Spacecrafts for Celestia

toutatis · Post #301by **toutatis** » 27.06.2018, 17:45

The solar panels of orbital spacecrafts looks like the atmosphere of the planets, around they rotate... if the satellite is on Earth's orbit, then they reflect more of the blue color ... around the moon is the color of the moon ... that is simple ...

gironde · Post #302by **gironde** » 27.06.2018, 20:28

LISA Pathfinder (ESA)

In orbit at Lagrange point L1
The role of LISA Pathfinder is to validate the technical devices for measuring gravitational waves.

:hi:

Post #303by **Croc** » 27.06.2018, 20:31

Deep Space Climate Observatory

The solar panels of orbital spacecrafts looks like the atmosphere of the planets, around they rotate... if the satellite is on Earth's orbit, then they reflect more of the blue color ... around the moon is the color of the moon ... that is simple ...

The play of light on solar batteries and on foil makes the spacecraft "alive" ... :smile:

=========================================
PS: Errore time
Beginning "2015 02 11 23:46" :sad:

Beginning "2015 02 12 23:44:54"

Gurren Lagann · Post #304by **Gurren Lagann** » 27.06.2018, 20:49

I never saw a collaborative project as active as this one in anywhere! Nice job on the crafts (and crashing my Celestia every frame)!

Post #305by **Croc** » 27.06.2018, 20:56

LISA Pathfinder (ESA)

Thank you for the Frenchwoman LISA ...

========================
PS: LISA Pathfinder is misoriented. This can be seen from the markers.
It is difficult to maneuver with this apparatus. With a glare problem ... :sad:

toutatis · Post #306by **toutatis** » 27.06.2018, 22:34

Errore time
Beginning "2015 02 11 23:46"
Beginning "2015 02 12 23:44:54"

True time is "2015 02 12 23:46"

Code: Select all

*******************************************************************************
 Revised: Aug 18, 2015          DSCOVR Spacecraft  / (Earth)                -78 
                             http://www.nesdis.noaa.gov/DSCOVR/

 BACKGROUND:
  DSCOVR was launched Feb 11, 2015 @ 23:03:02 UTC from Cape Canaveral, Florida, 
  USA using a Space-X Falcon 9 v1.1

  DSCOVR was placed in a six-month Lissajous orbit around Sun-Earth Lagrange 
  Point 1 (L1) on June 8, 2015, about 200 Earth radii upstream of Earth in the
  direction of the Sun.

  Main instrument are:
   (1) Sun-observing Plasma Magnetometer (PlasMag)
   (2) Earth-observing NIST Advanced Radiometer (NISTAR) 
   (3) Earth Polychromatic Imaging Camera (EPIC) 
   (4) Electron Spectrometer (ES)   
   (5) Pulse Height Analyzer (PHA)

  Objectives of the DSCOVR 5-year mission:
   * Observe unperturbed solar wind 15-60 minutes prior to it impacting
      the Earth's magnetosphere (geomagnetic storm warnings).
   * Provide early warnings of coronal mass ejections
   * Observe changes in Earth atmosphere ozone, aerosols, dust, nand cloud
      height at two hour intervals.

  DSCOVR (formerly known as Triana) was originally conceived in the late 1990s
  as a NASA Earth science mission. The mission was canceled and the satellite 
  was put into storage in 2001. NOAA and the USAF had DSCOVR removed from 
  storage in 2008 and subsequently funded NASA to test and refurbish the
  spacecraft and sensors.

  NOAA operates DSCOVR from its Satellite Operations Facility in Suitland, 
  Maryland and distributes the data to users and partner agencies. NOAA will 
  process the space weather data, providing products and forecasts through 
  the NOAA Space Weather Prediction Center in Boulder, Colorado, and archive 
  the data at the NOAA National Geophysical Data Center in Boulder, Colorado. 
  NASA is responsible for processing the Earth sensor data.

