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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

#161

Post by greglindahl »

goatherders wrote: post #160
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.

I disagree. Even without accounting for expectations, making a machine that works for years without regular scheduled maintenance in extreme conditions is a monumental feat. Ask people who work in the oilfield, extreme heats, extreme humidity, etc.

The discussion is about 90 days, not years. Years is awesome. 90 days was a planning goal used to set engineering priorities.

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

#162

Post by greglindahl »

slg wrote: post #99
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.

I wasn't just commenting on the physical durability of the rovers themselves although that is a huge part of it. It is also impressive from both a political and an organizational standpoint to keep a program like this running successfully for so much longer than initial plans dictated.

NASA has numerous programs running for this length of time. One of the people working on Voyager showed up at my grad school to get a degree between Uranus and Neptune.

NSF, too. The VLA opened in 1978 and the first data recorded by it can be reduced by the current radio astronomy analysis software. In fact the software data format developed for the VLA (FITS) is now popular with high-end camera people... 41 years later.

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

#163

Post by greglindahl »

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?

It was never an estimate. It was the minimum plan.

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

#164

Post by proactivesvcs »

Retric wrote: post #159
sramsay wrote: post #137

Earlier quoted context omitted.

Oversold? A group of engineers put a working robot on a moving object 140 million miles away, and that robot trucked along for fourteen years . I honestly do not see any aspect of this which is not totally and completely astonishing, marvelous, and awe-inspiring.

They designed it for a winter which means at least 687+ earth days days was considered achievable. Dust was expected to be a larger issue and in many ways they lucked out, but more so as a calculated risk than blind luck. Distance makes little difference past the first day. Doing the same thing on the moon would not be easier becase it’s closer. It’s local conditions that make this hard more so than simply getting to…

I can assure you that the distance took its toll on the rovers, in my understanding. Their wheel surfaces eroded, oil pumps failed, bearings degraded and they ended up dragging dead wheels in the end.

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

#165

Post by Timothycquinn »

m3at wrote: post #129
Evidlo wrote: post #97

Earlier quoted context omitted.

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.

Thanks for that clarification. After this, I was able to find the International System of Units Wikipedia page which clearly defines a second as per your summary. It's a relief to see that it's a constant formula like that of the Kilogram.

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

#166

Post by Timothycquinn »

mehrdadn wrote: post #152
m3at wrote: post #129

Earlier quoted context omitted.

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.

They said minute, not second. Even on Earth a minute isn't always 60 seconds.

How is this? According to the International System of Units, a minute is 60 seconds.

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

#167

Post by nindalf »

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?

Another comment explained this. They set a goal of 90 days to get the data they needed. When they presented the proposal for budgetary approval, 90 days of data collection was considered worthwhile enough to greenlight the project. So they accomplished it. However once you already have a working rover on the surface you might as well operate it as long as it lasts because the marginal costs are minimal compared to the initial costs. So they kept requesting additional funding to keep the program running.

I see nothing wrong with this.

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

#168

Post by craftyguy »

Timothycquinn wrote: post #165
m3at wrote: post #129

Earlier quoted context omitted.

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.

Thanks for that clarification. After this, I was able to find the International System of Units Wikipedia page which clearly defines a second as per your summary. It's a relief to see that it's a constant formula like that of the Kilogram.

I was suprised to learn (from the wiki page) that the kelvin, mole, and ampere do not have exact numerical definitions yet, though I guess that's expected to change in May of this year.

And then there's the candela, still basically defined by how luminous whale blubber is when it is burning:

> Current (1979): The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 5.4×1014 hertz and that has a radiant intensity in that direction of 1 / 683 watt per steradian.

> Note: both old and new definitions are approximately the luminous intensity of a whale blubber candle burning modestly bright, in the late 19th century called a "candlepower" or a "candle".

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

#169

Post by mehrdadn »

Timothycquinn wrote: post #166
mehrdadn wrote: post #152

Earlier quoted context omitted.

They said minute, not second. Even on Earth a minute isn't always 60 seconds.

How is this? According to the International System of Units, a minute is 60 seconds.

Leap seconds.

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

#170

Post by jamescostian »

proactivesvcs wrote: post #164
Retric wrote: post #159

Earlier quoted context omitted.

They designed it for a winter which means at least 687+ earth days days was considered achievable. Dust was expected to be a larger issue and in many ways they lucked out, but more so as a calculated risk than blind luck. Distance makes little difference past the first day. Doing the same thing on the moon would not be easier becase it’s closer. It’s local conditions that make this hard more so than simply getting to…

I can assure you that the distance took its toll on the rovers, in my understanding. Their wheel surfaces eroded, oil pumps failed, bearings degraded and they ended up dragging dead wheels in the end.

Are you talking about the distance the rovers traveled while on mars? Because that's not what Retric is talking about. Retric is talking about the distance from the earth to mars (hence why they compared it to the moon).
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