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Paper presented at the 164th Xiangshan Science Conference. Beijing , P.R.China May 9-11, 2001

The World Space Observatory/ (WSO/UV) Project: Current Status. Willem Wamsteker ESA/VILSPA P.O.Box 50727 28080 Madrid, Spain

I. Introduction.

The World Space Observatory/Ultraviolet (WSO/UV) represents a new mission implementation model for large space missions for . The process has been brought up to enable a, fully scientific needs driven, logic to be applied to the demands for the large collection powers required to make space missions which are complementary to the continuously increasing sensitivity of ground based . One of the assumptions associated with the idea of a WSO is to avoid the excessive complexity required for multipurpose missions. Although there may exist purely technological or programmatic policy issues, which would suggest such more complex missions to be more attractive, many other aspects, which do not need to be explored here, may argue against such mission model. Following this precept and other reasons explained below, the first implementation model for a World Space Observatory has been done for the ultraviolet domain WSO/UV [2, 8]. For the purpose of this discussion we will refer to the wavelength domain from ll120 nm to ll320 nm as the Ultraviolet (UV) domain, the range from ll80 nm to ll120 nm as the Lyman range and from ll10 nm to ll80 nm as the extreme Ultraviolet (EUV). Even though the boundaries between these domains are somewhat fuzzy, it is convenient to maintain the concepts. In the early 1970’s the fist orbiting UV missions were launched with ESA’s TD-1 UV photometric mission, NASA’s Copernicus mission for high resolution spectroscopy in the UV and Lyman range and the Astronomical Netherlands (ANS). From 1978 through 1996 of the Astrophysics in the Ultraviolet wavelength domain has been done with the highly successful International Ultraviolet Explorer satellite (IUE) [9], a joint project between NASA, ESA and PPARC. From 1984 through 1987 the Russian mission was in . In 1990 the (ESA/NASA) Hubble Space (HST) introduced a new capability for the UV community. This instrument was designed as a multiple purpose telescope, is in Low Orbit (LEO) and the observing time is necessarily shared between the different instruments and wavelengths domains. Regular instrument exchanges have been taking as part of the HST Programme. When a full complement of instruments is available only about 30% of the schedule can be dedicated to the UV range. The UV capability of HST was originally with the Goddard High Resolution Spectrograph (GHRS), the Wide Field Planetary Camera (WF/PC2), the Faint Object spectrograph (FOS), and the Faint Object Camera (FOC). Some of these instruments have been replaced by others and at this moment the UV capability of HST is limited to WF/PC2 and the Imaging Spectrograph (STIS) [4], which will be replaced in the future by the Cosmic Origins Spectrograph (COS) [3], the Advanced Camera for Surveys (ACS) and WF/PC3. The expected results of the first dedicated Ultraviolet Sky Survey mission GALEX which will be launched in 2003 by NASA, supply a very strong impetus for Page 2 of 10 the need of more efficient follow-up instrumentation to address the many new results to be expected from such survey. The GALEX survey is expected to supply catalogues with e.g. 1 million QSO’s; 1000 Clusters of Galaxies; 300,000 White Dwarfs; 10,000 Cataclysmic Variables etc. [15]. Also the combination with the major ground-based 10-m class telescopes in operation (see also [5]) together with the capabilities of the current generation of powerful X-ray telescopes (CHANDRA and NEWTON_XMM) supply additional unique mission goals in multi-ll science for the WSO/UV. In the following sections we will outline the philosophical background of the World Space Observatory concept in section II. The current situation in Space Astrophysics through a short overview of the implementation plans of the major Space Agencies with a Basic Space Science Programme, will be addressed in section III. In section IV we will expand on the details and capabilities of WSO/UV as presently agreed by the scientists who have been collaborating in the early assessment of WSO/UV. And in section V the current status and implementation planning is expanded upon. In this article we will not address the scientific impact of the WSO/UV in detail, since the other speakers will address these issues.

