Drone-Based Calibration System Improves 21 cm Array Sensitivity

The Precision Emitter for 21 cm Array Coherent Calibration (PEACC) represents a significant advancement in radio astronomy instrumentation. Foreground mitigation is a primary obstacle in 21 cm intensity mapping, demanding accurate and wideband calibration of telescope beams. PEACC addresses this challenge with a digitally synthesized calibration source producing Gaussian noise over a 1.2 GHz bandwidth, synchronized via GPS. Its dual-source architecture, with one unit on an aerial platform and another connected to the data acquisition system, enhances sensitivity in low signal-to-noise ratio environments and enables direct phase measurement. The system's configurable band selection allows adaptability to different 21 cm telescopes. Validation through anechoic chamber measurements and drone-based testing over a radio dish testbed confirmed the superiority of the correlated channel over the auto-correlation channel, highlighting the benefits of the dual-source design. This marks the first published demonstration of a free-space coherent calibration signal synchronized solely by clocks, the first drone deployment of such a source, and the first published beam measurements using this method. PEACC establishes the viability of high-fidelity digital calibration for future 21 cm instruments, offering a tangible path toward improved foreground control and beam calibration in subsequent arrays. This technology could significantly impact our ability to map the distribution of hydrogen in the early universe, providing valuable insights into the evolution of cosmic structures. The development of PEACC also highlights the increasing role of drone technology in astronomical research, offering new possibilities for remote sensing and calibration.

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