A history of near-Earth object research

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A history of near-Earth object research
by Erik M. Conway, Donald K. Yeomans and Meg Rosenburg
NASA, 2022
e-book, 394 pages, ill.
free

In six weeks from today, the Earth counterattacks the asteroids. At 7:14 p.m. EDT on September 26, NASA’s Double Asteroid Redirection Test (DART) spacecraft will collide with the small asteroid Dimorphos, which orbits a larger asteroid, Didymos. The impact will alter the period of Dimorphos’ orbit as a test of a technique to deflect the path of a potentially dangerous asteroid.

The book clarifies that the history of NEO research is relatively recent. The first major search for near-Earth objects didn’t begin until 1973, when NASA funded the Palomar Planet-Crossing Asteroid Survey.

DART is NASA’s first mission devoted to planetary defense: while the mission will perform some science, its main purpose is to test the effectiveness of the “kinetic impactor” approach to deflecting asteroids. That’s a far cry from less than 15 years ago, when NASA was spending less than $4 million a year on a handful of near-Earth object (NEO) search projects, a reasoned change to the both by science and politics, as described in the new book A history of near-Earth object research from the NASA history office.

The book clarifies that the history of NEO research is relatively recent. While the first asteroid was discovered in 1801, it took almost a century before the first near-Earth asteroid, 433 Eros, was discovered. For much of the 20th century, there was little focus on the study of near-Earth objects. The first major search for near-Earth objects didn’t begin until 1973, when NASA funded the Palomar Planet-Crossing Asteroid Survey.

What changed in the last decades of the 20th century to increase the rate of NEO discoveries were in part technological changes: electronic CCD cameras supplanted films, while computers facilitated the automation of searches and the detection of asteroids in these electronic images. At the same time, there was growing recognition of the threats NEOs posed to Earth as scientists came to understand the record of impact on Earth, from Meteor Crater in Arizona to Chicxulub in Mexico, the impact that killed 65 million dinosaurs. years ago. Soon there were targets for discovering near-Earth objects at least a kilometer in diameter and, in a 2005 NASA permitting act, those at least 140 meters in diameter.

However, as is often the case with NASA programs, appropriations were offset against authorizations. As of 2009, NASA was spending less than $4 million a year on NEO’s research efforts. What changed was not a new recognition of the asteroid threat, but rather a change in space exploration policy: the end of the Constellation program and the Obama administration’s intention to replace it with humans to a near-Earth asteroid, which turned into an Asteroid Redirect Mission (ARM). Although ARM never got very far, it had the lasting effect of increasing NASA’s NEO budget by a factor of ten, to $40 million in 2014. The findings of NEO, which ten years ago years were still less than 1,000 per year, now regularly exceed per year.

The authors argue that planetary defense is an applied science, or a public service of sorts, much like meteorology, where few people blame the government for funding the National Weather Service.

NASA’s efforts also evolved from a simple search for near-Earth objects to a broader “planetary defense” effort that included work to prepare for or prevent an impact. This includes the DART mission as well as coordination with other federal agencies. NASA now spends around $150 million a year on planetary defense, including missions like DART as well as ongoing NEO research.

Despite the scientific and political success, planetary defense still has to fight for funding. NASA’s 2023 budget proposal sharply cut funding for the next planetary defense mission, a space telescope called NEO Surveyor, pushing back its 2026 plan by at least two years. The House and Senate spending bills would at least partially restore that funding, but not enough to avoid a delay in a mission that scientists say is critical to achieving the law’s goal of authorizing 2005 from NASA.

A history of near-Earth object research is a comprehensive history of NEO studies, covering science, technology and policy. It is also a kind of defense of the domain, which has sometimes been criticized for not being purely scientific. (One of the book’s authors, Don Yeomans, worked on NEO studies for many years at JPL.) The authors argue that planetary defense is an applied science, or a public service of sorts, much like the meteorology, where few people blame the government for funding the National Weather Service. If successful, DART could not only demonstrate a way to protect the planet from impact, but also protect the budget for the planetary defense program.


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