Sitting in a side hangar of the Canada Aviation and Space Museum (CASM) is a special preservation project: an airplane that is the direct ancestor of the forthcoming RADARSAT Constellation Mission (RCM) that will launch in the coming months, upgrading RADARSAT-2’s capability with a trio of satellites.
Long before the RADARSAT series of satellites launched into space, long before Canadians got used to the images that are used for disaster relief, resource surveys, crop tracking, and ocean and sea-ice reconnaissance, the Convair 580 ran test flights of imaging radar equipment to see if the concept was suitable for space.
The Convair actually began its life as a commercial airliner for American Airlines before being converted to an executive transport for the Johnson & Johnson company in the 1958. Several other owners followed. In 1974, its mission changed permanently to an experimental radar remote sensing research for The Canada Centre for Remote Sensing (1974-1996) and finally Environment Canada (from 1996) – a mission it performed until 2010.
The museum’s David Pantalony says Canadians are lucky to have the entire aircraft preserved. There is only so much floor space available at the museum, so conservators need to make tough choices when presented with interesting aircraft. This one, though, got everyone’s attention. It was because of the Convair that RADARSAT-1’s instruments were so successful in space after launching in 1995.
“We realized that the whole aircraft was a big part of the story, as well as the community around that aircraft,” said Pantalony, a curator of physical sciences and medicine. “All the places they had been in the aircraft, as a unit, we realized that was a big part of the story. So that started the process.”
The Convair’s contribution to spaceborne remote sensing was considerable. In the early 1980s, an era when Canada’s astronaut program didn’t even exist, the European Space Agency put out a call for demonstrations of the potential of imaging technology for satellite systems. ESA reached out to all of its members, including Canada (which has associate membership) and fell under the enchantment of Convair, which already had several years of radar testing under its belt.
“It speaks to the time when we were a little bit ahead of the game in terms of being able to offer operational facilities to help a lot of other people who were also interested in this space technology,” said Laurence Gray, who back then was an advocate for imaging radar.
While the United States deployed the SeaSat-1 mission in 1978 – a satellite with radar capability that lasted for about 100 days – the country was mostly interested in using radar for military applications, according to Gray. It was the Europeans and the Canadians who were more interested in working on civilian radars, Gray said.
Given Canada’s big landmass, remote sensing was a natural fit. It was costly and thus impractical to keep an eye on all of the country’s large northern borders by plane, and it was difficult to monitor sea ice or environmental conditions over large areas without the benefit of a satellite anyway. In general, airborne radars of the era mapped the sea ice in critical regions of the Arctic to help with marine operations, while geologists and others also made use of this technology for natural resource mapping.
Gray was part of the Canada Centre for Remote Sensing, working with contracting companies (such as MDA) and other Government agencies to make sure future RADARSAT images would satisfy the observational requirements. The first product was the C-band airborne radar that served as a precursor to RADARSAT-1. This behemoth of an instrument took most of the seating space in the back of the aircraft, and required several crew stations for operation and data recording.
“One of the obvious areas [of application] was in Arctic ice reconnaissance, showing that we could map different sea-ice types, differentiate between sea-ice and open water, and detect the presence of thicker, stronger ‘multi-year’ ice” Gray said.
Like any technology, the radar did not stay static in terms of its capabilities. Within a couple of years of initial delivery, for example, it was changed to include an X-band channel and multi polarization. Also, additional antennas were added to improve the radar’s ability in mapping and moving target detection. The system required real-time motion compensation to account for the rolling of the aircraft. “This was a big deal, this evolution of the hardware,” said Bob Hawkins, a former member of the team that did calibration and processing.
The RADARSAT-1 team also needed to manage expectations for what it could do, compared to the aircraft. The twin-propeller plane flew much closer to the ground and produced good resolution images with a high signal-to-noise ratio. That’s not as easy from an altitude of 800 km (roughly the orbit of RADARSAT-1).
“The RADARSAT-1 team had to struggle with managing expectations from clients and what the could deliver,” Hawkins said. This equally held true for data processing, which needed to be robust and consistent, as well as turned around quickly.
The Convair performed its mission well into the RADARSAT-2 era, wrapping up operations in 2010. It arrived at the museum in 2015. Despite the fact that the aircraft was delivered to CASM in good condition, the preservation team seeks to restore its equipment configuration as well as finding ways to keep its history and science legacy before the public.
At first, the flying team worried the museum wouldn’t take the whole aircraft and would focus on only the radar equipment. The Convair was unique among radar-sensing aircraft, the volunteers say, because the whole thing acted as an integrated unit with a dedicated aircraft. NASA’s Jet Propulsion Laboratory used a Convair 990 and later, a DC-8 to perform the same work, they say – but after each mission, the equipment was removed so the airplane could perform different science research.
Pantalony pointed to conservation advantages the museum gained by bringing in the whole aircraft, such as having the research equipment portrayed in context. Also, the volunteers have experience with the software used for running the research, which means that the software can also be preserved. There is no real end date for the work, but as the project progresses visitors can take a look at the Convair during times when the ancillary hangar is open for visitors. In the future, the museum may also take 360-degree photos of the interior to post on the website.