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Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

nytimes.com

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Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#121

Post by jacquesm »

ChuckMcM wrote: post #118
jacquesm wrote: post #98

Earlier quoted context omitted.

That can't be that expensive unless you want it to be storm proofed. But it wouldn't be super cheap either, the receiver is probably going to be a bigger problem. http://www.astrosurf.com/luxorion/dish-antenna-building.htm Would be a good starting point. But keeping it stable under wind load is going to be the major challenge. That would be one heck of a project, it would likely take a few years of your time to pull…

This quora answer ( https://www.quora.com/What-bands-signals-and-protocols-are-u... ) claims that even the 70m DSN antennas have a hard time hearing the rover to earth transmissions. That is 10x the diameter so 1000x the surface area of a 4.8m dish like the one the guy built. That said, there are no doubt interesting hacks you can do to help this but steerability is always going to be a concern to maximize the SNR of…

Yes, the precision required would be insane. That is also what makes this an interesting project, even if you fail you will still learn a ton about all kinds of engineering principles. Expensive lesson though!

Another big factor would likely be how far Mars is away from Earth, at the close extreme it will probably be substantially easier to pull this off.

What an interesting article by the way, thank you for that link.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#122

Post by commonsense1234 »

omegaworks wrote: post #89
Retric wrote: post #87

Earlier quoted context omitted.

That story is very much over sold. They defiantly designed the things with a longer lifespan in mind. NASA simply had more reasonable minimum specks so if they died on day 220 nobody would call the program a failure.

Underpromise and over deliver :)

underpromise and way over deliver. This is unheard of.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#123

Post by stoops »

Ianworld wrote: post #105
slg wrote: post #23

Opportunity's and Spirit's original missions were planned to last 90 Martian days each. They ended up lasting over 8,000 combined. That is almost as impressive as getting the rovers to Mars in the first place.

I remember talking to a high up on the program at a FIRST robotics event who complained about them running so long. They weren't making any major new discoveries and sucking up resources and mindshare stopping him for kicking off and focusing on new projects. He said nobody would take the PR hit to decide to just end a mission like this so he was stuck.

Sounds like that person doesn't really understand that NASA is a political entity and the Public Relations of an ongoing successful mission is more valuable long term than more scientifically pragmatic experiments in the immediate.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#125

Post by tzs »

luizfzs wrote: post #82
wiremine wrote: post #34

Was looking through Opportunity's Wikipedia page, and found this cool comparison of the embedded systems used in Mars rovers: https://en.wikipedia.org/wiki/Comparison_of_embedded_compute... That lead me to the RAD6000 page, which was new to me: https://en.wikipedia.org/wiki/IBM_RAD6000 "Reported to have a unit cost somewhere between US$200,000 and US$300,000, RAD6000 computers were released for sale in the general co…

I saw a video once saying that SpaceX uses general purpose computers on the rockets instead of specific purpose hardware. If I'm not mistaken, they amount to 6 and have a checking system to assure the output of them is the same.

Those "have N copies and compare them" systems then have the issue that whatever does the comparison is a single point of failure. You could use multiple comparison units and have a second level comparison check them, but then that is your single point of failure, and so on.

I've been told, but never actually looked it up, that there is a theorem that proves you always have to have at least one single point of failure.

I don't know if the following is actually true, or just a rumor, but I've heard that at least one aircraft whose mission called for very high reliability didn't have a comparison unit: the redundancy extended all the way to having the 3 independent flight control computers each control a separate actuator on each flight control surface. If one of the systems went bad and tried to move the surface incorrectly, the other two would physically overpower it.

That still has a single point of failure, but now that point is the control surface itself. If your control surface itself has failed it no longer matters if the 3 computers controlling it agree.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#126

Post by JohnJamesRambo »

slg wrote: post #23

Opportunity's and Spirit's original missions were planned to last 90 Martian days each. They ended up lasting over 8,000 combined. That is almost as impressive as getting the rovers to Mars in the first place.

I’ve never found it impressive, it’s a horrible padded estimate meant to cover NASA and make them look good. A real estimate needs to be useful and somewhat close to the actual outcome. There’s no way they were this off without it being on purpose.

Imagine if your retirement planner or accountant was off by 44X in their number crunches for you. Would you say they were good at estimating?

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#127

Post by crushcrashcrush »

JohnJamesRambo wrote: post #126
slg wrote: post #23

Opportunity's and Spirit's original missions were planned to last 90 Martian days each. They ended up lasting over 8,000 combined. That is almost as impressive as getting the rovers to Mars in the first place.

I’ve never found it impressive, it’s a horrible padded estimate meant to cover NASA and make them look good. A real estimate needs to be useful and somewhat close to the actual outcome. There’s no way they were this off without it being on purpose. Imagine if your retirement planner or accountant was off by 44X in their number crunches for you. Would you say they were good at estimating?

Jesus dude, can’t you enjoy a crowning achievement of human and American excellence?

You think NASA is overly concerned about public perception to the tune 44x an original estimate?

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#128

Post by mturmon »

jessriedel wrote: post #111
DevX101 wrote: post #62

Earlier quoted context omitted.

It's physically possible but I'd have to imagine there's a security key required for the Rover to accept a message and there's no way in hell NASA would give you that key.

I was shocked to read that, apparently, there is no key? https://security.stackexchange.com/questions/18225/mars-curi... I get the argument for why nuclear weapons aren't physically locked -- there's always people guarding them -- but not having security on a remotely operated billion-dollar device seems crazy to me, even if the technical barriers to establishing a link are high.

The person answering doesn't really comment on deep space missions, but I think the conclusion you draw (no encrypted link) is almost certainly right for Spirit and Opportunity, which were launched in 2003.

The thinking used to be that a 70m radio dish (and all the accompanying deep knowledge about pointing, relative velocity, channel codes, etc.) would be enough of an obstacle.

This thinking has definitively changed in the meantime.

Re: Nasa’s Mars Rover Opportunity Concludes a 15-Year Mission

#129

Post by m3at »

Evidlo wrote: post #97
Timothycquinn wrote: post #81

Earlier quoted context omitted.

Excellent question. I assumed that one mars minute differs from an earth minute but I just learned that they don't. Seconds, minutes and hours are universal. Hours in a day is what varies by planets, moons etc. Funny that I never thought of that before :)

It just depends on what your definition of a Martian minute is. If you define it as 1/(24*60) of a Martian day, it is different from an Earth minute.

You're likely joking, but just in case: on earth the second is not defined as a fraction of the day, it's a SI unit defined as a constant count of energy level variations of an caesium-133 atom.
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