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Peer-reviewedCC BY 4.0The Astronomical Journal

PEACC—Precision Emitter for 21 cm Array Coherent Calibration

  • Kalyani Bhopi1
  • Morgan Cole2
  • Mallory Helfenbein2,3
  • Will Tyndall2,4
  • Audrey Whitmer2
  • Kevin Bandura1
  • Laura Newburgh2
4 affiliations
  1. 1West Virginia University
  2. 2Yale University
  3. 3University of Virginia
  4. 4McGill University
Open at sourcePDFDOICite

Abstract

Foreground mitigation remains a central challenge for 21 cm intensity mapping experiments, which require precise, wideband calibration of telescope beams and gains. We present the Precision Emitter for 21 cm Array Coherent Calibration (PEACC), a digitally synthesized calibration source that generates Gaussian noise across a 1.2 GHz bandwidth, time-synchronized to a 1 pulse-per-second output from a GPS-disciplined oscillator, and optimized for aerial deployment. PEACC uses a dual-source architecture with one unit mounted on an aerial platform and a second reference unit connected directly to the radio data acquisition system; this configuration enables improved sensitivity in the low signal-to-noise ratio (SNR) regime and direct phase measurement. The system further supports configurable band selection, allowing adaptation to various 21 cm intensity mapping telescopes. We validated PEACC through anechoic chamber measurements and by integrating the source on a drone flown over a local radio dish testbed. In both settings, the correlated channel substantially outperformed the autocorrelation channel across all signal-to-noise regimes of interest, confirming the key advantage of the dual-source architecture. To our knowledge, this is the first published demonstration of a free-space coherent calibration signal synchronized only by clocks, the first deployment of such a source on a drone, and the first published beam measurements made with such a source. Given the growing interest in drone-based calibration for 21 cm arrays, this work establishes the feasibility of high-fidelity digital calibration for next-generation 21 cm instruments and provides a practical path towards improved foreground control and beam calibration in future arrays.

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Cite

BibTeXRIS
BibTeX
@article{bhopi2026peaccprecision,
  title = {{PEACC—Precision Emitter for 21 cm Array Coherent Calibration}},
  author = {Kalyani Bhopi and Morgan Cole and Mallory Helfenbein and Will Tyndall and Audrey Whitmer and Kevin Bandura and Laura Newburgh},
  journal = {The Astronomical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-3881/aeab9c},
  url = {https://iopscience.iop.org/article/10.3847/1538-3881/aeab9c},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - PEACC—Precision Emitter for 21 cm Array Coherent Calibration
AU  - Kalyani Bhopi
AU  - Morgan Cole
AU  - Mallory Helfenbein
AU  - Will Tyndall
AU  - Audrey Whitmer
AU  - Kevin Bandura
AU  - Laura Newburgh
PY  - 2026
DA  - 2026/10/28
JO  - The Astronomical Journal
DO  - 10.3847/1538-3881/aeab9c
UR  - https://iopscience.iop.org/article/10.3847/1538-3881/aeab9c
AB  - Foreground mitigation remains a central challenge for 21 cm intensity mapping experiments, which require precise, wideband calibration of telescope beams and gains. We present the Precision Emitter for 21 cm Array Coherent Calibration (PEACC), a digitally synthesized calibration source that generates Gaussian noise across a 1.2 GHz bandwidth, time-synchronized to a 1 pulse-per-second output from a GPS-disciplined oscillator, and optimized for aerial deployment. PEACC uses a dual-source architecture with one unit mounted on an aerial platform and a second reference unit connected directly to the radio data acquisition system; this configuration enables improved sensitivity in the low signal-to-noise ratio (SNR) regime and direct phase measurement. The system further supports configurable band selection, allowing adaptation to various 21 cm intensity mapping telescopes. We validated PEACC through anechoic chamber measurements and by integrating the source on a drone flown over a local radio dish testbed. In both settings, the correlated channel substantially outperformed the autocorrelation channel across all signal-to-noise regimes of interest, confirming the key advantage of the dual-source architecture. To our knowledge, this is the first published demonstration of a free-space coherent calibration signal synchronized only by clocks, the first deployment of such a source on a drone, and the first published beam measurements made with such a source. Given the growing interest in drone-based calibration for 21 cm arrays, this work establishes the feasibility of high-fidelity digital calibration for next-generation 21 cm instruments and provides a practical path towards improved foreground control and beam calibration in future arrays.
SN  - 0004-6256
SN  - 1538-3881
ER  -