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Recent progress on the lunar farside crater Saha proposal
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Acta Astronautica Vol. 46, No. 10±12, pp. 661±665, 2000 7 2000 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0094-5765/00 $ - see front matter PII: S0094-5765(00)00029-1
RECENT PROGRESS ON THE LUNAR FARSIDE CRATER SAHA PROPOSAL J. HEIDMANN Paris Observatory, F-92195, Meudon, France AbstractÐThe aim of this review, whose title might as well be ``Toward a dedicated lunar farside radio observatory'', is to provide information for potential interested workers whom we invite to contribute to this multidisciplinary eort. First point: in view of the dramatic increase of radio interference due to the development of satellitebased human telecommunications, it will soon become impossible to conduct valuable high-sensitivity SETI observations from the terrestrial ground. It is why a few years ago I started an interdisciplinary and international endeavor to protect for the next 20/30 years a well speci®ed lunar farside crater (Saha) which no Earth- or geostationary orbit-based radio emission could reach. After raising technical, programmatic, legal, astronautical, industrial, political, ethical issues at a number of conferences of international learned institutions, this enterprise is now of interest for the wider ®eld of next generation high-sensitivity radioastronomy at large, from decametric to submillimetric waves. This last year, positive results were the creation of an IAA Sub-committee for ``A Lunar SETI Study'', the presentation of a Resolution to the IAU for the protection of a potential lunar radio observatory site, discussions at the IAA/IISL Scienti®c-Legal Roundtable on SETI & Society at IAF Congress in Torino, the organization of a half-day Scienti®c Event at next COSPAR Assembly in Nagoya and the initiation of an IAA Cosmic Study on the subject. We shall conclude by outlining the next eorts to be initiated up to a real Moon radio observatory. 7 2000 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved
1. INTRODUCTION
One of the main reasons Carl Sagan gave for endorsing his international petition in favor of a fastpaced search for extraterrestrial intelligence (SETI) was that, before long, this enterprise would be drowned in a deep sea of human-made radio frequency interference (RFI) [1]: While our radio SETI observations, over their three decades of existence, doubled their technological eciency every eight months, quite a feat indeed [2], our ground-based large radiotelescopes, evidently wide-open skyward, are blinded more and more by numerous and powerful telecommunication satellites [3]. In spite of timid legal `protections' [4,5], we are doomed, not only concerning SETI, but also for all future highsensitivity radioastronomical research in its classical range from decametric to submillimetric wavelengths. Though tremendous eorts are made to ®ght RFI, I particularly refer to the `Follow-up detection device' elaborated by the SETI Institute [6], the long-term battle is lost, unless we ®nd a still pristine relatively accessible site for which we should right now start to ®ght for its long-term radio protection. 2. THE LUNAR FARSIDE
The closest accessible pristine radio sites are on the farside of the Moon which is shielded from the main
sources of Earth- or near Earth-based RFI. With the already quarter century old Apollo expeditions, it takes only 3 days to go there. Though Apollo was ®nancially driven by fear, there is a possibility that, on a more modest budget scale, though technologically more advanced form, `Back to the Moon' international initiatives could be revived for scienti®c purposes [7]. Already in 1990, radioastronomical research from the lunar farside has been proposed by an European Space Agency (ESA) Lunar Study Steering Group [8]. However it is aimed at investigating a new ®eld of radioastronomy at very low frequencies (VLF, 100 kHz±30 MHz, 3 km±10 m wavelengths) and the reason to work from the farside is to be shielded from the Earth's natural VLF emissions (non-thermal continuum, auroral kilometric) in addition to RFI. Here with SETI we are more concerned with the very dierent wavelength range 1 m±1 cm, the middle part of the classical radioastronomy range of decametric to submillimetric waves. We have to get rid of the global telecommunication emitters located up to the geostationary orbits. All of these because, though they are each allocated a speci®c emission frequency: 1. these frequencies are often allocated without real consideration of scienti®c needs; 2. as we work at very high levels of sensitivity 661
662
J. Heidmann
(already now easily down to 10ÿ28 W mÿ2 in a single 1 Hz-wide frequency channel, [2], we are polluted in frequency by harmonics of the telecommunication emitters and in propagation by stray emissions in their secondary lobes. Realizing that VLF radioastronomy operates at frequencies some orders of magnitude lower than SETI, quite a dierent domain, we shall not include its speci®c requirements in our following considerations. However we would be glad if future VLF lunar projects concur with our enterprise. On the other hand, we think that SETI requirements can be easily pro®table to all of the wider frequency domain of the classical radioastronomy. This being said, it is out of question that we require all of the lunar farside to be radio protected; the con¯icts with future exploration, and also exploitation, of the Moon's environment, would put us in an unbalanced and undefensible perspective. Thus it is very important to reduce our requirements to a strict minimum compatible with good science, which should then be considered as a last ditch entrenchment. Our strategy is dierent from the one of the recent International Telecommunication Union Recommendation [9] which asks for protection of selected radio frequency bands on practically all of the farside, while we ask for protection of all frequencies at a selected modest locale. We need all frequencies because of the numerous unexpected new interesting frequencies we (most happily) keep discovering, or simply because of the reshifting due to the natural expansion of the universe. For the next 20±30 years we need protection from the radio emissions created up to the geostationary orbits, where the bulk of powerful industrial/commercial scale RFI originate. The further away satellites/probes, more in the scienti®c realm, could be taken care of by bodies such as COSPAR Panel on Potentially Environmentally Detrimental Activities in Space (PEDAS).
3. A MINIMUM RADIO OBSERVATORY LUNAR SITE
It is why in 1993 I presented the minimum requirements we need for a future farside site [10,11]: 1. to be in the equatorial lunar region, for all-sky access; 2. to be as close as possible to the visible side for logistic and communication reasons; 3. to be inside a strongly walled crater to escape any lunar±ground RFI; 4. large enough to permit the deployment of future radioastronomical paraphernalia. It happens that these very clear, simple and reasonable criteria lead to a practically unique candidate: the 100 km diameter Saha crater, with a 3000 m high circular rim, at 1028E, 28S. When you look at
the Moon (from the northern hemisphere), Saha is just behind the limb, on the right-hand side. The best morphological and topographic data are provided by a high resolution Lunar Orbiter II photograph and a 1:2,750,000 National Aeronautics & Space Administration (NASA) lunar map. From them it appears that geostationary orbits, as seen from the center of Saha ¯oor, are at least 28 under the top of the West rim, even during the worst 78 librations. Currently, A. Cook and C. Mosangini, at Berlin Deutsche Forschungsanstalt fuÈr Luft- und Raumfarht (DLR), are working on Clementine data to check the pro®le of this most important W rim. Should it fail, the 40 km diameter and 3000 m deep crater 40 km o to the South-East of Saha, though smaller, could be a good back-up.
4. PROGRAMMATIC ISSUES
The programmatic issues were presented to the Space Exploration Symposium: ``Lunar Exploration'' at the International Astronautical Federation (IAF) Jerusalem Congress [12]. The lunar region closest to Saha in view of the Earth is the western part of Mare Smythii. This region, until eventual con®rmation of water ice deposits at the South pole, is a favourite for a main lunar base, man-tended or more probably purely robotic. Material connection to Saha can be provided by a 350 km long trail, lightly bulldozed in the regolith, with slopes smaller than 58, along which rovers could insure transportation, deployment and maintenance of radio instruments. It appears that telecommunications up to Saha for robotic telepresence and observational data ¯ow could be insured by depositing three laser relays along the route. The main issue is of course to avoid any radio relay which would illuminate Saha crater ¯oor. An already much publicized radio relay satellite at the Langrangean point 64,000 km behind the Moon would be 108 above the horizon of Saha and should be prohibited right away. It would devastate the farside pristine radio environment. However, the down-sizing of radio astronomers requirements to just Saha crater would give opportunities for replacement solutions in a spirit of mutual understanding. For instance, any radio satellite in lunar orbits entirely under the Saha horizon would be acceptable; an example is provided by lunar polar orbits seen edge-on from the Earth. It is also probable that laser relays would become common practice, as indicated by the forerunners laser-optical communication satellites OICETS from Japan and SILEX from France.
5. LEGAL QUESTIONS
At the same Jerusalem Congress I presented the legal requirements to the International Institute of
Recent progress on the lunar farside crater Saha proposal
Space Law (IISL) Colloquium on the Law of Outer Space [13]. In this international legal environment, it was adequate to stress at the start that protecting a potential future radio observatory lunar site is a duty for humankind. I gave arguments based on perspectives for SETI well into the 21st century [14]; but, more generally, classical radioastronomers will not fail to develop strong arguments imploring right now the protection of a radio window opened at the universe at large. After raising the questions: how to initiate the discussion, what legal problems are raised, how can they be solved, how a mutual understanding can be planned, in which frame Ð a lively constructive discussion followed [15]. In particular Ambassador A. A. Cocca, IISL Director, stated that ``This proposal, besides its scienti®c merits, has an undeniable worth as a legal project. It oers an opportunity to invigorate the principle of the Common Heritage of Mankind . . . The reservation of a lunar zone for scienti®c activities, and its further utilization aiming to the common good of humanity, must be recognized and constitutes a precedent'' [16]. S. E. Doyle gave a series of preliminary leads for the various questions: in particular to contact the International Academy of Astronautics (IAA), IAF, the Committee on Space Research (COSPAR), the International Astronomical Union (IAU) and to set up an IAA/IISL Scienti®c-Legal Roundtable (see infra).
