Large reflector uplink arraying

Abstract

The promise of array technology in support of space operations has long been appreciated, and receiving array technology is now an important operational asset. Notable examples include the NRAO (National Radio Astronomy Observatory) array of twenty seven 25m reflectors and the DSN (Deep Space Network) ad hoc arraying of various assets, particularly 34m antennas, to realize significant G/T increases providing needed bandwidth and range extensions. However, uplink (transmit) arraying has not kept pace due to the difficulty of ensuring 'open loop' beam formation under the conditions of wide spacing, due to 1) transmission line and circuit variability, 2) precise antenna reference point determination, and 3) tropospheric effects especially at higher frequencies. Notable success in solving uplink array calibration issues has been achieved by two different groups at JPL, one arraying five 1.2m reflectors and the other three-34m reflectors. However, there are operational issues with each of these approaches. We present an approach for mitigating these difficulties, offering the potential for continual readiness operationally and extensibility to Ka band. Additionally the approach is suitable for use on a wide range of antenna sizes, including both 34m and 12m reflectors. Currently a transmit uplink experiment is underway at Harris Corporation using three-12m reflectors operating at DSCS X band. This array architecture provides continuous internal self-calibration using the transmit signal itself, a method to dynamically solve for the antenna reference points, and mitigation of propagation effects by using received signals from known sources. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.