dgatsoulis
ele2png user
First of all, many thanks to BrianJ for his excellent [ame="http://www.orbithangar.com/searchid.php?ID=3466"]Rosetta v3[/ame] addon and flug for the [ame="http://www.orbithangar.com/searchid.php?ID=6671"]Rosetta - Comet 67/P Landing Mission, ver. 3D [/ame] with the tweaks and improvements.
Also an additional thanks to Brian for his eye-opening trajectory and planning solutions (be it a Moon-Mars tutorial from way back in 2008 or his brilliant "marker-dummy planets" idea for trajectory matching purposes).
Copying a real spacecraft trajectory in Orbiter is a difficult but extremely satisfying task, when you get it right.
The first thing needed is to gather as many details as possible about the trajectory. Thankfully, Brian's excellent documentation has almost everything we need.
Rosetta's heliocentric trajectory starts off with a DSM, a mere ~2 months after launch. Normally, this would be a show-stopper as far as planning the whole thing from the ground goes, because neither TransX nor IMFD can handle pre-planning after a maneuver.
This means that we'd have to fly the mission in a "seat of our pants" mode, waiting for the maneuver to occur and then plan the next part.
To get around this problem, we will use custom "dummy" planets, placed in strategic locations along Rosetta's path. The dummy planets have small enough mass to allow us to setup our plan, but not enough to perturb the spacecraft's trajectory in any significant way.
Let's write down all the mission waypoints, in an Orbiter friendly format:
Now we need to add-up all the dV and check our budget:
158+32+789+794 = 1743 m/s. Rosetta has a budget of 2637 m/s, so we are left with 894 m/s. We also need to keep in mind the dV required for the spacecraft's maneuvers at the target; we will try not to use more than half the budget for corrections (approx 450 m/s).
With the budget checked, the next part is to use JPL's Horizons system and get the orbital elements we need for each of the DSMs. We will create 3 custom cfg files named DSM1, DSM2, DSM3 using those elements.
Each DSM will be setup as a dummy planet in our custom solar system, thus allowing us use them as "stages" in TransX.
1.Go to the link above
2.Click on web interface
3.Use the settings as in the pic below
4.Click on "Generate Ephemeris"
The result should look like this (scroll down a bit):
5. Go to your Orbiter directory\Config\ and create 3 copies of the Rosetta_marker.cfg file. Rename them to DSM1, DSM2 and DSM3.
6. Open the DSM1.cfg file with a text editor and then go to (Orbiterroot)\Utils and run the Date.exe
-Copying the elements in Orbiter format:
1. In the DSM1 file you have opened go to the "Name" line and change it to "Name = DSM1" (without the quotes).
2. Go to the Date app you have opened and enter 53135 in the Modified Julian Date Box. Copy the Epoch number and paste it to the Epoch line
3. From the JPL page, copy the value next to "A =", multiply it with 1000 and paste it over the value next to "SemiMajorAxis = " in the cfg file. (Orbiter uses meters/rads, while JPL's elements are in km/degrees, so we need to make the necessary changes).
4.Copy the value next to "EC=" and paste it over the value next to "Eccentricity = " in the cfg file.
5.Copy the value next to "IN=", convert it to rads and paste it over the value next to "Inclination = " in the cfg file.
6.Copy the value next to "OM=", convert it to rads and paste it over the value next to "LongAscNode = " in the cfg file.
7.Add the values next to "OM=" and "W =", convert the result to rads and paste it over the value next to "LongPerihelion = " in the cfg. (If the result is greater than 2pi, subtract 2pi until it's in 0-2pi range).
8.Add the values next to "OM=", "W =" and "MA=", convert the result to rads and paste it over the value next to "MeanLongitude = " in the cfg. (If the result is greater than 2pi, subtract 2pi until it's in 0-2pi range).
9.Save the file and exit
10. Repeat the process for the DSM2 and DSM3 files. Use the list of the mission waypoints and the Date.exe app to generate the correct elements for each file.
When you are done, the 3 cfg files should look like this:
Contents of (Orbiterroot)\Config\DSM1.cfg
Contents of (Orbiterroot)\Config\DSM2.cfg
Contents of (Orbiterroot)\Config\DSM3.cfg
Finally, open the (Orbiterroot)\Config\Rosetta_sol.cfg file and add the lines:
Save and exit.