6. IAA SETI SUB-COMMITTEE
At the IAF SETI business meeting in Oslo in 1995, I presented a series of arguments for a radio protected lunar farside site: 1. SETI is well rooted as a fundamental scienti®c research in more than a dozen universities and learned institutes; 2. its technological eciency doubles every 8 months; 3. as soon as an arti®cial signal is unravelled (if ever, of course), it will be proof that extraterrestrial technologies are plenty in the cosmos; 4. we shall have a strong drive to investigate their varieties; 5. human-made RFI will forbid SETI from Earth; 6. we need to save just one speci®c farside locale. We stressed that it is a political and philosophical duty for humankind to provide for such a lunar site from which SETI can be pursued well into the 21st century. Then we urged that our proposal be considered as a current plan for the next 20±30 years. I was then asked to set up a Sub-committee for a ``Lunar SETI Study'' [17]. I intend to use it as a yearly forum where people interested in the future of SETI will be able to present their ideas and debate.
663
7. INVITATION TO COSPAR
At the opening ceremony of the IAF Congress in Oslo in 1995, G. Haerendel, President of COSPAR, declared: ``Collaboration between the IAF and COSPAR has a long tradition . . . Space research is not thinkable without astronautics . . . One of the continuous links between space research and astronautics is the IAA. But even stronger ties would be established by more frequent joint events'' [18]. This encouraged me, in an invited paper at the 1996 COSPAR Scienti®c Assembly in Birmingham, to suggest that the Saha proposal, being a widely multidisciplinary joint venture between space research and astronautics, might get some support from COSPAR [19]. Most happily, I was given the task to be the main scienti®c organizer of a half-day meeting at the next COSPAR scienti®c assembly in 1998 in Nagoya, under the title: ``Protection of part of a celestial body for the scienti®c bene®t of humankind: the lunar farside crater Saha proposal'' [20], where I shall invite interested contributors.
8. TOWARD A RESOLUTION FROM THE IAU
At the 5th International Conference on Bioastronomy, alias IAU Coll. No. 161, in Capri in 1996, I presented the rationale for SETI well into the 21st century. We are no longer in the gloomy mood which arose when the United States Congress cut all fundings for SETI at NASA in 1993 [21], when too many people thought that in case a signal is not discovered ``before the next elections'', SETI should be dismantled. I gave nine good reasons to go on, from philosophical to cultural to ®nancial and political ones. Within the next generation, the S of SETI may come to mean Search, then Survey, Study and ®nally Sociology of extraterrestrial intelligence. So, at this very well attended Capri conference [22] the astronomical community at large was informed about importance of radio protection for safeguarding the future of the ®eld. This Summer, at the IAU General Assembly in Kyoto, a Joint Discussion on ``Astronomy from the Moon'' was organized by Y. Terzian between Divisions XI (Space and high energy astrophysics) and VIII (Galaxies and cosmology) and Commissions 28 (Galaxies), 40 (Radioastronomy) and 44 (Space and High Energy Astrophysics). There, I submitted a proposal for an IAU Resolution ``Concerning the protection of a potential observatory site on the farside of the Moon for the future of high-sensitivity radioastronomy'' [23], with the hope that a favorable vote and the additional supports of Commission 50 (Protection of existing and potential observatory sites) and 16 (Physical study of planets & satellites) will help to have it endorsed by the IAU Executive Committee at the next General Assembly.
664
J. Heidmann 9. IAA COSMIC STUDY
At the 1997 Spring meeting of the IAA Scienti®c Programs Committee in Paris, the Vice-President M. I. Yarymovych asked me to start work on a new Cosmic Study on protecting and establishing a radio observatory on the farside of the Moon. Already IAA has published such Cosmic Studies as booklets. Each one collects papers invited by the Editor on a
theme de®ned by a charter and may take a few years to be elaborated. 10. NEXT EFFORTS
Of course this lunar proposal is a very long-term adventure, aiming at a 20±30 year horizon, in line with the `Back to the Moon' ESA-initiated scheme
Fig. 1. How is it looking like up there? Upper left Ð On their way to the Moon, Apollo astronauts saw simultaneously the near- (left) and farside (right); Saha (a half-radius under center) is one among a jungle of craters, East of the black Mare Smythii plain (lower left). Upper right Ð The trail from Mare Smythii (upper left) to Saha (lower right) is 350 km long and is drawn for minimized slopes; three laser relays (tick marks) would provide telepresence and data ¯ows with Earth. Center left Ð Apollo rovers already drove tens of km with two passengers on board on the friendly low slopes regolith. Though the background mountain 3 km away is already 2000 m high, the landscape is soft. Center right Ð A robotic Lunar Orbiter over¯ew the West part of Saha in 1996; its 100 km diameter ¯oor harbors various useful topographic features and is circled by a strong 3000 m high rim (here North is to the right). Lower left Ð Thompson crater is here over¯own by an Apollo; its strong rim would protect its vast 150 km ¯oor from lunar ground-based RFI and, for the somewhat similar Saha, from earthly radio satellites. Lower right Ð Saha is not that far away! Here, an Apollo LEM, after a 3-day ¯ight, passes high above Saha and darts along the Moon equator toward the grey Mare Smythii, inundated by the earthly radio interference (NASA illustrations).
