107 votes
Accepted

Why do most space probes survive for far longer than they were designed for?

Very good question! The answer boils down to statistics of failure. Some aspects involve the statistics of "random" failures—for some reason some critical component just bites the dust—and some ...
Tom Spilker's user avatar
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95 votes
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Why A=2 and B=1 in the call signs for Spirit and Opportunity?

On MER we numbered the builds, but used letters for the launches. So MER-1 was built before MER-2. MER-A would both launch and arrive first, and MER-B would launch and arrive second. When we started, ...
Mark Adler's user avatar
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56 votes
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What was NASA's "Hack" to improve Opportunity's memory in 2015? Did it help?

They reformatted the flash memory area and, after finding the defective memory bank, modified the software in the rover to avoid using that area. The hack in itself reduces the amount of available ...
Diego Sánchez's user avatar
55 votes

Why do most space probes survive for far longer than they were designed for?

There are a lot of generic answers here about spacecraft. I will try to answer the question specifically for Spirit and Opportunity. 90 sols was deemed sufficient to conduct the primary mission of ...
Mark Adler's user avatar
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46 votes
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What was the last message to Opportunity today (13 Feb '19)?

From ArsTechnica: Late Tuesday night, scientists at NASA's Jet Propulsion Laboratory sent their final data uplink to the Opportunity rover on Mars. Over this connection, via the Deep Space Network, ...
Ingolifs's user avatar
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27 votes
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Why did NASA's Soujourner Mars rover die at the same time as Pathfinder?

The only way for the Soujourner rover to transmit data to Earth or receive commands from Earth was through the Pathfinder lander. If Pathfinder died, Sojourner was also essentially dead.
David Hammen's user avatar
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24 votes
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Why did Spirit (MER-A) lose a wheel?

No explanation has been established for the wheel failure, although a motor brush failure is one possibility. Source: Mars Exploration Rover Spirit End of Mission Report
Organic Marble's user avatar
20 votes

Why do most space probes survive for far longer than they were designed for?

They needed to guarantee that it would operate for its expected duration. Each component has a Mean Time Between Failure (MTBF). The important thing here is that the MTBF is an average. That means ...
ShadoCat's user avatar
  • 910
18 votes
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How did NASA's Deep Space Network encode and broadcast music to Opportunity?

TLDR; They didn't. I submitted NASA FOIA request 19-JPL-F-00295 asking about this, and they responded: [...] JPL confirmed that the song was not radiated to the spacecraft. It was just played on ...
Mark Omo's user avatar
  • 5,301
15 votes
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Why is Curiosity so light compared to Opportunity?

The number is slightly misleading. NASA provides a complete breakdown on the mass. Rover 185 kg Lander 348 kg Almost 2/3rds of the mass that soft landed was in the stand and airbags, only about 1/...
PearsonArtPhoto's user avatar
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15 votes
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Is there any chance that Opportunity might still recover from the dust storm?

The NASA announcement, available here, said specifically, "After more than a thousand commands to restore contact, engineers in the Space Flight Operations Facility at NASA's Jet Propulsion Laboratory ...
Tom Spilker's user avatar
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12 votes

Why do most space probes survive for far longer than they were designed for?

Although they're up for purchase, the fruits of labor from 58 years of space traveling excellence are not available at Radio Shack. Is it really that hard to predict how long a device will last? Yes....
Mazura's user avatar
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12 votes
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Opportunity's last tau was 10.8; what does that mean and how is tau defined and measured?

Vacuum would have a $\tau$ of zero. An opacity of $\tau$ means that the atmosphere is reducing the direct intensity of light from the Sun, if it were directly overhead, by a factor of $e^{-\tau}$. It ...
Mark Adler's user avatar
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10 votes
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What was the last message Opportunity sent?

From the Planetary Data System: Opportunity is currently in the midst of a severe dust storm though all subsystems are still operating as expected in RAM mode as of the Sol 5111 UHF pass. Solar array ...
PearsonArtPhoto's user avatar
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10 votes

Why do most space probes survive for far longer than they were designed for?

Most space probes don't survive far longer than they were designed for. Example: Mars missions. 30 failures, 18 successful missions and 8 missions in progress. I count 4 missions (Viking 1 and 2 ...
Hobbes's user avatar
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10 votes
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How many memory banks does Opportunity have?

