A document describes the Antenna Calibration & Measurement Equipment (ACME) system that will provide the Deep Space Network (DSN) with instrumentation enabling a trained RF engineer at each complex to perform antenna calibration measurements and to generate antenna calibration data. This data includes continuous-scan autoborebased data acquisition with all-sky data gathering in support of 4th order pointing model generation requirements. Other data includes antenna subreflector focus, system noise temperature and tipping curves, antenna efficiency, reports system linearity, and instrument calibration.
The ACME system design is based on the on-the-fly (OTF) mapping technique and architecture. ACME has contributed to the improved RF performance of the DSN by approximately a factor of two. It improved the pointing performances of the DSN antennas and productivity of its personnel and calibration engineers.
This work was done by David J. Rochblatt and Manuel Vazquez Cortes of Caltech for NASA’s Jet Propulsion Laboratory. NPO-47599
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Antenna Calibration and Measurement Equipment
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Overview
The document discusses the Antenna Calibration and Measurement Equipment (ACME) developed by NASA's Jet Propulsion Laboratory (JPL) to enhance the performance of the Deep Space Network (DSN). The DSN is a critical facility for maintaining communication with unmanned spacecraft, collecting telemetry data, transmitting commands, and conducting scientific observations. It consists of three complexes located in California, Spain, and Australia, strategically positioned around the globe.
ACME was designed to streamline the calibration processes for antennas, which are essential for ensuring optimal performance and efficiency in data transmission. The system interfaces with existing resources at the Signal Processing Center (SPC) and eliminates the need for routing encoder outputs via fiber optics, thereby reducing costs and complexity. ACME measures Intermediate Frequencies (IF) in the range of 200 to 1000 MHz, with varying numbers of interfaces depending on the antenna complex.
The system employs both narrow and wide bandwidth filters to cater to different applications. Narrow bandwidths (12.5 and 16 MHz) are used for precise antenna efficiency measurements, while wide bandwidths (90, 100, and 200 MHz) are necessary for detecting weak radio sources at Ka-band frequencies (26 and 32 GHz). The precision of ACME's measurements is notable, achieving a total power measurement accuracy of 1% and 1.2% in NAR mode.
ACME also features advanced pointing models, including a conventional first-order model and a higher precision fourth-order model, which significantly improves antenna pointing accuracy. The fourth-order model incorporates additional mathematical terms to address systematic errors that remain after applying the first-order model, enhancing mean radial error performance by approximately twofold.
The document highlights the importance of time synchronization between antenna positions and radio frequency data, achieved through time-tags and predict files loaded into the antenna controller. This synchronization is crucial for accurate data collection and analysis.
Overall, ACME represents a significant advancement in antenna calibration technology, enabling the DSN to operate more efficiently and effectively, ultimately supporting NASA's mission to explore and communicate with distant spacecraft. The document serves as a technical support package, providing insights into the capabilities and applications of ACME within the broader context of aerospace technology and scientific research.
