Canada’s leader in space technology, MacDonald, Dettwiler and Associates Ltd., may end up moving its head office to the United States within two years, but that’s only one possible outcome of its proposed takeover of Colorado-based DigitalGlobe. The Vancouver-based company has made a firm commitment that DigitalGlobe’s ultimate parent will be a U.S. company by the end of 2019 _ although there’s been no decision yet about how that will be done, MDA CEO Howard Lance said Friday.