NRAO Guide to the Virtual Observatory

This wiki is a resource for NRAO staff and observers to learn about the Virtual Observatory.

Summary of VO

The Virtual Observatory (VO) is a new paradigm in astronomy wherein technology standards are used to improve accessibility to distributed astronomical data and computation. In turn, technology standards result in more useful, more robust and faster data processing and analysis software. VO is intended to simplify common astronomy research procedures.

Formally, VO consists of the International Virtual Observatory Alliance (IVOA) and national VO affiliates in many countries. The national VO organization in the United States is the National Virtual Observatory (NVO), which may soon become known as the Virtual Astronomical Observatory (VAO).

VO in Practical Terms

The foundation of VO consists of standards for access to astronomical data and other resources. These standards describe how VO-compliant data servers operate. For example, an online, VO-compliant source catalog will operate according to standards set for VO catalogs. With standards in place, software developers can create tools that allow users to access VO-compliant servers. The typical VO user will access VO services through online or desktop tools.

There are no VO standards for tools; standards apply to data servers. Tools that wish to communicate with these servers must use communication protocols that conform to the standards. Apart from this one requirement, developers of user tools are free to design their software any way they like.

VO tools come in a variety of forms. Some examples are:

A longer list of VO tools is available on the NVO Tools and Software webpage.

Can VO do anything useful?

In terms of scientific research: Yes! For examples, see the IVOA Newsletter, which contains a list of publications concerning VO-enabled science, and the VO list of publications that made use of VO technologies.

VO is still in an early stage of development. Standards are being refined and improved, and likewise, new VO tools are being created and existing tools are being improved. It may be some time before a robust VO infrastructure is developed. So, at present, a VO user may encounter bumps along the way.

Keep in mind that providing VO-compliant data servers is not mandatory. Individual observatories voluntarily adopt VO standards. Many observatories have already adopted VO standards for their data servers. As the astronomical community becomes more aware of VO and more accustomed to using VO tools, it is likely that VO compliance will become more common. In the US, VO development is supported jointly by NSF and NASA. It can be expected that individuals and facilities that receive funding from either organization will increasingly make use of VO technologies.

Is my favorite data set available through the VO?

The easiest way to determine if your favorite observatory or data collection has a VO-compliant data server is to search the NVO Directory. For example, if you want to know what resources NRAO has published in the VO, simply search "NRAO"; to find a list of all catalogs derived from VLBA data, simply search "VLBA catalog".

How can I publish my data in the VO?

If you have a data set (source catalog, image collection, spectra collection, or other data) that you think should be made available to a wide audience through VO, let us know. Contact either JohnBenson (email) or DougTody (email). Tell them what data you've got and how you would like it to be accessed through the VO.

If you want to learn more about what's involved in publishing data to VO, check out these resources.

I'm new to VO. What's the fastest way to get to the goodies?

Learning the basic VO concepts, services, and tools is the ideal place to start (see Resources below). But if you don't have the time or energy for this, then try going straight to the NVO Portal. The Portal is still under development, but is already a useful starting point for using VO technologies.

What is NRAO's role in VO?

NRAO operates a number of VO-compliant image and catalog services. NRAO is also involved in development of VO standards and tools. NRAO's VO services can be found by searching for "NRAO" in the NVO Directory. The "publisher" column in the returned table shows who provides the service. Some of the notable VO services provided by NRAO are:

Image Services Catalog Services
NRAO VLA Sky Survey (NVSS) NVSS Source Catalog
Faint Images of the Radio Sky at Twenty-centimeters (FIRST) FIRST Catalog
NRAO VLA Archive Survey (NVAS)
Cosmic Lens All-Sky Survey
MITVLA Gravitational Lens Snapshot Survey
NRAO VLBA 2cm Survey
NRAO VLBA Calibrator Source Survey

NRAO Staff who work with VO

  • DougTody is involved in VO standards development within the IVOA, responsible for ongoing Data Access Layer (DAL) development within the NVO, and serving as the first Chair of the IVOA DAL working group, which is responsible for science data access standards development for the international VO. Doug is also responsible for DAL-related development within NVO including VOClient , a client-side interface to VO; DALServer, a framework for implementing VO Data Access Layer services, including Simple Image Access ( images and data cubes ), Simple Spectral Access ( spectra ) and Simple Cone Search and the new Table Access Protocol (catalogs and database tables); and the applications framework , a framework under development for constructing astronomical data processing and analysis applications and computational services.
  • JohnBenson developed and supports the VO services currently provided with the NRAO archive.
  • JaredCrossley works with VO services and tools to make NRAO archive data more accessible and more useful to astronomers. Jared also works on VO software development, and maintains this TWiki page (although contributions from others are encouraged!).
  • RonDuPlain and JaredCrossley have developed KML Now!, a Web tool for automatically importing VO images into Google Sky.
  • BrianKent is a Jansky Fellow interested in the VO usage for scientific data mining. He has created databases for large spectral line surveys with support for VO services, as well as links to Google Sky for the published catalogs. He is also interested in large wide-field mosaicking.

I'm having trouble. Who do I contact?

If you're having trouble using a VO tool, you should contact the person or organization that supports the tool. Questions and comments regarding the NVO and NVO Web-based tools can be directed to feedback at us-vo dot org. Concerns regarding NRAO's VO services can be directed to voserv at nrao dot edu.

Other questions can be directed to any of the NRAO staff who work on VO development.

Suggestions for changes or additions to this TWiki page should be sent to JaredCrossley.

Who is involved in VO?

  • The key people involved in US NVO development are listed on the NVO Personnel page.
  • On the international level, the people most involved in IVOA are listed on the IVOA Who is Who web page.
  • At NRAO, several staff members are involved in VO development. See the list of these staff members on this page.


The following is a list of resources for learning more about VO tools and services.

Topic revision: r14 - 2009-04-16, JaredCrossley
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