For me it seems strange that a 200Mlj Mars robot (like Insight,etc) meet the end of life becouse of dust on solar panels. Why they aren’t equiped with some kind of vibration mechanism or windshield wiper-similar thech to deal with a problem? This seems to me like WTF?
Everything in space is about efficiency, especially around weight. The robots were designed to survive a certain amount of time and that time included knowing the panels would get covered. The engineers had to decide to come up with ways to keep the panels clear (adding weight and complexity) or calculating they would keep working “long enough” to complete the mission.
The Martian dust is unfortunately not just resting on the panels, it is clinging there due to static charge, so the rover can’t just dump the dust off.
It’s extra weight and complexity, and you don’t know ahead of time that this is what’s going to finally end the mission. There are a thousand other possible failure modes that you could dedicate additional resources to mitigating. Everything is a tradeoff.
Your solution can also introduce new failure modes that might be worse than the original one, maybe a piece of rock gets stuck on your windshield wiper and gouges into the solar panel, breaking it. Maybe the vibration system causes fatigue failure of an electrical connection.
Keep in mind that Mars is ridiculously far away and we don’t understand it very well yet. Even successfully landing on the planet is hard enough. Across all countries, approximately half of attempts to reach Mars over the years failed or crashed.
Spacecraft, rovers, and landers are complex and there are thousands of things that could go wrong. It doesn’t make sense to go to great lengths to avoid one bad outcome while neglecting others. Given a limited budget, compromises need to be made. So nothing is designed to last forever – rather, a mission length is decided, and everything is overengineered with the goal that even if everything goes wrong, it will last at least as long as the mission length.
In 2003/2004, the Mars Exploration Rovers landed (Spirit and Opportunity). The mission length was just 90 days, but if successful would be the longest mission on the surface of Mars to date. It was already ambitious. It was expected that the solar panels would accumulate dust and that eventually if nothing else failed, the solar panels would eventually be the problem.
The mission was a tremendous success beyond everyone’s wildest hopes. Everything worked as designed, and to everyone’s surprise, dust storms cleaned off the solar panels. Both rovers kept driving around for more than 10 years.
InSight also had a mission length and it met its objectives. There was hope that it would last longer, thanks to those dust storms – but it turned out that the location where it landed didn’t get enough dust storms to clean off the panels.
That was a surprise. Now we know.
The next mission will probably take that into account. But still, within reason – the goal is never to last forever, just to find that right balance of minimizing the chances any one failure ends the mission too early.
InSight was NOT a failure. It wasn’t designed to last forever.
The dust isn’t just on the panels. It’s in the air. Massive duststorms on Mars can cover the entire planet and block out the Sun, and the rovers depend on solar power to keep their electronics warm enough to function.
They were equipped with a wide variety of ways to deal with dust. So much so that a mission only expected to last 90 days ended up lasting years.
But you can’t undo all the damage. Every so often one of those little rocks will be just massive and sharp enough to put a little scratch on the panel. And once they are there, they never go away. Combine that with all the little bits of damage building up on every other component and the fact that some things like batteries are going to be breaking down over time anyway and rover death becomes inevitable.