Recent progress on the lunar farside crater Saha proposal
and now handled by the International Lunar Exploration Working Group (ILEWG). It is also very multidisciplinary, as shown in this report, and needs support coming from very dierent learned bodies. Already IAF, IAA, IISL, COSPAR, IAU and ILEWG [24] were contacted. Practically, an action frame needs to be delineated, with 1. the IAA SETI Sub-committee, 2. this year IAA/IISL Scienti®c-Legal round table in Torino, 3. next year COSPAR half-day meeting in Nagoya, 4. the IAA Cosmic Study project. It is clear that in each of the ®elds involved it is necessary that specialists bring constructive contributions. This could start right now, in spite of the long-term range, as preliminary small scale investigations or discussions. One fundamental point should be stressed: radioastronomers will not be the ®rst people to deploy their next generation instruments on the farside of the Moon. Meanwhile the danger is looming that forerunners for the exploration/exploitation of the Moon may ruin the radio pristine farside: this needs immediate action for initiating, as urgently as possible a memorandum of understanding between all the parties involved for the future exploration of the Moon, Solar System and the Universe for the greater bene®t of humankind. The move toward such an international memorandum for a dedicated lunar farside scienti®c radio observatory would go hand in hand with astronautical research and development for its technological implementation (Fig. 1). NO PROTECTION, NO LUNAR DEPLOYMENT; NO DEPLOYMENT, NO MORE RADIO WINDOW ON THE UNIVERSE!
8. 9.
10.
11. 12.
13.
14.
15.
16.
17. 18. 19.
REFERENCES
1. Sagan, C., Extraterrestrial intelligence: an international petition. Science, 1982, 218, 426. 2. Klein, M. J. and Gulkis, S., The impact of technology on SETI. In Bioastronomy, the Search for Extraterrestrial Life, ed. J. Heidmann and M. J. Klein, 1991, p. 203 Lecture Notes in Physics, 390. 3. United Nations, Telecommunications. In Highlights in Space, Progress in space science, technology and applications, international cooperation and space law. Oce of Outer Space Aairs, Vienna, 1997 A/AC.105/654. 4. Kahlmann, H. C., SETI and the radiospectrum. In SETI-3: the Search for Extraterrestrial Intelligence, ed. J. Heidmann, 1992, pp. 213±217 Acta Astronautica, 26. 5. GeÂrard, E., La radioastronomie face aÁ la saturation du domaine hertzien. La Vie des Sciences, Acad. Sci. Paris, 1993, 10(3), 175. 6. Pardo, E., and Cullers, D.K., Design of the fast Fourier transform board in the SETI follow up detection device. In SETI-5: the Search for Extraterrestrial Intelligence, ed. J. Heidmann, Acta Astronautica, 1998, 42 (10±12), 619±633. 7. Balsiger, H. et al. 1994. Towards a World Strategy for the Exploration and Utilisation of Our Natural
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Satellite. International Lunar Workshop, Beatenberg, May 31±June 1, ESA SP-1170, ESA Paris Oce, 157. Booth, R. S. et al. 1992. Very low frequency astronomy. Mission to the Moon. ESA SP-1150, ESA Paris Oce, 50. ITU, Protection of frequencies for radioastronomical measurements in the shielded zone of the Moon. International Telecommunication Union, Study Group 7, Radiocommunication Assembly, Geneva, 1997 ITU-R RA.479-4. Heidmann, J., Search for extraterrestrial intelligence & the need for a lunar base. In International conference on space exploration & the future of humans in space, Dijon, March 29±30, 1993. In A Lunar-based analytical laboratory, Cyril Ponnamperuma Memorial Volume, eds C.W. Gehrke, M.K. Hobish, R.W. Zumwalt, M. Prost & J DegreÁs. Decpak Publishing 1997. pp. 201±205. Heidmann, J., Saha crater: a candidate for a SETI lunar base. Acta Astronautica, 1994, 32, 471±472. Heidmann, J., A proposal for a radio frequency interference-free dedicated lunar far side crater for high sensitivity radioastronomy. In 45th Congress of the International Astronautical Federation, IAF-94-O.1.330, Acta Astronautica, 2000, 46(8) 555±558. Heidmann, J., What legal questions are raised by the establishment of a dedicated lunar far side speci®c crater for high sensitivity radioastronomy? In Proc. 37th IISL Coll. Am. Inst. Aeronautics and Astronautics, 1994, p. 255. Heidmann, J., SETI from the Moon: an invitation to COSPAR, 31st COSPAR Scienti®c Assembly, July 14±21, Birmingham, Advances in Space Research 1996a; (in press). Masson-Zwaan, T. L., Report on the discussions held after the 4 sessions of the 37th colloquium on the law of outer space. In Proc. 37th IISL Coll., Am. Inst. Aeronautics and Astronautics, 1994, p. 301. Cocca, A. A., Reservation of a Lunar zone for SETI purposes. In 