Max L. Decker

Multispectral Thermal Imager mission overview

The Multispectral Thermal Imager (MTI) is a research and development project sponsored by the Department of Energy and executed by Sandia and Los Alamos National Laboratories and the Savannah River Technology Center. Other participants include the U.S. Air Force, universities, and many industrial partners. The MTI mission is to demonstrate the efficacy of highly accurate multispectral imaging for passive characterization of industrial facilities and related environmental impacts from space. MTI provides simultaneous data for atmospheric characterization at high spatial resolution. Additionally, MTI has applications to environmental monitoring and other civilian applications. The mission is based in end-to-end modeling of targets, signatures, atmospheric effects, the space sensor, and analysis techniques to form a balanced, self-consistent mission. The MTI satellite nears completion, and is scheduled for launch in late 1999. This paper describes the MTI mission, development of desired system attributes, some trade studies, schedule, and overall plans for data acquisition and analysis. This effort drives the sophisticated payload and advanced calibration systems, which are the overall subject of the first session at this conference, as well as the data processing and some of the analysis tools that will be described in the second segment.

Multispectral Thermal Imager (MTI) Payload Overview

MTI is a comprehensive research and development project that includes up-front modeling and analysis, satellite system design, fabrication, assembly and testing, on-orbit operations, and experimentation and data analysis. The satellite is designed to collect radiometrically calibrated, medium resolution imagery in 15 spectral bands ranging from 0.45 to 10.70 micrometer. The payload portion of the satellite includes the imaging system components, associated electronics boxes, and payload support structure. The imaging system includes a three-mirror anastigmatic off-axis telescope, a single cryogenically cooled focal plane assembly, a mechanical cooler, and an onboard calibration system. Payload electronic subsystems include image digitizers, real-time image compressors, a solid state recorder, calibration source drivers, and cooler temperature and vibration controllers. The payload support structure mechanically integrates all payload components and provides a simple four point interface to the spacecraft bus. All payload components have been fabricated and tested, and integrated.

Edge-based correlation image registration algorithm for the Multispectral Thermal Imager (MTI)

The Multispectral Thermal Imager Satellite (MTI), launched on March 12, 2000, is a multispectral pushbroom system that acquires 15 unique spectral bands of data from 0.45-10.7 microns, with resolutions of 5 m for the visible bands and 20 m for the infrared. Scene data are collected on three separate sensor chip assemblies (SCAs) mounted on the focal plane. The process of image registration for MTI satellite imagery therefore requires two separate steps: (1) the multispectral data collected by each SCA must be coregistered and (2) the SCAs must be registered with respect to each other. An automated algorithm was developed to register the MTI imagery. This algorithm performs a phase correlation on edge-maps generated from paired bands of data and then spatial-filters the result to calculate the relative shifts between bands. The process is repeated on every combination of band pairs to generate a vector of coregistration results for each SCA. The three SCAs are then registered to each other using a similar process operating on just one spectral band. The resulting registration values are used to produce a linearly shifted un-resampled coregistered image cube. This study shows the results of 791 image registration attempts using the EdgeReg registration code and compares them to a perfect reference data set of the same images registered manually.

Multispectral thermal imager (MTI) satellite hardware status, tasking and operations

MTI is a comprehensive R&D project, featuring a single satellite in a sun-synchronous orbit designed to collect radiometrically accurate images of instrumented ground sites in 15 spectral bands ranging from visible to long-wave infrared. The satellite was launched from Vandenberg AFB on March 12, 2000 aboard an Orbital Sciences Corporation Taurus rocket. After launch, the operations team completed a 3- month turn-on, check out and alignment procedure, and declared the satellite ready for its R&D mission on June 12, 2000. The satellite is currently healthy, having collected over 1,100 images during its first nine months of operation. This paper presents a brief satellite overview and documents on-orbit status and operational experience, including anomalies and their resolution.

Subpixel resolution with the multispectral thermal imager (MTI)

The Multispectral Thermal Imager Satellite (MTI) has been used to test a sub-pixel sampling technique in an effort to obtain higher spatial frequency imagery than that of its original design. The MTI instrument is of particular interest because of its infrared detectors. In this spectral region, the detector size is traditionally the limiting factor in determining the satellite’s ground sampling distance (GSD). Additionally, many over-sampling techniques require flexible command and control of the sensor and spacecraft. The MTI sensor is well suited for this task, as it is the only imaging system on the MTI satellite bus. In this super-sampling technique, MTI is maneuvered such that the data are collected at sub-pixel intervals on the ground. The data are then processed using a deconvolution algorithm using in-scene measured point spread functions (PSF) to produce an image with synthetically-boosted GSD.

MTI system design and operations lessons learned

The Multispectral Thermal Imager Satellite (MTI), launched on March 12, 2000, has now surpassed its one-year mission requirement and its three-year mission goal. Primary and secondary program objectives regarding the development and evaluation of space-based multispectral and thermal imaging technology for nonproliferation treaty monitoring and other national security and civilian application have been met. Valuable lessons have also been learned, both from things that worked especially well and from shortcomings and anomalies encountered. This paper addresses lessons associated with the satellite, ground station and system operations, while companion papers address lessons associated with radiometric calibration, band-to-band registration and scientific processes and results. Things addressed in this paper that went especially well include overall satellite design, ground station design, system operations, and integration and test. Anomalies and other problems addressed herein include gyro and mass storage unit failures, battery under-voltage trips, a blown fuse, unexpected effects induced by communication link noise, ground station problems, and anomalies resulting from human error. In spite of MTI’s single-string design, the operations team has been successful in working around these problems, and the satellite continues to collect valuable mission data.