from both countries, the Space Variable Objects Monitor, or SVOM, will seek out gamma-ray bursts, the light from which has traveled billions of light years to reach Earth. The 930-kilogram (2,050-pound) satellite carrying four instruments — two French, two Chinese — took off around 3 p.m. aboard a Chinese Long March 2-C rocket from a space base in Xichang, in the southwestern province of Sichuan,more