The first geostationary satellites were subject to a number of constraints stemming both from the relatively modest performance of the technique available at the time and from the payload capacity of the launchers used. Such constraints were either technological, eg, the modest power levels of the onboard transmitters or the highest usable frequency, or else economic, particularly the cost of placing a kilogram of satellite in geostationary orbit. At the time, these factors entailed the use of high-performance costly ground stations, which could be operated economically only for long-distance (intercontinental) communications between major traffic centres.