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A calibration uncertainty analysis was conducted for the Air Force Research Laboratory’s (AFRL) Advanced Compact Range (ACR) in 2000 [1]. This analysis was a key component of the Radar Cross Section (RCS) ISO-25 (ANSI-Z- 540) Range Certification Demonstration Project. The scope of the RCS uncertainty analysis for the demonstration project was limited to calibration targets. Since that time we have initiated a detailed RCS uncertainty analysis for a more typical target measured in the ACR. A “more typical” target is one that is much larger with respect to wavelength than the calibration targets and characterized by a wide dynamic range of RCS scattering levels. We choose a 10’ ogive as the target due to the fact it is a large target, exhibits a wide dynamic range of scattering, and the scattering levels can be predicted using readily available CEM codes. We will present the methodology for the uncertainty analysis and detailed analyses of selected component uncertainties. The aspects of the uncertainty analysis that are unique to the “typical target” (i.e., a non calibration target) will be emphasized.
The Range Commanders Council Signature Measurement Standards Group (RCC/SMSG) Performed a Demonstration program with three DOD Radar Cross Section Ranges to evaluate and improve their documentation and evaluation process and criteria documented in what is known as a "Range Book". After a successful Demonstration Program, The RCC/SMSG has embarked on the evaluation of Industry RCS Range Calibration and measurement processes and procedures and compliance with the RCC/SMSG ANSI-Z540 (ISO-25) evaluation criteria. The Lockheed Martin Helendale RCS Range was evaluated by a committee of industry volunteers appointed by the RCC/SMSG after a review of their experience and credentials. The Lockheed Martin Orlando RCS Range requested an evaluation of their "Range Book" shortly after the completion of the Helendale evaluation. Each review committee is made up of three RCC/SMSG approved reviewers, at least one of which has participated in a previous review either as a review requester or a review committee member. This paper will put forth the process used by this review committee and the lessons learned from this and previous reviews. This paper will also discuss the RCC/SMSG process for obtaining an RCC/SMSG review.
In June 2001, the DoD Range Commanders Council Signature Measurement and Standards Group (RCC/SMSG) certified that the Helendale Measurement Facility (HMF) outdoor radar cross section (RCS) measurement Range Book met the ANSI-Z-540 documentation standards established by the DoD demonstration project. This paper describes how Lockheed Martin Aeronautics (LM Aero) applied the ANSI Z-540 [1,2,3] standard to obtain National Certification of the HMF RCS range. The dual calibration results for Pit #1 and Pit #3 are presented showing upper and lower uncertainty error bounds established by this process. Schedule, cost, range book format, and “lessons learned” from the LM Aero experience are also discussed.
This paper reviews the Helendale Measurement Facility (HMF) ground plane range uncertainty analysis and associated data collection. Range uncertainty analysis is a requirement for ISO-25/ANSI-Z-540 range certification and is a priority one section in the Helendale Range Book. Targets used for the analysis were two sets of right circular “squat” calibration cylinders. These cylinders are the dual calibration cylinders for HMF. Calibration measurement uncertainties are established statistically from a large number of repeated measurements at S, C, X, and Ku bands. Each measurement was taken at two target support locations down range. The field data collected included monostatic scattering from two calibration cylinders, backgrounds with no target and support, and drift data for quality control. I and Q imbalance, frequency stability, range accuracy, linearity, and field uniformity at target locations were considered in the analysis. The uncertainty analysis is based on RSS addition of errors and assumes all errors are additive and that targets are not LO. The statistical approach used to perform the uncertainty analysis reported in this paper was developed cooperatively at AFRL and Mission Research Corporation.
During the last 6 years scientists at NIST have been focusing on radar cross section (RCS) measurements to improve RCS uncertainty analysis, and to develop new measurement and calibration artifacts and procedures. In addition, NIST has been asked to provide technical support to the DoD RCS self-certification effort. In this talk I review the technical accomplishments of the program, and will make suggestions for future research to improve RCS calibration and measurement technology. I will also present the structure of the certi fication process, and discuss NIST's role in the ongoing certification activities.
As a result of Government and Industry RCS Teaming, initial RCS range certification exercises are underway. One critical element of certification exercises is the modeling and characterization of error terms according to the unique properties and requirements of individual RCS ranges, and the development of a method for propagating these errors into overall RCS measurement uncertainty. Previously, we presented the statistical model for the case where errors are grouped into multiplicative and additive classes, as well as a robust methodology for the propagation of errors in both the signal space and RCS (dBsm) domains [1-3]. Initial data at the National RCS Test Facility (NRTF) RAMS site located in the White Sands Missile Range near Holloman AFB, NM, have been collected for range certification exercises. Preliminary analysis has been accomplished on certain dominant error terms for calibration uncertainty characterization only. A general approach [7] has been followed here, with the exception that multiplicative and additive error terms are treated separately. In addition, only variance effects are treated (not bias). This paper is a status of work in progress. The ultimate goal of this work is the full implementation of previously described concepts [1-3]. We plan to demonstrate an improved ability to capture the effects of both error bias and variance (as has been demonstrated mathematically to date) using a more complete set of data collections.
