“Virgo” in radio astronomy most commonly refers to a software package for running and analysing small radio telescope data using SDRs (software-defined radios)—not a single instrument or observatory.

It is distinct from other uses of the name “Virgo” (gravitational wave detector, cosmology consortium, ESO archive tool, etc.). The one relevant to SDR/radio astronomy work is the spectrometer software.

What Virgo software is

Virgo (radio astronomy spectrometer) is an open-source spectrometer and radiometer system designed for:

• Small radio telescopes (amateur → research-grade small instruments)
• SDR-based receivers (RTL-SDR, Airspy, etc. via GNU Radio)
• Hydrogen line (1420 MHz) observations
• Continuum and spectral monitoring

It is built in Python and GNU Radio, acting as a “complete pipeline” between SDR hardware and scientific plots.

Who produces it

It was originally created and maintained by:

• Apostolos Spanakis-Misirlis (main author)
• with contributions from radio astronomy community developers such as:
  • Cameron L. Van Eck (Dunlap Institute, University of Toronto)
  • E.P. Boven (CAMRAS, Netherlands)

The project is distributed as open-source software (GPL-style licensing depending on version) and is community-maintained rather than commercial.

Primary publication reference:

• Journal of Open Source Software paper (2021): “Virgo: A Versatile Spectrometer for Radio Astronomy”

What it is used for (practical function)

Virgo sits between your SDR hardware and your analysis:

1. Data acquisition

• Interfaces with GNU Radio + SDR hardware
• Tunes frequency (e.g. 1420 MHz hydrogen line)
• Records complex I/Q samples

2. Spectral processing

It automatically produces:

• Averaged spectrum
• Calibrated spectrum (system response corrected)
• Waterfall / dynamic spectrum (time–frequency)
• Total power vs time
• Statistical distributions of received power

3. Radio astronomy workflows

Typical uses:

• Hydrogen line mapping of the Milky Way
• Drift-scan observations
• RFI (interference) environment surveys
• System sensitivity estimation
• Educational telescope setups

It is widely used in amateur and teaching observatories, including small dish systems (1–18 m class instruments have been reported in deployments).

Where to find it

Main software distribution

• Python package: astro-virgo on PyPI
  https://pypi.org/project/astro-virgo/

Source code / development

• GitHub (primary community development): https://github.com/0xCoto/VIRGO

Documentation

• ReadTheDocs manual: https://virgo.readthedocs.io/

Includes:

• Installation guide
• Command-line examples
• SDR configuration
• Calibration procedures
• Observation planning tools

Publications / technical background

• JOSS paper (main reference implementation description)
• Zenodo release with DOI and figures: https://zenodo.org/records/4778382

What makes Virgo different from other radio astronomy software

Compared with heavier systems like CASA, Virgo is:

• Lightweight (designed for SDR + small telescopes)
• Real-time spectrometer (not just post-processing)
• Built-in plotting + calibration pipeline
• Focused on single-dish amateur / educational astronomy
• Runs directly from Python + GNU Radio instead of large observatory frameworks

Related tools you may also encounter

If you’re working in SDR-based astronomy, Virgo often appears alongside:

• GNU Radio (signal processing backbone)
• rtl-sdr tools (hardware interface layer)
• CASA (professional interferometry imaging pipeline)
• Hydrogen line-specific tools (various Python projects)