Huygens Landing on Titan to be Tricky

neutron_p writes "On Jan. 14, 2005, Huygens probe will plow into the orange atmosphere of Saturn's moon, Titan. It will be flying blind through hydrocarbon haze and methane clouds to a surface that could consist of seven-kilometer-high ice mountains and liquid methane seas. Scientists hope that Huygens will survive the plunge. I hope too, especially after Genesis mission accident, although condition were much better."

Comments

Tricky landing

[mknewman]

And this will be tricky how? I thought this was all preprogrammed for years.

Re:Tricky landing

[parvenu74]

Preprogrammed based on what we *think* are the actual conditions there... now the landing will prove whether or not the readings and predictions were right. Considering there is not going to be any way to adjust for surprises on the way down I think that would qualify for at least mildly ticky...

Re:Tricky landing

[purfledspruce]

Let's not forget that Cassini and Huygens have been in the cold vacuum of space for 7+ years...Genesis had only been in space for 2 years before its parachute didn't open.

Who would expect their car (a machine that is far less complex and delicate than Cassini/Huygens!) to work flawlessly after 7 years here on Earth? A car is a machine that we've had practice building, practice using, and practice repairing--we've never practiced building Cassini/Huygens, we've never had practice using either, and we can't repair them!

Well, unless YOU have a screwdriver that's 1,427,000,000 kilometers long!

Re:Tricky landing

[Profane MuthaFucka]

Let's also not forget that the chute mechanisms on Huygens are not the same as the ones on Genesis. The problem with Genesis was not a flawed parachute. If it had deployed, it would have opened.

Re:Tricky landing

[CheshireCatCO]

How do you figure we've never had practice building or repairing these things? Cassini/Huygens specifically, no. But it's not like the technology is brand new to us. There are Voyager spares on board Cassini, for example. And it's not like we've never had to do a long-distance repair on one of these guys before. So far, Cassini has had the main camera go foggy (repaired it) and the Huygen's probe turn out to be unable to communicate with Cassini (altered the flight plan to circumvent the problem). To use your car analogy, it's like saying that we're in the dark about building a given new model. Of course we aren't, most of what's there is old hat to the designers.

Besides, when you spend $3 billion on the thing, you buy a lot more quality control than your typical automobile.

Also, you shouldn't forget that Cassini has heaters on board. So "cold" might not be as much of a worry as you think.

Re:Tricky landing

[purfledspruce]

We have never built a spacecraft as large or as complex as Cassini/Huygens.

You are correct, we are not in the dark when we build a new automobile, or, for that matter, a spacecraft. However, just think about how many automobiles have been built and how many spacecraft have been built. You are knowledgable, so tell me: how many spacecraft have been built in all of human history that have gone beyond the moon's orbit? Your point is well taken, though, we have done it enough times to include heaters on board, and radiators for the RTGs, and (I assume) louvers for heat balance, and a main dish that doesn't fold, and...well, it goes on and on and on, doesn't it? That's kind of my point, spacecraft are extremely complex objects and Huygens's descent onto Titan isn't an event that we should assume will go smoothly.

You are knowledgable, but you are also a bit tricky in your description...Cassini's main camera did, in fact, get foggy. But this is was expected and we had designed it to heat up to remove the fog. This wasn't so much of a 'repair' as it was a 'planned operation.' The course correction for the doppler shift is a better example, but it's simply a course correction. This isn't Hubble; if something truly goes wrong, not only will we not be able to fix it, we may never know what happened.

Re:Tricky landing

[CheshireCatCO]

No, the fogging wasn't expected. They had the equipment on board to *deal* with it, but there were a LOT of scared people at NASA (and in the planetary community) for months over that one. They didn't even know for sure that it was fogging for quite a while. So you can't call that a "planned operation", I'm sorry.

The number of automobiles that have been built isn't what you're after; it's the number of MODELS that you need to look at. And whether a spacecraft passes the Moon's orbit or not doesn't change a lot of the design. We have a lot of experience with spacecraft. I'd agree, we probably have more with cars. But we also spend a lot more on checking spacecraft over and adding more redundancy to the system before we launch them. And we spend more time analyzing failures (large and small) in the spacecraft to learn from them than is typically done with cars. The two situations are just too different to compare. The very fact that cars are more numerous than spaceprobes also means that the latter get a lot more care and attention than the former.

The size of Cassini is also a red herring on your part. Sure, it's the biggest yet. But it's not really all that much bigger or more complex than, say, Galileo. Most of the parts on board are time-tested designs.

I doubt that anyone involved is assuming that things will go smoothly. NASA checks and rechecks these things (for a mission this size, anyway). But to pretend that NASA Cassini is some brand new territory for NASA is just wrong. As always, there are new aspects, but it's not like they have no experience with this stuff.