46th Congress of the International Astronautical Federation, IISL-95-4.14, IAF Oce, Paris, 1995. Billingham, J., Report. In IAA SETI Committee Business Meeting, Oslo IAF Congress, Sept. 30, IAA Paris Oce, 1995. Haerendel, G., Opening statement. COSPAR Inf. Bull., 1996, 135, 6. Heidmann, J., A call for SETI well into the 21st century. In 5th International Bioastronomy Conference, IAU Coll. No. 161, ed. C. Cosmovici, S. Bowyer and D. Werthimer, 1996, p. 777. COSPAR. Inf. Bull., 1997, 137, 35. Tarter, J., Klein, M. J. and Friedman, L. D., Congress axes NASA HRMS project: NASA loses funding for targeted and survey SETI eorts. Bioastronomy News, 1994, 6-1, 1. Cosmovici, C., Bowyer, S. and Werthimer, D., Astronomical and biochemical origins and the search for life in the universe. In 5th International Bioastronomy Conference, IAU Coll. No. 161, Capri, 1996. Heidmann, J., SETI from the Moon: avoiding radio pollution for future radioastronomy. In Joint Discussion No. 22, 23rd IAU General Assembly, Kyoto, August 17±30, 1997 Highlights of Astronomy, ed J. Anderson, 11B, pp 996±999, 1998. Heidmann, J., The farside lunar crater Saha project: to protect part of a celestial body for the future scienti®c bene®t of humankind. In 2nd International Lunar Workshop/ILEWG Meeting; toward a new stage of the exploration and utilization of the Moon, Kyoto, October 14±18, 1996 ed. H. Mizutami, Institute of Space and Astronautical Science, Japan, pp 7 & 71, 1997.
Acta Astronautica Vol. 46, No. 10±12, pp. 661±665, 2000 7 2000 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0094-5765/00 $ - see front matter PII: S0094-5765(00)00029-1
RECENT PROGRESS ON THE LUNAR FARSIDE CRATER SAHA PROPOSAL J. HEIDMANN Paris Observatory, F-92195, Meudon, France AbstractÐThe aim of this review, whose title might as well be ``Toward a dedicated lunar farside radio observatory'', is to provide information for potential interested workers whom we invite to contribute to this multidisciplinary eort. First point: in view of the dramatic increase of radio interference due to the development of satellitebased human telecommunications, it will soon become impossible to conduct valuable high-sensitivity SETI observations from the terrestrial ground. It is why a few years ago I started an interdisciplinary and international endeavor to protect for the next 20/30 years a well speci®ed lunar farside crater (Saha) which no Earth- or geostationary orbit-based radio emission could reach. After raising technical, programmatic, legal, astronautical, industrial, political, ethical issues at a number of conferences of international learned institutions, this enterprise is now of interest for the wider ®eld of next generation high-sensitivity radioastronomy at large, from decametric to submillimetric waves. This last year, positive results were the creation of an IAA Sub-committee for ``A Lunar SETI Study'', the presentation of a Resolution to the IAU for the protection of a potential lunar radio observatory site, discussions at the IAA/IISL Scienti®c-Legal Roundtable on SETI & Society at IAF Congress in Torino, the organization of a half-day Scienti®c Event at next COSPAR Assembly in Nagoya and the initiation of an IAA Cosmic Study on the subject. We shall conclude by outlining the next eorts to be initiated up to a real Moon radio observatory. 7 2000 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved
1. INTRODUCTION
One of the main reasons Carl Sagan gave for endorsing his international petition in favor of a fastpaced search for extraterrestrial intelligence (SETI) was that, before long, this enterprise would be drowned in a deep sea of human-made radio frequency interference (RFI) [1]: While our radio SETI observations, over their three decades of existence, doubled their technological eciency every eight months, quite a feat indeed [2], our ground-based large radiotelescopes, evidently wide-open skyward, are blinded more and more by numerous and powerful telecommunication satellites [3]. In spite of timid legal `protections' [4,5], we are doomed, not only concerning SETI, but also for all future highsensitivity radioastronomical research in its classical range from decametric to submillimetric wavelengths. Though tremendous eorts are made to ®ght RFI, I particularly refer to the `Follow-up detection device' elaborated by the SETI Institute [6], the long-term battle is lost, unless we ®nd a still pristine relatively accessible site for which we should right now start to ®ght for its long-term radio protection. 2. THE LUNAR FARSIDE
The closest accessible pristine radio sites are on the farside of the Moon which is shielded from the main
