widely separated along the east-west direction. Such a sharing of a satellite — which could be as large as necessary, within technological limits — would also contribute to reducing the pressure on the geostationary orbit (GSO). It is therefore suggested that: (a) Countries might examine the feasibility of using DBS to aid the spread of education, (b) Countries could explore the possibility of sharing the space segment of a DBS system, including the possibility of using any existing/planned satellites that might be suitable, (c) Studies should be undertaken to examine the feasibility of international or regional satellite system(s) for providing direct broadcast television service, (d) The United Nations and concerned specialized agencies should encourage and provide assistance — as appropriate and if requested — for the above, (e) Existing organizations such as INTELSAT may choose to consider developing broadcasting satellite systems which could be used for educational purposes. It should be noted that many countries which are now planning direct broadcast satellites intend to combine this service with telecommunications, with obvious economic advantages. Other countries — or an international satellite system — could examine the cost-effectiveness of such multimission platforms so as to increase the attractiveness of the system. Community reception will probably be — as noted earlier— the primary mode of receiving satellite television broadcasts in developing countries. Tens of thousands of receivers will be needed in each country and it is essential to reduce the cost of each installation as much as possible. Also, given the lack of rural electrification in most developing countries, it is necessary to think of power sources that are inexpensive, and preferably use renewable forms of energy rather than hydrocarbons. It is therefore desirable that strong encouragement — including financial and technical assistance, if necessary — be given to efforts aimed at developing low-cost community receivers for DBS and low-cost, preferably renewable, power sources to operate the system in unelectrified locations. Since the cost of the reception system for a given coverage area depends on the frequency and EIRP of the satellite, it is suggested that efforts at developing more powerful broadcasting satellites, within the constraints of international regulations, be pursued and encouraged. The question of frequency is a complex one, and the choice of an appropriate band involves many considerations and constraints. The ITU World Administrative Radio Conference (WARC) in 1977 agreed on an orbit/frequency assignment plan for countries in Africa, Asia and Europe for the 12 GHz Broadcast Satellite Service band. Because of existing services, space service allocations in the lower portion of the frequency spectrum are constrained by flux density limitations so as to cause no harmful interference. The absence of such constraints could have led to simpler and cheaper ground reception equipment. The importance of these bands (especially the 0.7, 2.5 and 4 GHz bands) is not merely due to the lesser technological complexities compared to higher bands, but also to the fact that they do not suffer the severe rain-attenuation that higher frequencies (e.g., 12 GHz) do — a point of particular importance to countries with high rainfall rates. It is therefore desirable that ITU study the feasibility of phasing out — in the long run — the terrestrial services in some of these bands, so that they can be assigned exclusively to satellite broadcasting and the flux density limits relaxed. In view of the existing investments and extensive spread of terrestrial networks that share these bands, any such changes would be difficult and do not seem feasible in the immediate future. Also, allowing higher radiated power from spacecraft and smaller terminals on the ground could result in decreasing the “capacity” of the GSO due to need for greater separation between satellites so as to avoid interference. However, should ITU recommend, and one of the World Administrative Radio Conferences adopt such steps, they would result in greatly reduced costs for DBS systems and provide a major stimulus to education via satellite. While considerations with regard to the hardware elements of a DBS are of obvious importance, the other “software” elements unfortunately tend to be neglected. Experience has, however, indicated that these aspects are crucial to the success of a DBS system for education. The main ones include: (a) system planning and integration; (b) organizational aspects including system management and co-ordination; (c) design and production of appropriate television programmes, relevant to the needs of the audience and in keeping with national priorities; (d) feedback and evaluation mechanisms, especially with regard to audience reac-
RkJQdWJsaXNoZXIy MTU5NjU0Mg==