MacLean's five-year-mandate was due to expire at the end of August, but he announced earlier this month that he would leave on Feb. 1.
The 58-year-old former astronaut and laser physicist is quitting to take up a position in a new venture tied to quantum physics in Waterloo, Ont.
MacLean has not granted any interviews to discuss his departure, but insiders suggest he is leaving because space policy has never advanced under the Harper government.
The government did not respond to an interview request. However, it said in an email that it plays a crucial role in the development of the Canadian space sector and remains committed to the Canadian Space Agency.
"We received a strong mandate to manage the economy and we're working to deliver world-class space programs in a cost effective way," said the note from Industry Canada.
One of MacLean's predecessors was surprised by news of MacLean's departure.
Former astronaut-turned politician Marc Garneau, now an opponent of the Harper government, said he didn't see the move coming.
The Liberal leadership candidate, a former CSA president, pointed out that MacLean first brought forward a long-term space plan in 2009 but the government never acted on it.
"I never saw anything come out and Steve went through three (industry) ministers — it never went anywhere," Garneau told The Canadian Press.
"In the space business, you need to be able to plan on five- to 10-year horizons and this would have defined in many ways what the main missions of the Canadian Space Agency were."
Last February, the space sector was only part of a broad review of the aerospace industry commissioned by the Conservative government.
Former cabinet minister David Emerson, the head of the review, was blunt when he issued his report in November.
He said the Canadian space program had "floundered" over the last decade.
"There's been some lack of clarity around priorities and uneven performance in the implementation of projects," he said at the time.
The treasurer for the Canadian Space Commerce Association, an industry group, lamented in an interview that the CSA was never treated as a full partner by the government.
Chuck Black said that much was clear on Jan. 9, when Industry Minister Christian Paradis finally announced plans to move forward with the construction of the multi-satellite RADARSAT Constellation Mission.
A $706-million deal was signed with MacDonald, Dettwiler and Associates (MDA) to build and launch three satellites in 2018.
MDA eventually agreed to a fixed contract with the government but, because of delays reaching that RCM agreement, the company said it was forced to lay off some employees. Sub-contractor COM-DEV International of Cambridge. Ont., also laid off workers because of the uncertainty surrounding funding.
The delays helped increase the final cost of the project, from $600 million to more than $1 billion.
MacLean attended the January announcement along with Industry Minister Christian Paradis, but Black said the Canadian Space Agency was perceived as just being along for the ride. Black said the agency was not involved in doling out the contract, which went from Industry Canada to MDA.
Less than a week later, the soft-spoken MacLean announced he was quitting.
"He's leaving with six months left in his mandate and, well, he's voting with his feet and he's out of there," Black said.
The state of the country's space industry even prompted the president of the Canadian Space Society, an association of sector professionals, to leave the country for a job in Germany.
"There was nothing going on in Canada," Kevin Shortt, the former president, said in an interview from Munich.
"There was a lot of uncertainty in the future in terms of what projects were going to be happening and generating business with the Canadian Space agency."
Shortt said good jobs were becoming scarce in Canada and, when the opportunity came up in May 2012 to work with the German Aerospace Center, he just had to take it.
He said he now never hears about the Canadian Space Agency in conversation with European colleagues; although, he said, private-sector Canadian firms are getting noticed for developing new technologies.
He said he believed the Ottawa-born MacLean was also frustrated at the CSA. Shortt met regularly with the CSA boss during his four-year term as space society president.
"I mean, Steve is a man of action who wants to see things happen and I think, from Day One, the deck was stacked against him," Shortt said.
"Here we are five years later and the industry is still without a long-term space plan so I feel bad for him in that respect."
Shortt said the government sent MacLean's long-term plan back for several revisions but never signed off on it. It then decided to do its own review, which led to the Emerson report.
On the positive side, Short said MacLean did manage to do some restructuring at the CSA to make it leaner.
Among others who had praise for MacLean was former astronaut Bob Thirsk, who described his fellow space traveller as "a very accomplished individual with a strong work ethic."
Thirsk, who is now a vice-president at the Canadian Institutes of Health Research, wouldn't discuss the possibility of replacing MacLean.
"I am completely committed to my current position (but) of course, I will also retain a strong interest in the plans and initiatives of the CSA," he said in an email.
Julie Payette, who is still a member of the Canadian astronaut corps, has been mentioned as a possible successor to MacLean.
In an email from Washington where she works as Quebec's science envoy, a spokesman said Payette was not interested in commenting on the subject.
It's still not known when the process will begin to find a replacement for MacLean, who was selected as one of the original six Canadian astronauts in December 1983.
Several of those interviewed by The Canadian Press said the next president should not be another astronaut.
Black described MacLean as a national hero — but he added that the father of three was not a "politician" and never wanted to become one.
He said the agency might benefit from having someone with political skills right now.
For his part, Garneau said that what's needed is someone who is not only technically competent, but who understands how the bureaucracy and government work in Ottawa, and who has the best leadership skills.
He urged the government not to waste any time finding "a strong leader."
It's believed that Chummer Farina, the CSA's vice-president and a long-term bureaucrat, will be appointed as interim president.
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