We have everything we need to proceed to the next part: Mission planning using TransX (and IMFD).
Also an additional thanks to Brian for his eye-opening trajectory and planning solutions (be it a Moon-Mars tutorial from way back in 2008 or his brilliant "marker-dummy planets" idea for trajectory matching purposes).
Copying a real spacecraft trajectory in Orbiter is a difficult but extremely satisfying task, when you get it right.
The first thing needed is to gather as many details as possible about the trajectory. Thankfully, Brian's excellent documentation has almost everything we need.
Rosetta's heliocentric trajectory starts off with a DSM, a mere ~2 months after launch. Normally, this would be a show-stopper as far as planning the whole thing from the ground goes, because neither TransX nor IMFD can handle pre-planning after a maneuver.
This means that we'd have to fly the mission in a "seat of our pants" mode, waiting for the maneuver to occur and then plan the next part.
To get around this problem, we will use custom "dummy" planets, placed in strategic locations along Rosetta's path. The dummy planets have small enough mass to allow us to setup our plan, but not enough to perturb the spacecraft's trajectory in any significant way.
Let's write down all the mission waypoints, in an Orbiter friendly format:
Code:
1.Launch and TEI burn. MJD 53066.303472 (Ariane 1st and 2nd stage, no Rosetta delta-v needed)
2.DSM1 MJD 53135, dV 158 m/s
3.Earth flyby1 MJD 53433.9240 Alt.1962km (Pe/Pl ratio 1.30796) Incl (Ecl) 167.45 Long -115.9 Lat -18.9
4.DSM2 MJD 54003, dV 32 m/s
5 Mars flyby MJD 54156.0732 ALT 260km (Pe/Pl ratio 1.0767) Inc.(Ecl.) 162.69 Long -58.28 Lat +43.56
6.Earth flyby2 MJD 54417.8702 Alt.5311km (Pe/Pl ratio 1.8336) Inc.(Ecl.) 131.39 Long -65.13 Lat -64.58
6a.Steins flyby 54714.7685 dist 1644 km (not used in planning, but as a check during the flight)
7.Earth flyby3 MJD 55148.3116 Alt. 2491km (Pe/Pl ratio 1.391) Inc.(Ecl.) 149.97 Long +113.05 Lat -8.14
7a. 21 Lutetia flyby MJD 55387.6683 Alt.2953km (not used in planning, but as a check during the flight)
8.DSM3 MJD 55584 dV 789 m/s
9.67P rendezvous MJD 56818.28 - insertion dV 794 m/s158+32+789+794 = 1743 m/s. Rosetta has a budget of 2637 m/s, so we are left with 894 m/s. We also need to keep in mind the dV required for the spacecraft's maneuvers at the target; we will try not to use more than half the budget for corrections (approx 450 m/s).
With the budget checked, the next part is to use JPL's Horizons system and get the orbital elements we need for each of the DSMs. We will create 3 custom cfg files named DSM1, DSM2, DSM3 using those elements.
Each DSM will be setup as a dummy planet in our custom solar system, thus allowing us use them as "stages" in TransX.
1.Go to the link above
2.Click on web interface
3.Use the settings as in the pic below
4.Click on "Generate Ephemeris"
The result should look like this (scroll down a bit):
5. Go to your Orbiter directory\Config\ and create 3 copies of the Rosetta_marker.cfg file. Rename them to DSM1, DSM2 and DSM3.
6. Open the DSM1.cfg file with a text editor and then go to (Orbiterroot)\Utils and run the Date.exe
-Copying the elements in Orbiter format:
1. In the DSM1 file you have opened go to the "Name" line and change it to "Name = DSM1" (without the quotes).
2. Go to the Date app you have opened and enter 53135 in the Modified Julian Date Box. Copy the Epoch number and paste it to the Epoch line
3. From the JPL page, copy the value next to "A =", multiply it with 1000 and paste it over the value next to "SemiMajorAxis = " in the cfg file. (Orbiter uses meters/rads, while JPL's elements are in km/degrees, so we need to make the necessary changes).
