On May 4, 1976, NASA sent into orbit a very unusual satellite called LAGEOS (LAser GEOdynamics Satellite, pictured). He had no electronics, motors or power supplies on board. In fact, it is just a brass ball with a diameter of 60 cm and a mass of 407 kg with an aluminum coating. On the ball, 426 corner reflectors are evenly located, of which 422 are filled with fused quartz, and 4 are made of germanium (for infrared radiation). The satellite entered orbit 5860 km, where it will rotate for the next 8.4 million years, keeping a plate with a message to descendants from a group of scientists led by Carl Sagan.
On October 22, 1992, a similar satellite LAGEOS-2 was launched, built by the Italian Space Agency (orbit altitude 5620 km). As you might guess from the design and materials used, these passive satellites have a single role – to reflect the laser beam. Laser ranging is performed from dozens of observation points of the International Laser Ranging Service, which has more than 40 stations around the world.
The international scientific community is now planning to build a third such satellite, LAGEOS-3, which will make laser ranging much more accurate than its predecessors.
Unfortunately, Russia does not participate in this international project. But it is going to launch its own two satellites-reflectors made of glass “Blitz-M”, a thousand times more accurate than foreign ones, the newspaper Izvestia writes.
LAGEOS-3 is a joint international program that will be the result of collaboration between scientists from France, Germany, Great Britain, Italy, Spain and the USA. According to the plans of the developers, LAGEOS-3 will allow for the first time in history to measure the quasi-stationary property of the Earth – the gravitational magnetic dipole moment predicted by Einstein’s General Theory of Relativity.
In 2009, Russia also launched its first reflector satellite called BLITS (Ball of the Lens In The Space). The glass sphere is placed in an orbit with an altitude of 800 km. However, in 2013, the satellite crashed after colliding with a debris from another spacecraft. Presumably, it was a fragment of the Chinese meteorological spacecraft Fengyun-1C, on which Beijing tested its anti-satellite weapons in 2007. Or the wreckage of two communication satellites Russia and the United States, which collided in 2009. According to NASA, now a third of all space debris in orbit was formed as a result of these two incidents in 2007 and 2009, and there is a lot of debris at an altitude of 800 km.
The upgraded Blitz-M devices will be a continuation of the Blitz project. They have a larger diameter (220 mm) and mass (16.56 kg) than that of the first satellite (170 mm and 7.53 kg). In addition, they will be launched into a higher orbit of 1,500 km.
“These specialized satellites and laser reflectors, which are produced in our country, are the best in the world,” Aleksandr Ipatov, scientific director of the Institute of Applied Astronomy, said in a comment to Izvestia. – It is not for nothing that our reflectors are installed on foreign devices. The main function of “Blitz-M” is to create the most accurate coordinate system on Earth. The difficulty is that the core of our planet is liquid and changes its position. Binding a coordinate system to the geocenter of the Earth is the most difficult thing. Current measurements with lasers and radio interferometry differ by 6 cm. Nobody knows why. “
Glass balls will help clarify the model of the Earth’s gravitational field and its effect on the orbits of spacecraft. Consequently, they will improve the accuracy of satellite positioning systems such as GPS and GLONASS. In addition, these data will clarify the models of tectonic plate movement, which means that it will be possible to predict earthquakes more reliably.
Russian satellites will ensure the reflection of the laser signal with an error of no more than 0.1 mm. This is a thousand times higher accuracy than LAGEOS, noted in the Precision Instrumentation Systems Research and Production Corporation. It was there that the technology for ultra-precise production of multilayer spherical lenses was developed and three spherical space satellites were released (two will be sent into orbit, one will remain on Earth as a test specimen).
Thus, Russian reflector satellites will help refine the International Terrestrial Reference System (ITRS), which is referenced to the Earth’s center of mass. Refinement of the ITRS will also help to clarify the Russian system of earth coordinates PZ-90 (Earth Parameters 1990) – a system of geodetic parameters, including fundamental geodetic constants, parameters of a common terrestrial ellipsoid, parameters of the Earth’s gravitational field, geocentric coordinate system and parameters of its connection with other coordinate systems (see scientific brochure “Earth parameters of 1990” published by the Military Topographic Directorate of the General Staff of the Armed Forces of the Russian Federation).
Geodetic constants and parameters of the common terrestrial ellipsoid PZ 90.02
Two Russian satellites “Blitz-M” are planned to be launched together with the spacecraft of the “Gonets” system in October 2018.