English: Is it a spacecraft? An asteroid? Well, both. This small central speck is the first image of a spacecraft on its way home, carrying with it a sample from an asteroid hundreds-of-millions, if-not-billions-of-years old. The spacecraft is NASA’s OSIRIS-REx, the asteroid is Bennu.
On Sunday 24 September, the mission will drop its rocky sample off to fall through Earth’s atmosphere and land safely back home, before it continues on to study the once rather scary asteroid Apophis.
Spotted on 16 September by ESA’s Optical Ground Station (OGS) telescope in Tenerife, OSIRIS-REx was 4.66 million km from Earth. This image is a combination of 90 individual images, each 36-second exposures. They have been combined in a way that takes into account the motion of the spacecraft, which is not travelling in a straight line, causing the seemingly stretched background stars to curve and warp.
ESA’s 1-metre OGS telescope was originally built to observe space debris in orbit and test laser communication technologies, but since broadened its horizons to also conduct surveys and follow-up observations of near-Earth asteroids and make night-time astronomy observations and has even discovered dozens of minor planets.
For this observation, ESA’s Near-Earth Object Coordination Centre (NEOCC) took over the reins, directing it at the returning asteroid explorer. The NEOCC, part of the Agency’s Planetary Defence Office, is a little like Europe’s asteroid sorting hat; the centre and its experts are scanning the skies for risky space rocks, computing their orbits and calculating their risk of impact.
From our small but mighty Space Safety telescope, we say ‘Hello, OSIRIS-REx, good luck NASA and welcome safely to Earth, asteroid Bennu!’.
(Read all about ESA’s Hera mission that launches next year to examine the first test of asteroid deflection, the first mission to rendezvous with a binary asteroid system.)