1420 MHz Neutral-Hydrogen Drift Scan Survey

Survey Summary

Between May 1 and August 11, 2026, the Deep Space 1420 radio telescope conducted a systematic drift-scan survey of Galactic neutral-hydrogen emission at 1420.4058 MHz. Observations were made from Mishawaka, Indiana, using the 4.5-meter radio telescope at a constant 58° elevation while progressively sampling azimuth positions from 65° to 97°.

The completed data set contains 63 individual drift scans at 16 azimuth positions. Multiple observations were obtained at most positions to establish repeatability and to show the changing strength and structure of the H I emission across the surveyed region. Individual azimuth groups contain between one and nine observations, with particularly dense coverage between AZ 71° and 79°.

Peak strength in the accompanying scan report was calculated as the smoothed peak signal minus the lower of the starting or ending 15-minute baseline during a 180-minute observation.

Scan Coverage

The survey began with the May 1 AZ 75° observation, which produced the largest individual reported peak in this data set at 0.95 dB. It concluded with the August 11 AZ 97° observation, where the measured peak was 0.25 dB. Across the azimuth groups, average measured peaks range from approximately 0.25 dB to 0.74 dB.

Figure 1 — Drift Scans Used in the Survey

The grouped drift-scan plot provides the observational foundation of the survey. It shows the actual measurements at each azimuth and demonstrates that the broad hydrogen feature is reproduced over successive observations. Signal strength generally increases from the lower-azimuth edge of the survey, remains strong through the central portion, and decreases toward AZ 97°.

Figure 2 — 1420 MHz Hydrogen-Line Survey Heat Map

The individual scans were combined to construct the 1420 MHz Hydrogen Line Heat Map. This representation places the measurements according to survey position and drift progression, allowing the distribution of relative H I intensity to be viewed as a continuous structure rather than as separate one-dimensional scans.

Figure 3 — Reconstructed 3D H I Radio-Intensity Distribution

The survey data was transformed into celestial coordinates to produce the 3D Hydrogen Line Radio Cloud. Right ascension and declination provide the two spatial coordinates while measured relative H I intensity forms the third dimension. A top-down projection beneath the surface preserves the two-dimensional intensity distribution.

The resulting structure is a data-derived visualization of the measured radio-brightness distribution. The vertical dimension represents signal intensity and should not be interpreted as the physical three-dimensional distance, depth, or literal shape of a hydrogen cloud.

Figure 4 — Location of the Surveyed H I Region

The Observational Geometry — Local H I Survey Matrix places the observations in astronomical context. The principal drift feature is centered near RA 20h 30m, Dec +41°, corresponding in the supplied geometry rendering to approximately Galactic longitude l = 79.6° and Galactic latitude b = +1.1°. The geometry therefore places the observed H I structure very close to the Galactic plane and shows the line of sight sampled by the telescope.

Survey Interpretation

Together, the grouped scans, heat map, celestial-coordinate 3D rendering, and Galactic geometry map document the progression from repeated observations to a combined survey product.

actual drift-scan measurements → measured survey intensity distribution → reconstructed radio-intensity surface → astronomical location of the surveyed structure.

The repeated scans are important because they show that the large-scale H I feature persists across observations and azimuth settings. The later visualizations are therefore constructed from the measured survey data rather than representing a single observation.