II. WSO Concept and Purpose.

History has shown that development in a socially peaceful environment is extremely difficult to achieve and that revolutionary changes, driven by intellectually advanced (and at times extreme) ideas, can become dominant. Therefore sustainable development in the modern world needs a culturally appropriate and sociologically stable development. This can only be accomplished when the educational processes also supply professional outlets for those motivated to learning and development in a broad sense. For the post-industrial times this presents an important challenge to the world at large, as a consequence of the complex and fast information distribution capabilities. Economic globalization in the industrialized world is accompanied by a strong democratization drive, but regional cultural identity should not be ignored. The influence of these cultural factors defy quantitative analysis and the absence of proper consideration of them, has been one of the main problems associated with the implementation of sustainable development programmes. It appears now clear that the activation of sustainable development schemes will have to be based on original and innovative approaches to the development process, where sharing must be an part of the collaborative efforts of all countries involved The current development strategies in many developing countries, include a significant investment in education which does not appear to bear the desired fruits, because of strong emigration pressures on the best educated people. One reason for this may be that participation in advanced science can only function efficiently if also access to advanced investigation tools are accessible. Consequently, investment in education often results only in the creation of a consumer market, without the creation of the professionally well-formed, culturally and intellectually identifiable and academically oriented cadre of scientists that is necessary for sustainable development. In hindsight, it is very clear that the success of the western industrial revolution was based on a fruitful interplay between the academic community and the commercial sector of the population. Over the centuries, has played a major cultural role as the predecessor of all scientific and philosophical development. This is because it uses scientific method to approach a most fundamental question, basic to many religious as well as non-religious philosophical concepts: Page 3 of 10

What is the place of (the people of) Earth in the Universe? During the United Nations/ESA workshops on Basic Space Science [1], the concept of a World Space Observatory has been recognized as an important tool to bring about the necessary quantum leaps in development. The World Space Observatory embodies a twofold goal: a. To create opportunities for all countries of the world, to participate in the frontiers of space science, on a sustainable basis and at the national level, without the need for excessive investment. In doing so, a WSO will make an important contribution to the development of an academically mature and competitive cadre in many developing countries within 5 to 10 years after inception of the project by offering equal opportunities to highly trained scientists all over the world; b. To support worldwide collaboration and to assure that the study of the mysteries of the universe from space can be shared in a sustainable way by scientists from all countries. This will then, not only maintain the curiosity-driven spirit of discovery that is an integral part of sustainable development, but also make a reality in the scientific world of the visionary principle that “space is the province of all mankind”.

For scientific reasons upon which we will expand below, the choice for the assessment study of a World Space Observatory [2] has been made to be the UV domain. The obvious reasons being that UV can only be reached from beyond the atmosphere and, that already considerable expertise exists in the developing world for the associated astrophysical problems. This will incorporate a direct application of the “headstart”principle. Thus it is possible to benefit greatly from a new space observatory to be launched in the 2nd half of the first decade of the 21st Century. Considering the combination of the WSO concept and the UV needs for a dynamic science program, the WSO/UV mission was conceived:

Mission concept WSO/UV The driving principles behind the design of the mission are: a. Operation of a 1-2 meter-class telescope in Earth orbit with a spectroscopic and imaging capacity specific to the ultraviolet domain; b. High throughput and optimized operational and orbital efficiency; c. Optimum benefit to be derived from the fact that ultraviolet cosmic background radiation is at a minimum around 200 nm; d. Minimal operational costs without affecting the scientific excellence of mission products; e. Direct access to a front-line facility for basic space science for the international astrophysics and planetary science community; f. Limitation of the technological developments needed for a prime science mission; g. Data distribution and data rights established as in UN A/AC 105.723 [1]

III. Astrophysics from Space

The astrophysical studies from space have been historically driven by the major Space Agencies from the United States, Europe, Russia, and Japan. The table below shows the past and future Astrophysics missions in the quarter century spanning the turn of the century. Page 4 of 10

