Table of Contents

  1. Introduction
  2. GUI - Main Window
  3. Create SSAP VOTables
  4. Analysis Tools
  5. Fitting Utilities
  6. SED Spectra
  7. Photometric services
  8. Simple Line Access
  9. Theoretical Access
  10. Interoperability
  11. References
  12. User Feedback


The European Space Agency (ESA) has been heavily involved in the development of the Simple Spectral Access Protocol (SSAP) of the International Virtual Observatory Alliance (IVOA) by providing access to the Infrared Space Observatory (ISO) mission spectral data as part of its general VO activities.

The European Space Astronomy Centre (ESAC) at Villafranca del Castillo near Madrid, Spain, is the centre for Space Based Virtual Observatory activities within the European Space Agency.

There are lots of tools for spectra analysis and display in the astronomical community. However, there was a need for a “VO-enabled” tool that can superimpose spectra coming from different projects within the VO and in VO-format.

One of the main reasons for the current absence of such a tool is the fact that astronomical spectra are not as well defined as, e.g., images are. The IVOA has made a significant effort in trying to define a Simple Spectral Access Protocol by which part of this problem is solved, giving the rules to be able to handle spectral data in the VO context.

An old problem in dealing with flux energy densities is the handling of different units. This problem has been traditionally dealt with by calling string parsers that convert between unit names fixed by some standard. Despite the different efforts to create a single standardized convention for unit names, several of these standards do currently exist. This creates a burden in the handling of units in the traditional way. On top of this, making legacy data available to the VO is crucial to the success of the VO as a whole. Those legacy data are normally not well formatted to conform to any standard, and therefore it is important to be able to deal with them with a simple definition of certain metadata.

Led by the aforementioned reasons, the Sciences Archives Team at ESAC decided to develop a tool to handle VO-compatible spectra and implement an algorithm based on dimensional analysis to handle units in a simple yet effective way.
(see paper by Osuna-Salgado: Dimensional Anaysis applied to Spectrum Handling in Virtual Observatory Context).

You can find a tool to help you with the unit conversion: Spectrum Units Convertor

The tool contains also general astronomical functionality useful for any wavelength range. The most obvious initial one, coming from the definition itself of the algorithm for spectra superimposition, is the ability to change the display between different units, allowing for better qualitative analysis depending on the range of interest. The tool also supports many analysis operations... Efforts are being co-lead by ESA in several fields within the IVOA, among them the creation of a protocol for Simple Line Access (together with French VO) and for Synthetic Spectra Modeling (together with the Spanish VO). As these technologies mature, they will be included in the VOSpec.

The VOSpec tool can be accessed at

More info at: VOSpec Info

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