KEYWORDS: Calibration, Image quality, Image processing, Sensors, Data modeling, Image enhancement, Temperature metrology, Black bodies, Signal to noise ratio, Near infrared
Ground-based high-resolution, calibrated, near-infrared (NIR) imagery of the Space Shuttle STS-134 Endeavour during
reentry has been obtained as part of NASA's HYTHIRM (Hypersonic Thermodynamic InfraRed Measurements) project.
The long-range optical sensor package called MARS (Mobile Aerospace Reconnaissance System) was positioned in
advance to acquire and track part of the shuttle re-entry. Imagery was acquired during a few minutes, with the best
imagery being processed when the shuttle was at 133 kft at Mach 5.8. This paper describes the processing of the NIR
imagery, building upon earlier work from the airborne imagery collections of several prior shuttle missions. Our goal is
to calculate the temperature distribution of the shuttle's bottom surface as accurately as possible, considering both
random and systematic errors, while maintaining all physical features in the imagery, especially local intensity
variations. The processing areas described are: 1) radiometric calibration, 2) improvement of image quality, 3)
atmospheric compensation, and 4) conversion to temperature. The computed temperature image will be shown, as well
as comparisons with thermocouples at different positions on the shuttle. A discussion of the uncertainties of the
temperature estimates using the NIR imagery is also given.
Joseph Zalameda, Thomas Horvath, Robbie Kerns, Eric Burke, Jeff Taylor, Tom Spisz, David Gibson, Edward Shea, C. David Mercer, Richard Schwartz, Steve Tack, Brett Bush, Ronald Dantowitz, Marek Kozubal
High resolution calibrated near infrared (NIR) imagery of the Space Shuttle Orbiter was obtained during hypervelocity
atmospheric re-entry of the STS-119, STS-125, STS-128, STS-131, STS-132, STS-133, and STS-134 missions. This
data has provided information on the distribution of surface temperature and the state of the airflow over the windward
surface of the Orbiter during descent. The thermal imagery complemented data collected with onboard surface
thermocouple instrumentation. The spatially resolved global thermal measurements made during the Orbiter's
hypersonic re-entry will provide critical flight data for reducing the uncertainty associated with present day ground-to-flight
extrapolation techniques and current state-of-the-art empirical boundary-layer transition or turbulent heating
prediction methods. Laminar and turbulent flight data is critical for the validation of physics-based, semi-empirical
boundary-layer transition prediction methods as well as stimulating the validation of laminar numerical chemistry
models and the development of turbulence models supporting NASA's next-generation spacecraft. In this paper we
provide details of the NIR imaging system used on both air and land-based imaging assets. The paper will discuss
calibrations performed on the NIR imaging systems that permitted conversion of captured radiant intensity (counts) to
temperature values. Image processing techniques are presented to analyze the NIR data for vignetting distortion, best
resolution, and image sharpness.
A portable low earth orbit satellite (LEO) tracking mount is described which has dimensions of 21' X 15' X 10' and weighs 58 pounds. Using 22 bit encoders on 9.5' worm gears, an integral microcontroller is capable of adjustable slew rates to six degrees per second. With a CCD and tracking software LEO pointing is demonstrated on f/10 eight inch telescope to less than 8 urad for periods of 10 seconds, and 50 urad for entire orbit passes. A closed loop one Hz video tracker is also described with automatic tracking of mag 7/8 satellites using a 12' telescope. Requiring only one operator, this system can be transported by a small car and be operational in a few hours. Possible uses and other recent work is also explained.
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