During the 6th UN/ESA Workshop on Basic Space Science it was noted that of all the developing regions in the world, Africa showed the least progress in the space sciences. It could be argued that with the manifold problems facing countries in the region, why should Africa be involved in the space sciences? The answer, of course, is that the more application-oriented fields of the space sciences hold the key to solving some of the region's most daunting problems. However, it is important for Africa to develop strong indigenous capabilities in the space sciences if it is to take full advantage of the broad spectrum of end products of space technology. Without indigenous capabilities, the rapid development of the space sciences rapidly renders acquired technologies obsolete, thus prolonging technological dependence on industrialised countries.
There are additional benefits to be realized by countries which harness the space sciences for development. The space sciences have high visual appeal and are therefore particularly effective at capturing the imagination of young and old alike. This is an important factor in inducing young people to consider entering into science and technology oriented careers, which provides the skilled workforce required to assimilate and exploit new technologies. This in turn allows a country to develop technologies that add value to its natural products, thus boosting national income.
Whilst most African countries may not individually have the resources and skills to engage in ambitious programmes in the space sciences, there is no reason why this could not be done on a regional basis. Indeed, this sort of thinking applies not only to the space sciences, but to all other endeavours as well. If Africa does not move towards greater regional cooperation as a means of strengthening its position globally, it risks falling further behind the developing regions of Asia and Latin America. One of the principal aims of this Working Group is to encourage greater regional cooperation and self reliance in the space sciences among African countries.
For this organization to meet its long-term objectives it must enter into a strong growth phase. Individual members are strongly encouraged to consider activities through which they may raise the profile of the Working Group within their regions. These activities could include: drawing attention of potential new members to the existence of the WGSSA, convening small regional workshops, distributing African Skies among colleagues and decision makers in their regions, etc. The strength of the WG depends on members keeping in touch with each other, and on the regional Deputy Coordinators giving leadership in their regions. I believe that strong regional programmes will be critical to the long-term success of this Working Group.
I wish all members of the Working Group success in their endeavours during 1997.
Peter Martinez
Coordinator, WGSSA
Ile-Ife is situated at about 200 km NE of Lagos. The Obafemi Awolowo University is located to the North of the city. One active area of research in the Physics Department is in Solar-Terrestrial Physics and Geomagnetic Observations. The research group has a Proton Vector Magnetometer operating under the control of an IBM-compatible PC which logs one-minute values of the total field F, declination D, and inclination I measured by the system.
The measured values are used, among other uses, to monitor the geomagnetic variations due to the interactions of the solar wind and terrestrial magnetism. In effect, ``space weather'' is closely monitored on a daily basis at a location close to the magnetic dip equator.
The interest of a Rotating Slit-Aperture Telescope (RSAT), among other synthetic aperture telescopes, is its capability of being easily coupled with a spectrograph in order to give reconstructed images of an astronomical object as a function of optical wavelength. Each monochromatic image is compared with respect to others at taken at different wavelengths for fruitful astrophysical applications.
The principle of image reconstruction used in the RSAT is well known; it consists of the inversion of the set of projections (Radon transform) given by the telescope's rotation around its optical axis. A full coverage of the two-dimensional Fourier plane can be obtained by rotating the SAT. This problem has led to intense developments for medical imaging (tomography).
One of the main difficulties in the image reconstruction process arises from the jitter of the rotation axis of the RSAT. A set of projections uncorrected for this jitter produces very fuzzy reconstructed images. I found an elegant solution to the necessary phasing between successive projections which makes use of a small auxilliary telescope. Some numerical simulations are presented in my PhD Thesis (Université Hassan II, Faculté des Sciences Ain Chock, Royaume du Maroc, May 1995).
Le télescope à pupille fente fournit des images unidimensionnelles
et opère en synthèse d'ouverture. En l'absence de turbulence
atmosphérique, l'image focale fournie par un télescope à pupille fente est quasiment une projection unidimensionnelle de l'objet
observé.
Aprés une rotation complète autour de son axe optique, on obtient un
ensemble de projections de l'objet observé qui n'est autre que la
transformée de Radon de l'objet.
Une étude de l'utilisation de cet instrument en présence de la turbulence
atmosphérique a été effectuée (qualité des images, reconstruction
d'images, etc.). L'apport de l'optique adaptative a été étudié.
