Having been initiated in 2011, NASA’s NEOWISE mission has recently concluded its work after identifying more than 3,000 near-Earth objects (NEOs), which are asteroids and comets that can potentially hit our planet. This is a significant chapter in the ongoing planetary defence quest, as it officially ended on August 8.
The survey of NEOs is critical to the area of planetary defence that focuses on evaluating and mitigating risks posed by large asteroids capable of causing significant harm to Earth.
In fact, NEOWISE has been instrumental in this endeavor by providing critical information that has increased our comprehension of these heavenly bodies. Notably, over 200 unknown NEOs were discovered by it, significantly expanding the knowledge base.
NEOWISE, which is no longer functioning, will re-enter Earth’s atmosphere before the year ends. This brings up important questions about future defense strategies for our planet.
From Infrared Astronomy to Planetary Defence
When conceived, this project was called the Wide-field Infrared Survey Explorer (WISE) and aimed to explore infrared emissions by distant galaxies. Just after visible light is the invisible infrared that comes as heat from different sources such as the sun.
NASA redirected the spacecraft towards NEO detection after WISE’s coolant ran out. This allowed NEOWISE mission to use its sensitivity to infrared signals for finding asteroids and comets that were coming close to Earth and the Sun.
NEOWISE demonstrates NASA’s ability to extend a mission’s life beyond expectation by transforming it from one purpose into another critical planetary defense asset.
Future Prospects for Earth’s Defence
This follows revolutionary findings by NEOWISE, which prepared NASA for its next dedicated planetary defense mission, called NEO Surveyor, that has been scheduled for launch in 2027. It looks forward to identifying about two-thirds of all NEOs larger than 140 meters during a five-year survey period.
Such a move is in line with US Congress instruction requiring NASA to discover 90% of such NEOs since they are capable of causing significant casualties when they strike highly populated areas due to their large mass.
When considering the imminent launch of NEO Surveyor, this could make the shutdown of NEOWISE appear bizarre. Nevertheless, the possibility of a severe asteroid impact is very low. Studies have revealed that asteroids with a diameter similar to this strike Earth only once every 20 000 years.
Hence, in any three-year period, one would expect minimal risk, especially because urbanized areas cover approximately 3 percent of the earth’s surface.
The decision to decommission NEOWISE was mainly influenced by an increase in solar activity affecting the upper atmosphere of Earth. The ionosphere’s thickening makes it harder for NEOWISE to keep its orbit and necessitates it to return onto Earth.
The Transition to NEO Surveyor
By 2023, construction on NEO Surveyor had already started and as such, it was quickly launched. This accelerated development seeks to fill the void left behind by closure and ensure that there is uninterrupted surveillance of NEOs.
As NEOWISE prepares for re-entry into the atmosphere, it weighs almost 700 kilograms, whereas some parts are predicted to reach earth’s surface. Hopefully these chunks will fall over sparsely populated regions, as there has been case where debris have fallen next to dwellings during previous re-entries.