So what happened?

The arguments in favor of an extensive NEO survey program are not any different today than they were in 2005. Everyone knew that getting hit by a big asteroid would be bad and that we needed to search for potential threats; that's why Congress passed the law it did. In the absence of new arguments, we should look to politics: why would the NEO observations suddenly warrant increased political attention required to drive funding?

A key report from the National Research Council (NRC), released in early 2010, helped establish the scientific and policy foundations for increased NEO funding. It included examples of how increased budgets would enable improved detection and mitigation efforts.

However, in repeated congressional budget proposals, NASA reached beyond the NRC report to its human spaceflight program to justify funding increases for NEO observations. I believe it is no accident that 2 significant jumps in funding—from $3.8 million to $20 million as proposed in fiscal year 2011, and from $20 million to $40 million in fiscal year 2014—both align with major changes in the human spaceflight program that involved near-Earth asteroids.

In 2009, the Obama Administration convened the Review of United States Human Space Flight Plans Committee to evaluate NASA's human spaceflight efforts, including Constellation, the over-budget and behind-schedule effort to return humans to the Moon. The report, released later that year, declared the current program "unsustainable" and proposed a "flexible path" for human exploration, including a visit to a near-Earth asteroid as an interim destination.

The congressional budget justification for fiscal year 2011, released months after this report, canceled the lunar program and stated that NASA would lay "ground work that will enable humans to safely reach multiple potential destinations, including the Moon, asteroids, Lagrange points, and Mars and its environs." This same budget request also proposed a significant budget increase in NEO observations. In addition to referencing the recent NRC report, the budget request leveraged the new direction for human spaceflight to justify this decision, saying that NASA "will significantly expand [its] efforts to find and characterize asteroids and comets approaching Earth which may be destinations and resources for our exploration of the solar system." Later that year, the Obama Administration released its national space policy, which directed NASA to send humans to an asteroid by 2025.

NASA further revised these plans by proposing the Asteroid Redirect Mission (ARM) in its fiscal year 2014 budget request. As initially conceived, ARM would have moved, via robotic spacecraft, a small asteroid to lunar orbit to be explored by astronauts. To succeed, NASA needed to find a suitable near-Earth asteroid, a problem potentially solved by further expanding NEO searches. NASA proposed to double funding for NEO observation and once again explicitly referenced human spaceflight goals as part of its justification, saying that "information gathered in this effort will support the proposed mission to retrieve an asteroid.