sources of Earth- or near Earth-based RFI. With the already quarter century old Apollo expeditions, it takes only 3 days to go there. Though Apollo was ®nancially driven by fear, there is a possibility that, on a more modest budget scale, though technologically more advanced form, `Back to the Moon' international initiatives could be revived for scienti®c purposes [7]. Already in 1990, radioastronomical research from the lunar farside has been proposed by an European Space Agency (ESA) Lunar Study Steering Group [8]. However it is aimed at investigating a new ®eld of radioastronomy at very low frequencies (VLF, 100 kHz±30 MHz, 3 km±10 m wavelengths) and the reason to work from the farside is to be shielded from the Earth's natural VLF emissions (non-thermal continuum, auroral kilometric) in addition to RFI. Here with SETI we are more concerned with the very dierent wavelength range 1 m±1 cm, the middle part of the classical radioastronomy range of decametric to submillimetric waves. We have to get rid of the global telecommunication emitters located up to the geostationary orbits. All of these because, though they are each allocated a speci®c emission frequency: 1. these frequencies are often allocated without real consideration of scienti®c needs; 2. as we work at very high levels of sensitivity 661
662
J. Heidmann
(already now easily down to 10ÿ28 W mÿ2 in a single 1 Hz-wide frequency channel, [2], we are polluted in frequency by harmonics of the telecommunication emitters and in propagation by stray emissions in their secondary lobes. Realizing that VLF radioastronomy operates at frequencies some orders of magnitude lower than SETI, quite a dierent domain, we shall not include its speci®c requirements in our following considerations. However we would be glad if future VLF lunar projects concur with our enterprise. On the other hand, we think that SETI requirements can be easily pro®table to all of the wider frequency domain of the classical radioastronomy. This being said, it is out of question that we require all of the lunar farside to be radio protected; the con¯icts with future exploration, and also exploitation, of the Moon's environment, would put us in an unbalanced and undefensible perspective. Thus it is very important to reduce our requirements to a strict minimum compatible with good science, which should then be considered as a last ditch entrenchment. Our strategy is dierent from the one of the recent International Telecommunication Union Recommendation [9] which asks for protection of selected radio frequency bands on practically all of the farside, while we ask for protection of all frequencies at a selected modest locale. We need all frequencies because of the numerous unexpected new interesting frequencies we (most happily) keep discovering, or simply because of the reshifting due to the natural expansion of the universe. For the next 20±30 years we need protection from the radio emissions created up to the geostationary orbits, where the bulk of powerful industrial/commercial scale RFI originate. The further away satellites/probes, more in the scienti®c realm, could be taken care of by bodies such as COSPAR Panel on Potentially Environmentally Detrimental Activities in Space (PEDAS).
3. A MINIMUM RADIO OBSERVATORY LUNAR SITE
It is why in 1993 I presented the minimum requirements we need for a future farside site [10,11]: 1. to be in the equatorial lunar region, for all-sky access; 2. to be as close as possible to the visible side for logistic and communication reasons; 3. to be inside a strongly walled crater to escape any lunar±ground RFI; 4. large enough to permit the deployment of future radioastronomical paraphernalia. It happens that these very clear, simple and reasonable criteria lead to a practically unique candidate: the 100 km diameter Saha crater, with a 3000 m high circular rim, at 1028E, 28S. When you look at
the Moon (from the northern hemisphere), Saha is just behind the limb, on the right-hand side. The best morphological and topographic data are provided by a high resolution Lunar Orbiter II photograph and a 1:2,750,000 National Aeronautics & Space Administration (NASA) lunar map. From them it appears that geostationary orbits, as seen from the center of Saha ¯oor, are at least 28 under the top of the West rim, even during the worst 78 librations. Currently, A. Cook and C. Mosangini, at Berlin Deutsche Forschungsanstalt fuÈr Luft- und Raumfarht (DLR), are working on Clementine data to check the pro®le of this most important W rim. Should it fail, the 40 km diameter and 3000 m deep crater 40 km o to the South-East of Saha, though smaller, could be a good back-up.
