A Nasa-funded space lab misidentified UAE’s Hope spacecraft as a near-Earth object, after sunlight reflections on the probe’s solar panels caused it to appear brighter than usual.
The sighting was recorded on August 26 by space observers at the Catalina Sky Survey (CSS) at University of Arizona’s Lunar and Planetary Laboratory.
Their telescope captured the Mars-bound probe, even though it is already 11.8 million kilometres from Earth since its launch on July 20 – a distance that should not have made the spacecraft observable.
"Our 1.5-metre telescope detected six new near-Earth object candidates that did not correspond to any known asteroid," Eric Christensen, CSS director, told The National.
“We did not realise it at the time, but one of these objects, which we designated C332UJ2, was actually UAE’s Hope mission, on its way to Mars. To our telescope, it appeared identical to a large near-Earth asteroid in orbit around the sun.”
Near-Earth objects, commonly known as ‘NEOs’, could be anything from asteroids to comets and are monitored to spot any potential threats from space.
Mr Christensen said they reported their sighting to the Minor Planet Centre – a global organisation founded in 1947 that collects asteroid and comet data – and the “asteroid” was provisionally designated as C332UJ2.
He said that most spacecraft can be readily distinguished from asteroids by their orbit, as satellites move much faster than asteroids and trace a more curved path as seen from the ground.
“But in the case of Hope, it is already quite distant from Earth and orbiting the Sun, so its motion was perfectly consistent with an asteroid, and not easily identified as a spacecraft,” Mr Christensen said.
“I find it interesting that the predicted brightness of Hope would have been far too faint for our telescopes to see. It appeared many times brighter than predicted, probably because sunlight is glinting off some surface of the spacecraft, making it more easily visible from Earth, at least temporarily.”
The Minor Planet Centre removed C332UJ2 from its listing after a day once it was matched as the Hope spacecraft.
As spacecrafts orbit around the sun, they could be mistaken for asteroids until further, detailed observations are made.
An amateur astronomer in 2002 recorded a sighting of an unknown asteroid, formerly designated as J002E3, but it turned out to be leftover parts of an Apollo rocket.
Space observers have described the recent sighting of Hope as a possible “distance record for optical observation of a spacecraft”.
The Hope probe has completed 20 per cent of its journey and cruised more than 105.79 million kilometres.
With about 388 million kilometres remaining, the spacecraft is expected to arrive to the Marian orbit in February.