
Computing glitch may have doomed Mars lander - okket
http://www.nature.com/news/computing-glitch-may-have-doomed-mars-lander-1.20861
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LordWinstanley
>>>...Then thrusters, designed to decelerate the craft for 30 seconds until it
was metres off the ground, engaged for only around 3 seconds before they were
commanded to switch off, because the lander's computer thought it was on the
ground...

>>...The lander even switched on its suite of instruments, ready to record
Mars’s weather and electrical field...

It's a shame. But, reading that, I can't help imagining the lander in the role
of the Blue Whale from Hitchhiker's Guide to the Galaxy:

"I wonder what this big flat thing rushing toward me is? I think I'll call it
'The Ground'"

~~~
Fiahil
At least it wasn't a unit-conversion problem. It would be really shameful for
an _European_ lander to mix up an altitude reading between feet and meters.

But it's not the case, isn't it?

~~~
3chelon
That seems exceedingly unlikely. No-one in Europe would even consider using
anything other than metric units even for buying their groceries, let alone a
critical engineering task.

That said, _if_ there were any US companies involved then perhaps there might
have been complications. Many years ago I worked on guidance software for
tunnelling machines and we had a US client who insisted that we reprogrammed
the entire system for them to work in "centifeet", i.e. 100th of a foot or
approx 3mm.

I well remember the chaos and arguments caused by adopting such a ridiculous
chimera of a unit, and was struck by how resistant some people are to adopting
something as universal and transferrable as SI units.

~~~
sethrin
There are actually a fair few problems with SI units. The candela is fairly
ridiculous, the kilogram needs to not depend on a physical object (it's also a
little silly to have a prefixed base unit). The ampere is not practical to
measure with its current definition, and apparently with the current
definitions of Hz and radians, 1 Hz = 1/s = 1 radians/second. Other people
take issue with the mole, as well.

SI is an improvement but it is not quite perfect. As long as we have a choice
of imperfect systems, we have to pick which is most convenient.

~~~
3chelon
> it's also a little silly to have a prefixed base unit

I somewhat agree with that - I had the exact same conversation with my kids
very recently.

Re. physical object: well, whatever physical reference artefact is used, to
all intents and purposes the physical stuff is water, with the basically
sensible equivalence 1L = 1kg = 1000cc. As you point out, it's not perfect
because of the somewhat arbitrary scales (kg, cc), and it gets worse when you
bring temperature into it (I believe it's supposed to be measured at 4 degrees
C, but I'm not totally sure of that).

You're right in that it is not perfect, but at least it is a fair attempt at
coherence.

~~~
tremon
_I believe it 's supposed to be measured at 4 degrees C_

Correct; it's because at that temperature water is at its densest:
[https://en.wikipedia.org/wiki/Water#States](https://en.wikipedia.org/wiki/Water#States)

------
dzdt
Is software easier or harder than hardware?

Somehow people seem to assume software is easier, but then there are at least
as many critical failures blamed on software as on hardware.

Maybe there are different curves: software is easy to get to 90% working but
hard to get from there to 99.9%. Hardware is hard to get to 90% working but
easy to get from there to 99.9%.

~~~
SixSigma
> the lander's computer thought it was ...

> led the craft to believe it was...

Don't anthropomorphize computers, they hate that.

As an armchair space explorer, I would have imagined such a crucial part of
the mission had serious redundancy.

~~~
dzdt
I think the anthropomorphizing in this case is fine. Someone familiar with
programming easily takes "computer thought it was on the ground" as shorthand
for "computer began executing subroutines designed to activate when the craft
was on the ground."

The anthropomorphized version is more concise for someone familiar with and
more understandable for someone unfamiliar with the inner details of computer
systems.

~~~
andars
I think it was a joke, seeing as SixSigma proceeded to anthropomorphize
computers ("they hate that").

~~~
SixSigma
A bit of both.

I actually don't think anthropomorphization is helpful in discussions with the
lay public but I'm not that serious about it.

------
Pigo
I know this is off-topic, but reading about it's mission has me wondering why
(as far as I know) no agencies are sending devices that could return more
sophisticated visuals. Even something simple like the 360 YouTube videos would
be beyond words, and everyone could experience it. I've really enjoyed the
panoramic images. I just wish they'd focus more on trying to get people there
virtually since it's a fraction of the effort of getting them there
physically, and it could be shared with everyone. Is there some kind of
barrier to sending that much data through space? Or should the focus always be
on looking for signs of life?

