Development of satellite technology in Bulgaria
Satellite technologies are particularly significant in our modern times. Their application starts from the distribution of media content and develops to providing internet connectivity, communications, earth observation, navigation/GPS, technological developments, supporting vital services in various sectors including agriculture, banking and transport. Satellite technologies help save lives during emergencies and disasters, provide important environmental information and support urban planning.
Despite their diverse applications, all satellite technologies depend on one key factor, namely the availability of radio frequencies that are protected from receiving harmful interference. The International Telecommunication Union is the UN specialised agency that works globally to ensure sustainable and equitable access to radio frequency resources, satellite assignments in outer space and to resolve disputed situations. It is important to seek ways to overcome attempts to infringe the right of access to the radio spectrum, which, as a global natural resource, belongs to all countries.
The protection of the frequency resource for the first Bulgarian satellite in geostationary orbit BulgariaSat is a classic example in this respect.
The dream of a Bulgarian communications satellite was born long ago, at the dawn of satellite communications, when the first satellite rose in the starry sky in 1957. First the research satellite "Bulgaria 1300" was born in 1981. Securing a frequency resource for a large communications satellite requires a lot of effort from many people and exceptional assistance from the International Telecommunication Union, celebrating its 160th anniversary in 2025. As early as 1977 at the World Administrative Radio Conference (WARC-77) 1.2°W position of the geostationary orbit (GSO) was designated for use for Bulgaria jointly with 5 other countries and only in the satellite television broadcasting band, with only 5 channels with a bandwidth of 27 MHz and for national coverage only. In 1983, a plan for the use of the frequency resources under Annex 30B of the International Radio Regulations for FSS use in the C and Ku-bands was also drawn up, but a different position was defined for Bulgaria and also only for national coverage.
Each country, by protecting the interests of its satellite operator(s), shall apply to the Radio Communications Bureau of the International Telecommunication Union for the required radio frequency resource from the most appropriate GSO position and coverage for its interests. In 2010, BulgariaSat made a request for a radio frequency resource at position 1.9°E. Given the constraints on the use of the sector around this BSS position for Area 1, as well as the overloaded GSO sector around this position, the BulgariaSat had to defend the requested frequency resource as much as possible to make possible and efficient use of the satellite. The active participation in the ITU-R forums (Preparatory Conferences and World Radio Conferences in 2012, 2015 and 2019), as well as in the work of the ITU-R Working Party 4A of the Radio Communications Bureau on the efficient use of spectrum and orbital resources for FSS and BSS, led to proposals from the Bulgarian side for:
¨ Amendment to Annex 7 to Appendix 30 of the Radio Regulations, which would allow for the approval of the stated position 1.9°i.d.;
¨ Amendment approved in 2015 as version 1 of Recommendation ITU-R S.1717 (Annex 2 added for electronic presentation of a measured azimuth and elevation antenna pattern of a receiving earth station (RES)), and
¨ Adoption in 2014 of a new Recommendation ITU-R BO.2063 for an alternative radiation pattern of a BSS earth station antenna in the 12 GHz band with an effective radiation aperture of 55-75 cm.
These efforts lead to the successful launch of BulgariaSat and its positioning at the requested orbital position. The two additions to the range of the Radio Communications Bureau recommendations in the field of satellite radio services contribute to a more efficient use of the available radio frequency resource for them and in particular to the protection of the requested resource for BulgariaSat.
During the years of protecting frequency resources for BulgariaSat, assistance has been provided by employees of the Radio Communications Bureau: Vera Dimitrova, a former employee of the Communications Regulation Commission, Violeta Milcheva and Nedyalko Milchev, who previously worked at NIIS-Sofia, and especially by the staff of the Radio Communications Bureau of ITU-R Space Plans Systems Division, Mr. Nick Sinanis, Advisor to the SG4 (Space Services) Research Group, and Mr. Jack Wengrenick, Honorary Chair of Working Group WP-4A (Efficient orbit/spectrum utilization for FSS and BSS), and others.
Satellite technology is constantly evolving and in recent years we have witnessed the rise of small satellites in low Earth orbit. They have their progressive development also in Bulgaria.
The first Bulgarian nanosatellite in non-geostationary low Earth orbit, ENDUROSAT ONE, was launched on 21 May 2018 with an orbital altitude of about 400 km - an orbit with an inclination of about 51 degrees. Its mission is non-commercial, for purely educational purposes, and the frequencies used to communicate with it are in the designated bands for amateur-satellite radio service in the UHF band. ENDUROSAT ONE beacon data are freely intercepted by amateurs worldwide.
In 2021, the Bulgarian SPARTAN satellite followed ENDUROSAT ONE, and after its launch, on 21 July, it was positioned in a sun-synchronous orbit with an altitude of about 500 km. SPARTAN is a test satellite with a mission - a technology demonstration of EnduroSat's software-defined platform and a demonstration of the operation of communication devices in the UHF, S and X-bands.
The first Bulgarian satellite in low Earth orbit with an Earth exploration mission: the PLATFORM-1, was launched the following year on 25 May 2022 and repositioned at an orbital altitude of about 500 km. PLATFORM-1 is a commercial satellite equipped with three Earth exploration cameras and communication modules using frequency assignments in the UHF and X-bands. The satellite has not yet completed its mission and continues to send to the Earth information about our planet.
On November 11, 2023, another small Bulgarian satellite was launched into a sun-synchronous non-geostationary low Earth orbit - PLATFORM-5, and, like its predecessors, it is also positioned at an orbital altitude of about 500 km. PLATFORM-5 is a test satellite with a mission - a technology demonstration for space navigation using frequency assignments for communication with Earth in UHF and S-bands and is the first one of a small constellation of 8 satellites with independent missions in non-geostationary low Earth orbit - SHAREDSAT_22, planned by EnduroSat Trading. After the successful completion of its mission, PLATFORM-5 re-entered the Earth's atmosphere this year.
The newest Bulgarian satellite in non-geostationary low Earth orbit - BALKAN-1 was launched on 14 January 2025. It is the first satellite of another planned constellation of EnduroSat Trading - BALKAN SENTINEL, consisting of more than 100 satellites in low Earth orbit in its final stage. BALKAN-1 is also positioned at 500 km. orbital altitude and is equipped with a multispectral camera and communication modules operating in UHF, S and X-bands. BALKAN-1's mission is to provide images to the European Union's Space Programme “Copernicus”, which are critical for monitoring agriculture and forestry, land cover change management, climate impacts, as well as biodiversity and vegetation monitoring.
The next satellite of the BALKAN-2 constellation is already in preparation for its launch into orbit by the end of 2025.
The aim of the new Bulgarian satellite constellation BALKAN SENTINEL, which has been planned, is to create a single platform where end users will be able to receive, analyse and disseminate data from space. Thanks to its extremely powerful data processing capabilities already on board the satellite, the new system will enable the collection of valuable datasets from sensors launched into orbit, and this in turn will enable the possibility to conduct unique analyses of the collected information and to improve Earth observation systems. The services it would provide would open up new opportunities for regional business in many sectors of the economy as transport and logistics, energy, ecology, infrastructure among others.