Chatroom
 

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Bad Astronomy and Universe Today Forum > Space and Astronomy > Space Exploration
Register FAQ Members List Calendar Mark Forums Read

   

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 23-December-2004, 06:08 PM
ToSeek's Avatar
ToSeek ToSeek is online now
Vulcan Administrator
 
Join Date: Oct 2001
Location: Greenbelt, MD
Posts: 24,460
Default Huygens encounter with Titan

I'm going to start a new topic for this (mostly because the erroneous apostrophe in the title of the topic I've been using annoys me!).

Splash, Thud, or Whimper? Cassini's Huygens Probe Rendezvous with Titan



Quote:
On December 24th, 2004, at 7:08 PM Pacific Standard Time, the Cassini spacecraft will release a probe that has hitched a ride all the way from Earth out to Saturn. The Huygens Probe, named after the Dutch scientist Christiaan Huygens, who discovered Titan and Saturn’s rings in the 17th century and built by the European Space Agency, will spend 22 days traveling to its rendezvous with Saturn’s mysterious moon Titan on January 14th. Titan is one of the remaining puzzles of the solar system – while Cassini’s imaging cameras and radar instrument have begun to reveal the details of its surface, the Huygens probe will be the first spacecraft to venture beneath Titan’s thick clouds
__________________
Everything I need to know I learned through Googling.
Reply With Quote
  #2 (permalink)  
Old 23-December-2004, 08:22 PM
Disinfo Agent Disinfo Agent is offline
Senior Member
 
Join Date: Apr 2004
Posts: 6,600
Default

Why will it be so long between separation and entry?
__________________
"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire
Reply With Quote
  #3 (permalink)  
Old 23-December-2004, 08:39 PM
ToSeek's Avatar
ToSeek ToSeek is online now
Vulcan Administrator
 
Join Date: Oct 2001
Location: Greenbelt, MD
Posts: 24,460
Default

Quote:
Originally Posted by Disinfo Agent
Why will it be so long between separation and entry?
Since Huygens has no propulsion system, Cassini must be on the same track as Huygens at the time of release, i.e., a collision course with Titan. The long lead time gives Cassini enough room to change its course so as not to collide with Titan.
__________________
Everything I need to know I learned through Googling.
Reply With Quote
  #4 (permalink)  
Old 23-December-2004, 09:38 PM
Christopher Ferro's Avatar
Christopher Ferro Christopher Ferro is offline
Senior Member
 
Join Date: Oct 2001
Location: The Space Coast
Posts: 1,288
Default

Is a 2.5 hour battery the best that could be done? Was this an engineering contraint, budgetary or was that the best battery when the thing was originally designed/built?

CJSF
__________________
Two years ago moved from my town
I was looking up past the city lights
But the city lights got in my way

See the constellation ride across the sky
No cigar, no lady on his arm
Just a guy made of dots and lines

-from "See The Constellation"
by They Might Be Giants
Reply With Quote
  #5 (permalink)  
Old 23-December-2004, 09:42 PM
kucharek's Avatar
kucharek kucharek is offline
Senior Member
 
Join Date: Feb 2002
Location: Karlsruhe, Germany, Old Europe
Posts: 4,052
Default

Don't know if this was posted here before, but here is a webpage with some test images taken by the camera. Just to give an idea what to expect.


Harald
__________________
"Flying in space is risky business, but just staying on this planet is risky business too." - John Young, astronaut
Reply With Quote
  #6 (permalink)  
Old 23-December-2004, 09:43 PM
kucharek's Avatar
kucharek kucharek is offline
Senior Member
 
Join Date: Feb 2002
Location: Karlsruhe, Germany, Old Europe
Posts: 4,052
Default

Quote:
Originally Posted by Christopher Ferro
Is a 2.5 hour battery the best that could be done? Was this an engineering contraint, budgetary or was that the best battery when the thing was originally designed/built?

CJSF
Cassini will go below the horizon after this time, so it wouldn't pay to have a battery that lasts longer.

Harald
__________________
"Flying in space is risky business, but just staying on this planet is risky business too." - John Young, astronaut
Reply With Quote
  #7 (permalink)  
Old 24-December-2004, 03:02 AM
Jerry's Avatar
Jerry Jerry is offline
Senior Member
 
Join Date: Mar 2004
Location: Earth
Posts: 3,794
Default

Quote:
Originally Posted by kucharek
Quote:
Originally Posted by Christopher Ferro
Is a 2.5 hour battery the best that could be done? Was this an engineering contraint, budgetary or was that the best battery when the thing was originally designed/built?
CJSF
Cassini will go below the horizon after this time, so it wouldn't pay to have a battery that lasts longer.
Harald
This one I do not understand. I can run my trawlin motor for a days on one battery, and Cassina completes another orbit in a month, why not shut Huygens down for a month and and fire it up again?????
__________________
jwj

