Randy A. Nicholson

Test and Evaluation of Sensor Platforms in the AEDC Space Sensor Test Chambers

The space simulation test chambers at the Arnold Engineering Development Center (AEDC) offer a means of performing high-quality, economical, and timely state-of-the-art test and evaluation (T&E) to satisfy a variety of space system testing requirements. These requirements include sensor and focal plane array level characterization (including radiometric calibration and characterization and goniometric evaluation) and mission simulation. Such a ground test capability is crucial for reducing system development risk by testing the latest technologies developed for space-based, interceptor, and airborne sensor platforms. In response to the evolving requirements for testing sensor platforms, AEDC continues to develop new methodologies and techniques to maintain a suite of facilities capable of testing sensor systems at any level of development. This involves the integration of high-fidelity, complex, and dynamic scene projection systems in conjunction with comprehensive analysis and measurement of the properties of the optical systems. This paper describes the AEDC methodology for space sensor T&E, including uncertainty methodology and enhancements that are currently planned for the space sensor test facility.

Ground Testing of Space-Based Imaging Sensors in AEDC's Space Chambers *

Arnold Engineering Development Center (AEDC) space chamber facilities offer a means of satisfying a variety of space system testing requirements, including sensor and focal plane array level characterization and mission simulation, radiation effects simulation, spacecraft contamination effects, spacecraft propulsion testing, and thermal/vacuum environment simulation. Such a ground test capability is very important in testing the latest technologies developed for spacecraft components. AEDC has developed a suite of chambers and a methodology that addresses the complex, high-fidelity issues of the test and evaluation (T&E) community. This methodology encompasses the testing of sensor systems at any level of development, from characterization of the imaging chip to full-scale testing of the sensor. This paper discusses the AEDC space chamber facilities and some of the tests performed there recently.

Cryogenic optical system development for AEDC's 10V chamber

The 10V Chamber Test Facility at the Arnold Engineering Development Center (AEDC) is being upgraded to provide a closed-loop capability to assess multi-band electro-optical sensor performance under realistic operational scenarios against evolving threats. This test facility will leverage existing facilities and expertise from several Government agencies including AEDC, Army/AMCOM, and USAF/KHILS to investigate performance issues during ground testing at cryogenic conditions. Radiometrically accurate simulated scenes will be presented to the test article using dual-band infrared point sources, a dual-band infrared emitter array projector, and a visible array projector. Various optical assemblies will be required to project the images from these radiometric source systems onto the sensor aperture. The infrared point sources will be positioned in the XY plane using two-stage linear translators, which must meet stringent spatial coverage and position accuracy requirements to create realistic closed-loop target motion. A large two-axis steering mirror will simulate sensor line of sight movements for the blackbody sources. A high-speed jitter mirror will simulate high frequency image motion for the emitter arrays. These mirror systems must be vibrationally isolated to minimize the jitter induced in other optical elements. Narcissus and ghost image effects will be minimized using appropriate fabrication, shielding, and calibration techniques. A multi-spectral calibration and alignment system will be integrated into the facility to ensure proper radiometric and goniometric operation of the various target sources. The target and optical systems must all meet performance specifications at cryo-vacuum conditions. Code V will be the primary tool used to evaluate wave front error and distortion coating performance for ghosting/polarization/transmission effects, optical manufacturing errors, and energy-on-detector (EOD). Finite element models of the facility will be used to analyze the structural rigidity and dynamics of the components due to the cryogenic environment.

Applying Test and Evaluation Technologies, Techniques, and Methodologies to Enhance the Space Sensor Test Infrastructure at AEDC *

The Arnold Engineering Development Center (AEDC) continues to apply emerging test and evaluation (T&E) technologies, techniques, and methodologies to enhance the significant T&E infrastructure that has been developed for the characterization and calibration of space-based, airborne, and interceptor sensor systems. The 7V and 10V Chambers both provide a suite of radiometric target systems that operate in a simulated space background (~ 20K) and allow complete evaluation of sensor performance within a single test installation. These space simulation test chambers offer a means of performing high-quality, economical, and timely state-of-the-art T&E to satisfy a variety of space system testing requirements. Such ground-test capabilities are crucial for reducing the system development risk of the latest technologies developed for sensor platforms. Complex target systems that provide the ability to evaluate system performance against representative mission scenarios are included in both test chambers. The 7V Chamber emphasizes calibration and characterization of infrared seekers and sensors against a low-infrared background, but is also capable of mission simulation testing. The 10V Chamber hardwarein-the-loop (HWIL) chamber is dedicated to real-time interceptor testing. Upgrades to each chamber are being pursued to keep pace with evolving sensor technologies, as well as the development of methodologies to test wide-field-of-view (WFOV), polarimetric, space situational awareness (SSA) and multispectral/hyperspectral imaging systems. This paper reports the current status of these chambers and planned modifications for their continued development to meet test customer requirements.

Test and Evaluation of Space and Airborne Imaging Sensor Platforms

The space simulation test chambers at the Arnold Engineering Development Center offer a means of performing high-quality, economical, and timely state-of-the-art tests and evaluations to satisfy a variety of space system testing requirements. These requirements include sensor and focal plane array level characterization (including radiometric calibration and characterization and goniometric evaluation) and mission simulation. Such a groundtest capability is crucial for reducing system development risk by testing the latest technologies developed for spacebased, interceptor, and airborne sensor platforms. In response to the evolving requirements for testing sensor platforms, new methodologies and techniques are being developed to maintain a suite of facilities capable of testing sensor systems at any level of development. A roadmap has been created that integrates high-fidelity, complex, and dynamic scene projection systems in conjunction with comprehensive analysis andmeasurement of the properties of the optical systems to meet imaging sensor test needs.

