The Antenna Controller Replacement (ACR) software accurately points and monitors the Deep Space Network (DSN) 70-m and 34-m high-efficiency (HEF) ground-based antennas that are used to track primarily spacecraft and, periodically, celestial targets. To track a spacecraft, or other targets, the antenna must be accurately pointed at the spacecraft, which can be very far away with very weak signals. ACR’s conical scanning capability collects the signal in a circular pattern around the target, calculates the location of the strongest signal, and adjusts the antenna pointing to point directly at the spacecraft. A real-time, closed-loop servo control algorithm performed every 0.02 second allows accurate positioning of the antenna in order to track these distant spacecraft. Additionally, this advanced servo control algorithm provides better antenna pointing performance in windy conditions.

The ACR software provides high-level commands that provide a very easy user interface for the DSN operator. The operator only needs to enter two commands to start the antenna and subreflector, and Master Equatorial tracking. The most accurate antenna pointing is accomplished by aligning the antenna to the Master Equatorial, which because of its small size and sheltered location, has the most stable pointing. The antenna has hundreds of digital and analog monitor points. The ACR software provides compact displays to summarize the status of the antenna, subreflector, and the Master Equatorial.

The ACR software has two major functions. First, it performs all of the steps required to accurately point the antenna (and subreflector and Master Equatorial) at the spacecraft (or celestial target). This involves controlling the antenna/subreflector/Master-Equatorial hardware, initiating and monitoring the correct sequence of operations, calculating the position of the spacecraft relative to the antenna, executing the real-time servo control algorithm to maintain the correct position, and monitoring tracking performance.

Second, the ACR software monitors the status and performance of the antenna, subreflector, and Master Equatorial for the safety of personnel and of the antenna equipment. While tracking occurs during scheduled periods every day of the week, the ACR software continuously monitors the antenna equipment.

This work was done by Roger Y. Chao, Scott C. Morgan, Martha M. Strain, Stephen T. Rockwell, Kenneth J. Shimizu, Barzia J. Tehrani, Jaclyn H. Kwok, Michelle Tuazon-Wong, and Henry Valtier of Caltech; Reza Nalbandi of MTC; Michael Wert of ITT; and Patrick Leung of ISDS/Averstar for NASA’s Jet Propulsion Laboratory. For more information, contact This email address is being protected from spambots. You need JavaScript enabled to view it..

This software is available for commercial licensing. Please contact Daniel Broderick of the California Institute of Technology at This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to NPO-47002.

Software Tech Briefs Magazine

This article first appeared in the September, 2010 issue of Software Tech Briefs Magazine.

Read more articles from this issue here.

Read more articles from the archives here.