A human-crewed Russian spacecraft successfully docked at the International Space Station Monday, four days after its original launch date. The Soyuz MS-25 spacecraft delivered NASA astronaut Tracy Dyson, Belarusian cosmonaut Marina Vasilevskaya, and experienced Russian cosmonaut Oleg Novitsky to the orbiting outpost. The trio blasted off from the Baikonur spaceport in Kazakhstan on Saturday for a two-day journey to join seven other crew members of Expedition 70 at the station.

The original launch date was Thursday, but due to a technical issue, it was scrubbed on the launchpad. Engineers took a day to review telemetry and replace suspect batteries, which allowed a second attempt on Saturday.

Upon reaching the ISS, the Soyuz will attach to the Prichal docking module on the station’s Russian segment. It is scheduled to arrive at 11:09 a.m. ET and will be welcomed by ISS Commander Oleg Kononenko, cosmonauts Nikolai Chub and Alexander Grebenkin, and astronauts Michael Barratt, Matthew Dominick, and Jeanette Epps.

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The Soyuz is carrying cargo for the ISS, including food and supplies. It also includes a number of experiments that the station’s new crew will conduct. One of the experiments involves studying how water and other particles behave in the ISS’s microgravity environment. The results could be applied to Earth’s water resources and help scientists develop strategies for preserving oceans and lakes in the face of climate change.

Another experiment uses an ultraviolet laser to study the composition of atmospheric gases. The research could eventually lead to a better understanding of global pollution and how it impacts human health, allowing experts to create strategies for cleaner air.

Russia’s space agency says the new crew will spend the next six months at the station and return in September in the identical Soyuz spacecraft with Novitsky and Vasilevskaya. Dyson is replacing cosmonaut Loral O’Hara, who launched at the station in December. O’Hara will come home in the older Soyuz MS-24, which she shared with Novitsky and Vasilevskaya last year.

Russia’s Soyuz rockets have a reputation for reliability and are currently the only way to get to the ISS. However, the space program has become a flashpoint of tension between the United States and Russia over Moscow’s actions in Ukraine and other geopolitical issues. The US plans to replace the Soyuz with an American-built capsule in 2023. Meanwhile, an uncrewed SpaceX Dragon cargo ship will dock at the ISS on Thursday, bringing supplies and experiments.