Hayabusa and OSIRIS-REx: Rendevous with an asteroid

Asteroids are the rocky debris left over from the creation of the Solar System, so understanding them can give us an insight into our planet’s history. Two separate missions will see spacecraft approach asteroids and return samples to Earth during 2018. The first of these will be JAXA’s Hayabusa 2, launched in December 2014. The spacecraft will reach its target, the carbonaceous asteroid 162173 Ryugu, in June or July. Its aim is to bring back asteroid samples to Earth in order for scientists to study their composition and compare it with Earth to unravel the mysteries of the origin of life. The spacecraft is expected to stay around the asteroid for a year and a half, before leaving in 2019 and reaching Earth at the end of 2020. Meanwhile, NASA will be attempting something similar.

Having launched in September 2016, NASA’s Origins Spectral Interpretation Resource Identification Security – Regolith Explorer (OSIRISREx) will reach its target asteroid,

Bennu, in August 2018. Two months after it arrives, the spacecraft will start a year-long detailed survey of the asteroid, during which time it will carefully select a site to recover a sample from. In a five-second contact with Bennu, a sample of at least 60 grams (2.1 ounces) will be taken from its surface, by releasing a burst of nitrogen gas that will break up the rock and soil, allowing it to be captured. The spacecraft has enough gas for three of these attempts. In March 2021, the spacecraft will leave the asteroid and begin its two-and-ahalf-year journey back home, where the sample capsule will separate from the spacecraft and enter the Earth’s atmosphere.

Proximity to Earth When Bennu was selected as the target there were over 7,000 known near-Earth objects orbiting within 1.3 AU of Earth. Size A diameter bigger than 200m prevents an asteroid from rotating too rapidly allowing a spacecraft to approach...