Table 1. Photon Astrophysics from Space Mission llRange 1990 1995 2000 2005 2010 2015 2 - 40 MeV gg n .2 MeV - 3 GeV CGRO gg gg GLAST 20 MeV – 300 GeV n gg======??????????? 10 keV - 10 MeV INTEGRAL n g ???? 0.2 keV - 150 keV SWIFT n gg 170 - 650 nm 1 -400 keV X n ROSAT .1 - 2.4 keV X X n ASCA 1 - 12 keV X X RXTE 2 - 200 keV X SAX .1 - 200 keV X X CHANDRA .1 - 10 keV X HETE II 0.5 - 400 keV X XMM/NEWTON .2 - 10 keV X –X-g 4 eV – 150 keV n X/gg????????? CONSTELL.-X .25 – 40 keV n X????? ????????????? IUE 110 - 320 nm U n EUVE 1 - 75 nm U U FUSE 91 - 120 nm U GALEX 135 – 300 nm U WSO/UV 115 - 340 nm n U???????? ???????????? HIPPARCOS 375 - 750 nm O n HST 110 - 1000 nm U/O/I COROT 500 – 800 nm n O SIM 400 – 1000 nm n o======FAME 500 - 950 nm n O 300 – 1000 nm n O======DIVA O/I=== COBE 1 - 300 mm I n IRTS 1.2 - 800 mm I I n ISO 3 - 200 mm I I n SWAS 500 GHz I = 119-560 Ghz U/R/I === 1270 nm 280-800nm MAP 22 – 90 GHz I ===== SIRTF 3 – 180 mm I IRIS 1.2 - 800 mm I FIRST/Herschel 80 - 670 mm n I 30 – 857 GHz n I 4 – 30 mm R??? NGST 0.5 – 20 mm n I HALCA 1.6, 5, 22 GHz R RADIOASTRON .3,1.6,4.8,22.2 GHz n R???? ????? LISA GRAV G====

Table I: Space Astrophysics; a 25 year overview of photon astrophysics. The current is indicated by the square filled blocks and the missions are coded according to energy, wavelength or frequency domain (as customary in the field). The symbols to identify the wavelength domains are gg (for the MeV to GeV range); X (for the .1 keV to 500 keV range) ; U (for the UV range from 1 to 320 nm) ; O (for the optical NIR range 320 to 1000 nm) ; I (for the IR-mm range from 1mm to 1000 mm) and R (for the domain in GHz). If the coding symbol (gg, X, U, O, I, R) is given to the left and right of the horizontal duration bar in the table it indicates a mission which has been completed.

Over the last part of the 20th Century each Space Agency developed its own scientific program with priorities mostly driven by local academic and industrial capabilities and interests. Collaborations in projects were usually driven by the fact that the Page 5 of 10 defined science missions tended to exceed the available funding and an acceptable contribution could be delivered by a potential partner. As the frequency of launch opportunities for science missions was relatively low, this supplied also a strong impetus for collaborations. On the other hand the introduction of such collaborations did normally occur in rather late phases of the implementation of a mission, which could be as long as 10-15 years, with the associated complexities in engineering adjustments and cost effects. As the results of the missions over the past 30 years have been digested by the scientific communities, the needs for more sensitive instruments has become obvious, with the associated growth in size and cost of missions. An increase in sensitivity is normally obtained by more or less unrelated properties: Þ the telescope size, Þ optical design and coatings, Þ new detector development, all of which have significant impact on the mission costs. One critical issue, which has to be kept in mind here, is that the available launch capabilities represent a determining factor in mission size and associated weight. To illustrate the development and future plans of the space fairing nations in the Astrophysics area we show in Table 1 the missions flown and planned between 1990 to 2015. As indicated in the footnote, this table is arranged according photon energy. The WSO/UV is indicated in this overview with a shading to illustrate its relation to the plans for future missions in Astrophysics. It is interesting to note here that the large collecting area requirements of Astrophysics is already starting to show a less consistent approach to the need for observing facilities for Astrophysics. The future mission types fall clearly into two domains, very large and probably even exceeding the capabilities of the strongest economies, clearly requiring international cooperation, or small missions with a very specific, narrowly defined, science goal. The WSO concept claims to overcome these limitations and the WSO/UV mission has been designed to be within the realism of the current world economy, and to demonstrate the efficiency of the mission model, and to illustrate that even purely scientific goals can efficiently accelerate global and sustainable development.