Re:Tricky landing

[purfledspruce]

I have to ask you...if it wasn't expected, why did they have equipment to deal with it? It seems to me that the engineers expected it...in fact, here is a quote from JPL's press release in 2002 that proves my point:

"Lens hazing from engine exhaust or other sources is always a possibility on interplanetary spacecraft. Planners designed heaters for Cassini's cameras to cope with just such a situation."

http://saturn.jpl.nasa.gov/news/press-releases-02/ 20020723-pr-a.cfm

I agree with you that my comparison was a stretch--in fact, that was the point of the analogy. By concentrating on the analogy, though, you are missing my point: Huygens landing on Titan is something that we've never done, we don't know what's on Titan, and the landing has a non-zero chance of failure. You actually agree with this, I think, so I'm not sure what we're talking about any more. :)

Re:Tricky landing

[CheshireCatCO]

Providing equipment to deal with a problem isn't the same as expecting in. Cars are designed to handle a roll, but I don't expect it to happen to me. Which is just the point, really: NASA is ready to provide mid-mission fixes to all kinds of problems, including ones that they don't anticipate or really expect.

And since I was privy to what was going on when the fogging was being dealt with, I can say that (unless my sources, who are very much involved with this, are lying), they didn't really expect the fogging and they certainly didn't know for sure that that's what it was. I heard alternate theories right up until the last baking fixed the problem.

Re:Tricky landing

[purfledspruce]

I just got a memo that states NASA will be using the sythetic aperture radar instrument during Cassini's flyby of Titan on the 26th of this month. This will help us know what the Huygens's landing site is like. I don't know what that will do to the eventual landing, but I can imagine that it might change things.

For us geeks who love numbers, the total information gathered by all the instruments during the Titan flyby on the 26th will be around 3.6 Gbits.

Re:Tricky landing

[mattr]

That's a cool number you have there pardner.

Leapt out at me something like the 2.147 in the 2GB limit (2^31). No it's a bit more than 1 gig (which is 1.074).

But, and I'll thank you to forget that we are moving past each other so it is only true for the moment, but here is an easy way I just figured to remember the distance to Titan. Or T1T42 in my l33t-sp34k. (leet speak). Well the 2 is an N sideways okay?

So anyway, remove the T's (for terameter), and you get 142. 1,427,000,000 kilometers is 1,427,000,000,000 meters, or 1.427 terameters. Who cares about rounding up, we're flying through space at x meters per second! So Titan is only about a terameter and a half away from here.

Re:Tricky landing

[WormholeFiend]

some news are reporting today that a switch installed backwards could be the reason why the drogue chute didnt deploy.

IEEE spectrum

[ballpoint]

There is an interesting article (http://www.spectrum.ieee.org/WEBONLY/publicfeatur e/oct04/1004titan.html) in the current issue of IEEE spectrum. They discuss how a disaster was avoided by Boris Smeds who pushed for stringent tests of the communication between Cassini and Huygens. It turns out that the Italian manufacturers of the radio didn't take into account the significant doppler shift between both craft. As the firmware of the radio could not be remotely upgraded, Cassini's trajectory was altered (further away from Titan) to lower these doppler shifts.

Let's hope no other misfortunes turn up.

Re:IEEE spectrum

[Tablizer]

The Dopler problem you link to sounds like its cause is similar to the Hubble lens problem: secrecy and paranioa prevented or hampered integrated testing. In the Hubble case it was military secrecy, but in this case is was trade-secret secrecy. In the software business one knows that integrated testing is paramount, and more so when the computer is billions of miles away and you have only one shot to get it right.

Re:IEEE spectrum

[Anonymous Coward]

It turns out that the Italian manufacturers of the radio didn't take into account the significant doppler shift between both craft.

Why does this matter? You only need to deal with the doppler shift on one end. If it actually became an issue, you could just change the transmission or reception of the signal on the ground.

Re:IEEE spectrum

[Anonymous Coward]

The radio link is between two spacecraft:

- Huygens, which descends into/onto Titan and
- Cassini, on a trajectory passing Titan.

Indeed, the doppler shift must only be dealt with on one end. But in this case that end is the radio in the Cassini spacecraft. That radio cannot handle large doppler shifts, and its firmware cannot be updated remotely.

Tricky descent, hope ESA got the tech right.

[Nagus]

This page describes how the descent of the Huygens probe will hopefully be achieved. It's quite complicated, here's a synopsis:

• Before the Huygens probe separates from Cassini, a timer is set which will awaken it prior to entry into Titan's atmosphere. This timer triple-redundant.
  
• The probe separates from Cassini, and shuts down all systems (except for the timer). It coasts for 21 days before reaching Titan.
  
