Imaging of Shuttle STS-96 was obtained on June 6, 1999 at the NASA Kennedy Space Center. The orbiter reentered on an orbit earlier than nominal and passed nearly over the acquisition site prior to entering the terminal approach area. Images were obtained using both a 24-inch (61 cm) aperture telescope system (fig. 3) and a 12.5-inch (31.75 cm) aperture system (fig. 4). It was desired to capture images with the 12-bit digital data stream from the mid-wave IR camera as well as with the 8-bit analog data stream, however, problems with the digital data recording allowed only the analog data to be recorded. The orbiter was acquired and tracked while approaching from the south but the trackers were unable to keep up with the high angular rates (at elevation angles near 90°) as the shuttle passed overhead. Orbital vehicles at high inclinations can have a vastly different ground track when reentering from a different orbit number (earlier or later than nominal). Images were obtained between Mach numbers of 1.95 (immediately after acquisition) down to approximately 1.48. The conditions recorded were much later than those for the expected transition region (M∞ ~ 8 to 10) but proved the basic techniques. Discovery, like the other orbiters, has several thermocouples located on the windward surface that are used for diagnostic purposes after each flight. These data were available to compare and calibrate the infrared thermography data that was collected from the ground. Because of the resolution sensitivity of the IR sensor set prior to image acquisition, the hottest regions (nose and wing leading edges) are saturated. That is they are hotter than the highest temperature shown on the associated scale.
Figure 3. ISAFE STS-96 IR image with ISTEF 24-inch telescope.
Figure 4. ISAFE STS-96 IR image with ISTEF 12.5-inch telescope.
Imaging of Shuttle STS-103 was obtained on December 27, 1999. To increase the odds of capturing the shuttle reentry given the variability of the ground track with entry orbit number, two systems were deployed on the Florida west coast. One system was deployed south at Sanibel Island and one north at Cedar Key. The northern deployment was successful in capturing the returning shuttle. Data were acquired from an initial altitude of 135,000 ft (M∞ ~ 6) down to approximately 90,000 ft (M∞ ~ 3). At that site the ground track was due south and the images tended to show more of the port side of the shuttle except during roll maneuvers, when the windward surface became visible. These images were obtained with a 24-inch (61 cm) diameter f/12 telescope. Figure 5 shows a single frame of the raw processed image while figure 6 shows this same image after it was processed and calibrated for resultant surface