First glimpse at a comet’s nucleus through Hungarian eyes

The Venera–Halley (VEGA) program remains the largest Hungarian space physics undertaking to this day. About one-third of the onboard instruments were built in Hungary, primarily at the Central Research Institute for Physics (KFKI), especially within its Institute for Particle and Nuclear Physics (RMKI)—a predecessor of the HUN-REN Wigner Research Centre for Physics—and at the Budapest University of Technology (BME).

Particularly outstanding was the Hungarian-developed television system (TVS), which was the first in the world not only to capture images of a comet’s nucleus but also to independently recognize and track it, automatically directing the instruments toward it. This marked the first time a space device operation was based on real-time image processing without human intervention. Researchers at RMKI also created the TÜNDE (Hungarian for “fairy”) charged particle detector. Another detector for plasma studies, PLAZMAG, was developed under the leadership of the Institute for Atomic Energy Research of KFKI, with contributions from the Budapest University of Technology and the Space Research Institute (IKI). (The Institute for Atomic Energy Research has since been integrated into the HUN-REN Centre for Energy Research.) The BLISZI onboard data collection unit was developed by space researchers at the Budapest University of Technology, as was the power supply system for the Hungarian scientific instruments.

Comets orbit the Sun as time capsules preserving the memory of the formation of the solar system. These celestial bodies, typically a few kilometres in diameter, consist of frozen dust, ice, and gases. Sometimes the gravitational influence of larger bodies, such as planets or stars, displaces them from their usual orbits. When they approach the Sun, their surfaces heat up, causing them to emit spectacular tails of gas and dust, called coma.

The elliptical orbit of Halley’s Comet was first calculated by the 17th-century English astronomer Edmond Halley. According to his calculations, the comet, eventually named after him, approaches Earth approximately every 76 years. During its 1986 appearance, the VEGA probes flew within just a few thousand kilometres of it, but due to their opposing trajectories, they had barely an hour to carry out measurements. Thanks to the trajectory data provided by the VEGA probes, the ESA’s Giotto spacecraft, which followed them, was able to get even closer to the comet’s nucleus.

The measurements yielded surprising results: contrary to previous theories, the comet’s nucleus is not spherical but elongated, resembling a potato, and its surface is almost completely black. Several tons of dust and gas erupted from the nucleus every second, about 80 percent of which was water vapour, but researchers also detected carbon dioxide, ammonia, and methane.

The international success of the VEGA program was enormous. Influential American newspapers such as The Washington Post and The New York Times described it as one of the most impactful Soviet space missions since Sputnik, highlighting the role of Hungarian researchers. The prestigious scientific journal Nature published the results in a special issue; of the 15 articles, six included co-authors from KFKI and the Budapest University of Technology. The Hungarian researchers involved in the project (five from KFKI and three from the university) were awarded the State Prize in 1986, the predecessor of today’s Széchenyi Prize.