Developing the Test and Evaluation Infrastructure at AEDC for Space Sensor Testing

The Arnold Engineering Development Center (AEDC) has developed significant test and evaluation (T&E) infrastructure for the characterization and calibration of space-based and airborne sensor systems. The 7V and 10V Chambers both provide a suite of radiometric target systems that operate in a simulated space background (~ 20K) and allow complete evaluation of sensor performance within a single test installation. These space simulation test chambers offer a means of performing high-quality, economical, and timely state-of-theart T&E to satisfy a variety of space system testing requirements. Such ground test capabilities are crucial for reducing the system development risk of the latest technologies developed for sensor platforms. Complex target systems that provide the ability to evaluate system performance against representative mission scenarios are included in both test chambers. The 7V Chamber is a state-of-the-art cryogenic/vacuum facility providing calibration and high-fidelity mission simulation for infrared seekers and sensors against a low-infrared background. The 10V Chamber hardware-in-the-loop (HWIL) chamber has undergone several checkout tests in the past two years to establish its performance. Upgrades to each chamber are being pursued to keep pace with evolving sensor technologies, such as a short focal length collimator (SFLC) system for 7V to enhance dynamic 2-D projection over a larger test field of view. This paper reports the current status of these chambers and planned modifications for their continued development to meet test customer requirements in areas such as satellite emulation and wide- field-of-view (WFOV) testing.

Expanding AEDC's Space Sensor Test Infrastructure to Meet Future Test and Evaluation Requirements *

The Space Systems Test Facility (SSTF) at the Arnold Engineering Development Center (AEDC) was established to provide the Test and Evaluation (T&E) infrastructure to accomplish the characterization and calibration of space-based, airborne, and interceptor imaging sensor systems. The 7V and 10V Space Simulation Chambers provide a suite of radiometric target systems that operate in the cryovacuum environment (~ 20 K) to achieve a low radiometric background and allow complete evaluation of sensor performance within a single test installation. These ground-test facilities offer a means of performing highquality, economical, and timely state-of-the-art T&E to satisfy a variety of space system testing requirements and are crucial for reducing the system development risk of the latest technologies developed for sensor platforms. Each chamber can provide simple calibration targets or dynamic mission scenarios to a sensor under test (SUT) so that its system performance against representative mission scenarios can be evaluated. The 7V Chamber emphasizes calibration and characterization of infrared seekers and sensors against a low-infrared background, but is also capable of mission simulation testing. The 10V hardware-inthe-loop (HWIL) Chamber is dedicated to real-time interceptor testing. The expansion of these capabilities, including the possibility of new chambers, is being pursued in order to keep pace with evolving sensor technologies, including wide field of view (WFOV), polarimetric, space situational awareness (SSA), and multi/hyperspectral imaging systems. This paper reports the current status of these facilities and plans for their continued development to meet emerging test customer requirements.

Support technologies involved in the development and implementation of radiometric systems for sensor calibration, characterization, and HWIL testing at AEDC

The characterization, calibration, and mission simulation testing of space-based, interceptor, and air-borne sensors require a continual involvement in the development and evaluation of radiometric projection technologies. Activities at Arnold Engineering Development Center (AEDC) include Hardware in the Loop (HWIL) testing with high-fidelity complex scene-projection technologies as well as improvements in the radiometric source-calibration systems. These technologies are integrated into a low cryo-vacuum (~20 K) environment. The latest scene simulation and HWIL projection technologies are being investigated that can produce desired target temperatures and target-to-sensor ranges such that sensor mission performance can be evaluated. These technologies include multiple-band source subsystems and special spectral-tailoring methods, as well as comprehensive analysis and optical properties measurements of the components involved. Emphasis areas include the development of methodologies to test wide field of view (WFOV), polarimetric, and multi/hyperspectral radiometric imaging systems.

Specialized focal plane array tests in the focal plane characterization chamber (FPCC)

The Focal Plane Characterization Chamber (FPCC) at the Arnold Engineering Development Center is configured to provide highly accurate radiometric characterization of focal plane arrays (FPAs). The chamber offers several inherent advantages that render it a unique and highly versatile facility. In addition to the excellent radiometric calibration capability provided by the FPCC, the chamber contains systems to allow several special FPA performance issues to be evaluated. Four of the principal capabilities that have been implemented provide the capability to evaluate performance issues such as crosstalk, FPA response blooming, radiometric flash recovery, and response in various spectral bands. These specialized test capabilities are described and discussed herein.

Testing of focal-plane arrays at the AEDC

A facility was developed at the Arnold Engineering Development Center (AEDC) to provide complete radiometric characterization offocal plane arrays (FPAs). The highly versatile facility provides the capability to test single detectors, detector arrays, and hybrid FPAs. The primary component of the AEDC test facility is the Focal Plane Characterization Chamber (FPCC). The FPCC provides a cryogenic, low-background environment for the test focal plane. Focal plane testing in the FPCC includes flood source testing, during which the array is uniformly irradiated with JR radiation, and spot source testing, during which the target radiation is focused onto a single pixel or group of pixels. For flood source testing, no optical elements are required between the source output aperture and the array. During flood source testing, performance parameters such as power consumption, responsivity, noise equivalent input, dynamic range, radiometric stability, recovery time, and array uniformity can be assessed. Sufficient data are acquired to permit complete parametric characterization of the array. Crosstalk is evaluated during spot source testing. Spectral response testing is performed in a spectral response test station using a three-grating monochromator. Because the chamber can accommodate several types oftesting in a single test installation, a high throughput rate and good economy ofoperation are possible. Data from the focal plane characterization tests can be presented in a wide variety of formats.