IV. UV Astrophysics in the future

IV.1. The Instruments The time in which the window of opportunity for the WSO/UV mission is defined, with launch around 2006/7 can not be realistically evaluated without taking into consideration the capabilities of the (HST), which is the only UV capability foreseen in that time frame, with its lifetime extension to 2010. The last foreseen servicing mission to HST will install the Cosmic Origins Spectrograph (COS) [3] together with the Advanced Camera for Surveys (ACS). To evaluate the comparison of WSO/UV with the basic capabilities in the extended UV domain foreseen for the next decade, we show in table 2 the planned missions in the programs of ESA and NASA. Due to the heavy demand on technological innovation for a SUVO type mission (an 8m UV Space Telescope), there are no plans in the programs for any UV mission until well beyond 2010 [6, 7]. The earliest opportunity for such mission seems to be beyond the projected end-of-life of WSO/UV. Thus WSO/UV is important to maintain an active science and technology community for the UV, which otherwise is likely disappear due to the lack of intellectual and practical stimulus. Page 6 of 10

Table 2 Ultraviolet Spectroscopic Capabilities Instrument Orbit Life time ll nm. Resolution EUVE 1992 -2000 ll 7 - ll 76 400 HST/STIS Low Earth Orbit 1997 - 2003 ll115-ll1000 103 - 105 FUSE Low Earth Orbit 1999 – 2005? ll91 - ll120 2.4 104 XMM/NEWTON Highly Elliptical 1999 - ?? ll150- ll900 400 OM Orbit HST/ACS Low Earth Orbit 2003 - 2010 ll115- ll1100 ~100 HST/COS Low Earth Orbit 2003 - 2010 ll115 - ll320 2-2.4 104 (750) GALEX Low Earth Orbit 2002 - 2005 ll135- ll300 Sky Survey ; 150

WSO/UV High Orbit (L2) 2006 - 2015 ll100- ll340 5.5 104 (1000)

The ESA study [2] showed that a distributed implementation plan as foreseen for WSO/UV with a technology cut-off in 2002, using the following detailed mission constraints and contributions, represents an practical feasible mission:

WSO/UV mission model: Ø Telescope: 1.7 m diameter (T-170 Russian model; IoA Acad. of Sciences [10]), PSF(550 nm): » 0.2 arcsec Ø Spectrograph for the UV only: primary 110 - 340 nm. (HIRDES German model; IAAT [11]) with spectral Resolution 5 - 6 x 10**4; as well as a low resolution capability (500-1000) Ø Imaging : 115 - 340 nm with quality ~ 0.1- 0.3 arcsec (MCP based Israelian model; TAU; [12]); 2 UV Imagers : one for Max. spatial resolution; one for Max. sensitivity; and one Imager for visual domain Ø High Earth Orbit (non- around L2). Ø Distributed Mission Operations Ø Science Operations fully distributed at level of Nations Ø Further overall properties of the mission as a whole as described in [1]

It was judged that the engineering requirements of the WSO/UV mission and associated risk evaluation, were well within the current capabilities of space technologies and the specific mission model would allow a very fast implementation possibility with launch in the 2006/7 time frame.

IV.2. The Science

We will below summarise some of the astrophysics areas for which the WSO/UV defined above will be capable to answer fundamental questions and contribute, in an essential way, to solve currently pending questions with respect to evolution of the Planetary System, , Galaxies and the Large Scale Structure of the Universe. These issues will be considered in more detail by the other presentations.