~~~
wwggggoi
this is something I never got: why don't they just chuck a whole bunch of
cheap consumer gadgets on these things ? Is it really that hard to attach an
array (for redundancy) of gopros to constantly transmit video at 60fps (and
sound, even if Mars doesn't really propogate sound) ?

~~~
lucozade
> why don't they just chuck a whole bunch of cheap consumer gadgets on these
> things

This [0] is an interesting read on some of the considerations for the
Curiosity rover cameras.

[0] [https://www.dpreview.com/articles/0353350380/curiosity-
inter...](https://www.dpreview.com/articles/0353350380/curiosity-interview-
with-malin-space-science-systems-mike-ravine)

~~~
wwggggoi
great link thanks!

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farhanhubble
I hope they didn't mix up metric and imperial units this time again. Or is it
the Agile specter that haunts software made in Europe?

~~~
dignati
Given that it's an European project I'd be surprised if it was a metric vs
imperial unit mixup.

~~~
dogma1138
UK says hi.

~~~
mattlondon
For what it is worth - apart from road signs and speeds - I've not really seen
imperial measurements used for much any more in the UK.

I would be _amazed_ (and saddened) if someone had started a new, large-scale,
serious, rigorous, engineering project in the past couple of decades (i.e.
since the 90s) and used imperial units (I am sure there are lots of small-
scale/personal/etc stuff done in imperial though - I dont count interplanetary
space flight as small-scale!)

Imperial is pretty much dead in the UK (or maybe just London?) apart from
roads and conversational/casual usage where its often easier to say the
imperial equivalent than the metric (e.g. "pint of beer" is easier than saying
"568 millilitres of beer", "about a foot" is easier than saying "about 30
centimetres" just because of fewer syllables if nothing else).

~~~
dogma1138
If you think imperial measurements are dead in london you never had to deal
with plumbing in your apartment where you have a mixture of imperial and
metric pipes and threads ;) And the best is always finding a metric pipe with
an inch thread pitch on it....

Also IIRC technically most engineering schools in the US also use metric these
days, it doesn't mean stuff doesn't get screwed up, imperial on it's own is
also annoying since you have both decimal (thous) and fractional units which I
always found frustrating on it's own.

------
axonic
thruster_test(3000); // todo: add powered descent code

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CoryG89
Everyone has a plan, until they get hit by a planet.

~~~
xeromal
-Mars Tyson

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skoczymroczny
They should have used Haskell.

~~~
planteen
I assume this is a joke? Is Haskell suitable for hard real-time systems with
things like lazy evaluation and a GC?

~~~
tome
I think it's a joke. Haskell is manifestly not suitable for writing a Mars
lander.

A verified DSL written in Haskell on the other hand ...

[http://ivorylang.org/ivory-introduction.html](http://ivorylang.org/ivory-
introduction.html)

------
fabriceleal
Reminds me of that robocop scene "You call this a glitch???"

------
JoeAltmaier
This was my first thought actually. Faulty ground sensing has doomed many a
craft.

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hliyan
I was about to suggest n-version programming redundancy, when it occurred to
me: aren't we starting to reach a point where deep learning systems are good
enough for unmanned spacecraft? How we would generate the learning data would
be a question though.

~~~
hvidgaard
You wastely overestimate the capabilities of the equipment we send into space.
It is nowhere near powerful enough to power any meaningful deep learning
system in an online fashion. Offline has either to high latency, or a problem
getting data to seed the initial learning (and even then we have a problem
actually running the network).

~~~
lorenzhs
Well than and there just isn't a whole lot of training data to play with. It's
doubtful that a simulator could ever model actual landing situations well
enough that the whole thing will a) work on Mars and b) not overfit weird
behaviour in the simulator. Faulty ground sensing has resulted in the loss of
more than one mission, and deep learning isn't going to fix any of that.

Oh, and s/wastely/vastly/ ;)

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int0x80
this days, almost every failure can be related in some way to a "computing
glitch".

~~~
coldcode
Glitch is a strange word to blame everything on. It implies a temporary
problem. This sounds more like a more permanent problem, as in it's
permanently crashed into the ground.

~~~
archgoon
Blasted clipping errors.

------
riskable
It seems no matter the problem there's always someone trying to blame IT.

