On Wednesday, April 19, an asteroid missed Earth by 1.1 million miles – a distance closer than you might think. This week, Tech Briefs spoke with NASA’s Planetary Defense Officer about the efforts behind tracking this type of flyby.

The sighting of asteroid “2014 JO25” demonstrated the importance of collaborative observations and advanced imaging technology to follow and characterize potentially hazardous comets and asteroids in the sky.

What is JO25?

Approximately 1,500 near-earth objects (NEOs) are detected each year, and more than 13,500 NEOs have been discovered since NASA-led surveys began in 1998.

The composite of 30 images of asteroid 2014 JO25 was generated with radar data collected using NASA's Goldstone Solar System Radar in California's Mojave Desert. (Credits: NASA/JPL-Caltech/GSSR)

Last week’s “JO25” asteroid, however, stood out because of its size: just under 1 kilometer in its long axis and 650 meters in its short axis. The asteroid's peanut-like shape is considered "bifurcated," appearing almost like two asteroids stuck together.

JO25 was the largest asteroid to approach Earth since September of 2004, when a 3.1-km-wide asteroid known as Toutatis came within four lunar distances of the planet.

As NASA’s Planetary Defense Officer, Lindley Johnson leads the global effort to detect and follow near-earth objects like JO25 – ones capable of speeds as high as 12 miles per second.

"An object of that size, if it were to impact on land somewhere, it could pretty much wipe out a region of a large state,” said Johnson. “The effects could well affect the climate globally for a period of several months."

Bringing Together Survey Teams

NASA’s Planetary Defense Coordination Office (PDCO), managed at NASA Headquarters in Washington, D.C, is responsible for early detection of potentially hazardous objects, like asteroids and comets, and issuing warnings about their potential impacts.

To characterize and track an asteroid like JO25 requires teamwork from observatories around the world. Ground-based telescopes provide observations of moving objects in the sky.

The images and orbital data are then sent them to a database at the International Astronomical Union Minor Planet Center. The NASA-supported and internationally sanctioned facility, based in Cambridge, MA, analyzes the data related to small bodies in the solar system.

NASA’s Jet Propulsion Laboratory, headquartered in Pasadena, CA, uses its Center for NEO Studies (CNEOS) to predict orbits, like JO25’s three-year path around the Sun.

Additionally, the agency funds several survey teams that are run by different universities and space institutes. The University of Hawaii, for example, operates NASA’s Infrared Telescope Facility (NASA IRTF).

Asteroid 2014 JO25 was originally discovered through NASA's Near-Earth Objects Observations Program, in collaboration with the University of Arizona. In May 2014, astronomers first spotted the bifurcated asteroid at the Catalina Sky Survey near Tucson, Arizona.

The Arecibo Observatory, a facility of the National Science Foundation, was the first to spot last week’s asteroid as it made its 2017 approach. The Puerto-Rico-based station features a 300-ft dish placed in a natural depression in the country’s hills.

The facility picked up the asteroid on April 16. Once the asteroid passed over the top of the Earth’s orbit and into the night sky, optical telescopes, like Hawaii’s Infrared Telescope Facility, began taking observations of JO25. NASA’s Goldstone Deep Space Communications Complex in California produced radar images of the asteroid days later.

The Challenges of Tracking Asteroids

Spotting asteroids is especially difficult, given the objects’ dark characteristics. Because the asteroids only reflect 10 to 15 percent of sunlight, ground-based telescopes are tasked with finding dim bodies in a wide field of view.

The planetary radar facility at Puerto Rico's Arecibo Observatory determines shape and surface features of near-Earth objects, and characterizes their orbits. (Credits: Courtesy of the NAIC - Arecibo Observatory, a facility of the NSF)

“Although [the telescopes are] pretty sophisticated technology, relatively speaking, they still lack what we need to be able to cover as much of the sky, as deep as we need to, to detect these objects,” said Johnson.

A possible way to upgrade asteroid-discovery capabilities is the use of space-based infrared (IR) telescopes. Instead of looking for the reflection of light against dark objects, IR technology detects an object’s re-emitted heat, offering a full surface area of an asteroid and better signature against the cold background of the sky.

The Wide-field Infrared Survey Explorer (WISE), launched in 2010 as part of an astrophysics-focused mission, used an IR telescope to build a deep-sky infrared map in support of eventual James Webb Space Telescope operations.

In addition to WISE’s primary mission, the NEO Observations Program funded an adjunct use of the telescope's data to detect asteroids and comets. By 2013, the WISE spacecraft was considered a full-time NEO detection and characterization asset.

For a technology not designed to track asteroids, NEOWISE has been a suitable prototype – with noticeable weaknesses. The telescope’s field of view is small, requiring six months to cover the entire sky at once, and the NEOWISE imager is not sensitive enough to spot smaller-sized NEOs.

As heat from the Sun and Earth will effectively "blind" the tool's infrared detectors, NASA’s Planetary Defense Officer sees the importance of a space-based IR telescope – designed specifically for asteroid characterization. An infrared telescope operating in space would be a much more effective way of detecting and tracking objects, according to Johnson.

“What has been learned from NEOWISE provides a solid basis for building an IR telescope specifically designed to detect, track, and characterize NEOs,” said Johnson. "With the NEOWISE lessons learned, we could now build a robust space-based telescope that will find tens of thousands of asteroids each year for the cost of a Discovery-class mission."

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