Boeing is currently pursuing certification of their 9-77 indoor compact range facility as a voluntary industrial participant in the ongoing DoD/NIST RCS certification demonstration program. In support of that process, V EI has applied a novel statistical method for analysis to VHF measurements of a canonical target from the Boeing 9-77 range. The dominant error sources in the range were identified and categorized according to their dependence on frequency, aspect angle, and the target under test. Range characterization data were collected on canonical targets and then used to estimate the statistical parameters of each of the errors. Finally, these were incorporated into expressions for the combined RCS measurement uncertainty for a test body whose RCS exhibits many of the characteristics of modern, high-value targets. The results clearly demonstrate the importance of accounting for the target-dependence of the errors and the bias they introduce into the overall uncertainty.
This paper describes how ANSI standard Z-540 [l,2,3] was applied in a DoD demonstration project to organize radar cross section (RCS) range documentation for the Air Force Research Laboratory Advanced Compact Range (ACR) and Patu:xent River Atlantic Test Range (ATR) Dynamic RCS measurement facility. Both parts of this paper represent a follow-up report on the DoD demonstration program introduced at AMTA 97 [4]. In June 2000, the DoD Range Commanders Council Signature Measurement and Standards Group (RCC/SMSG) certified that these two facilities met the ANSI-Z-540 documentation standards established by the DoD demonstration project. Since AFRL plans to require mandatory ANSI-Z-540 compliance for DoD contractors performing RCS measurements with AFRL after January 1, 2004, the review process described in this paper will be the likely model for industrial compliance. After a brief review of the ANSI-Z-540 standard, Part 1 of this paper will outline the certification review process and discuss the outcomes, results, and lessons learned from the DoD demonstration program from the perspective of the AFRL range and volunteer range reviewers.
This paper describes how ANSI/NCSL standard Z- 540 [1, 2] was applied in a DoD demonstration project to organize radar cross section (RCS) range documentation for the Air Force Research Laboratory (AFRL) Advanced Compact Range (ACR) and the Naval Ai:r Warfare Center - Aircraft Division (NAWC-AD) Atlantic Test Range (ATR) Dynamic RCS measurement facility. Both parts of this paper represent a follow-up report on the DoD demonstration program introduced at AMTA 97 [3]. In June 2000, the DoD Range Commanders Council Signature Measurement and Standards Group (RCC/SMSG) certified that these two facilities met the ANSI/NCSL Z-540 documentation standards established by the DoD demonstration project. Since AFRL plans to require mandatory ANSI/NCSL Z- 540 compliance for DoD contractors performing RCS measurements with AFRL after January 1, 2004, the review process described in this paper will be the likely model for industrial compliance. Part I of this paper contained a brief summary of the ANSI/NCSL Z-540 standard, outlined the certification review process and discussed the outcomes, results, and lessons learned from the DoD demonstration program from the perspective of the AFRL range and volunteer range reviewers. Part II will discuss the review process as it applied to ATR, as well as the outcomes, results, and lessons learned.
RATSCAT has been heavily involved, as part of the DoD Range Certification Demonstration Program, in examining and documenting the underlying principles of all aspects of the outdoor measurement process. Our goal is to replace historical or "anecdotal" measurement approaches with processes founded on validated and documented procedures. This paper reports on the results of two areas of study. These are the effects on measurements caused by wind and calculation of target rotation rates. When RCS targets are measured outdoors on pylons or columns, some uncertainty will be introduced due to the effect of wind on the target and target support structure. This paper will present the results of an investigation into the errors introduced by wind motion on targets mounted on pylons or columns. When rotation rates are determined for target collection, the usual procedure is to employ a rule of thumb like "collecting three points per lobe" or "meeting the Nyquist criterion." This paper examines these common methods to determining rotation rates, and their impact on the measurement of the peak values of RCS magnitude and phase. Finally, the significance of these two measurement errors will be examined in light of their impact on outdoor range operations as well as on decisions based upon the collected RCS data.
The maintenance, test, and repair workload for the Air Force's AN/MSQ-118 satellite ground-based receiving communication system has been transferred from the closing McClellan Air Force Repair Facility in Sacramento, California to Tobyhanna Army Depot located in Tobyhanna, Pennsylvania. The workload requires the support of four maintenance shops and two planar near-field ranges. The shops are the antenna repair, power supply repair, low-noise amplifier (LNA) repair, and radome repair shops. The near-field ranges are a 4' x 4' planar scanner used for antenna diagnostics and an 8' x 8' planar scanner used for certification of the repaired antenna-under-test (AUT). This paper will bring the AMTA community up to date on the status of the new Tobyhanna Antenna Repair Facility, focusing on the techniques and methods used to quantify the alignment and performance characteristics of the planar near-field antenna measurement system used for certification. With the relocation complete, test data obtained at both locations will be analyzed and compared to show differences between the baseline measurements taken at McClellan Air Force Base versus those taken at Tobyhanna Army Depot.
