It is currently Thu, 19-10-17, 11:09 GMT

All times are UTC




Post new topic Reply to topic  [ 119 posts ]  Go to page 1, 2, 3, 4, 5 ... 8  Next
Author Message
 Post subject: Building Vega 2
PostPosted: Sun, 08-06-08, 15:12 GMT 
Offline
Site Admin
User avatar

Joined: Fri, 31-08-07, 20:59 GMT
Posts: 1605
Location: Norway
Andrea and i have begun preparations for creating the Soviet Vega 2 mission of 1985/86 for Celestia.

In short, Vega 2 was a pretty exiting - and very complex - multi-purpose mission where (mirrored by Vega 1) the spacecraft sucessfully delivered both a lander and a balloon aerostat to Venus, then went on to meet up with Halleys Comet.

We are going to treat this mission in the same fashion we did the Buran: a detailed scenario, covering every aspect of each part of the mission.

This is a somewhat bigger job than Buran was, as we must design all the models from scratch. But we will first concentrate on writing a correct XYZ trajectory for each element (launch rocket, lander and aerostat entry, Halley rendezvous, and finally insertion of the bus into a solar orbit.

Andrea has begun collecting the data we need, and we will collect it here, for easy reference. Comments and further information is of course very welcome. Later on, we will also need detailed images of the various components - but that is Phase 2.

Quote:
Mission Profile
The lander separated from the Vega 2 spacecraft two days before arrival at Venus and entered the planet's atmosphere on an inclined path, without active maneuvers, as was done on previous Venera missions. (The flyby spacecraft was then retargetted using Venus gravity assistance to intercept Comet Halley in March 1986.) After separation from the Vega 2 spacecraft the lander entered the Venus atmosphere on 15 June 1985 at 01:59:30 UT at 10.80 km/s with an entry angle of 19.08 degrees. The pilot parachute was deployed at 02:00:05 UT at an altitude of 65 km and the braking parachute opened 11 seconds later at 64.5 km. The upper heat protection hemisphere was released at this time and the lower hemisphere 4 seconds later at 64.2 km. The upper hemisphere contained the deployment system for the balloon aerostats. The parachute was released at 02:09:15 at 47 km. After this the lander was allowed to aerobrake through the thick Venus atmosphere, with drag devices minimizing vibrations and spin and providing stability. A toroidal system similar to that on Veneras 13 and 14 was designed to absorb shock on landing. The lander touched down at 03:00:50 UT on 15 June 1985 at 8.5 S, 164.5 E, in eastern Aphrodite Terra. The altitude of the touchdown site was 0.1 km above the planetary mean radius. The measured pressure at the landing site was 91 atm and the temperature was 736 K. The surface sample was found to be an anorthosite-troctolite. The balloon measured downward gusts of 1 meter/s and found horizontal winds up to 240 km/hr.

Balloon Aerostats
In addition to the lander probe, a constant-pressure instrumented balloon aerostat was deployed after entry into the atmosphere from the upper heat protection hemisphere at an altitude of 54 km. The balloon released from the hemisphere, deployed a two-stage parachute, and then unfolded and inflated. The 3.4 meter diameter balloon supported a total mass of 25-kg. A 5-kg payload hung suspended 12 meters below the balloon. It floated at approximately 50 km altitude in the middle, most active layer of the Venus three-tiered cloud system. Data from the balloon instruments were transmitted directly to Earth for the 47-hr lifetime of the mission. (The batteries had a lifetime of 60 hrs.) Onboard instruments were to measure temperature, pressure, vertical wind velocity, visibility (density and size of local aerosols), light level and to detect lightning. Very long baseline interferometry was used to track the motion of the balloon to provide the wind velocity in the clouds. The tracking was to be done by a 6-station network on Soviet territory and by a network of 12 stations distributed world-wide (organized by France and the NASA Deep Space Network). After two days the balloon entered the dayside of Venus and expanded and burst due to solar heating.


