

How a Swedish engineer saved a once-in-a-lifetime mission to Titan (2004) - ablutop
http://spectrum.ieee.org/aerospace/space-flight/titan-calling

======
jessriedel
Hopefully everyone realized that this article is from 2004 and Huygens
completed its descent onto Titan in January 2005. The problem discussed in the
article was successfully fixed, saving the mission, but an unrelated problem
(also with the telemetry) means a modest chunk of data was lost:

> Huygens was programmed to transmit telemetry and scientific data to the
> Cassini orbiter for relay to Earth using two redundant S-band radio systems,
> referred to as Channel A and B, or Chain A and B. Channel A was the sole
> path for an experiment to measure wind speeds by studying tiny frequency
> changes caused by Huygens's motion. In one other deliberate departure from
> full redundancy, pictures from the descent imager were split up, with each
> channel carrying 350 pictures.

>As it turned out, Cassini never listened to channel A because of an
operational commanding error. The receiver on the orbiter was never commanded
to turn on, according to officials with the European Space Agency. ESA
announced that the program error was a mistake on their part, the missing
command was part of a software program developed by ESA for the Huygens
mission and that it was executed by Cassini as delivered.

>The loss of Channel A means only 350 pictures were received instead of the
700 planned. All Doppler radio measurements between Cassini and Huygens were
lost as well. Doppler radio measurements of Huygens from Earth were made,
though not as accurate as the expected measurements that Cassini would have
made; when added to accelerometer sensors on Huygens and VLBI tracking of the
position of the Huygens probe from Earth, reasonably accurate wind speed and
direction measurements could still be derived.

[http://en.wikipedia.org/wiki/Huygens_(spacecraft)#Channel_A_...](http://en.wikipedia.org/wiki/Huygens_\(spacecraft\)#Channel_A_data_lost)

~~~
antimagic
Well, being pedantic for a moment, the problem never was fixed. The flightpath
of Cassini was simply altered so that there was negligeable Doppler shift of
the radio signal from Huygens, meaning that the inability to handle a Doppler
shift.

Happily enough this was possible to do without using too much fuel, and indeed
Cassini had more fuel available than planned, as the original launch and early
course corrections had been so precise that fuel planned for course correction
burns was available for other uses. One of the consequences of all of this is
that Cassini is still operational today, more than 5 years passed the planned
end of it's mission.

~~~
keithpeter
_" Well, being pedantic for a moment, the problem never was fixed."_

But a work round was found. And I have a _really good_ example for teaching
resolving vectors...

------
onion2k
Amazing work by a tenacious and talented engineer. Great story.

(Question: What does his nationality have to do with it though? Seems like an
odd addition to the headline.)

~~~
andyjohnson0
_" Question: What does his nationality have to do with it though? Seems like
an odd addition to the headline."_

Seemed strange to me too. There was another instance of this a few days ago
with the article "How British satellite company Inmarsat tracked down MH370"
[1]. Is this a journalistic practice?

[1]
[https://news.ycombinator.com/item?id=7463181](https://news.ycombinator.com/item?id=7463181)

~~~
rayiner
It lends human interest. Humans are inherently tribalistic, and one of the key
ways we understand and categorize other humans is according to tribal
affiliations.

~~~
nitrogen
This is an aspect of humanity that should be fought, not embraced and
exploited.

~~~
rayiner
I strongly disagree. Tribalism is what allowed humans to survive into the
modern age, and is a force that in this era of individualism keeps societies
from unraveling. Humans will be tribal, it's just a matter of how tribal lines
are drawn. In the era of globalization, tribal lines are increasingly being
drawn along lines of wealth, class, and education which is in my opinion worse
than drawing them along geographical boundaries.

In practice, the alternative to geographic tribalism isn't some broadly-
inclusive egalitarianism. It's relatively wealthy and educated folks like us
receding into circles with other relatively wealthy and educated folks.

~~~
meric
Very much agree. Taken to the extreme, complete suppression of tribalism would
not only be extremely difficult but also extremely harmful to society, as even
the love between children and parents will be destroyed in favor of
egalitarian love. Our biological nature causes children to prefer their
parents more than any other parents, and in doing so, prefer their siblings
(their parent's other children), more than any other children, and prefer
their parents' siblings and parents more than any other elderly persons and
adults. It is this nature, as it radiates outwards, that causes one to feel
greater love to those who are similar than those who are different.

I don't want to live in a world where children are taught to betray their
parents in favor of their state, where children are taught to report on their
parents for their crimes, where brothers treat each other as strangers, where
husband betrays wife and vice versa, at the same time. I've already read about
it in 1984.

The harm in suppressing this aspect of humanity comes from having to involve
the state. It takes the state to educate children to report on their parents
crimes. It takes the state to force children to attend schools to study the
same subjects. It takes the state to extract wealth from parents to distribute
it to other children. It takes the state to enact taxes on children to
distribute their income amongst other parents. Taken to the extreme - you'll
get a very big, very powerful state, because it must involve itself in
everyone's personal relationships, to ensure equality amongst all. And with a
big state, you get corruption, you get misallocations of capital, you get a
concentration of power, all of which would lead to a state that would monitor
its citizens every communication, to protect its power in actuality, and to
maintain equality and protect its citizens in name. And, as you reduce every
person's natural relationships, people will form relationships with others,
leading to divisions not amongst genetic or even geographic lines, but amongst
other arbitrary lines such as class and wealth, government and private. As a
group of people gain control of state, the actions of the state will begin to
benefit some, but not others, arbitrarily, so that in actuality equality (in
wealth, status, whatever) will always only be an illusion, and inequality will
always manifest itself in other ways, so that all those resources supporting a
very big state to maintain equality, are mostly wasted, except in so far as it
provides an _illusion_ of equality, which it can maintain for only so long.

Oh, wait.

