(CNN)Just days after the International Space Station’s crew reached 10 people, three are ready to return to Earth.
Russian cosmonauts Sergey Ryzhikov and Sergey Kud-Sverchkov and NASA astronaut Kate Rubins will end their 185-day mission on the space station Friday. Their departure in the Soyuz MS-17 spacecraft will air live on NASA’s TV channel and website. The hatch will close on their spacecraft at 6:10 p.m. ET Friday after the crew has bid farewell to the others on the station, and they are expected to undock from the station’s Poisk port at 9:34 p.m. ET. The trio will land at 12:56 a.m. Saturday on the Kazakhstan steppe. Kate Rubins of NASA and Sergey Ryzhikov (middle) and Sergey Kud-Sverchkov of Roscosmos will return home after spending 185 days in space.The cosmonauts will return to their training base in Star City, Russia, and Rubins will fly home to Houston.Together, the crew’s time on the station encompassed 2,960 orbits of Earth and 78.4 million miles after their arrival in October. Read MoreLots of time aboard the space stationPreviously unknown bacteria discovered on the space station could help grow plantsThis was the second flight for Rubins, which means she has now spent 300 days in space, and the second flight for Ryzhikov helped him reach 358 cumulative days. Kud-Sverchkov experienced his first spaceflight.This second spaceflight experience for Rubins included hundreds of hours working on space station experiments. She also served as an ambassador for science during calls to the space station with the National Science Foundation, National Institutes of Health and the US Centers for Disease Control and Prevention, among others. She was the first person to sequence DNA in space in 2016 and continued that work with more sequencing during her second stay on the space station. This capability could allow astronauts to diagnose illnesses while in space or even identify microbes that grow on the space station to determine whether they pose any risks. She collected samples from different locations across the space station to understand the microbiome of the space station. (The microbiome is the genetic material of the bacteria, virus and other microbes that live inside the space station, including inside its residents.) This unique environment has hosted the coming and going of hundreds of astronauts for 20 years while remaining separate from Earth. Rubins also worked on heart research to study the effects of gravity on cardiovascular cells and grew and harvested radishes to create a better understanding of plant growth in the absence of gravity.Seven crew members remainAstronauts harvest radishes grown aboard the International Space StationThe departure of Rubins, Ryzhikov and Kud-Sverchkov leaves the space station with seven crew members. This includes the newly arrived NASA astronaut Mark Vande Hei and Russian cosmonauts Oleg Novitskiy and Pyotr Dubrov, as well as the crew from the historic NASA SpaceX Crew-1 mission that arrived in November. They are NASA astronauts Victor Glover Jr., Michael Hopkins and Shannon Walker, and Japan Aerospace Exploration Agency (JAXA) astronaut Soichi Noguchi. Sign up here for Wonder Theory, our CNN science newsletterApril is a busy time on the space station, and it feels a bit like a revolving door as crews arrive and depart. On April 22, the space station’s occupancy is scheduled to grow to 11 when NASA’s SpaceX Crew-2 members, including NASA astronauts Shane Kimbrough and Megan McArthur, JAXA astronaut Akihiko Hoshide, and European Space Agency astronaut Thomas Pesquet arrive.Astronauts on the space station have prepared for the new crew by setting up extra sleep stations and freeing up ports for the arrival of new spacecraft.Then, Crew-1 is scheduled to return to Earth on April 28, leaving the space station with seven crew members again.