La lune est notre satellite naturel d'un diamètre de 3476 km, sans vie. Elle tourne autour de la terre à une distance moyenne de 384000 km, et apparait dans le ciel sous forme d'un disque de de diamètre. De la terre nous ne pouvons voir qu'une partie de l'hémisphère illuminée; c'est pourquoi nous observons la lune au cours de plusieurs phases.
Lorsque la pleine lune passe tout prés de la ligne imaginaire reliant le centre du soleil au centre de la terre, elle peut pénétrer dans la zone d'obscurité complète (ombre) entourée d'une obscurité moins intense (pénombre). Dans ce cas la lune s'éclipse. En effet, la terre éclairée par le soleil, projette derrière elle, dans l'espace, un cône d'ombre dont la longueur moyenne est de 1 400 000 km, et un cône de pénombre. Périodiquement, la lune les traverse; elle n'est alors plus éclairée par le soleil, et l'on assiste à une éclipse de lune.
Si la lune se trouve dans la pénombre, on parle d'une éclipse de lune par la pénombre qui se traduit seulement par une légère diminution de la clarté de la lune. Si la lune toute entière est noircie, on parle d'une éclipse totale; si seule une partie de la lune est obscurcie, on parle d'une éclipse partielle.
Si les orbites respectives de la terre et de la lune étaient situées dans le même plan, il y aurait une éclipse de lune à chaque pleine lune (tous les mois du calendrier musulman). En réalité, le plan de l'orbite lunaire est incliné d'environ 5° sur celui de l'orbite terrestre. Aussi, à la nouvelle lune, l'ombre de la lune passe-t-elle en général au-dessus ou au-dessous de la terre, et, à la pleine lune, le globe lunaire passe-t-il le plus souvent au-dessus ou au-dessous de l'ombre de la terre, ce qui réduit le nombre d'éclipses.
Selon la position de la lune par rapport au cône d'ombre de la terre, la phase de la totalité de l'éclipse dure de quelques minutes à 1 h 50 mn au maximum. Il est rare que la lune disparaisse complètement lorsqu'elle se trouve totalement plongée dans l'ombre. Notons que l'ombre de la terre étant à l'opposé du soleil, la lune ne peut la traverser qu'au moment d'une pleine lune.
Lors d'une éclipse totale, comme celle qui s'est produite dans la nuit du 26 au 27 Septembre 1996, la lune commence par pénétrer dans la pénombre par son bord et prend peu à peu une coloration grisâtre. Au bout d'une heure environ, la totalité du disque lunaire est envahie par l'ombre et sa teinte vire progressivement vers le rouge cuivré.
En effet, en traversant l'atmosphère terrestre, les rayons lumineux du soleil sont déviés (phénomène de réfraction) et pénètrent dans l'obscurité géométrique de la terre, ce qui tend à diminuer fortement la longueur du cône d'obscurité ombrale et à rapprocher le sommet du cône d'ombre bien plus près de la terre que n'est la lune. Celle-ci apparait alors faiblement éclairée même durant l'éclipse totale.
Les éclipses de lune ne sont, en moyenne, pas plus nombreuses que celles de soleil, mais contrairement à l'éclipse de soleil, elles sont visibles de n'importe quel point de la moitié de la terre où la lune se trouve plus haut que l'horizon.
Dès les premières heures du vendredi 27 Avril 1996, nous étions au rendez-vous d'une éclipse totale de lune. Elle a débuté à 1h 12mn, moment du premier contact de la lune avec la pénombre, projetée par la terre. Ensuite notre satellite naturel était totalement voilé. Vers 2h 19mn, il était totalement éclipsé. Le maximum de l'éclipse est survenu à 2h 53mn. Cette phase de l'éclipse, où la lune est apparue rougeâtre, a duré 70 minutes. Puis, à 3h 29mn, notre satellite naturel a commencé à sortir de l'ombre. A 4h 37mn, la lune était entièrement en dehors du cône d'ombre pour continuer sa rotation autour de la terre. Cette éclipse était visible sur tout le territoire national marocain.
Je saisis cette occasion pour saluer la télévision et la radio marocaine, pour l'effort déployé afin de couvrir cet évènement astronomique d'une importance majeure. Elles ont enregistré toutes les étapes de cette éclipse pour les présenter le vendredi 27 Septembre 1996, dans les bulletins d'informations du 13 heures et du 20h 30.
