Technicians will work this weekend to prepare space shuttle Discovery's external tank for a tanking test planned for no earlier than Wednesday. Because the test hopes to glean a great deal of information, technicians will place 89 instruments including strain gauges to the tank to precisely record movement and temperatures from the tank's ribbed intertank area as it chills and warms again during the fuel loading and emptying process. The tank holds super-cold liquid oxygen at minus-297 degrees and liquid hydrogen at minus-423 degrees. The cryogenic propellants cause the tank to shrink by about half an inch.