It's ok not to know. We should try harder to find out.
Reply With Quote
  #8 (permalink)  
Old 24-December-2004, 03:11 AM
ToSeek's Avatar
ToSeek ToSeek is online now
Vulcan Administrator
 
Join Date: Oct 2001
Location: Greenbelt, MD
Posts: 24,460
Default

Quote:
Originally Posted by Jerry
This one I do not understand. I can run my trawlin motor for a days on one battery, and Cassina completes another orbit in a month, why not shut Huygens down for a month and and fire it up again?????
How would you do that? If Huygens is shut down all the way, then there's no way of waking it up again. If you want to allow for waking it up again, then it has to either have some sort of timer running or have some portion of the communications system remain on and listening. Even then you've got to assume it's going to survive the landing and then be able to hold out for a month. It doesn't seem like a possibility worth planning for.
__________________
Everything I need to know I learned through Googling.
Reply With Quote
  #9 (permalink)  
Old 24-December-2004, 03:16 AM
frogesque frogesque is offline
Senior Member
 
Join Date: Mar 2004
Location: Kingdom of Fife: 56.2°N, 3.2°W
Posts: 2,860
Default

Quote:
Originally Posted by Jerry
Quote:
Originally Posted by kucharek
Quote:
Originally Posted by Christopher Ferro
Is a 2.5 hour battery the best that could be done? Was this an engineering contraint, budgetary or was that the best battery when the thing was originally designed/built?
CJSF
Cassini will go below the horizon after this time, so it wouldn't pay to have a battery that lasts longer.
Harald
This one I do not understand. I can run my trawlin motor for a days on one battery, and Cassina completes another orbit in a month, why not shut Huygens down for a month and and fire it up again?????
My guess would be, apart from size and weight issues, that without heating the battery, once it drops below a critical temperature it wouldn't be able to emerge from hibernation

Solar Views: Titan

Quote:
Titan's surface temperature appears to be about -178°C (-289°F).
That's a real low temperature to kep a battery at for a month. To keep the battery warm would take power which would drain the battery so it would be self defeating.
__________________
By asking questions we sometimes get the wrong answers, from wrong answers we learn to ask the right questions.
Reply With Quote
  #10 (permalink)  
Old 24-December-2004, 05:28 AM
Van Rijn's Avatar
Van Rijn Van Rijn is offline
Senior Member
 
Join Date: Mar 2004
Posts: 10,819
Default

Quote:
Originally Posted by ToSeek
Quote:
Originally Posted by Disinfo Agent
Why will it be so long between separation and entry?
Since Huygens has no propulsion system, Cassini must be on the same track as Huygens at the time of release, i.e., a collision course with Titan. The long lead time gives Cassini enough room to change its course so as not to collide with Titan.
The signal timing problem was another issue. I found this article absolutely fascinating:

http://www.spectrum.ieee.org/WEBONLY...1004titan.html

The Cassini receiver for the Huygens probe couldn't fully account for doppler shift. The article covers how the problem was found and a workaround devised. From the article:

Quote:
FROM A VARIETY OF PROPOSED FIXES, the Cassini team crafted a response plan that centered on reducing the Doppler shift sufficiently to keep the data signal within the recognition range of the receiver. They accomplished this trick by altering the planned trajectory of Cassini. Now, Cassini will be much farther from Titan when Huygens enters its atmosphere.
and ...
Quote:
So the navigators designed a trajectory in which Cassini initially enters a lower and faster orbit around Saturn, drops off Huygens, and then hits a specific point in space that coincides with a point on the previously planned path. There Cassini fires its rocket engine again to get back on the original course.
The effect is that the flight takes longer and the landing is later than originally planed. If they hadn't done the testing and had gone with the original plan, though, we likely woudn't have gotten any useful data from the probe. Still, I hope there aren't any other real issues yet to be found ...
Reply With Quote
  #11 (permalink)  
Old 24-December-2004, 12:08 PM
Kaptain K's Avatar
Kaptain K Kaptain K is offline
Senior Member
 
Join Date: Oct 2001
Location: Elgin, Tx
Posts: 7,589
Default

Quote:
This one I do not understand. I can run my trawlin motor for a days on one battery, and Cassina completes another orbit in a month, why not shut Huygens down for a month and and fire it up again?????
And just how long will your motor last at -300F?
__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson
Reply With Quote
  #12 (permalink)  
Old 24-December-2004, 01:56 PM
ngc3314's Avatar
ngc3314 ngc3314 is offline
Senior Member
 