La prochaine éclipse de lune, qui sera cette fois-ci partielle, aura lieu le 23 Mars 1997. Par contre, celle qui se produira le 16 Septembre 1997, sera totale. Elle sera visible en Asie, en Europe, en Afrique et aussi en Australie.
Taking the occasion of the lunar eclipse of 26-27 September 1996, the author explains the phenomena associated with a lunar eclipse, detailing the colours of the moon during the various eclipse phases.
Mr Abdel Fattah A. Attia, Assistant Researcher and Electrical Engineer at the National Institute of Astronomy and Geophysics (NRIAG), in Helwan, Cairo, visited SAAO for two months to study telescope control systems in use at SAAO. The visit was arranged under the aegis of an agreement between the Egyptian Academy of Science and Technology and the South African Foundation for Research Development.
Kottamia Observatory has a 1.9-m telescope identical to the one at Sutherland. The Egyptian government has recently decided to modernize this telescope. A new mirror has been ordered from the Carl Zeiss company and is due to be installed shortly. The control system is also being modernized. Since the SAAO has an identical 1.9-m telescope, the Egyptians expressed an interest in learning how the SAAO controls its telescope. With the help of SAAO electronics technicians Mr Attia has constructed some of the electronic circuits necessary to move the Kottamia telescope. The SAAO system is only partly computer controlled in the sense that telescope pointing is invoked by the observer operating the controls. Mr Attia plans to have the Kottamia telescope under full computer control, for which additional software and circuitry will have to be constructed in Egypt.
Prof. Pius Okeke of the University of Nigeria at Nsukka, visited the SAAO and HartRAO in February to attend the Annual Review of South African Astronomy and Astrophysics. Prof. Okeke serves on the South African National Astronomy Facilities Board, which advises the Council of the Foundation for Research Development (FRD) on the performance of these national facilities and their future plans and requirements. Professor Okeke is also involved in scientific collaborations with astronomers at SAAO and HartRAO.
On Friday March 21 Case Rijsdijk, the Education Officer, of the South African Astronomical Observatory (SAAO) visited the University of Zimbabwe to establish better links between the Observatory and this University. Whilst there he met the Head of the Physics Department, Dr Martin Mushayandebvu, and Dr Francis Podmore, and discussed issues of common interest, including the annual summer school run by the SAAO in January each year.
As part of its final year Physics course the University of Zimbabwe offers three extra modules, of which students must do two. The topics covered in these modules are Astronomy, Geophysics and Meteorology.
The SAAO is trying to promote the teaching of astronomy at both senior school and tertiary level, not only in South Africa, but in southern Africa in general, and it is with this in mind that the SAAO is hoping to get one lecturer from the University of Zimbabwe to attend the annual SAAO summer school in January 1998 in Cape Town. This would enable the lecturer to acquaint him/herself with modern trends in astronomy thereby enhancing their interest in the subject and their teaching of it.
The Office for Outer Space Affairs of the United Nations has recently issued a publication titled Centres for Space Science and Technology Education dealing with educational curricula for such Centres. This UN initiative is of great interest to this Working Group as it addresses one our our principal aims, namely that of establishing a regional centre for space science technology and education. We quote from the opening paragraph of this document:
In response to the General Assembly's endorsement of the recommendation of UNISPACE 82, that the United Nations Programme on Space Applications should assist Member States in enhancing their indigenous capability at the local level, the Office for Outer Space Affairs developed a proposal for the establishment of Centres for Space Science and Technology Education in developing countries.The objective of these Centres is to enhance the capabilities of member states, including those in Africa, in different areas of space science and technology that can advance their social and economic development.This Working Group should strive to create the necessary conditions for the establishment of one of these Centres in Africa as part of a long-term programme to promote the development of the space sciences in Africa.
One of the aims of this Working Group is to identify and address the resource needs of African Space Scientists. Chief among these needs is adequate access to information processing technology.
In order to establish the levels of access to this technology the Working Group is conducting a survey of computing facilities among its members. Readers are cordially invited to participate in this survey by completing the questionnaire which is being distributed with this issue of African Skies. Additional questionnaires are available in paper or electronic form from the addresses on the cover of this publication. Information gathered from the returned questionnaires will be reported in a future issue of African Skies.
The Working Group on Space Sciences in Africa is compiling a data base of active African space scientitsts. If you are interested in being included in this inventory and/or becoming a member of the Working Group please complete the Membership/Inventory form distributed with this issue of African Skies and return it to the address given on that form. The form is also available electronically from wgssa@saao.ac.za.