4. PROGRAMMATIC ISSUES
The programmatic issues were presented to the Space Exploration Symposium: ``Lunar Exploration'' at the International Astronautical Federation (IAF) Jerusalem Congress [12]. The lunar region closest to Saha in view of the Earth is the western part of Mare Smythii. This region, until eventual con®rmation of water ice deposits at the South pole, is a favourite for a main lunar base, man-tended or more probably purely robotic. Material connection to Saha can be provided by a 350 km long trail, lightly bulldozed in the regolith, with slopes smaller than 58, along which rovers could insure transportation, deployment and maintenance of radio instruments. It appears that telecommunications up to Saha for robotic telepresence and observational data ¯ow could be insured by depositing three laser relays along the route. The main issue is of course to avoid any radio relay which would illuminate Saha crater ¯oor. An already much publicized radio relay satellite at the Langrangean point 64,000 km behind the Moon would be 108 above the horizon of Saha and should be prohibited right away. It would devastate the farside pristine radio environment. However, the down-sizing of radio astronomers requirements to just Saha crater would give opportunities for replacement solutions in a spirit of mutual understanding. For instance, any radio satellite in lunar orbits entirely under the Saha horizon would be acceptable; an example is provided by lunar polar orbits seen edge-on from the Earth. It is also probable that laser relays would become common practice, as indicated by the forerunners laser-optical communication satellites OICETS from Japan and SILEX from France.
5. LEGAL QUESTIONS
At the same Jerusalem Congress I presented the legal requirements to the International Institute of
Recent progress on the lunar farside crater Saha proposal
Space Law (IISL) Colloquium on the Law of Outer Space [13]. In this international legal environment, it was adequate to stress at the start that protecting a potential future radio observatory lunar site is a duty for humankind. I gave arguments based on perspectives for SETI well into the 21st century [14]; but, more generally, classical radioastronomers will not fail to develop strong arguments imploring right now the protection of a radio window opened at the universe at large. After raising the questions: how to initiate the discussion, what legal problems are raised, how can they be solved, how a mutual understanding can be planned, in which frame Ð a lively constructive discussion followed [15]. In particular Ambassador A. A. Cocca, IISL Director, stated that ``This proposal, besides its scienti®c merits, has an undeniable worth as a legal project. It oers an opportunity to invigorate the principle of the Common Heritage of Mankind . . . The reservation of a lunar zone for scienti®c activities, and its further utilization aiming to the common good of humanity, must be recognized and constitutes a precedent'' [16]. S. E. Doyle gave a series of preliminary leads for the various questions: in particular to contact the International Academy of Astronautics (IAA), IAF, the Committee on Space Research (COSPAR), the International Astronomical Union (IAU) and to set up an IAA/IISL Scienti®c-Legal Roundtable (see infra).
6. IAA SETI SUB-COMMITTEE
At the IAF SETI business meeting in Oslo in 1995, I presented a series of arguments for a radio protected lunar farside site: 1. SETI is well rooted as a fundamental scienti®c research in more than a dozen universities and learned institutes; 2. its technological eciency doubles every 8 months; 3. as soon as an arti®cial signal is unravelled (if ever, of course), it will be proof that extraterrestrial technologies are plenty in the cosmos; 4. we shall have a strong drive to investigate their varieties; 5. human-made RFI will forbid SETI from Earth; 6. we need to save just one speci®c farside locale. We stressed that it is a political and philosophical duty for humankind to provide for such a lunar site from which SETI can be pursued well into the 21st century. Then we urged that our proposal be considered as a current plan for the next 20±30 years. I was then asked to set up a Sub-committee for a ``Lunar SETI Study'' [17]. I intend to use it as a yearly forum where people interested in the future of SETI will be able to present their ideas and debate.
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7. INVITATION TO COSPAR
At the opening ceremony of the IAF Congress in Oslo in 1995, G. Haerendel, President of COSPAR, declared: ``Collaboration between the IAF and COSPAR has a long tradition . . . Space research is not thinkable without astronautics . . . One of the continuous links between space research and astronautics is the IAA. But even stronger ties would be established by more frequent joint events'' [18]. This encouraged me, in an invited paper at the 1996 COSPAR Scienti®c Assembly in Birmingham, to suggest that the Saha proposal, being a widely multidisciplinary joint venture between space research and astronautics, might get some support from COSPAR [19]. Most happily, I was given the task to be the main scienti®c organizer of a half-day meeting at the next COSPAR scienti®c assembly in 1998 in Nagoya, under the title: ``Protection of part of a celestial body for the scienti®c bene®t of humankind: the lunar farside crater Saha proposal'' [20], where I shall invite interested contributors.