- rthorvald


Top
 Profile  
 
 Post subject:
PostPosted: Sun, 08-06-08, 21:55 GMT 
Offline
Site Admin
User avatar

Joined: Fri, 31-08-07, 20:59 GMT
Posts: 1605
Location: Norway
Timeline:
This is what we have so far. Unknowns are marked red.

---------------------------------

Vega 2:

09:13:52 UTC, 21. dec. 1984: Lift-Off from Baikonur
--- ? --- Separation from rocket when? Stages?

13. june 1985: lander separation.
-- At what time?

15. june 1985: main spacecraft Venus flyby.
-- closest approach at what time, and how far away?

01:59:30 UTC, 15. june 1985:
Lander enters Venus atmosphere (at 125 km altitude) at 10.80 km/s with an entry angle of 19.08 degrees, nightside - aiming for Aphrodite Terra.

02:00:05 UTC: pilot parachute opens, 65 km up
02:11:05 UTC: braking parachute opens, 64.5 km up. Upper heat shield released.
02:15:05 UTC: lower heat shield released, 64.2 km up. Aerobraking.
02:15:45 UTC: The balloon pulled out by parachute at 61 km altitude, at 7.45 degrees S, 179.8 degrees east.

02:18:05 UTC: second parachute opened at an altitude of 55 km, extracting the balloon
02:19:45 UTC: Balloon inflated at 54 km and parachute and inflation system were jettisoned.
02:20:00 UTC (approx): Ballast jettisoned at 50 km and balloon floated back to 53.6 km

03:00:50 UTC: lander touchdown, eastern Aphrodite Terra, Coords: 7.14°S 177.67°E.

Balloon floating at approximately 50 km altitude for 47 hours, then enters dayside (from East to West) and balloon bursts. Crossed terminator at 9:10 UT (+6.5 mins?) on 16 June after traversing 7400 km. Final transmission received at 00:38 UT on 17 June from 7.5 S, 76.3 E


07:20 UTC, 9. march 1986: main spacecraft closest approach to Halleys comet - at at 8,030 km for three hours. Follows Halley until 11. March.

18:00 UTC, 17. march 1986: Heliocentric orbit (as per Chris L´s datafile)

--------------------

- rthorvald


Last edited by rthorvald on Sat, 19-07-08, 22:47 GMT, edited 6 times in total.

Top
 Profile  
 
 Post subject:
PostPosted: Mon, 09-06-08, 23:06 GMT 
Offline
User avatar

Joined: Wed, 05-09-07, 0:09 GMT
Posts: 57
Location: Seattle, WA, USA
It's great news that you are working on this project! I'll help out as I can:


Quote:
07:20 UTC, 9. march 1986: main spacecraft closest approach to Halleys comet - at at 8,030 km for three hours. Follows Halley (distances? Position relative to Halley?) until 11. March.


There are SPICE kernels for Vega 1 and 2 that cover that Halley encounter. The dates are 1 Mar 1986 to 16 Mar 1986. I can convert these to an xyzv file for you.

I'll see what else I can dig up.

--Chris


Top
 Profile  
 
 Post subject:
PostPosted: Mon, 09-06-08, 23:41 GMT 
Offline
Site Admin
User avatar

Joined: Fri, 31-08-07, 20:59 GMT
Posts: 1605
Location: Norway
chris wrote:
There are SPICE kernels for Vega 1 and 2 that cover that Halley encounter. The dates are 1 Mar 1986 to 16 Mar 1986. I can convert these to an xyzv file for you.


That would be great! Many thanks indeed :-D

- rthorvald


Top
 Profile  
 
 Post subject:
PostPosted: Tue, 10-06-08, 9:49 GMT 
Offline
User avatar

Joined: Sun, 02-09-07, 16:06 GMT
Posts: 346
Location: Rome, Italy
chris wrote:
There are SPICE kernels for Vega 1 and 2 that cover that Halley encounter. The dates are 1 Mar 1986 to 16 Mar 1986. I can convert these to an xyzv file for you. I'll see what else I can dig up.
--Chris

