WASHINGTON — After kicking its space exploration plans into high gear in 2005, NASA had to downshift in 2006.

Budget realities forced the U.S. space agency to tap the brakes on a proposed acceleration of the Orion Crew Exploration Vehicle and reassess what it can afford to spend on robotic trailblazers meant to lead the way back to the Moon.

Yet NASA still managed in 2006 to get Orion under contract and return the space shuttle it is designed to replace to a nearly normal flight tempo, a critical step toward completing the international space station by the end of 2010 so that the shuttle can be retired.

NASA also firmed up plans for the rockets it needs to return to the Moon, unveiled a plan for what it wants to do once there, and began to convince a skeptical international community it does not intend to go it alone.

For a year that began with a smaller-than-expected budget request and lingering doubts about the agency’s resolve to resume shuttle launches after a less-than-perfect return to flight the previous summer, NASA in some ways exceeded expectations.

“In retrospect, NASA has made more progress than many people thought they would,” said George Whitesides, executive director of the National Space Society.

“NASA in 2006 has established forward momentum that will be hard to reverse,” said John Logsdon, the director of George Washington University’s Space Policy Institute who spent the year helping NASA engage non-U.S. space agency’s. Logsdon noted a “positive turnaround” in the NASA’s dealings with the international and commercial sectors, citing a year-long engagement with both communities culminating in an early December unveiling of lunar architecture that provides “the first answers to ‘why the Moon?’ and “what do we do when we get there?’”

The outline NASA officials presented at its second annual space exploration conference in Houston called for laying a foundation for a permanent lunar outpost that international and commercial contributions would help improve, service and operate.

While NASA’s year ended on an up note with the long-awaited release of the lunar architecture, the third successful shuttle launch of the year, and tantalizing findings from the recently deceased Mars Global Surveyor strongly suggesting water may still occasionally flow on the red planet’s surface, the agency spent much of 2006 criticized at seemingly every turn.

The criticism began in earnest in February when NASA presented a five-year budget plan that projected flat funding for science programs and cut aeronautics research to cover a $6 billion shortfall for the shuttle and station. That the $11 billion increase NASA was seeking for the Exploration Systems Mission Directorate for 2007-2011 was less than what the agency needed to develop Orion and the Ares 1 rocket on an accelerated timetable was small comfort to scientists and researchers pinched by the plan.

While scientists were bemoaning mission deferrals, canceled projects and reduced grant funding, NASA was undertaking a rewrite of its public affairs policies following allegations that a political appointee had attempted to muzzle a top NASA climatologist, James Hansen, from speaking out on global warming. The appointee, 24-year-old George Deutsch, abruptly resigned after it was revealed that he had misrepresented his academic credentials to NASA.

On the exploration front, NASA had decided by early in the year to go for more commonality between the Ares 1 crew launch vehicle and Ares 5 heavy-lift rocket and in the process reduced some of the shuttle-derived content — one of the main selling points of the launchers. The biggest changes were made to Ares 1.

NASA dropped plans to use a modified space shuttle main engine for the rocket’s upper stage, opting instead to use an updated version of the Apollo-era J-2 engine. NASA also opted to use a larger five-segmented solid-rocket booster for the Ares 1 main stage instead of the existing four-segment booster used by the shuttle. Agency officials said the design changes would save money in the long run because the Ares 5 also would use the J-2 and five-segment boosters.

NASA officials would spend the rest of the year defending those changes and batting down rumors that the Ares 1 design it had settled on was technically unworkable.

In late August a $3.9 billion Orion prime contract was awarded to Denver-based Lockheed Martin Space Systems in a surprise victory over the combined team of Northrop Grumman and Boeing. Earlier that same month, NASA made good on a promise to place what NASA Administrator Mike Griffin had described as a $500 million bet on a pair of companies that intend to combine NASA’s money with private capital to field new launchers and use them to conduct space station re supply demonstrations before 2010. The Commercial Orbital Transportation Services demonstration awards went to Oklahoma City-based Rocketplane Kistler and El Segundo, Calif.-based Space Exploration Technologies.

In September, after Orion was under contract, Griffin publicly conceded that the pledge he had made in 2005 during his first weeks on the job to field the new vehicle as close to the shuttle’s 2010 retirement as possible no longer appeared possible given the agency’s funding outlook.

“Orion will not be operational until [fiscal year] 2014, the last year allowed by Presidential policy guidance,” Griffin said in a Sept. 12 speech at NASA’s Greenbelt, Md.-based Goddard Space Flight Center. “It had been hoped by many in NASA, the White House and Congress that we could deploy Orion as early as 2012. The later delivery of this key first element in the exploration architecture was accepted precisely because no one wanted to cut the science budget in order to deploy a shuttle replacement vehicle earlier.”

Goddard also would serve as the backdrop for Griffin’s most popular decision of the year. On Oct. 31, accompanied by Sen. Barbara Mikulski (D-Md.), Griffin announced that NASA would send a space shuttle to service the Hubble Space Telescope in 2008.

Mikulski, a longtime NASA ally, emerged as the agency’s unrivaled champion this year with the resignation of Rep. Tom DeLay (R-Texas), the former House Majority Leader, who in the past couple of years had almost single-handedly secured bigger budget increases for the space agency. Mikulski proved more than willing to pick up the slack, prodding the White House to increase NASA’s budget and laying the groundwork for a $1 billion supplemental meant to reimburse NASA for what it spend in the aftermath of the 2003 Space Shuttle Columbia accident.

NASA was reminded that political support is a two-way street when it butted heads with Mikulski over plans to award a fixed-price contract for a Landsat replacement. NASA capitulated, announcing this fall that it would award separate contracts for the spacecraft bus, instrument and ground systems, putting Goddard in charge of the integration.

Mikulski’s influence is expected to grow in 2007 if Democrats take over both chambers of Congress for the first time in 12 years. NASA faces a changed political landscape in the year ahead, with key Democrats vowing more oversight of the agency’s programs and an interest in providing more balance between the budget for human spaceflight and spending on science and aeronautics.

Incoming House Science Committee Chairman Bart Gordon (D-Tenn.), told Space News in a written statement that a fundamental challenge for NASA in the year ahead will be ensuring it maintains a balanced and productive program across its portfolio. “That challenge will be made easier if the president sends over a budget request for [fiscal year] 2008 that is equal to the needs,” he said.

Fred Gregory, NASA’s deputy administrator from 2002 to 2005, said he believed NASA made solid progress on its space exploration agenda in 2006, but said he was not sure it was being noticed beyond the space community — and that, he said, raises questions about the long-term sustainability of the endeavor.

“Folks who are in the club will acknowledge and recognize the progress, but Joe Bag o’ Donuts just has no idea what’s been accomplished, and I think that also includes the majority of people in Congress,” Gregory said.