 SPACECRAFT PHYSICAL CHARACTERISTICS:
  Mass      :  570 kg at launch
  Dimensions:  1.4 x 1.8 meters
  Power     :  600 Watts (two deployed solar arrays)

 SPACECRAFT TRAJECTORY: 
  Concatenated trajectories (DSN)
  Based on tracking data through 2015-Aug-4, prediction thereafter. 

  Trajectory name                            Start (TDB)          Stop (TDB)
  ------------------------------------    -----------------   -----------------
  DSCO-2015-02-11-Nominal_withMCC.V0.1    2015-Feb-11 23:46   2015-Mar-09
  23month_20150309_01.V0.1                2015-Mar-09         2015-Jul-13
  21day_20150803_01.V0.1                  2015-Jul-13         2015-Aug-03
  21day_20150803_01.V0.1                  2015-Aug-03         2015-Aug-04
  18month_20150804_01.V0.1                2015-Aug-04         2017-Jan-03 12:06
*******************************************************************************
 

 

*******************************************************************************
Ephemeris / WWW_USER Tue Jun 26 02:06:15 2018 Pasadena, USA      / Horizons    
*******************************************************************************
Target body name: DSCOVR (spacecraft) (-78)       {source: DSCOVR_merged}
Center body name: Sun (10)                        {source: DE431mx}
Center-site name: BODY CENTER
*******************************************************************************
Start time      : A.D. 2015-Feb-12 23:46:00.0000 TDB
Stop  time      : A.D. 2017-Jan-03 12:06:00.0000 TDB
Step-size       : 180 minutes
*******************************************************************************
Center geodetic : 0.00000000,0.00000000,0.0000000 {E-lon(deg),Lat(deg),Alt(km)}
Center cylindric: 0.00000000,0.00000000,0.0000000 {E-lon(deg),Dxy(km),Dz(km)}
Center radii    : 696000.0 x 696000.0 x 696000.0 k{Equator, meridian, pole}    
Output units    : KM-S                                                         
Output type     : GEOMETRIC cartesian states
Output format   : 2 (position and velocity)
Reference frame : ICRF/J2000.0                                                 
Coordinate systm: Ecliptic and Mean Equinox of Reference Epoch                 
*******************************************************************************
            JDTDB,            Calendar Date (TDB),                      X,                      Y,                      Z,                     VX,                     VY,                     VZ,
**************************************************************************************************************************************************************************************************
$$SOE
2457066.490277778, A.D. 2015-Feb-12 23:46:00.0000, -1.188947203513210E+08,  8.723942906959282E+07, -3.891252311195433E+04, -1.660570788947667E+01, -2.490166001206716E+01, -2.165532927303246E-01,
2457066.615277778, A.D. 2015-Feb-13 02:46:00.0000, -1.190741228867049E+08,  8.697054785047184E+07, -4.117955755501986E+04, -1.661549180066717E+01, -2.489251552356685E+01, -2.036282107236698E-01,
2457066.740277778, A.D. 2015-Feb-13 05:46:00.0000, -1.192535863549679E+08,  8.670172523286454E+07, -4.331769015211985E+04, -1.661730900228754E+01, -2.489047667013994E+01, -1.925967360559984E-01,

Added after 4 minutes 40 seconds:

I never saw a collaborative project as active as this one in anywhere! Nice job on the crafts (and crashing my Celestia every frame)!

toutatis · Post #307by **toutatis** » 27.06.2018, 22:55

Versions of Celestia before v1.5.0 use UTC to calculate times and positions. Unfortunately, UTC includes "leap seconds" in order to stay aligned with the Earth's varying rotation. Leap seconds happen essentially randomly, when they are needed. Although Celestia does incorporate a table of leap second times, its use of UTC causes problems when used with ephemerides which are defined using TDB. Starting with v1.5.0, although it still displays UTC on the screen, Celestia uses the TDB time scale internally for everything else. As a result, Celestia places objects much more accurately than before....

