_ Jan. 16, 9:39 a.m.: Columbia rockets into orbit from Kennedy Space Center.
_ Feb. 1, 7:15 a.m.: Columbia fires braking rockets, streaks toward touchdown.
_ 7:53 a.m.: NASA loses temperature measurements for shuttle's left hydraulic system.
_ 7:58 a.m.: NASA loses measurements from three temperature sensors on shuttle's left side.
_ 7:59 a.m.: NASA loses eight more temperature measures and pressure measures for left inboard and outboard tires. One of the measurements remains visible to crew on a display panel; which crew acknowledges.
_ 7:59 a.m.: Final transmission. Mission Control radios: "Columbia, Houston, we see your tire pressure messages and we did not copy your last." Columbia replies: "Roger, uh, ..."
_ 8 a.m.: NASA loses all data and contact with Columbia at 207,135 feet. _ 9 a.m.: Residents of Texas, Arkansas and Louisiana report hearing "a big bang" and seeing flames in the sky.
_ 8:16 a.m.: Columbia's scheduled landing time.
_ 8:29 a.m.: NASA declares an emergency.
_ 8:44 a.m.: NASA warns residents to stay away from possibly hazardous debris.
_ 10 a.m.: Kennedy Space Center lowers flag to half-staff.