# First Demonstration of ECHO: an External Calibrator for Hydrogen Observatories

> Research article (Publications of the Astronomical Society of the Pacific, 2017) · cited 30× · AI/ML

**Wikidata**: [openalex:W2583769595](https://www.wikidata.org/wiki/openalex:W2583769595)  
**Source**: https://4ort.xyz/entity/first-demonstration-of-echo-an-external-calibrator-for-hydrogen-observatories