The Senate Judiciary Committee is holding its first hearing today on the government surveillance operations exposed by National Security Agency whistleblower Edward Snowden. Top officials from the Justice Department and the NSA are expected to testify. The journalist who has published the bulk of Snowden’s revelations, Glenn Greenwald of The Guardian, was due to testify by video-link to a separate hearing in the House, but the panel was cancelled after President Obama scheduled a meeting with House Democrats.