Washington, Oct 26 (IANS) Astronauts aboard the International Space Station have started planting their third on-orbit crop of red romaine lettuce, NASA said.

"Early this morning, NASA astronaut Shane Kimbrough initiated the Veg-03 experiment, one of his first science assignments as a new crew member aboard the orbiting laboratory," the US space agency said in a statement on Wednesday.

Astronomers are using a plant growth system called "Veggie" for their experiment.

The Veg-03 crop will be the Veggie team's first on-orbit attempt at a new, repetitive harvest technique termed ‘Cut-and-Come-Again'.

"Once the plants are approximately four weeks old, a selection of leaves can be harvested for a bit of fresh lettuce and possibly science samples. Meanwhile, some leaves are left intact along with the core of the plant, and will continue to grow and produce more leaves," explained said Nicole Dufour, NASA's Veggie project manager. 

"We expect this will increase the on-orbit crop yield, as well as allow for more opportunities to supplement our astronauts' diets with fresh, nutritious food from the same plants, which is an important goal of the ‘pick-and-eat' food concept," Dufour noted.

The team is anxiously awaiting germination results, expected early next week, Dufour said.

Astronauts on future long-duration space missions will need to be able to grow their own food to supplement their diets. 

Using the Veggie plant growth facility aboard the station, Veg-03 builds on the successes of previous studies, including Veg-01, which resulted in the first-ever on-orbit harvest and sampling of fresh produce during the summer of 2015. 

Techniques learned from Veggie crops will help NASA prepare for the Journey to Mars.