A Soyuz 2.1b rocket launched from Site 1S at Vostochny Cosmodrome in Russia, carrying two Ionosfera-M satellites into a Sun-synchronous orbit. Launch took place on Friday, July 25, at 05:54 UTC and saw Soyuz fly on a northern trajectory over vast but sparsely populated territory.
The Ionosfera-M no. 3 and no. 4 satellites are flying to a circular orbit around 800 km altitude on a Fregat-M upper stage to complete the four-satellite Ionosfera science satellite constellation. The Ionosfera-M no. 1 and no. 2 satellites were launched in November 2024 aboard a similar Soyuz/Fregat launch vehicle from Vostochny.
The Soyuz rocket carried 18 secondary payloads on this flight, with 17 of them being Russian and one from the Iranian Space Agency. One of the Russian satellites is a 16U CubeSat, while 16 3U CubeSats flew for three different Russian commercial organizations. Iran’s Nahid-2 telecommunications satellite was also launched.
The Soyuz 2.1b/Fregat-M vehicle for the Ionosfera 3/4 mission during processing. (Credit: TSENKI)
This flight was only the third Soyuz 2.1b flight of 2025 and the first launch of the year from Vostochny. Russia developed the Vostochny Cosmodrome as a domestic alternative to the Baikonur Cosmodrome in Kazakhstan. Russia is leasing the cosmodrome from the Kazakh government, paying $115 million USD per year to lease Baikonur until 2050.
Roscosmos initiated the Ionosfera-M constellation as part of Project Ionozond, a program designed to study the geophysical environment around Earth as well as space weather and its effects on our planet. Four Ionosfera satellites were developed and procured for these studies, while a fifth satellite was also proposed.
The fifth satellite for this project, known as Zond-M, is designed to observe the Sun from a Sun-synchronous orbit (SSO) around Earth. However, the Zond-M portion of the project was suspended in late 2024 due to budget cuts. Roscosmos has faced funding shortfalls in recent years due to the Russian invasion of Ukraine and its demands on the country’s resources.
The overall Ionozond project is managed by Roscosmos in cooperation with the All-Russian Scientific Research Institute of Electromechanics (JSC VNIIEM), the Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet), and the Russian Academy of Sciences. Roshydromet will use data from Ionosfera-M for space weather forecasting, while JSC VNIIEM developed and built the satellites.
The Ionosfera satellites, each massing roughly 400 kg, are designed for an eight-year service life. The first pair of Ionosfera satellites was launched into SSO with an ascending node corresponding to roughly 21:00 hours on the evening terminator of Earth, while the second pair was launched into an orbital plane 90 degrees away from the first pair.
The Ionosfera-M 3 and 4 satellites during processing. (Credit: TSENKI)
The second pair is orbiting along a line corresponding to the afternoon hours — roughly 15:00 hours — at the orbit’s ascending node. This will enable the overall constellation to collect measurements of Earth’s ionosphere at different times of the day. The measurements will be obtained by nine instruments aboard each spacecraft.
These instruments include four spectrometers, a short-wave sounder, a magnetometer, an energetic particle sensor, and a radio-wave sounder. The Ionospheric Plasma Energy Spectrometer (ESIP), the Plasma and Energetic Radiation Spectrometer (SPER/1), the Galactic Cosmic Ray Spectrometer (GALS/1), and the Gamma Spectrometer (SG/1) will study different aspects of the ionosphere’s plasma, particles, and radiation.
ESIP will measure the ionospheric plasma and study the ionosphere’s structure, while SPER/1 will measure differential energy spectra of low-energy electrons and protons. GALS/1 will measure proton flux energy as well as total proton and electron fluxes, while SG/1 will study hard X-ray and gamma radiation in Earth’s atmosphere.
In addition to the four spectrometers, five other instruments will take complementary measurements. The Ozonometer-TM short-wave sounder will measure solar ultraviolet (UV) radiation reflected by Earth’s atmosphere, while the low-frequency wave complex (NVK2) magnetometer will measure magnetic and electric fields of near-Earth space.
An Ionosfera satellite in processing. (Credit: TSENKI)
The GPS total electron content receiver (PES) will observe the altitude distribution of electrons in Earth’s ionosphere, and the Laertes radio wave sounder will measure electron density and total electron content. In addition, a dual-frequency beacon (MAYAK) will probe Earth’s ionosphere with emphasis on the region not accessible by satellites.
Though the Ionosfera satellites will not communicate with each other, they will use an onboard science and data collection system to store and transmit the science data obtained by the satellites to ground stations in Russia. The ESIP, SPER/1, GALS/1, SG/1, Ozonometer-TM, NVK2, PES, Laertes, and MAYAK instruments are present on all four spacecraft.
Earth’s atmosphere is divided into several layers, with the troposphere being the lowest atmospheric layer and extending from sea level up to roughly 10 km altitude. The stratosphere extends from approximately 10 km to 50 km in altitude and contains Earth’s protective ozone layer.
Illustration of the layers of the Earth’s atmosphere. (Credit: NASA)
After the stratosphere comes the mesosphere, which extends to roughly 85 km in altitude, and from there, the thermosphere rises to altitudes of 500 to 1000 km. Most meteors burn up in the mesosphere as they impact Earth’s atmosphere at high velocities.
The thermosphere absorbs high-energy X-rays and UV radiation, and many satellites, including the International Space Station, orbit within the thermosphere. Finally, the exosphere is where Earth’s atmosphere fizzles into space, reaching up to 190,000 km from Earth’s surface — half the distance to the Moon.
The ionosphere, extending roughly from 80 km to 650 km in altitude, is a set of layers in the mesosphere and thermosphere where high-energy solar radiation strips electrons from atoms and molecules. These atoms and molecules become electrically charged ions as a result, and the ionized layers of the atmosphere not only create aurorae during solar storms but also affect radio and navigation signals.
Soyuz 2.1b rolls out to Site 1S at Vostochny. (Credit: Roscosmos)
The Ionosfera-M constellation is the latest effort by space agencies to study the ionosphere, which was discovered in 1902 when Guglielmo Marconi conducted radio experiments. While the Soviet Union flew missions to study the ionosphere as part of its Kosmos series of satellites, Ionosfera-M marks the first major Russian effort to study space weather in many years.
(Lead image: A Soyuz 2.1b with a Fregat-M upper stage on the pad at Vostochny Cosmodrome ahead of the Ionosfera-M 3/4 launch. Credit: Roscosmos)
