added margins must be accounted for which lead to higher TPS mass and reduced RLV performance. While it is typical to attach some sensors to the windward surfaces (surfaces with highest heating), it is impractical to populate much of the surface or to have sensors on many critical areas. Furthermore, the sensors and associated equipment add weight and reduce vehicle performance. Infrared (IR) imaging has been used very successfully in the past to image and characterize boundary-layer transition and surface heating (refs. 1–3). Infrared imaging is global and nonintrusive, and in addition has the ability to show other flow features such as shock waves and some separated areas. Any flow phenomena that creates a measurable temperature change can be imaged by IR.
In an effort to develop the techniques and methods to image reentering RLVs NASA teamed with the Missile Defense Agency/Innovative Science and Technology Experimentation Facility (MDA/ISTEF) in an effort called the Infrared Sensing Aeroheating Flight Experiment (ISAFE). Using ground-based optical systems developed by MDA (formerly BMDO, the Ballistic Missile Defense Organization) two reentering Space Shuttle flights were imaged and analyzed. The results of the study (refs. 4, 5) were very favorable. The MDA equipment, however, while mobile, was difficult to rapidly deploy, had other commitments, and was costly because of its other capabilities. NASA has been designing a system that incorporates those capabilities that are needed for the reentry imaging but keeps the system very portable. The system uses commercially available components, where possible, to minimize cost and development time. In addition, NASA had been developing IR systems to image other targets of aeronautical interest, notably transition on subsonic and supersonic aircraft wings (refs. 1–3). These systems included in situ and remote airborne units. The design of this ground system would include the capability to image these and other aeronautical targets where practical.
The Mobile Aerial Tracking and Imaging System (MATrIS) is currently capable of tracking objects either optically or with global positioning system (GPS) data transmitted from the target. Infrared images can be recorded analog or digital, while simultaneously-captured visual wavelength images are recorded analog. The main optics are a multi-spectral telescope with a Cassegrain focus, 12.5-inch (31.75 cm) main mirror, 300-inch (762 cm) focal length, f/24, with a field of view (FOV) of 0.06 degrees also configured as an f/12, 150-inch (381 cm) focal length with an FOV of 0.12 degrees. This is optically equivalent to the MDA/ISTEF 12.5-inch telescope used in the initial study. The unit utilizes a shared aperture for mid-wave infrared (MWIR) and visible wavelength cameras. The gimbal is capable of azimuth velocity from < 0.1 to 100 deg/sec, elevation velocity from < 0.1 to 60 deg/sec, azimuth a c c e l e r a t i o n t o 1 0 0 d e g / s e c 2 , e l e v a t i o n a c c e l e r a t i o n t o 6 0 d e g / s e c 2 , m i c r o - s t e p p o s i t i o n c o n t r o l , a four-microradian step resolution. n d
This report will present the development and design of, and the results from, the system.
This section will discuss the technical background, past experimental results, and the development of the tracking and imaging system.
Windward Reusable Launch Vehicle Aerothermal Measurements
The study of windward aerothermal characteristics of RLVs or any reentering vehicle is of vital interest to designers of these vehicles. The TPS is a major design constraint of any reentering vehicle.