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
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
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 http://esavo.esa.int/vospec/
More info at: VOSpec Info
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