8. TOWARD A RESOLUTION FROM THE IAU
At the 5th International Conference on Bioastronomy, alias IAU Coll. No. 161, in Capri in 1996, I presented the rationale for SETI well into the 21st century. We are no longer in the gloomy mood which arose when the United States Congress cut all fundings for SETI at NASA in 1993 [21], when too many people thought that in case a signal is not discovered ``before the next elections'', SETI should be dismantled. I gave nine good reasons to go on, from philosophical to cultural to ®nancial and political ones. Within the next generation, the S of SETI may come to mean Search, then Survey, Study and ®nally Sociology of extraterrestrial intelligence. So, at this very well attended Capri conference [22] the astronomical community at large was informed about importance of radio protection for safeguarding the future of the ®eld. This Summer, at the IAU General Assembly in Kyoto, a Joint Discussion on ``Astronomy from the Moon'' was organized by Y. Terzian between Divisions XI (Space and high energy astrophysics) and VIII (Galaxies and cosmology) and Commissions 28 (Galaxies), 40 (Radioastronomy) and 44 (Space and High Energy Astrophysics). There, I submitted a proposal for an IAU Resolution ``Concerning the protection of a potential observatory site on the farside of the Moon for the future of high-sensitivity radioastronomy'' [23], with the hope that a favorable vote and the additional supports of Commission 50 (Protection of existing and potential observatory sites) and 16 (Physical study of planets & satellites) will help to have it endorsed by the IAU Executive Committee at the next General Assembly.
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J. Heidmann 9. IAA COSMIC STUDY
At the 1997 Spring meeting of the IAA Scienti®c Programs Committee in Paris, the Vice-President M. I. Yarymovych asked me to start work on a new Cosmic Study on protecting and establishing a radio observatory on the farside of the Moon. Already IAA has published such Cosmic Studies as booklets. Each one collects papers invited by the Editor on a
theme de®ned by a charter and may take a few years to be elaborated. 10. NEXT EFFORTS
Of course this lunar proposal is a very long-term adventure, aiming at a 20±30 year horizon, in line with the `Back to the Moon' ESA-initiated scheme
Fig. 1. How is it looking like up there? Upper left Ð On their way to the Moon, Apollo astronauts saw simultaneously the near- (left) and farside (right); Saha (a half-radius under center) is one among a jungle of craters, East of the black Mare Smythii plain (lower left). Upper right Ð The trail from Mare Smythii (upper left) to Saha (lower right) is 350 km long and is drawn for minimized slopes; three laser relays (tick marks) would provide telepresence and data ¯ows with Earth. Center left Ð Apollo rovers already drove tens of km with two passengers on board on the friendly low slopes regolith. Though the background mountain 3 km away is already 2000 m high, the landscape is soft. Center right Ð A robotic Lunar Orbiter over¯ew the West part of Saha in 1996; its 100 km diameter ¯oor harbors various useful topographic features and is circled by a strong 3000 m high rim (here North is to the right). Lower left Ð Thompson crater is here over¯own by an Apollo; its strong rim would protect its vast 150 km ¯oor from lunar ground-based RFI and, for the somewhat similar Saha, from earthly radio satellites. Lower right Ð Saha is not that far away! Here, an Apollo LEM, after a 3-day ¯ight, passes high above Saha and darts along the Moon equator toward the grey Mare Smythii, inundated by the earthly radio interference (NASA illustrations).
Recent progress on the lunar farside crater Saha proposal
and now handled by the International Lunar Exploration Working Group (ILEWG). It is also very multidisciplinary, as shown in this report, and needs support coming from very dierent learned bodies. Already IAF, IAA, IISL, COSPAR, IAU and ILEWG [24] were contacted. Practically, an action frame needs to be delineated, with 1. the IAA SETI Sub-committee, 2. this year IAA/IISL Scienti®c-Legal round table in Torino, 3. next year COSPAR half-day meeting in Nagoya, 4. the IAA Cosmic Study project. It is clear that in each of the ®elds involved it is necessary that specialists bring constructive contributions. This could start right now, in spite of the long-term range, as preliminary small scale investigations or discussions. One fundamental point should be stressed: radioastronomers will not be the ®rst people to deploy their next generation instruments on the farside of the Moon. Meanwhile the danger is looming that forerunners for the exploration/exploitation of the Moon may ruin the radio pristine farside: this needs immediate action for initiating, as urgently as possible a memorandum of understanding between all the parties involved for the future exploration of the Moon, Solar System and the Universe for the greater bene®t of humankind. The move toward such an international memorandum for a dedicated lunar farside scienti®c radio observatory would go hand in hand with astronautical research and development for its technological implementation (Fig. 1). NO PROTECTION, NO LUNAR DEPLOYMENT; NO DEPLOYMENT, NO MORE RADIO WINDOW ON THE UNIVERSE!
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11. 12.
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17. 18. 19.
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