A scientific mission, 9:16 am EST expected landing, expected loss of contact just prior to that.
Communication and tracking of the shuttle was lost at 9 a.m. at an altitude of about 203,000 feet above north central Texas while traveling approximately 12,500 miles per hour (Mach 18).
From 3:30-ish pm EST NASA press conference:
-Following information from Milt Heflin (Chief Flight Director) and Ron Dittemore (Shuttle Program Manager)-
8:53 am EST: In and out board hydrolic systems, connection to temperture indicators lost
8:56 am EST: Left main gear tire wheel well, increase in temperature registered. However, the shuttle was entering the atmosphere.
--During this time the craft was operating just as it was meant to, which means it wasn't a vehicle loss of control issue. There were no real/other indication if problems as connection to sensor readings are occasionally lost.
8:58 am EST: Left side wing area "bondline" temperture indicators connection lost
8:59 am EST: Left in/out board tire temperature and pressure indicators connection lost (all 8 sesnors)
One of these sensors on the shuttle signaled an indicator/alert to the crew, who noted such with ground control. That was the last contact with the crew.
~9 am EST: Lost all vehicle data
207,135 ft, Mach ~18.3: "That's when we clearly began to know we had a bad day."
On the shuttle's take off, January 16th, there was an impact with a piece of foam debris from one of the external fuel tanks on the underside of the left wing of the orbiter. After much scrutiny and judgement by professionals and technitions nation wide it was determined the impact did not pose a safety threat for the shuttle. They were planning to review the fuel tank (which the shuttle seperates from during the latter stages of take off). NASA plans to review everything again to see if there is or is not a connection with the accident.
Status of the shuttle program: So far, only have slowed down manufacturing at NASA supply sites around the country to preserve current evidence. They say they cannot say yet how this accident will effect the flight program. Tomorrow's launch meant to send supplies up to the space station is still going to go off as scheduled to make sure those still in the station will have enough supplies to last as long as they need. They supplies will let them hold out until at least the end of June. Both NASA and the President have said the space program will go on.
Random additionals: The Columbia was the oldest shuttle in NASA's fleet. It was on it's 28th space flight.