Mars solar conjunction

03 September 2019

Interview with 

Paul Meacham, Airbus

MARS-ROVER

The picture shows an illustration of a rover on Mars.

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There’s something getting between us and the rovers on the Martian surface collecting data... Adam Murphy has the details.

Adam - NASA's Curiosity rover has been trundling around Mars for nearly eight years now, dutifully sending back data giving us brand new information about the red planet. But from the 28th  August until the 7th September, NASA will stop sending signals to Curiosity and all their other rovers. But what sort of thing could possibly get between NASA and their beloved rovers? Well, it's one of the biggest things that could get in the way.

Paul - Something is occurring called a solar conjunction. In simple terms, Mars is on the opposite side of the sun to the earth and thus the sun is blocking the direct line of sight.

Adam - That's Paul Meacham, lead systems engineer for the ExoMars rover at Airbus.

Paul - Because there is no essentially relay system to sort of bounce the signal either side of the sun, what you end up with is effectively a communication blackout period where you cannot talk to the rover and it cannot talk to you.

Adam - It's a bit like an eclipse, but instead of something blocking out the sun, the sun is quite rudely getting in the way of Mars. And we have no way to bounce signals around something as absolutely massive and enormous as the sun. So does that mean we have to completely shut down all of the rovers?

Paul - It depends on exactly where they are in the mission, and what their particular science goals are. I think the NASA rovers do have some sort of background scientific tasks they are able to do whilst it is essentially blacked out. So the NASA engineers have been uploading activity plans lasting about two weeks to allow them to do that.

But certainly anything that would require some sort of oversight from Earth, even if the rover was doing it autonomously, like driving or some sort of scientific experiment, cannot be done.

Adam - So it's just crunching some numbers, doing the bare basics parked somewhere safe. You don't want to park your very expensive rover on a sandy hill and hope for the best! Powering these rovers down isn't that dissimilar to putting your computer into sleep mode, still ticking along doing nothing too intensive. You just want the essential systems on. So what are the essential systems?

Paul - The communication system, the power system, and the computer, all of which will be in a sort of a low power configuration and sort of waiting to almost be woken up. But because it’s sometimes a bit difficult to predict when the first signals will come back, you have to lead the rover in a configuration where you can talk to it as soon as the solar conjunction in this case is over. So primarily it's just having your essential equipments on in as lower power mode as possible.

Adam - So the Mars rovers will be getting a much-deserved holiday and we'll be back trundling around the planet very soon.

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