It may be helpful for Celestia users to understand the various time scales that are used in the field of astronomy. The most familiar is local time, which is probably what you see if you look at a nearby clock. The local time zone determines the difference between local time and Coordinated Universal Time, or UTC. UTC is the current time at the zero degree meridian; it replaces Greenwich Mean Time as the standard world clock.

Astronomical ephemerides are typically defined in terms of Barycentric Dynamical Time, or TDB. TDB is the time measured by a clock at the solar system barycenter. It differs from Terrestrial Time (TT)--the time measured by a clock on the Earth--because of relativistic effects, but the difference between the two scales is always less than 0.002 seconds. The two scales can usually be considered equivalent in Celestia.

TT is ahead of International Atomic Time (TAI) by constant value of 32.184 seconds. Finally, UTC differs from TAI by some integer number of leap seconds. Leap seconds are inserted occasionally because the Earth's rotation is irregular, and it's desirable to keep our everyday time scale from drifting with respect to the terrestrial day-night cycle--except at the poles, the sun should be in the sky at noon. The most recent leap second occurred at 23:59:60 on December 31, 2008 and made UTC 34 seconds behind TAI. (See Wikipedia on TAI)

To briefly summarize the relationship between time scales:

TT = TAI + 32.184
TAI = UTC + leap second count
Thus, TT = UTC + 32.184 + leap second count
UTC is used in the Celestia's Set Time dialog and it's also the time displayed in the upper right of the screen. Unless you're creating scripts or add-ons for Celestia, UTC is all that you will see. But everywhere else, the time scale is TDB: xyz trajectory files, attitude files, beginning, ending, and epoch times in .ssc files.

https://en.wikibooks.org/wiki/Celestia/Time_Scales

That is about time scale... and I use TDB too... :biggrin:

Post #308by **Croc** » 28.06.2018, 01:52

Toutatis,
In the xyz file, the reference point in the JD format (Julian date) is 2457066.490277778, which corresponds to February 12, 2015 23:45:59 UTC
In the ssc file, the time is set
Beginning "2015 02 11 23:46" ...
The difference - DAY !!! :think:

: JD.jpg (30.6 KiB) Viewed 8462 times

In the guide for DSCOVR, I specify the time from the ssc file ( tdb_dt = celestia:utctotdb(2015, 02, 11, 23, 46, 00)):

Code: Select all

Sol2222Box.Action = (function()
    return 
        function()      
            local obj = celestia:find("Sol/DSCOVR");           
            celestia:select(obj);            
            if not(empty(obj)) then
               tdb_dt = celestia:utctotdb(2015, 02, 11, 23, 46, 00)
               celestia:settime(tdb_dt) 
               obs:follow(obj);
               obs:goto(obj); 
               celestia:settimescale(100);  
            end
        end
    end) ();

I click on the guidebook button [DSCOVR], the point is flying, but the device is not visible.
Cause: an error in the ssc file in the Beginning parameter :biggrin:

gironde · Post #309by **gironde** » 28.06.2018, 08:12

Generally when one wants to visualize a satellite in celestia one does not look for a very precise date and time.
the satellite was launched on February 11, 2015, 23:03:02 UTC. At this time, he is still on the firing point of the rocket. With LUT5, I schedule the next day to be sure of being in orbit. In the ssc "Beginning" must correspond to the start date of the programmed orbit, after for the visualization it is necessary to be placed between "Beginning" and "Ending" if the satellite does not appear.

With Kaguya I only programmed the lunar orbit at 100km altitude according to the dates when the satellite was at this altitude. There is no point trying to see it outside this time range.

gironde · Post #310by **gironde** » 28.06.2018, 08:22

following the remarks of Croc on the LISA Pathfinder addon, I looked for the error in the original 3D file (.dae). In this model, there is a second object to the left of Lisa. Not knowing what it was, I deleted it. In doing so I did not see a tiny object that had remained and which decentred LISA on the final model. I fixed this oversight and took the opportunity to add a texture on the solar panel.

