The World Space Observatory concept was originally proposed at the 7 th UN/ESA Workshop for Basic Space Science and formulated in the context of the needs of Basic Space Science in the developing countries [1]. The WSO was defined as a mutually beneficial and valid scientific mission for all scientists in the world and not confined only to the developing world . In the context of the Long Range Planning of the European Space Agency an Assessment Study [2,3] was made for the UN Outer Space Division, evaluating a WSO Mission for the ultraviolet domain (WSO/UV). The study was based on the characteristics defined during a meeting held on 26-29 Nov. 1999 between scientists who had expressed interest in a WSO/UV. The WSO/UV mission studied has the following characteristics:

•  Telescope: 1.7 m diameter ( T-170 Russian heritage; IoA Acad. of Sciences [4]), PSF(550 nm): » 0.2 arcsec

•  Spectrograph for the UV only: primary 110 - 340 nm. ( HIRDES German heritage; IAAT [5]) with spectral Resolution 5 - 6 x 10**4; as well as a low resolution capability (500-1000)

•  Imaging : 115 - 340 nm with quality ~ 0.1- 0.3 arcsec ( MCP based Israelian heritage; TAU ; [6]); 2 UV Imagers : one for Max. spatial resolution; one for Max. sensitivity; and one Imager for visual domain

•  High Earth Orbit (Non-Halo orbit around Lagrangian 2).

•  Distributed Mission Operations

•  Science Operations fully distributed at level of Nations

•  Further overall properties of the mission as a whole as described in Ref [7]

The WSO/UV is an Astrophysical Observatory rather than a targeted mission for a single science goal, and would be launched optimally in 2006/7. It fills an important gap in the capabilities, available to the astronomical community [8,9]. The sensitivity and resolution supplied in WSO/UV are matched to the capabilities of the current generation of X-Ray Observatories in space, the 8m size ground-based telescopes, and future IR missions (e.g. NGST). The capabilities of WSO/UV have been chosen to be such that it will not duplicate any capability available from the ground nor in space . The operations philosophy of the WSO/UV [3] will assure that it can support a very dynamic science program over the extended life span of up to 10 years. This is essential for a mission of this nature which permits full participation from its very beginning of the scientific and technical community on a world-wide scale . The WSO/UV is very timely, since there exists a critical "time slot" associated with the UV Survey (GALEX), to explore the rich new data from this Survey. Current top technology available now is foreseen to be used for WSO/UV (technology cutoff 2002).

Science Goals : In the Planetary System Science , the major gaseous planets present a superb laboratory for the understanding of weather patterns on scales less stochastic than the terrestrial patterns, and present very important questions matched to the WSO/UV capabilities.

For Stellar Science the complete life cycle of stars can be studied. The WSO/UV Project is expected to make major breakthroughs for stellar evolution in the presence of multiplicity in star systems, through studies of the effects of close binary mass exchange and accretion on condensed objects. Also Young Stellar Objects and the physical mechanisms driving jets, form an extremely exciting area for WSO/UV.

The study of Interstellar matter and Galaxy population will evaluate the chemical evolution of Galaxies and the cycling of Interstellar Matter over a significant redshift range, addressing fundamental questions. Systematic studies at the resolution supplied by WSO/UV, will connect the early Universe with the current epoch.

Cosmological questions associated with the re-Ionisation phase are well within the capabilities of the WSO/UV, as is the study of the Inter-Galactic Matter and its relation to Clusters of Galaxies.

In the area of unforeseen or unpredicted occurrences , we mention here discoveries of e.g. Comets close to perihelion, Novae, Supernovae, Gamma-ray Bursts, OVV's. The rapid response capability, required in the mission, will present new major challenges to the scientists.

Relation of the WSO/UV to the developing World : The main reasons for the importance of a World Space Observatory in this context have been outlined in Ref. [2], WSO/UV embodies a three-fold goal:

•  To create opportunities for participation at the frontiers of Basic Space Science, on a sustainable basis at the national level, by all countries in the world, without the need for excessive investment . The observatory will stimulate the creation of an academically mature and competitive cadre within 5 to 10 years after inception by offering equal opportunities to astronomers all over the world;

•  To generate the possibility that engineers/specialists from the developing countries to work with the engineering groups for short periods of time and learn to built, handle and test etc. the WSO/UV hardware in an academic environment.

•  To support world-wide collaboration and to ensure that the study of the universe from space can be maintained in a sustainable way by scientists from all countries. This will make a reality in the scientific world of the visionary principle that space is the province of all mankind .

Also many aspects of the Vienna Declaration [10] are in their totality applicable to the WSO/UV. Further information can be found at:


  1. Report of the 7 th UN/ESA workshop UN A/AC 153.702.
  2. WSO/UV Assessment Study, 2000, ESA CDF-05 (A)
  3. Rodriguez-Pascual, P.M., 2000, UE-CEES PX0116000 [CDF-05 (C)]
  4. Boyarchuk,A. et al., 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP-413 ,809-814
  5. Kappelmann,N., 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP-413 ,8319-835
  6. Brosch,N., 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP-413 ,789-896
  7. Report of the 8 th UN/ESA workshop UN A/AC.105.723
  8. Wamsteker, W . , 1999, in UV-Optical Astronomy beyond HST, A.S.P. Conf. Ser. 164, 261 � 267.
  9. Panel Discussion WSO, 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP-413 ,849-856.
  10. Report of the UNISPACE III Conference UN A/CONF.184/6

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