Processing near-infrared imagery of hypersonic space shuttle reentries

ABSTRACT High-resolution, calibrated, n ear-infrared imagery of the Space Shuttle during reentry has been obtained by a US Navy NP-3D Orion aircraft as part of NASA’s HYTHIRM (Hyp ersonic Thermodynamic InfraRe d Measurements) project. The long-range optical sensor package is calle d Cast Glance. Three sets of imagery ha ve been processed thus far: 1) STS-119 when Shuttle Discovery was at 52 km away at Mach 8.4, 2) STS-125 when Shuttle Atlantis was 71 km away at Mach 14.3, and 3) STS-128 when Shuttle Discovery was at 80 km away at Mach 14.7. The challenges presented in processing a manually-tracked high-angular rate, air-to-air image data collection include management of significant frame-to-frame motions, motion-induced blurring, changing orientations and ranges, daylight conditions, and sky backgrounds (including some cirrus clouds). This paper describes processing the imagery to estimate Shuttle surface temperatures. Our goal is to reduce the detrimental effects due to motions (sensor and Shuttle), vibration, and atmospherics for image quality improvement, without compromising the quantitative integrity of the data, especially local intensity variations. Our approach is to select and utilize only the highest quality images, register many co-temporal image frames to a single image frame, and then add the registered frames to im prove image quality and reduce noise. These registered and averaged intensity images are co nverted to temperatures on the Shuttle’s windward surface using a series of steps starting with preflight calibration data . Comparisons with thermocouples at different points along the space Shuttle and be tween the three reentr ies will be shown. Keywords: near-infrared imagery, image pro cessing, image registration, hyperson ic space Shuttle reentry, HYTHIRM