:hi:

Post #311by **Croc** » 28.06.2018, 09:57

In the illustration below, the difference between the model and the original is very noticeable:
1. there are not many small details. Probably, the original model is not detailed enough.
2. On the model the bottom is painted with yellow paint. On the original, the surface is covered with a golden film, on the folds of which is a play of light.
The texture is poorly matched.

Many models of space vehicles have already been made. The time has come when you expect that the quantity will go into quality.

gironde · Post #312by **gironde** » 28.06.2018, 11:00

Pleiades-HR satellites are telescopes directed towards the Earth and provide HR photos. They were designed by the CNES of France.

:hi:

gironde · Post #313by **gironde** » 28.06.2018, 11:03

Yes, the original model of LISA Pathfinder is not very accurate.
Textures do not apply to all faces.

while waiting better!

:smile:

Post #314by **Croc** » 28.06.2018, 14:17

Pleiades-HR satellites

PS: On the model Pleiades-HR satellites there are glare and on solar batteries and on a gilded film. I think the glare should be more contrast. The flares should be more specular and on the batteries and on the gilt film (foil) ...

gironde · Post #315by **gironde** » 28.06.2018, 16:56

SPOT-1 SPOT-2 SPOT-3
SPOT-4
SPOT-5

3 models, 5 satellites (CNES)

same mission that Pleiades-HR

Post #316by **Croc** » 28.06.2018, 21:09

SPOT-1 SPOT-2 SPOT-3
SPOT-4
SPOT-5

3 models, 5 satellites (CNES)

gironde · Post #317by **gironde** » 28.06.2018, 22:59

Thaicom-4 (IPSat 1) is a communication satellite manufactured by Space Systems / Loral for Thaicom Public Company Limited. At the time of its launch by an Ariane 5 rocket it is the largest communication satellite (6T500).

Added after 23 minutes 20 seconds:
Spot-1-2-3.cmod and Spot-4.cmod modified.
thank to Croc

toutatis · Post #318by **toutatis** » 29.06.2018, 00:30

In the xyz file, the reference point in the JD format (Julian date) is 2457066.490277778, which corresponds to February 12, 2015 23:45:59 UTC
In the ssc file, the time is set
Beginning "2015 02 11 23:46" ...

Croc... not a day... Beginning time is "2015 02 12 23:46"... yes, I asked HORIZONS from 11 Feb... but they gave me orbit from 12 Feb...
So fully correct is "2015 02 12 23:46" TDB... not need to use UTC in Celestia... only TDB in SSC-files... read attentive my messages above...
and this....

Code: Select all

*******************************************************************************
Target body name: DSCOVR (spacecraft) (-78)       {source: DSCOVR_merged}
Center body name: Sun (10)                        {source: DE431mx}
Center-site name: BODY CENTER
*******************************************************************************
Start time      : A.D. 2015-Feb-12 23:46:00.0000 TDB
Stop  time      : A.D. 2017-Jan-03 12:06:00.0000 TDB
Step-size       : 180 minutes
*******************************************************************************
Center geodetic : 0.00000000,0.00000000,0.0000000 {E-lon(deg),Lat(deg),Alt(km)}
Center cylindric: 0.00000000,0.00000000,0.0000000 {E-lon(deg),Dxy(km),Dz(km)}
Center radii    : 696000.0 x 696000.0 x 696000.0 k{Equator, meridian, pole}    
Output units    : KM-S

toutatis · Post #319by **toutatis** » 29.06.2018, 00:32

Gironde... Thanks for work!.. but please, read about color of the solar panels... :smile:

gironde · Post #320by **gironde** » 29.06.2018, 06:51

Toutatis,

Yes I have read. The parameter "specular" is the quantity of light reflected by the surface (0 <= n <= 1, 1 = mirror), "shininess" is the amount of brightness of the surface (n> = 0, 0: very bright) . All is a question of dosage and visual comfort.

We learn every day.

Another subject: do you have a method to generate data .xyz files starting from the ephemeris data of the Horizon site? In this I think of the orbits of the satellites at the point of Lagrange.