Chris, very happy for your precious help, appreciated!
Bye

Andrea :D

_________________
Andrea
WorldPoss Sn Team Member
Core 2 Quad Q6600 G0 3.6 GHz- 4 GB DDR2- DELL 2709W 1920x1200-WinXP 32 SP3- VISTA 64- ASUS P5K-E- 8800 GTX 768MB- SATA II 320-300 GB-IDE 1 TB- 169.21- Celestia1.4.1_patch3- 1.5.1-LUA Edu Tools


Top
 Profile  
 
 Post subject:
PostPosted: Tue, 10-06-08, 12:44 GMT 
Offline
User avatar

Joined: Sun, 02-09-07, 16:06 GMT
Posts: 346
Location: Rome, Italy
I found this page:

http://ntrs.nasa.gov/search.jsp?No=10&N=4294913369

with one link to a document regarding VEGA balloon experiment
"The Vega balloon experiment - Initial results from the global radio tracking",
but I'm having problems in understanding if and how such documents are available. :oops:
Any experience on the matter?
Bye

Andrea :D

_________________
Andrea
WorldPoss Sn Team Member
Core 2 Quad Q6600 G0 3.6 GHz- 4 GB DDR2- DELL 2709W 1920x1200-WinXP 32 SP3- VISTA 64- ASUS P5K-E- 8800 GTX 768MB- SATA II 320-300 GB-IDE 1 TB- 169.21- Celestia1.4.1_patch3- 1.5.1-LUA Edu Tools


Top
 Profile  
 
 Post subject:
PostPosted: Tue, 10-06-08, 13:11 GMT 
Offline
User avatar

Joined: Sun, 02-09-07, 16:06 GMT
Posts: 346
Location: Rome, Italy
Hello Runar and Chris, I found this link
http://pdssbn.astro.umd.edu/sbnhtml/comets/IHW/
from the Halley Watch Program.
At bottom page there is a link to VEGA 2
http://pdssbn.astro.umd.edu/volume/hal_0026/vega2/
whose I opened the ducma directory
http://pdssbn.astro.umd.edu/volume/hal_ ... ga2/ducma/
and the ducma.doc file, containing the VEGA 2 telemetry of Halley close encounter.
May it be useful?
Bye

The digging Andrea :D

_________________
Andrea
WorldPoss Sn Team Member
Core 2 Quad Q6600 G0 3.6 GHz- 4 GB DDR2- DELL 2709W 1920x1200-WinXP 32 SP3- VISTA 64- ASUS P5K-E- 8800 GTX 768MB- SATA II 320-300 GB-IDE 1 TB- 169.21- Celestia1.4.1_patch3- 1.5.1-LUA Edu Tools


Top
 Profile  
 
 Post subject:
PostPosted: Tue, 10-06-08, 13:42 GMT 
Offline
User avatar

Joined: Sat, 13-10-07, 18:18 GMT
Posts: 373
Don't know if it helps or not, but HERE's a page with some more information concerning the Halley encounter and some interesting photos/details.


Top
 Profile  
 
 Post subject:
PostPosted: Tue, 10-06-08, 14:21 GMT 
Offline
User avatar

Joined: Sun, 02-09-07, 16:06 GMT
Posts: 346
Location: Rome, Italy
rthorvald wrote:
Timeline:
This is what we have so far. Unknowns are marked red.
---------------------------------
[Floating at approximately 50 km altitude for 47 hours, then enters dayside and balloon bursts.
Which direction? East-to-west?
- rthorvald

Runar, here
http://www.answers.com/topic/vega-2-1?cat=technology
I found this:

