Observations of the 21 cm HI Line from the Milky Way galaxy using Pyramidal Horn Radio Telescope

TL;DR

This study demonstrates that a low-cost, SDR-based pyramidal horn telescope can detect the Galactic 21 cm HI line and produce meaningful HI sky maps, a Milky Way rotation curve, and spiral-arm features. It details the mechanical construction, RF front-end, CST-based antenna simulations, and a GNU Radio pipeline that together support drift-scan observations and automated data processing. RFI mitigation, hot/cold calibration, and beam-convolution with HI4PI data enable calibration against reference spectra, while a tangent-point analysis yields a rotation curve consistent with a flat profile at large radii and supports spiral-arm topology. The work highlights the educational value and scientific viability of accessible radio astronomy instrumentation, and provides public data and code to encourage broader participation and reproducibility.

Abstract

We present the design, implementation, and operation of a pyramidal horn radio telescope built for detecting the Galactic 21 cm neutral hydrogen line emission. The system employs an SDR-based pipeline to obtain drift-scan observations, which were calibrated and processed to generate HI sky maps, a Galactic rotation curve and spiral arm features. This demonstrates that this low-cost system is effective both for educational purposes and scientific exploration of Galactic structure at radio frequencies.

Figures (13)

• Figure 1: Pyramidal Horn Radio Telescope.
• Figure 2: Construction of the feedhorn assembly.
• Figure 3: The support mechanism.
• Figure 4: Block diagram of the RF signal chain.
• Figure 5: Image of the RF signal chain.