Radio Astronomy · Student research portal

Observing the Milky Way through the H I 21-cm Line

A research and teaching project that maps neutral hydrogen in our Galaxy with a 5 m steerable radio telescope, DISH222, and a software-defined radio receiver. Students can learn the physics, explore real observations and join open research questions.

Start Here Explore the data Open the lecture

Sky chart with the Galactic plane as a red curve and a contour map of H I line strength covering the outer-Galaxy region scanned by DISH222 on 26 Aug 2026. — DISH222 raster of the outer Galaxy, 26 Aug 2026: 313 positions, H I line peak in dB above baseline (relative scale). The recommended starting dataset.

5 msteerable dish, DISH222, the active research telescope

1420.4 MHzthe H I 21-cm line of neutral hydrogen

L0 → L8every dataset tagged with its processing level and calibration scale

2025published IEEE Antennas and Propagation Magazine article

What you can explore

From the instrument to open research questions

New to the project? Start Here gives a six-step path through these sections.

Step 1Telescopes

Fixed dishes to DISH222

How the project moved from fixed transit telescopes to a steerable research dish, and how DISH222 observes.

Meet the telescopes

Step 2Data Library

Real observations, level by level

Every dataset with its processing level, calibration epoch, source availability and limitations.

Browse the data

Step 3Data to Science

From spectrum to Galactic map

Baselines, interference, velocities, calibration, cubes and comparison with the LAB survey.

Follow the chain

Step 4Calibration

Five stages to a kelvin scale

How calibration epochs C0–C4 evolved, the current reference, and why old products keep their scale.

See the history

Steps 5–6Student Research

Open research tracks

Eight entry points, from reproducing a reduction to rebuilding a full-Galaxy map.

Choose a question

RecordProject Log

Milestones, dated

Observations, processing, calibration and software milestones in order.

Read the log

Where it started

The published fixed transit telescope

Before the steerable dishes, the project designed and replicated a fixed, zenith-pointing educational telescope, reported in the 2025 IEEE paper.

Published implementation reported in the 2025 IEEE paper

Reflector: 5 m parabolic reflector with approximately f/D = 0.35.
Feed: Choke-horn/feed and low-noise receiving chain.
Performance: Approximately 35 dBi gain and approximately 2.5° beamwidth.
Method: Fixed zenith transit-scan observations using Earth rotation.

Today

The steerable telescope DISH222 is now the project's active research instrument. The fixed network and the first steerable dish, DISH1, are part of the project's history.

Compare the telescopes · Project story · Publication

Engineering to Science

From radio emission to Milky Way structure

Radio emissionReceived signalAveraged spectrumBaseline & RFI H I measurementCalibrationSky position + velocityMilky Way science

The conceptual endpoint is the H I brightness-temperature data product (\(T_B(\alpha,\delta,v_{\mathrm{LSR}})\)), connecting signal processing to sky coordinates and velocity.

α: Right Ascension
δ: Declination
v_LSR: Radial velocity relative to the Local Standard of Rest
T_B: H I brightness temperature

Follow the full chain for DISH222 data · Explore this in the lecture

Learning and reference