In Planetary System Science, we consider the study of global atmospheric circulation and magnetospheric interaction. The gaseous present an excellent laboratory for the understanding of weather patterns less stochastic than the terrestrial patterns which are, in only partially understood ways, affected by human activities. The study of these undisturbed natural phenomena contributes not only to planetary studies per se, but will supply a better understanding of our own planetary environment. Of course a major contribution is also in the study of Comets. Page 7 of 10

For Stellar Science the complete life cycle of stars can be studied with many new discoveries to be expected. The project could make major breakthroughs in stellar evolution as a consequence of the multiplicity in systems, through the detailed studies of the effects of close binary exchange and accretion on condensed objects. Also the rapidly changing shock phenomena in Young Stellar Objects and the physical mechanisms driving jets in such objects, form an extremely exciting area of application of the WSO/UV. The studies of Interstellar matter and Galaxy population will allow the full evaluation of the cycling of Interstellar Matter and the subsequent chemical evolution of Galaxies. The capability to study such phenomena systematically over the full range from zero to high redshifts at the resolution supplied by WSO/UV, presents a very important contribution to these , and 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. The general problem to establish the nature, location and time of the Galaxy formation can be expected to be addressed in a highly meaningful way. The study of the Inter-Galactic Matter and its relation to Clusters of Galaxies and other sources of ionisation will present a superb challenge for the capabilities of the WSO/UV. The nature of Astrophysics is that many breakthroughs in the field are the consequence of unforeseen or unpredicted occurrences. We mention here discoveries of Comets and their behavior during their passage near the Sun, Novae, Supernovae, -ray Bursters, OVV’s and others, are a strong components in the science addressed by the WSO/UV. It is specifically the rapid response capability required in the mission, which, together with the extended visibility periods, will present new opportunities and major challenges to the scientists. Of course, in all these fields the capability to make simultaneous multi-ll observations of variability phenomena will add and extra dimension to all these studies.

V. WSO/UV current Status

After the first mention of a WSO concept at the 7th UN/ESA Workshop the ideas were further expanded by the participants in the 8th UN/ESA Workshop were an overall motivation and concept was developed [1]. The scientific aspects of these ideas have been broadly addressed in a joint NASA/ESA/PPARC Conference in Sevilla, Spain in late 1997 specifically dedicated to UV astrophysics [16]. At the conference “UV Astrophysics Beyond HST” the combination of the WSO concept and the UV requirements for Astrophysics to bring them together in the WSO/UV model was introduced [13]. To define a scientifically sensible model, a meeting was held between interested parties to supply the science requirements [14]. These were used as input for the assessment study made by ESA in the context of its long term planning. This has been published in [2].

The current status is that indications of interest from the scientific community have come to the attention of a number of space organizations on the national level. Non- commitment expressions of interest have been received from Russia, Germany, Italy, Argentina, India, Romania, Spain, Ukraine, Israel and the fact that we are here suggests that one could also add China to this list. Page 8 of 10

Further developments have taken place in various national environments of which I would like to mention the following:

1. Evaluation of Flight mirror production capabilities (Russia). 2. Phase A study of HIRDES spectrograph adaptation to WSO/UV (Germany). 3. Availability of one for WSO/UV (Argentina). 4. Study of distributed Science Operations model (ESA). 5. Reconfirmation of interest (Italy, Russia, Germany). 6. Confirmation of availability of T-170 for WSO/UV (Russia). 7. Independent review of ESA-CDF 05 study (USA). 8. Internal national Science Interest meetings (Italy, Spain, France). 9. WSO/UV incorporated in WGFLSF (IAU). 10. Re-evaluation of national interest in WSO/UV (India). 11. XianShang Symposium #164 (China). 12. Joint Discussion at JENAM 2001 meeting in Munich (September 2001) (EAS).

The WSO/UV mission should be really considered a mission with a “window of opportunity”, where the concept opportunity has a wide range of applications extending from launch capability, technological maturity, and communications infrastructure, to the availability of the GALEX survey data, pressing science problems and matched sensitivities at other wavelength domains. Also the non- scientific and non-technological aspects addressed in Section II are currently at a stage where the benefits of the WSO/UV concept could have major impact.