As shown in the picture below, there are 8 banks of flash out of which 7 banks are used as data storage and bank 0 is used for flight software (FSW) and Entry, Descent and Landing (EDL). Source: R. ...
wooooooooosh's user avatar
9 votes
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Is there any chance that Opportunity survived, but NASA kept pinging it at the wrong time?

Short answer is, it's most likely very dead. Opportunity had several issues leading into the storm period, including failing memory. Once it was not getting enough light, the expected sequence of flat ...
GremlinWranger's user avatar
8 votes
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Is Opportunity still in shape to explore the landing site of the Schiaparelli lander?

No, certainly not within a year. Maybe, if its incredible luck holds out, in 17 years. Opportunity would need longer than it has already been there to make such a journey, based on the traverse to ...
Mark Adler's user avatar
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8 votes
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What was the solution to the half-amp the heater on Opportunity was drawing?

As Mark indicated, the solution was and continues to be to use deep sleep to overcome the heater being stuck on. This was first implemented on Sol 101, and even though mini-TES was below the ...
PearsonArtPhoto's user avatar
  • 121k
7 votes

What were Spirit and Opportunities wheels made out of?

Aluminum and foam according to this page that describes the wheels as manufactured from a single Aluminum block with foam inserts into the spiral suspension system spokes. The black surface of the ...
GremlinWranger's user avatar
7 votes

Why do most space probes survive for far longer than they were designed for?

There's some very good answers here on failure modes and statistics, looking at the specific cases of Spirit and Opportunity there is a bit more to it. NASA had just experienced 2 consecutive failures ...
GdD's user avatar
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6 votes

Have any systems on any Mars rovers failed (even partially) as a result of a dust storm? (besides loss of solar power)

Not specifically during a single storm, but: One interesting case of a partial failure of a system is that of the optical calibration targets on Opportunity, Spirit and Curiosity. They were ...
Jack's user avatar
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6 votes
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Do Mars rovers have irises? How do they safely look at the Sun?

They use neutral-density filters to look at the Sun, which reduce the light by a factor of 100,000. The two Pancam cameras each have one neutral-density filter, with the left one filtering blue and ...
Mark Adler's user avatar
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6 votes
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How did Spirit and Opportunity identify ferric sulfate and jarosite on Mars?

Reference [1] describes the finding of jarosite in the Mawrth Vallis region of Mars. The NASA Mars rovers include IR spectroscopy in their instrumentation, and that was the method used. The finding ...
Oscar Lanzi's user avatar
  • 8,505
6 votes

Why do most space probes survive for far longer than they were designed for?

Might be better to see this as: "Why are some estimates of longevity so conservative?". I think this is clear. They deal with a lot of unknowns. The mars rovers are a great example of this. "How long ...
ANone's user avatar
  • 3,432
6 votes

Why was a nuclear battery system not used for the Mars Spirit and Opportunity rovers?

Mars Spirit and Opportunity rovers exceeded expectations by working for many years than the planned 90 day mission. Ninety days was not the planned mission. It was instead the bare minimum amount of ...
David Hammen's user avatar
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5 votes
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Why was a nuclear battery system not used for the Mars Spirit and Opportunity rovers?

Spacecraft design is based on conservative, pessimistic estimates, "stuff that's proven to work". When those estimates are (usually) exceeded, the next generation "faster horse" ...
SE - stop firing the good guys's user avatar
5 votes
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Curiosity landing system versus Spirit/Opportunity's

Because Curiosity massed almost ten times more. Airbags wouldn't have sufficed to get it upright, once the dust had settled. Curiosity weighs as much as a passenger car. Airbags (admittedly ...
Camille Goudeseune's user avatar
5 votes

Why do most space probes survive for far longer than they were designed for?

As a tech guy at work, I'm sometimes faced with with the question "Why didn't it work?". It's sometimes difficult to get people to grasp that things like The Internet requires lots and lots of things ...
Machavity's user avatar
  • 7,905
5 votes

Is there any chance that Opportunity might still recover from the dust storm?

Is there any chance? Yes. But, it's very, very, very, unlikely. There have been NASA missions which failed and disappeared only to mysteriously reawaken and continue to work. Most notably the IMAGE ...
Dragongeek's user avatar
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