Balloon
The Vega 2 Lander/Balloon capsule entered the Venus atmosphere (125 km altitude) at 2:06:04 UT (Earth received time; Moscow time 5:06:04 a.m.) on 15 June 1985 at roughly 11 km/s. At approximately 2:06:19 UT the parachute attached to the landing craft cap opened at an altitude of 64 km. The cap and parachute were released 15 seconds later at 63 km altitude. The balloon package was pulled out of its compartment by parachute 40 seconds later at 61 km altitude, at 7.45 degrees S, 179.8 degrees east. A second parachute opened at an altitude of 55 km, 200 seconds after entry, extracting the furled balloon. The balloon was inflated 100 seconds later at 54 km and the parachute and inflation system were jettisoned. The ballast was jettisoned when the balloon reached roughly 50 km and the balloon floated back to a stable height between 53 and 54 km some 15 to 25 minutes after entry. The mean stable height was 53.6 km, with a pressure of 535 mbar and a temperature of 308-316 K in the middle, most active layer of the Venus three-tiered cloud system. The balloon drifted
westward in the zonal wind flow with an average speed of about 66 m/s at nearly constant latitude. The probe crossed the terminator from night to day at 9:10 UT on 16 June after traversing 7400 km. The probe continued to operate in the daytime until the final transmission was received at 00:38 UT on 17 June from 7.5 S, 76.3 E after a total traverse distance of 11,100 km. It is not known how much further the balloon traveled after the final communication.

So it went westward. :wink:
I think you can eliminate this doubt from your list. :wink:
Bye

Andrea :D

_________________
Andrea
WorldPoss Sn Team Member
Core 2 Quad Q6600 G0 3.6 GHz- 4 GB DDR2- DELL 2709W 1920x1200-WinXP 32 SP3- VISTA 64- ASUS P5K-E- 8800 GTX 768MB- SATA II 320-300 GB-IDE 1 TB- 169.21- Celestia1.4.1_patch3- 1.5.1-LUA Edu Tools


Top
 Profile  
 
 Post subject:
PostPosted: Tue, 10-06-08, 14:37 GMT 
Offline
User avatar

Joined: Sun, 02-09-07, 16:06 GMT
Posts: 346
Location: Rome, Italy
I found here:

http://articles.adsabs.harvard.edu/full/seri/SvAL./0012//0000002.000.htm

a very interesting long paper on VEGA 2 mission, whose IMO the first page is the most useful, actually. 8)
Bye

Andrea :D

_________________
Andrea
WorldPoss Sn Team Member
Core 2 Quad Q6600 G0 3.6 GHz- 4 GB DDR2- DELL 2709W 1920x1200-WinXP 32 SP3- VISTA 64- ASUS P5K-E- 8800 GTX 768MB- SATA II 320-300 GB-IDE 1 TB- 169.21- Celestia1.4.1_patch3- 1.5.1-LUA Edu Tools


Top
 Profile  
 
 Post subject:
PostPosted: Tue, 10-06-08, 19:03 GMT 
Offline
User avatar

Joined: Wed, 05-09-07, 0:09 GMT
Posts: 57
Location: Seattle, WA, USA
Here's my work on the Vega mission so far:

http://www.shatters.net/~claurel/celest ... s/vega.zip

This package includes an ssc file and xyzv files for Halley encounter phase of the Vega 1 and Vega 2 spacecraft. The xyzv files were produced from SPICE files using the new spice2xyzv tool that I've been using for Cassini. The SPICE files only cover the dates between March 1 and March 17 1986. I used the state vectors (position and velocity) at the ends of the trajectory segment to get elliptical orbits for times outside the span covered by the SPICE kernels. These orbits are only valid if there were no thrust maneuvers performed before or after the Halley encounter. This assumption is certainly not valid before the encounter. But, it very well may be the case that the spacecraft engines were not used after the encounter. In that case, the post-encounter elliptical orbit should be reasonable, although it neglects perturbations from the planets. We could do a better extrapolation by letting HORIZONS integrate the spacecraft position.

The add-on will only work with recent SVN versions of Celestia. It uses two Celestia 1.6.0 features: Timeline and xyzv files. An xyzv file is like an xyz file except that it contains velocity information. For a given file size, and xyzv file gives considerably more accurate positions than an xyz file. If you want to convert an xyzv file to an xyz file, just strip out the last three columns (but accuracy will suffer.) Also, only recent SVN versions of Celestia are able to parse the comment header in the xyzv file; you can simply remove it to make the file compatible with older versions of Celestia. Timeline is used to paste together the three phases of the mission: pre-Halley, Halley encounter, and post-encounter. The alternative to using the Timeline is to either create a single xyzv file covering the whole trajectory or split the spacecraft into separate objects for each phase.