• Five days after separation, Cassini (not Huygens, it's asleep, remember?) will perform a deflection maneuver to position itself such that it can receive data from Huygens via radio (which will be relayed to Earth).
  
• A few hours before entering the atmosphere, Huygens will be awakened by its timer.
  
• At the time that Huygens starts to enter the atmosphere, Cassini will start to listen for signals from the probe. It will continue to listen until 30 minutes after the landing of Huygens.
  
• When Huygens has decelerated to 1440 km/h, a mortar will deploy the "pilot" parachute, which in turn will remove the aft cover and deploy the main parachute.
  
• After the 8.3 meter parachute is deployed, the front shield is released and falls away.
  
• After a delay of 30 seconds (to prevent instrument contamination from the shield), inlet ports are opened and atmospheric instruments are activated. At this time, the Atmospheric Structure Instrument boom is also deployed.
  
• 2 minutes later, the Imager/Spectral Radiometer cover is ejected.
  
• 15 minutes after the main parachute has been deployed, it is ejected and in its place the descent parachute (3 meters) is deployed.
  
• From this point on, the descent will last between 2 and 2.5 hours.
  

The Huygens probe will shoot 1100 pictures during its descent. I had been hoping for full-motion video of the descent :), the 1800 Watt-hour batteries they have should be powerful enough for a camera. Maybe there are bandwidth issues. Who am I to complain?

One thing that is unclear is that Cassini will turn away its antenna from Huygens 30 minutes after it lands. Does this mean that no further data will be received afterwards? I had the impression that there was a series of surface experiments to be done after landing. Seems kind of cruel to abandon the brave little probe just 30 minutes after it lands.

But I'm happy to hear (according to this) that Huygens seems to be in good shape. It has recently passed its 15th in-flight system check.

Best of luck to the scientists at ESA and NASA - I look forward to having a picture of Titan's surface as my desktop wallpaper.

Re:Tricky descent, hope ESA got the tech right.

[Chuck1318]

One thing that is unclear is that Cassini will turn away its antenna from Huygens 30 minutes after it lands. Does this mean that no further data will be received afterwards? I had the impression that there was a series of surface experiments to be done after landing.

The Huygens probe instruments are primarily designed for measurements during the descent through the atmosphere, along with some measurements at the time of landing and immediately after. The probe batteries are sized for 153 minutes of operation, so there would be no point in listening after the batteries have drained.

Re:Tricky descent, hope ESA got the tech right.

[cmowire]

Camera, yes.

Power and computing ability to handle the storage and transmission of a lot of video, no.

Besides, the main thing that they need is a few good frames at high resolution, not a whole bunch of low resolution frames. Unfortunately, we're not at the point where you can put stuff in a probe that's not necessary for science or spacecraft engineering but looks cool yet.

Although, on the earth side, it's different. Notice how it seems to take a mission control room with 16 NASA scientists, none of whom are doing anything *other* than watching their screens because of the massive light-speed delay prevents them from commanding it before it'll be too late, where any data is already being recorded for later analysis, etc. I mean, it looks cool and if I was a NASA scientist, I'm sure *I'd* be nagging my pointy haired boss to let me sit in the control room during landing, but it's not really necessary. ;)

I think the answer to your question about abandoning poor Huygens is that it's a communications window. After 3 hours, it's no longer at the right angles and range and whatnot to properly make contact. Plus it'll be out of juice by that point.

Re:Tricky descent, hope ESA got the tech right.

[stevelinton]

It's not so much a landing as a crash. If it lands on something reasonably level soft and solid, or possibly on a dense liquid that doesn't cause any immediate chemical or electrical problems, it MIGHT still be alive enough to transmit for a few minutes after it lands.

Re:Tricky descent, hope ESA got the tech right.

[Alsee]

light-speed delay
if I was a NASA scientist, I'm sure *I'd* be nagging my pointy haired boss to let me sit in the control room during landing

I'll tell ya what - you can sit at the screen in the control room during landing, you can have a half hour. Then you get the boot and I get the next half-hour, when the landing video actually arrives :D

-

Wow

[CodeWanker]

I think Prince said it best when he sang "I only want to see you landing in the Methane Rain."

Been There; Done That

[Kozar_The_Malignant]

> It will be flying blind through hydrocarbon haze and methane clouds

Interstate 5 near Bakersfield.

Re:Been There; Done That

[NardofDoom]

> It will be flying blind through hydrocarbon haze and methane clouds

Interstate 5 near Bakersfield.

After stopping at Taco Bell for a few bean burritos.

First deadly contact with offsite life?

[Anonymous Coward]

If there is life on Titan and the landing is not controlled isn't the potential for murder high?

First? First public?

Contact, anthill, squish.