A private, unmanned spaceship heads to the International Space Station Sunday, and along the way, it will test a new Canadian technology that will be critical to future missions.

Orbital Sciences Corp.'s Cygnus cargo spacecraft was rescheduled Friday to launch from NASA's Wallops Flight Facility in Virginia on Sunday at 12:52 p.m. ET. It's expected to arrive at the space station Wednesday carrying 1,360 kilograms of science experiments, spare parts, food and other supplies. 

As it approaches the space station, it will test a system built by Ottawa-based technology firm Neptec Design Group Ltd., designed to guide it to dock at the space station.

Cygnus spacecraft with TriDAR

The TriDAR will be the primary guidance system for later Cygnus flights. Two of the systems have already been installed on the next spacecraft. (Neptec Design Group)

"It will be the guidance system, the eyes that will drive the thrusters, telling them where to go," said Mike Kearns, president of space systems for Neptec, in an interview with CBC News ahead of the launch.

"Obviously, it's very exciting…. Seeing it actually fly in space is what we're in business for."

On this mission, the Cygnus spacecraft will carry a single Neptec TriDAR automated rendezvous and docking sensor, mainly for testing. It will act as a backup to another guidance system.

But on future missions, Cygnus will carry two TriDAR units each (one as a backup), and will use them as the main sensors that guide the spacecraft to dock at the space station.

Dulles, Va.-based Orbital has a $1.9-billion NASA contract to conduct eight launches to deliver cargo to the International Space Station using its unmanned Cygnus cargo ships. It delivered its first official commercial load in January, but Neptec's system wasn't aboard that flight.

Cygnus also completed a demonstration mission last September.

Bouncing lasers

Neptec's TriDAR works in a way that is similar to a radar or sonar, but instead of bouncing radio or sound waves off objects to detect their shape and location, it bounces lasers. It then compares the object it detected to a computer model of the space station in its memory, in order to direct the spacecraft how to orient itself.

All that has to be done very precisely, Kearns said.

TriDAR thermal tests

Each TriDAR unit undergoes rigorous testing before being installed on the Cygnus spacecraft, including thermal testing at extremely hot and cold temperatures. (Neptec Design Group)

"In space, vehicles are moving at an incredible speed," he said. "You just don't want one to bang into the other."

Most automated guidance systems help a spacecraft dock by looking for a "target" — a specific pattern such as a group of black-and-white polka dots stuck onto the side of an object like the International Space Station. But that has disadvantages, Kearns said.

"They degrade, things happen…. They're expensive to put on because you've got to get them absolutely accurate."

Because the TriDAR system relies on an object's shape, it doesn't need targets. That makes it far more flexible.

Kearns forsees that it could be used for more than just docking. For example, it could scan a large chunk of space junk such as an old satellite to generate a 3D model for its on-board computer, then use that model to guide a spacecraft to remove it, he said.

For Cygnus, however, the system will be used to guide the spacecraft to a "berthing box" — a region about 12 metres away from the space station, where it will sit and wait for the station's Canadarm2 robotic arm to pick it up and pull it into a docking port.

Kearns said the TriDAR system is fully capable of guiding the spacecraft directly to the docking port, but NASA has chosen not to allow that.

After Cygnus has been unloaded, it will be filled with garbage, leave the space station and burn up in the Earth's atmosphere — unlike the reusable Dragon capsule from Orbital's competitor SpaceX, the Cygnus is not designed to return to Earth.

Disposable spaceship

The TriDAR will burn up with the spacecraft, so Neptec needs to build and test new units for each of the next six flights.

The two for the next flight have already been installed, after being tested for their ability to withstand pressures such as extreme hot and cold temperatures, the vacuum of space, high radiation levels and forceful vibrations or shocks.

Neptec was contracted by Orbital to build a guidance system for Cygnus following  tests on three NASA space shuttle flights.

The first version of the device was developed for an unmanned mission to repair the Hubble telescope, which was later scrapped in favour of a manned mission. Neptec received development money from both NASA and the Canadian Space Agency.

The Canadian Space Agency said in an emailed statement that the use of the TriDAR on the Cygnus mission "illustrates how an initial investment by the Canadian Space Agency to develop innovative space technologies can lead to a made-in-Canada commercial success story. "

The mission will not count toward Canada's space station credits, which are traded in for astronaut trips to the space station. Canada used up most of its existing credits during Chris Hadfield's five-month trip.