Figure 1. Engineering model (operational configuration) of WSO/UV as defined in CDF-05. The background in his image is composed of a composite image of and the interacting active galaxy pair NGC2207/IC2163. This illustrates clearly the range of astrophysical problems where the availability of the WSO/UV project will have great impact on our science. These will extend from the active studies of atmospheric phenomena and Heliospheric interaction on planets to chemical evolution of 90 % of the intergalactic material in the Universe and the possible study of Black Hole evolution 8 over a range of from 10 M¥ extending to 10 M¥ for the central Black hole masses in the nuclei of Active Galaxies (AGN) and Quasars. (Background images courtesy Hubble Heritage Project) Page 9 of 10

The challenge now before us is the following: In the presence of broad scientific interest and the prospect, that a major step forward can be made through the implementation of a really global activity with strong participation at the national level in a local environment, can the next step be made??

Of course to be able to respond to this question a clarification of the next step should be established. It is clear that the next step for WSO/UV is obviously a Phase A study. The direct challenge here is that a Phase A study by a single agency would not learn us anything new. A multinational Phase A study is required, addressing the following issues,

· Develop an overall WSO/UV management model. · Definition at a national level where the participant’s interest is for Hardware and Software development, fabrication and operations. · Reconfirm the technical feasibility of WSO/UV. · Definition of participant costing requirements. · Definition of total funding need for the WSO/UV project. · Detailed definition of a Science programme for WSO/UV, which will allow space for serendipitous science, and is technically consistent with the mission model. · Assuring that the mission model guarantees the fully global scientific participation in the project (following [1]), even in the absence of a direct pre-launch participation.

Only when these issues have been properly addressed in a world-wide collaborative context, will any national funding Agency be able to make studied decisions on support for the implementation of WSO/UV.

The challenge is now to reach a mutual agreement in an equal partners environment, where the possible real contributions to the WSO/UV can be demonstrated to show the validity and time scales of the WSO/UV. On this basis interested parties will have to agree on an implementation model maintaining the principles outlined in [1] and express a commitment to a joint multi-national Phase A study of the WSO/UV. At this stage discussions are ongoing in various countries in the scientific community to prepare for such phase.

It is only after this that the actual funding for WSO/UV can be obtained. This represents one of the major innovations in the WSO/UV Project in that it not only requires a unilateral national decision which will than possibly later expanded, but it presents the opportunity to join at a very early stage in a really global space project. This will allow the national scientific communities to participate directly in front-line science without having to build up first the economic strength to carry the full load of major Space Science missions. Through this a major step forward will be made in the realization of some of the goals envisioned in the UN Treaty.

References: 1. Report of the 8th UN/ESA workshop UN A/AC.105.723 2. WSO/UV Assessment Study, 2000, ESA CDF-05 (A) 3. Green, J.C., Morse,J.A., and COS Instr. Team, 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP-413, 805- 808. 4. Woodgate, B.E., Kimble,R.A., 1999, in UV-Optical Astronomy beyond HST, A.S.P. Conf. Ser. 164, 166 – 175. Page 10 of 10

5. Green R.F., 1999, in UV-Optical Astronomy beyond HST, A.S.P. Conf. Ser. 164, 346 – 351. 6. Weiler, E.J., 2000, Space Science Strategic Plan, NASA. 7. Horizons 2000, ESA Space Science Plans, 8. Rodriguez-Pascual, P.M., 2000, UE-CEES PX0116000 [CDF-05 (C)] 9. Wamsteker,W.,Gonzalez-Riestra, R., Eds., 1998, UV Astrophysics beyond the IUE Final Archive, ESA SP-413 ,809-814 10. Boyarchuk,A. et al., 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP- 413 ,809-814 11. Kappelmann,N., 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP-413, 831-835 12. Brosch,N., 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP-413 ,789- 896 13. Wamsteker, W., 1999, in UV-Optical Astronomy beyond HST, A.S.P. Conf. Ser. 164, 261 – 267. 14. Minutes WSO/UV Definition Technical meeting, 25-27 Nov. 1999 15. Bianchi,L., and the GALEX Team, 2000, Mem. Soc. Astron. It., Vol. 70, in press 16. Panel Discussion WSO, 1998, in UV Astrophysics beyond the IUE Final Archive, ESA SP-413 ,849-856.