Join Date: Mar 2004
Location: 87.5W 33.2N
Posts: 1,455
Default

From looking through the PDF on the Huygens misison from the NASA/ESA site, here's a head's-up. To verify the exact departure trajectory, the orbiter will take a 5x5 imaging mosaic to show the probe at about 1400 UT on Christmas Day. After 11 hours or so it may look like just another faint star, but it should be encouraging enough to just see the thing. The timeline shows a 2.5-day window allotted for probe imaging, in fact.
Reply With Quote
  #13 (permalink)  
Old 25-December-2004, 02:22 AM
Tom Ames Tom Ames is offline
Member
 
Join Date: Mar 2004
Posts: 96
Default Disappointing mission coverage on Cassini homepage

On a slightly whining note:

Does anyone else find the Cassini mission homepage incredibly disappointing, especially as compared to the MER effort?

I mean, one of the top items STILL remains the story of the high school ballet dancer who participated in the planning. That stuff is fine for the cruise segment of the mission. But Cassini is in orbit and Huygens is being released. Can't we see more than the occasional wallpaper and human-interest story?

Who do I complain to about this?

(Done venting now.)
Reply With Quote
  #14 (permalink)  
Old 25-December-2004, 03:41 AM
01101001's Avatar
01101001 01101001 is offline
Senior Member
 
Join Date: Mar 2004
Posts: 11,626
Default Re: Disappointing mission coverage on Cassini homepage

Quote:
Originally Posted by Tom Ames
Who do I complain to about this?
It might help: http://saturn.jpl.nasa.gov/news/contact-us.cfm

On the MER mission page, I used a similar outreach address to ask a technical question that got answered.

The bottom of http://saturn.jpl.nasa.gov/home/index.cfm lists editor and writer credits if you want to go into JPL and do some persuading.
__________________
0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
Reply With Quote
  #15 (permalink)  
Old 25-December-2004, 04:13 AM
Squink Squink is online now
Senior Member
 
Join Date: Jun 2002
Posts: 542
Default

On its way:
Quote:
Ground controllers received a signal at about 7:24 p.m. Pacific time (10:24 p.m. EST) indicating that Huygens had separated from NASA's Saturn probe Cassini, as small explosives sheared away locking bolts and a set of springs gently pushed the probe off on a collision course with Titan.
Reply With Quote
  #16 (permalink)  
Old 25-December-2004, 05:20 AM
Tom Ames Tom Ames is offline
Member
 
Join Date: Mar 2004
Posts: 96
Default Re: Disappointing mission coverage on Cassini homepage

Quote:
Originally Posted by 01101001
Quote:
Originally Posted by Tom Ames
Who do I complain to about this?
It might help: http://saturn.jpl.nasa.gov/news/contact-us.cfm

On the MER mission page, I used a similar outreach address to ask a technical question that got answered.

The bottom of http://saturn.jpl.nasa.gov/home/index.cfm lists editor and writer credits if you want to go into JPL and do some persuading.
Thanks, 69,

I was being kinda' facetious -- I don't really intend to complain. It just seems like the web coverage on Cassini has been a big letdown in comparison to what has been done with MER.

Thankfully S & O have been keeping me entertained longer than I had counted on.
Reply With Quote
  #17 (permalink)  
Old 25-December-2004, 05:25 PM
01101001's Avatar
01101001 01101001 is offline
Senior Member
 
Join Date: Mar 2004
Posts: 11,626
Default

Quote:
Originally Posted by Squink
Live pictures! Just kidding. Artwork:













__________________
0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
Reply With Quote
  #18 (permalink)  
Old 25-December-2004, 07:22 PM
01101001's Avatar
01101001 01101001 is offline
Senior Member
 
Join Date: Mar 2004
Posts: 11,626
Default

Just for scale, a picture of Huygens with people.



It's 2.7 meters, about the same diameter as a MER spacecraft.
__________________
0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
Reply With Quote
  #19 (permalink)  
Old 25-December-2004, 10:34 PM
Jerry's Avatar
Jerry Jerry is offline
Senior Member
 
Join Date: Mar 2004
Location: Earth
Posts: 3,794
Default Re: Disappointing mission coverage on Cassini homepage

Quote:
Originally Posted by Tom Ames
On a slightly whining note:

Does anyone else find the Cassini mission homepage incredibly disappointing, especially as compared to the MER effort?

I mean, one of the top items STILL remains the story of the high school ballet dancer who participated in the planning. ...
Who do I complain to about this?

(Done venting now.)
I have been harping about the lack of detail in the orbital science work, doppler measurements, the list goes on and on. The ESA site is slightly better, but they are holding the science data close to the vest
__________________
jwj

It's ok not to know. We should try harder to find out.
Reply With Quote