103

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 involve event-driven failures, such as failures induced by landing shocks, long engine burns, atmospheric entry stresses, etc. When someone (a government, usually) ...


93

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, we weren't sure which hardware would launch first. Due to how the design testing split across the two flight units was arranged, it turned out that MER-2 became ...


54

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 memory (you lose one bank), but as the rover was avoiding flash memory entirely, you have a net gain by being able to reenable it. https://www.jpl.nasa.gov/news/...


50

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 the rovers, so the systems were designed and tested to assure full capability through the entire 90 sols. The first thing expected to take a rover below full ...


46

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, the American jazz singer Billie Holiday crooned "I'll Be Seeing You," a song that closes with the lines: I'll find you in the morning sun And when the ...


34

Not a chance. From NASA, here's the locations of everything that's landed on Mars (Well, NASA missions) Curiosity is kind of close to Spirit, but keep this in mind. The equatorial circumference is about 13,000 miles. I'd guess the distance is over 1000 miles, far further than any rover has gone before, or is likely to ever go. There's just much more ...


30

Opportunity is roughly 10,000 km away from Spirit in a straight line. At its top speed of 0.05 m/s (0.18 km/h), it would take approximately 2300 days to reach Spirit -- not that Opportunity can maintain that speed. Between limited electrical power, needing to slow down to navigate, and being unable to drive at night, driving is much slower. Based on the ...


22

Almost all in C on the rover computer. On MSL, some of the C was generated automatically using UML state charts. I don't know the exact team sizes. On the order of 20 on MER and 40 on MSL for the flight software on the rover computer. You would also need to consider the software on the instruments. And the radio. And the motor controllers. Here's a ...


20

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 that half of the similar components will fail before that time. The MTBF like most statistical measurments follows a bell curve (see below): In this chart, ...


18

Two alternatives (RTG or solar) were investigated in the Mars Science Laboratory Environmental Impact Statement. In summary, solar arrays would limit the MSL to operate between 5°N and 20°N, and for one Martian Year only if at exactly 15°N, whereas RTGs would permit it to operate for at least one Martian year anywhere from 60°S to 60°N. From page 2-1 (PDF ...


15

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 (JPL) made their last attempt to revive Opportunity Tuesday, to no avail." [Emphasis mine] They also said, "The final transmission, sent via the 70-meter Mars ...


15

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 someone’s laptop in mission control as the transmission began. So it seems the original story's information had sifted through one too many people or stretched ...


14

According to Wikipedia, it's likely that Spirit has suffered permanent damage from cold as a result of insufficient power to run its heaters; any future rover which had the ability to fix that sort of thing would be so much more sophisticated than our current rovers that there would be no point in doing so. In any case, Spirit operated more than 20 times ...


14

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 1/3rd of the mass of the rover. The bottom line is, Curiosity was more effective in terms of the mass of the rover to the mass of the EDL package. The skycrane ...


12

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. Quality control tells you how many cycles something should be able to go through until it is unreliable. The parts you choose to use should be based on their ...


10

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. Sosland, M. Seibert, E. Ferguson, R. Steele and K. Zittle, "Getting back on the road: Reformatting Flash memory on-board the Mars Exploration Rover Opportunity," ...


10

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 energy is approximately 22 W-hrs, with a measured tau of 10.8. This Tau measurement is the highest ever recorded from a ground station on the planet Mars. Dust ...


9

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 was measured by the rovers every sol by pointing the PanCam at the Sun, or where the Sun is supposed to be, measuring the intensity, correcting for the slant ...


9

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 landers, Spirit and Opportunity) that lasted far longer than their primary mission. So 4/56 is 7% of Mars missions. There's a bathtub curve at work: if a mission ...


8

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 qualification limits, it still seemed to work. It stopped functioning in 2007 for the unrelated reason of dust reaching its mirror.


7

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 with the Mars Climate Orbiter and Mars Polar Explorer, both of which were caused by errors in development, seen as the result of NASA's "Better, Faster, ...


7

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 wheel itself is just an anodized coating. Interestingly the wheels are described as being by design less effective in sand than they could have been by having ...


6

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 the right one filtering red. per comment: no, no irises.


6

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 before dust accumulates?" is a difficult question to answer without having been there. This isn't always the case BTW. Sometimes the limiting factor is ...


6

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 frequently photographed by on-board cameras (Pancam for Spirit and Opportunity, Mastcam for Curiosity) and the images used to calibrate the colour and brightness of the ...


5

While I've not yet found explicit back up to my recollection of this, the explanation I remember is that solar panels would not provide adequate power to operate the rover and the instruments on it and still fit within the mission profile. Curiosity/Mars Science Laboratory is much larger and more massive and has more instruments than the previous Mars ...


5

Glenn Reeves talks about troubleshooting the flash issue, and specifically mentions a 224 MB flash filesystem. At 7x32 MB, this indeed looks like it's 7 banks. In a more scientific paper, he confirms the 224 MB allocated to the file system. I can imagine that the 8th bank of flash holds the Spirit firmware, not a filesystem. Spirit has >30 MB of code, and ...


5

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 to work and, if any of them fail, the whole thing falls apart. I call this a Logistics Chain. Any space project is going to face lots and lots of failure ...


5

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 of potassium jarosite, $\text{KFe}_3\text{(SO}_4\text{)}_2\text{(OH}\text{)}_6$, is rendered graphically in this figure taken from the reference. The jarosite ...


4

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 satellite broke and was abandoned until 13 years later a amateur found it transmitting. Opportunity is most likely permanently damaged and it's unclear what ...


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