The Orbital ATK Cygnus cargo ship S.S. John Glenn pulls away from the International Space Station on June 4, 2017 in this view from a NASA camera on the station exterior.

The last few days have been non-stop action for astronauts on the International Space Station, and there's still more work on the way.

Today (June 2), NASA astronauts Jack Fischer and Peggy Whitson bid farewell to a robotic Orbital ATK Cygnus cargo ship, an event that came amid four days of spaceship landings, launches, departures and arrivals.

"It's a remarkable time at the international space station. One of the busiest times of vehicle traffic in history," NASA spokesman Rob Navias said today as Fischer and Whitson worked to release the Cygnus cargo ship.

It all began on Friday (June 1), when two space station crewmembers returned to Earth on a Soyuz space capsule. Russian cosmonaut Oleg Novitskiy and French astronaut Thomas Pesquet of the European Space Agency landed in the remote steppes of Kazakhstan to end a six-month mission to the International Space Station. Their return left Whitson, Fischer and Russian cosmonaut Fyodor Yurchikhin behind on the station.

One day later, on Saturday (June 2), a SpaceX Falcon 9 rocket launched a Dragon cargo ship packed with 6,000 lbs. (2,721 kilograms) of fresh supplies toward the space station. That launch marked a major milestone for SpaceX: It's the first time the company reused a Dragon capsule (it first flew in 2014).

Then came today's Cygnus departure. The Orbital ATK cargo ship launched to the space station in mid-April to deliver 7,600 lbs. (3,500 kilograms) of supplies. It will be intentionally disposed of by burning up in Earth's atmosphere on June 11.

"This is the first time in history that two U.S. commercial cargo vehicles will be in free flight at the same time," Navias said.

But we're not done yet.

On Monday (June 5), the Dragon spacecraft that launched Saturday will arrive at the space station. Whitson and Fischer will use the station's robotic arm to capture the Dragon capsule and attach it to a berthing port so the craft can be unpacked.

According to Navias, the space station crew will get a bit of a breather after the Dragon arrival. But in 10 days, they'll see another arrival: an uncrewed Russian Progress cargo ship packed with still more supplies, he added.

Then on July 28, a new crew is scheduled to launch to the space station on a Russian Soyuz spacecraft. So, whew! There's still more space action to come this summer!

Editor's Note: This article has been corrected to reflect that NASA astronaut Jack Fischer remains on the space station, not French astronaut Thomas Pesquet.

Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik and Google+. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.