The maintenance, test and repair workload for the Air Force MSQ-118 satellite ground-based The current MSQ-118 work requires the support of four maintenance shops and a planar near-field certification range. About one dozen employees maintain and test 148 phased-array antennas, each containing thousands of components, including radio-frequency (RF) stripline and microelectronics circuitry. This paper will detail the planning and start of the relocation of the antenna repair and test facilities.
The National Institute of Standards and Technology (NIST) is coordinating a radar cross section (RCS) interlaboratory comparison study using a family of standard cylinders developed at Wright Laboratories. As an important component of measurement assurance and of the proposed RCS certification program, interlaboratory comparisons can be used to establish repeatability (within specified uncertainty limits) of RCS measurements within and between measurement ranges. We discuss the global importance of intercomparisons in standards metrology, examine recently conducted comparison studies at NIST, and give a status report on the first national RCS intercomparison study. We also consider future directions.
The National Institute of Standards and Technology (NIST) is coordinating a radar cross section (RCS) interlaboratory comparison study using a rotating dihedral. As an important component of measurement assurance and of the proposed RCS certification program, interlaboratory comparisons can be used to establish repeatability (within specified uncertainty limits) of RCS measurements within and among measurement ranges. The global importance of intercomparison studies in standards metrology, recently conducted comparison studies at NIST, and the status of the first national RCS intercomparison study using a set of cylinders are discussed in [1]. In a companion program, we examine full polarimetric calibration data obtained using dihedrals and rods. Polarimetric data is essential for the complete description of scattering phenomena and for the understanding of RCS measurement uncertainty. Our intent is to refine and develop polarimetric calibration techniques and to estimate and minimize the correstponding measurement uncertainties. We apply theoretical results [2] to check on (1) data and (2) scattering model integrity. To reduce noise and clutter, we Fourier transform the scattering data as a function of rotation angle [2], and obtain the radar characteristics using the Fourier coefficients. Calibration integrity is checked by applying a variant of the dual cylinder calibration technique [3]. Future directions of this measurement program are explored.
Radar cross section (RCS) range characterization and certification are essential to improve the quality and accuracy of RCS measurements by establishing consistent standards and practices throughout the RCS industry. Comprehensive characterization and certification programs (to be recommended as standards) are being developed at the National Institute of Standards and Technology (NIST) together with the Government Radar Cross Section Measurement Working Group (RCSMWG). We discuss in detail the long term technical program and the well-defined technical criteria intended to ensure RCS measurement integrity. The determination of significant sources of errors, and a quantitative assessment of their impact on measurement uncertainty is emphasized. We briefly describe ongoing technical work and present some results in the areas of system integrity checks, dynamic and static sphere calibrations, noise and clutter reduction in polarimetric calibrations, quiet-zone evaluation and overall uncertainty analysis of RCS measurement systems.
A new approach for certification of RCS ranges is discussed. This new approach is based on evaluating the major expected sources of errors in a RCS range rather than evaluating each and every error source and then defining the error bar for a given RCS measurement. The new approach is, therefore, called a top-down approach. Based on our experience with many indoor RCS ranges, we can say that the main sources of errors in RCS measurements are range related. (stray signals, chamber drift, target/mount interactions etc.) One should, therefore, critically evaluate these errors such that the performance level of the range can be verified. A test approach is defined to characterize the range related errors. Various tests are based on the RCS measurement of specific targets, and thus, can be easily performed using standard RCS measurement procedure. This approach will provide range operators with the needed information to justify the use of their range to measure RCS of a given target. Also, one can spend more effort fixing the error sources which lead to large RCS measurement errors.
In 1993, we presented the newly completed compact range and tapered chamber facility [1]. As part of this presentation, the issue of “range certification” was presented. This paper will discuss the work that we have done with the compact range for radar cross section (RCS) measurement acceptance. For customer acceptance, we had to “prove” that the compact range made acceptable measurements for the fixtures and apertures involved. Schedule and funding did not permit the full exploitation of the uncertainty analysis of the chambers, not was it felt to be necessary [2]. The determination of our range capabilities and accuracy was based on system parameters and target measurements. Targets that were calculable either in closed form solutions (spheres) or by numerical methods (cylinders and rods) were used. Finally, range to range comparisons with the Rye Canyon Facility [3] of a standard target was used. The range to range comparison proved especially difficult due to customer exceptions, feed differences, and target mounting. This paper will discuss the “success” criteria applied, the procedures used, and the results. The paper will close with a discuss of RCS standards and the range certification process.
The National Institute of Standards and Technology (NIST) has written a certification plan to ensure that a proposed planar near-field facility is capable of measuring high-performance phased arrays. Generally for a complete plan, one must evaluate many aspects including scanner alignment, near-field probe alignment, alignment of the antenna under test, RF crosstalk, probe position errors RF path variations, the receiver's dynamic range and linearity, leakage, probe-antenna multiple reflections, truncation effects, aliasing, system drift, room multipath, insertion loss measurements, noise, and software verification. In this paper, we discuss some of the important aspects of the certification plan specifically written for the measurement of high-performance phased-array antennas. Further, we show how the requirements of each aspect depend on the measurement accuracies needed to verify the performance array under test.