--Chris


Top
 Profile  
 
 Post subject:
PostPosted: Wed, 11-06-08, 21:50 GMT 
Offline
Site Admin
User avatar

Joined: Fri, 31-08-07, 20:59 GMT
Posts: 1605
Location: Norway
Wow, thank you everyone for the contributions!
Give me a couple of evenings to sort everything...

Chris, it would be a pity not to take advantage of the 1.6 functionality, so i will take some time to get to know it before i proceed.

My original intention was to write one single XYZ for everything, so that the user would not need to detach/move/attach the camera at any point. I´ll do some experiments with the Timeline function instead, and see what i can make it do...

- rthorvald


Top
 Profile  
 
 Post subject:
PostPosted: Thu, 12-06-08, 15:41 GMT 
Offline
Site Admin
User avatar

Joined: Fri, 31-08-07, 20:59 GMT
Posts: 1605
Location: Norway
chris wrote:
Vega 2 spacecraft. The xyzv files were produced from SPICE files using the new spice2xyzv tool that I've been using for Cassini. The SPICE files only cover the dates between March 1 and March 17 1986. I used the state vectors (position and velocity) at the ends of the trajectory segment to get elliptical orbits for times outside the span covered by the SPICE kernels. These orbits are only valid if there were no thrust maneuvers performed before or after the Halley encounter.


Chris,
The info i have says Vega 2 comes within 8,030 kilometers of Halley at March 09. Yet, in Celestia, using your code, the closest approach is 2851900 km, at March 07.

Perhaps Halley´s orbit is too inaccurate? I got a clean install of Celestia off SVN today.

- rthorvald


Top
 Profile  
 
 Post subject:
PostPosted: Thu, 12-06-08, 15:55 GMT 
Offline
User avatar

Joined: Wed, 05-09-07, 0:09 GMT
Posts: 57
Location: Seattle, WA, USA
rthorvald wrote:
chris wrote:
Vega 2 spacecraft. The xyzv files were produced from SPICE files using the new spice2xyzv tool that I've been using for Cassini. The SPICE files only cover the dates between March 1 and March 17 1986. I used the state vectors (position and velocity) at the ends of the trajectory segment to get elliptical orbits for times outside the span covered by the SPICE kernels. These orbits are only valid if there were no thrust maneuvers performed before or after the Halley encounter.


Chris,
The info i have says Vega 2 comes within 8,030 kilometers of Halley at March 09. Yet, in Celestia, using your code, the closest approach is 2851900 km, at March 07.

Perhaps Halley´s orbit is too inaccurate? I got a clean install of Celestia off SVN today.

- rthorvald


Right--Halley's orbit is modeled as a simple ellipse. I have a more accurate version of the orbit that we can use to replicate the encounter better. I'll have a link soon.

--Chris


Top
 Profile  
 
 Post subject:
PostPosted: Thu, 12-06-08, 16:04 GMT 
Offline
Site Admin
User avatar

Joined: Fri, 31-08-07, 20:59 GMT
Posts: 1605
Location: Norway
Andrea wrote:
The Vega 2 Lander/Balloon capsule entered the Venus atmosphere (125 km altitude) at 2:06:04 UT (Earth received time; Moscow time 5:06:04 a.m.) on 15 June 1985 at roughly 11 km/s. At approximately 2:06:19 UT the parachute attached to the landing craft cap opened at an altitude of 64 km. The cap and parachute were released 15 seconds later at 63 km altitude.


Andrea,
There seems to be some discrepancies between this info and the data i have on the timing.
I got my from this page:
http://www.atm.ox.ac.uk/user/fwt/WebPag ... ew%204.htm
(See the last paragraph under "Entry And Descent Phase".

The difference is about seven minutes. I guess there might be some confusion on when the data was recieved on Earth and when it actually happened. What do you think?

- rthorvald


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 119 posts ]  Go to page 1, 2, 3, 4, 5 ... 8  Next

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group