~~~
saraid216
Presentism: making sure one doesn't have to acknowledge history in order to
advance one's own tribal ideology. Good job!

~~~
meric
You've dismissed someone's carefully thought out reply with not arguments but
with a one-liner with a word of jargon, an accusation of someone advancing an
ideology through making comments buried many levels deep in random hacker news
threads and a dash of sarcasm thrown in for good measure.

Go ahead and feel proud you've defended your mind from reasoning another
person's thoughts and thinking up a rebuttal based on reasonable arguments.
lol. :)

~~~
saraid216
Wow. Self-describing your post as "carefully thought out".

Yeah, accuse me of pride. There's "takes one to know one", and then there's
_this_.

> thinking up a rebuttal based on reasonable arguments.

Your post is rebutted by history. When you have a reasonable argument to make,
go ahead and make it. Until then, your wall of sarcastic text is best answered
by "a dash of sarcasm".

~~~
meric
You're a troll, and I'm going to take the bait.

How is it rebutted by history? Tell me the specific historical events you have
in mind.

------
jimktrains2
Perhaps I missed it when I read the article: Why did he originally have the
hunch that the radio wouldn't work when Doppler shifted?

Also, I guess something like Manchester encoding wasn't use because of the
data rate limitations? IIRC Manchester encoding is self-clocking, which seemed
like the issue here.

~~~
natep
He didn't have a hunch, he just knew that the standard comprehensive test was
skipped, which is why the standard test procedure only detected a problem, and
he had to end early and go off book in order to reveal the doppler problem.

~~~
gwern
> Fortunately, Claudio Sollazzo, Huygens's ground operations manager at ESA's
> European Space Operation Centre (ESOC) in Darmstadt, Germany, had a nagging
> worry about the lack of a full-up communications systems test. Sollazzo knew
> there was time to run some tests during Cassini's long, uneventful stretches
> between the planets.

------
mistermann
> In proposing this more complex test with simulated telemetry, Smeds "had to
> argue with those who didn't think it was necessary," recalled JPL's
> Mitchell. Smeds was persistent and continued championing the test even after
> it was initially rejected. In the end, with the backing of Sollazzo and
> Huygens's project scientist, Jean-Pierre Lebreton, Smeds's plan was accepted
> because it was easy to do, even though hardly anybody seemed to think it was
> worth doing. On such seeming trivia US $300 million missions can turn: the
> simpler carrier-signal-only test, Mitchell noted, would never have uncovered
> any problems.

Is there any place you can go to escape the forces of willful ignorance?

------
ludoo
"An Alenia Spazio spokeswoman said that none of the company's officials were
available to comment because of a company-wide summer vacation period."
Typical Italian... (I'm Italian myself btw)

~~~
stygianguest
The French do the same. I see nothing wrong with it.

~~~
RA_Fisher
The whole set of top management taking off at one time? Maybe for a remote
startup company, but c'mon as a taxpayer it must be infuriating.

~~~
frandroid
As a taxpayer, you don't think about being infuriated as you're on the beach
yourself during your own summer vacation.

~~~
Rovanion
It is the same in Sweden. Most of the country shuts down during summer and
we're fine with it because we do too have our vacations right then.

------
_Robbie
_Alenia Spazio’s insistence on confidentiality may have played a role in this
oversight. NASA reviewers were never given the specs of the receiver. As JPL’s
Mitchell explained to Spectrum, “Alenia Spazio considered JPL to be a
competitor and treated the radio design as proprietary data.”_

I am surprised that NASA would allow a piece of hardware on a spaceship that
they do not have the specs for. Unless NASA/ESA do very extensive testing,
this seems like a terrible practice.

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anovikov
That's like that famous "sce to aux" moment... except in a slow-mo.

~~~
jboggan
Very cool story, thanks for bringing it up:

[http://en.wikipedia.org/wiki/John_Aaron](http://en.wikipedia.org/wiki/John_Aaron)

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ilovecookies
I'm 100% sure this was posted by a swedish person. Even saying so i'm pretty
proud tbh

------
jgreen10
Typical Sweden.