4.Copy the value next to "EC=" and paste it over the value next to "Eccentricity = " in the cfg file.
5.Copy the value next to "IN=", convert it to rads and paste it over the value next to "Inclination = " in the cfg file.
6.Copy the value next to "OM=", convert it to rads and paste it over the value next to "LongAscNode = " in the cfg file.
7.Add the values next to "OM=" and "W =", convert the result to rads and paste it over the value next to "LongPerihelion = " in the cfg. (If the result is greater than 2pi, subtract 2pi until it's in 0-2pi range).
8.Add the values next to "OM=", "W =" and "MA=", convert the result to rads and paste it over the value next to "MeanLongitude = " in the cfg. (If the result is greater than 2pi, subtract 2pi until it's in 0-2pi range).
9.Save the file and exit
10. Repeat the process for the DSM2 and DSM3 files. Use the list of the mission waypoints and the Date.exe app to generate the correct elements for each file.
When you are done, the 3 cfg files should look like this:
Contents of (Orbiterroot)\Config\DSM1.cfg
Code:
; === Configuration file for marker planet Rosetta_marker ===
Name = DSM1
EllipticOrbit = TRUE ; assume unperturbed orbit
HasElements = TRUE ; orbital elements follow
; === Osculating Elements ===
;***cfgBatchDataCalculator
Epoch = 2004.35455168
SemiMajorAxis = 1.478830696317216E+11
Eccentricity = 1.036821048173092E-01
Inclination = 0.0071814632805789
LongAscNode = 2.8122986160937
LongPerihelion = 4.5193050015973
MeanLongitude = 4.2372287127742
; === Physical Parameters ===
Mass = 1e9
Size = 10000 ; mean radius
SidRotPeriod = 2.034E+8 ;
SidRotOffset = 0
Obliquity = 0 ; n/a
LAN = 0
AlbedoRGB = 1 1 1
; === Visualisation Parameters ===
MaxPatchResolution = 1Contents of (Orbiterroot)\Config\DSM2.cfg
Code:
; === Configuration file for marker planet Rosetta_marker ===
Name = DSM2
EllipticOrbit = TRUE ; assume unperturbed orbit
HasElements = TRUE ; orbital elements follow
; === Osculating Elements ===
;***cfgBatchDataCalculator
Epoch = 2006.73100616
SemiMajorAxis = 2.054446954840060E+11
Eccentricity = 2.786757013485404E-01
Inclination = 0.024657522087164
LongAscNode = 6.0030264968506
LongPerihelion = 2.7559875894959
MeanLongitude = 2.6168509245667
; === Physical Parameters ===
Mass = 1e9
Size = 10000 ; mean radius
SidRotPeriod = 2.034E+8 ;
SidRotOffset = 0
Obliquity = 0 ; n/a
LAN = 0
AlbedoRGB = 1 1 1
; === Visualisation Parameters ===
MaxPatchResolution = 1Contents of (Orbiterroot)\Config\DSM3.cfg
Code:
; === Configuration file for marker planet Rosetta_marker ===
Name = DSM3
EllipticOrbit = TRUE ; assume unperturbed orbit
HasElements = TRUE ; orbital elements follow
; === Osculating Elements ===
;***cfgBatchDataCalculator
Epoch = 2011.05954825
SemiMajorAxis = 4.712512592116447E+11
Eccentricity = 6.566888656335083E-01
Inclination = 0.10253896450906
LongAscNode = 0.8001206382389
LongPerihelion = 1.1638184966692
MeanLongitude = 2.4897116917226
; === Physical Parameters ===
Mass = 1e9
Size = 10000 ; mean radius
SidRotPeriod = 2.034E+8 ;
SidRotOffset = 0
Obliquity = 0 ; n/a
LAN = 0
AlbedoRGB = 1 1 1
; === Visualisation Parameters ===
MaxPatchResolution = 1Finally, open the (Orbiterroot)\Config\Rosetta_sol.cfg file and add the lines:
Code:
Planet12 = DSM1
Planet13 = DSM2
Planet14 = DSM3We have everything we need to proceed to the next part: Mission planning using TransX (and IMFD).
