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A European probe to Mars is scheduled to arrive on Wednesday. One part of the ExoMars mission, called Schiaparelli, will land on the Red Planet. The other, known as Trace Gas Orbiter, will study the Martian atmosphere from orbit.
The lander will operate for only a couple of days. Although it’ll make some scientific observations, its main goal is to pave the way for a Mars rover in a couple of years. It will allow European engineers and scientists to gain experience at landing on Mars.
To help make that landing as precise as possible, navigators here on Earth are getting help from quasars. These cosmic beacons are brilliant disks of hot gas around supermassive black holes in distant galaxies.
Navigators use more than one tracking station here on Earth to triangulate the craft’s position. But Earth’s atmosphere can alter its radio waves. So the tracking stations also monitor one or more quasars at the same time.
The radio characteristics of the quasars are well known. Any change in the quasar signal tells engineers what’s happening to radio waves in the atmosphere. That allows them to correct signals from ExoMars. Engineers say that’ll make it possible to pinpoint the craft’s position to within about a half mile — making it easier to hit the bullseye on Mars.
We’ll have more about ExoMars tomorrow. In the meantime, look for the planet low in the south as night falls. It looks like a bright orange star, to the left of teapot-shaped Sagittarius.