In fiscal year 2006, a Linux-based image-acquisition system was demonstrated at the NASA Glenn Research Center. The system consists of an off-the-shelf industrial computer with a 100-GB hard drive, a Global Positioning System (GPS) receiver, an orientation sensor, and a custom image-acquisition board, which was developed in Glenn’s Flight Electronics Lab to acquire “pushbroom” hyperspectral data as a part of the Great Lakes Environ-mental Monitoring project, which is a collaboration between Glenn and the National Oceanic and Atmospheric Administration.
The system is built around an industrial personal computer running Linux-2.6.9 (Free Software Foundation, Incorporated, MA) with custom software. The software consists of a device driver for the image acquisition board, a GPS daemon, an orientation daemon, a memory management daemon, and application software, which transfers image data from the image acquisition board to the database. The application software and daemons communicate via a region of shared memory. Furthermore, there is a small server that implements a subset of the Hypertext Transfer Protocol (HTTP). The server provides live Portable Network Graphics (PNG) snapshots of the context camera and hyperspectral imager, a histogram of hyperspectral data, and GPS and orientation data. It allows users to download the database. In addition, the software controls the camera exposure and gain and data bus timing.
The database is stored on an unformatted, 99-GB partition on the hard drive and is written via raw input/output: that is, there is no file system. It is organized as a series of up to approximately 160,000 records. Each record is of fixed size and contains image, position, and orientation information needed to reconstruct images from the hyperspectral data.
The device driver provides access to the image data and allows software to acquire snapshots. In order to maximize the data rate, the driver changes the clock speed of the PC-104 bus to 16.7 MHz upon initialization.
The GPS, orientation, and memory management daemons are small applications that continuously run in the background. Each daemon is responsible for a particular task. For example, the GPS daemon parses data from the GPS receiver and stores the position in shared memory. Shared memory usage allows several applications to have access to current data simultaneously.
The system was tested aboard a manned aircraft, and images were acquired at approximately 2 frames per second. The results are currently being analyzed. It is expected that the system will be demonstrated in an unmanned-aerial-vehicle-based experiment in the near future.
The system has been shown to operate in the field. It is a low-power system consuming approximately 13 W over a range of 6 to 40 V and is compact. The personal computer, with the power supply and acquisition board shock absorbers, is4.5 in. wide, 6.5 in. long, and approximately 4 in. high (see the photograph).
Image acquisition system: industrial computer (bottom board), power supply (middle), image acquisition board (top board and cabling). The 2.5-in. hard drive is not shown.
In the future, hardware changes will allow us to increase the frame rate and to acquire data from additional sensors, such as a point spectrometer. The combined operating system and application software can be reduced to under 16 MB by eliminating unused libraries and other files. The system can also be adapted to other image-acquisition applications where power and weight are a concern.
Ohio Aerospace Institute (OAI) contact: Joseph M. Flatico, 216-433-5053, Joseph.M.Flatico@nasa.govLast updated: October 15, 2007
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