Two USA employees, Tim Seymour (at left) and Danny Brown (at right), look at the network signal processor (NSP) that was responsible for postponement of the launch of STS-90 on Apr. 16. The Space Shuttle Columbia's liftoff from Launch Pad 39B was postponed 24 hours due to difficulty with NSP No. 2 on the orbiter. This device formats data and voice communications between the ground and the Space Shuttle. The unit, which is located in the orbiter's mid-deck, was removed and replaced on Apr. 16. Mission managers first noticed the problem at about 3 a.m. during normal communications systems activation prior to tanking operations. As a result, work to load the external tank with the cryogenic propellants did not begin and launch postponement was made official at about 8:15 a.m. STS-90 is slated to be the launch of Neurolab, a nearly 17-day mission to examine the effects of spaceflight on the brain, spinal cord, peripheral nerves and sensory organs in the human body.