Huygens shortlived?

Is it true that Huygens ceased transmission less than 2 hours after
touchdown? Whilst it was a magnificent achievement to travel so far and
land perfectly, it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

dexx wrote:
I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

As I understand, the issue was that Huygen's relay satellite, Cassini,
was only going to be in a position to listen to Huygens for a few
hours. There was no point in giving Huygens a longer life.
Mike Miller, Materials Engineer

"dexx" bravely wrote to "All" (16 Jan 05 06:18:31)
--- on the heady topic of "Huygens shortlived?"

de From: "dexx"
de Xref: aeinews sci.space.tech:388 sci.space.policy:6670 sci.astro:6725

de Is it true that Huygens ceased transmission less than 2 hours after
de touchdown? Whilst it was a magnificent achievement to travel so far
de and land perfectly, it seems a great shame that the probe was so short
de lived. I'm suprised the designers didnt make it rugged enough and
de powered enough to survive several days.


I'm already impressed they got the batteries to last 7 years!

A*s*i*m*o*v

.... A REAL test for that pink bunny: Build a Huygens Space Probe

dexx writes:

Is it true that Huygens ceased transmission less than 2 hours after
touchdown? Whilst it was a magnificent achievement to travel so far and
land perfectly, it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

But there was nobody to talk to. Cassini couldn't stay in
communications range for several days.

In sci.space.tech dexx wrote:
Is it true that Huygens ceased transmission less than 2 hours after
touchdown? Whilst it was a magnificent achievement to travel so far and
land perfectly, it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

Why?
It had a low resolution camera, and all the data from that had already been
recieved.
It would have needed a bigger transmitter, bigger battery, ...

All that would have been gained would be atmospheric pressure and
identical pictures.

dexx wrote:
Is it true that Huygens ceased transmission less than 2 hours after
touchdown? Whilst it was a magnificent achievement to travel so far and
land perfectly, it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

one design limitation factor was the length of time that Cassini would
be "over the horizon" wrt the lander. Huygens doesn't have powerful
enough transmitters to relay the datastream directly to Earth, so having
longer batt life wouldn't do anything but waste money and resources if
it couldn't see its mothership and thus transmit data.

Building enough transmitter power to send to Earth directly would very
likely have major scalability issues, which in turn would have a direct
impact on other mission profiles (maybe they could have had a powerful
transmitter but little or no instrumentation to feed it data, f'rinstance).

Mission planning for any tpye of space vehicle is a series of tradeoffs
between various things: time, money, propellant, payload, *type* of
payload, mission duration, mission capability, etc. etc.

Bottom line: for any launcher and any vehicle and any mission profile,
there's only so much you can include. Add more of thing X and you have
to take away from things Y, Z and A'.

--
Terrell Miller


"Every gardener knows nature's random cruelty"
-Paul Simon George Harrison

dexx wrote:
Is it true that Huygens ceased transmission less than 2 hours after
touchdown? Whilst it was a magnificent achievement to travel so far and
land perfectly, it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

I suspect you're going to be snowed under by responses to this, but...

Huygens was specifically designed as an *atmospheric* probe. It was supposed
to descend through the atmosphere, take readings, hit the surface and die.
Anything beyond that was gravy. They were hoping for ~30 minutes of surface
data; they reckon it was actually transmitting for about five hours.

The second point is that Huygens couldn't contact Earth directly. It had to
relay all its data through Cassini, and Cassini was due to drop below
Titan's horizon (that was the two hour figure). I believe --- can anyone
confirm this? --- that Cassini had to repoint its main antenna at Huygens
to pick up anything at all, which meant that it wasn't pointed at Earth,
which meant that it was completely out of touch, and since Cassini is a
hell of a lot more valuable than Huygens that's probably not a good idea.

The third point is that since noone knew anything about Titan's environment,
there was no way of designing a complex, long-duration lander that could
survive. The designers opted for a limited lifetime probe because that way
they could be sure of getting *some* data. The next probe will get more.

That said, I sympathise --- Huygens has returned just enough information to
let us know that Titan's really interesting without actually telling us
much about it. I wish Huygens had landed within sight of the coast! And I
do wish that it had been politically feasible to power Huygens with an RTG
instead of batteries; that would have been a simple way to increase the
lifetime without increasing the complexity (and reducing the reliability).

When's the next Titan mission due? Not for years and years and years, isn't
it?

--
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"dexx" wrote in news:1105885111.638247.89710
@z14g2000cwz.googlegroups.com:

Is it true that Huygens ceased transmission less than 2 hours after
touchdown? Whilst it was a magnificent achievement to travel so far and
land perfectly, it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

Powered with what? Chemical batteries were the only
practical method, and payload margins were extremely
tight.

--Damon

dexx (or somebody else of the same name) wrote thusly in message
. com:

Is it true that Huygens ceased transmission less than 2 hours after
touchdown? Whilst it was a magnificent achievement to travel so far and
land perfectly, it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

Did we know how long a day is on Titan?
--
Paul Townsend
Pair them off into threes

Interchange the alphabetic letter groups to reply

In article . com,
dexx wrote:
Is it true that Huygens ceased transmission less than 2 hours after
touchdown?

Exact numbers aren't on hand, but that's generally right. Bear in mind
that Cassini went below Huygens's horizon around that time, so no further
data relaying was possible anyway.

The primary mission was complete three *minutes* after touchdown. Huygens
was mostly an atmosphere probe; the surface imaging and instruments were
an extra.

...it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

It would have greatly increased the cost and complexity, unfortunately,
because it would almost certainly have required an RTG. Moreover, several
days is not enough -- it'll be a month or two (I forget exactly) before
Cassini goes past Titan again. You can't really do a long-lived Titan
surface mission without better communications support, that is, either a
Titan orbiter or a lander that's big enough and heavy enough to carry its
own high-power transmitter and steerable high-gain antenna (plus the power
source needed to run them).
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |