As the National Aeronautics and SpaceAdministration (NASA) plans for the next launch of the space shuttle, acritical aspect of the program's safety is being assured by 5 millionpieces of data collected recently by the National Institute ofStandards and Technology (NIST).
To help prevent a repeat of the 2003 accident when launchdebris damaged the shuttle Columbia, causing it to break up onre-entry, NASA has begun illuminating shuttles with tracking radarsduring launches and ascent to detect and quantify potential hazards.Concerns about possible disruption of onboard electronic guidance andcontrol systems led NASA to request NIST's help in determining how muchradar energy can penetrate the orbiter in key locations.
During the launch of Discovery in July, radar was used to trackdebris during ascent and NASA considered the NIST shielding data vitalto the resumption of shuttle flights.
NIST has been conducting research in this area for severalyears and has developed a portable system that efficiently measures theelectromagnetic shielding characteristics of airframes. Thesystempreviously has been used to evaluate both commercial and militaryaircraft. NIST engineers visited the Kennedy Space Center in Florida toevaluate the space shuttle Endeavor and the hanger in which themeasurements were made.
The NIST system incorporates ultra-wideband antennas, aprecision optical link between them, and a computerized data analysissystem. The two-step measurement process consisted of a referencemeasurement with the transmitting and receiving antennas outside theshuttle, and a penetration measurement with the receiving antennas atselected locations inside the orbiter. A computerized comparison ofthese two measurements over specific time periods and frequency bandsprovided a measure of shielding characteristics in the frequency range30 megahertz to 6 gigahertz. The data enabled NASA to set safe powerlevels on radar systems used to detect debris.
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