Would it have been possible to lower the orbit of the ISS down to a point where Columbia could have gotten near it? I don't know myself, but it seems like a possibility.
CAPE CANAVERAL, Feb. 3 — Two days before the Columbia disaster, a NASA engineering team sent an internal memo calculating a high probability that launch debris had caused a gash 7½ by 30 inches on the shuttle’s left wing, NBC’s Jay Barbree reported Monday. NASA engineers have talked of a heat spike and drag on the left wing, suggesting a potential problem with the thermal tiles there. But NASA’s chief told NBC News on Monday that the tiles are just one of many variables being investigated.
http://www.msnbc.com/news/867336.asp?0cv=CA01>>...Would it have been possible to lower the orbit of the ISS down to a point where Columbia could have gotten near it?...<<
It's not the altitude, it's the inclination.
The inclination of a satellite is the highest latitude line the satellite passes over during its orbit. For instance, if a satellite stays over the equator, it's inclination is 0 degrees.
The ISS is about 51 degrees (if I'm not mistaken).
It takes a lot of energy to put a shuttle at 51 degrees inclination. Columbia was too heavy for a misson to the ISS. It sure wouldn't be able to reach the ISS once it was in orbit for this mission.
Now, I'm not well versed on orbital mechanics, but I don't think you can change the ISS's orbit without substancial energy either.
