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

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...

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.

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 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.

Been There; Done That

[Kozar_The_Malignant]

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

Interstate 5 near Bakersfield.