Orbit matching

[Starchaser]

I've been playing for a few weeks. I started playing unmodded, and got to circularizing my orbit before beginning to flail. At that point I started looking into the community and looking for resources to help me progress, I added mechjeb, at that point, and restarted career mode, with a goal of being more efficient in my progress. I was successful, kept reading, kept watching tutorials, and restarted again.

On my third playthrough I'm doing well...I've lifted some pretty crazy payloads into orbit to run 3 or 4 contracts at once. Now I've unlocked deployable photo-voltaic panels and have begun trying to match described orbits.

Here is my current problem.

I'm trying to match the red orbit. I'm on the blue orbit. The upcoming node is to match longitude of AN. I match apo, peri, and inclination. After the upcoming burn I will only be off by the 'argument of periapsis'

I've been researching for several hours now, and can't find anything on how to adjust that. I've tugged a maneuver node around and can't seem to match it either. Any nudges in the proper direction to find out more information would be appreciated.

Edited March 24, 2015 by Starchaser

[Taki117]

I've been playing for a few weeks. I started playing unmodded, and got to circularizing my orbit before beginning to flail. At that point I started looking into the community and looking for resources to help me progress, I added mechjeb, at that point, and restarted career mode, with a goal of being more efficient in my progress. I was successful, kept reading, kept watching tutorials, and restarted again.

On my third playthrough I'm doing well...I've lifted some pretty crazy payloads into orbit to run 3 or 4 contracts at once. Now I've unlocked deployable photo-voltaic panels and have begun trying to match described orbits.

Here is my current problem.

http://s1335.photobucket.com/user/kekkomartin/media/KSP%201_zpsnedfk9a5.png.html?sort=3&o=0

I'm trying to match the red orbit. I'm on the blue orbit. The upcoming node is to match longitude of AN. I match apo, peri, and inclination. After the upcoming burn I will only be off by the 'argument of periapsis'

I've been researching for several hours now, and can't find anything on how to adjust that. I've tugged a maneuver node around and can't seem to match it either. Any nudges in the proper direction to find out more information would be appreciated.

Don't worry about Argument of PE, instead work on your inclination (Which is going take a lot of dV unless you push your AP out as far as you dare) And make sure you are orbiting the same direction as the dots along the orbit. Everything else will fall into place.

[impyre]

the argument of periapsis is one of the most difficult things to adjust (but usually doesn't result in the inability to fulfill a contract, I'd recommend checking other requirements). Radial-in/out will "rotate" your orbit around a point that is decided by where you are along your current orbit, and the specifics of your orbit. Try creating a maneuver node with a significant radial-in/out burn, and move it around your orbit. Here's the basic process:

1) Pivot your orbit until the argument is correct (altitude may be off). Maneuver nodes can help here, radial burns adjust this.

2) Burn prograde/retrograde at the appropriate times to match the orbit exactly. This *must* occur at peri/apoapse in order to avoid changing the argument.

3) Once close, argument can become a bit jumpy (especially for a circular orbit), use a combination of prograde/retrograde and radial to adjust the height of your peri/apoapse to the desired point without changing argument. If you're approaching your apoapse, radial-out will shift it ahead of you in your orbit, and radial in will shift it backwards.

4) Note that the more you are angled towards radial, the less the burn will affect prograde (and vice versa). Use this fact to make the smallest possible adjustments to whatever orbital attribute you're trying to alter (in addition to decreasing throttle limiter and using capslock for fine control).

Once you practice a bit, you'll get the hang of it. It's kindof a balancing act when trying to adjust one thing while keeping another the same.

Again though, for contracts which describe a "circular" orbit, argument of periapsis/apoapsis is displayed, but generally ignored.

- - - Updated - - -

Wow, you're *way* off... with extremely inclined target orbits, the best bet is to try to match the inclination directly from launch. Forgoing that, the second best method (though more costly) is usually to enter an extremely elliptical orbit and execute the inclination change at apoapsis.

[StrandedonEarth]

I ignore the numbers in the contract, except to maybe make sure the inclination isn't near 180 degrees, which is retrograde. I just match up the orbits in map view using my MkI Eyeball, paying attention to get the An/Dn close to zero (+/- maybe 0.2, 0.1 is definitely allowable, at which point you will be moving in the same direction as the pips in the target orbit), and matching the Ap/Pe within a few km and roughly the same spot.

[Deutherius]

Frankly, I think it would be better to just launch a new satellite. This one is on a completely different orbit and fixing it would be costly. Important thing to note is that you don't have to launch into an equatorial orbit, in this case it's actually very inefficient.

Just put a new satellite on the launchpad and timewarp until you are almost below the desired trajectory. Then launch directly into the desired orbit (e.g. going north if the dots on the closest side are going up, south if they are going down - just use common sense), trying to correct inclination while early in the launch (where it's cheap). Once you're in an orbit with the correct inclination, matching the contract orbit is just a matter of pushing around Ap and Pe.

[Starchaser]

Don't worry about Argument of PE, instead work on your inclination (Which is going take a lot of dV unless you push your AP out as far as you dare) And make sure you are orbiting the same direction as the dots along the orbit. Everything else will fall into place.

That's the thing. The inclination is supposed to be 63° and that's what I launched at, Mechjeb's orbit information confirms I am at 63° inclination. so...I am really lost...:/

The Ap on this orbit is halfway to the Mun already, and I am orbiting in the same direction.

[Kryxal]

That looks like a highly elliptical orbit, it MIGHT be reasonable to go from the one to the other ... the first step would be to raise your orbit (probably at the AN/DN) at least to near the Mun's orbit, maybe as high as near-Minmus. Execute your inclination change when you're out there and have your orbit intersect the target orbit (inclination is more important, intercept points can be fine-tuned easily with pro/retrograde). At an intersection point, use pro/retro and normal/anti-normal to match AP, PE, and position of AP and PE.

[Starchaser]

Ok, an update. I reloaded to my pre-launch quicksave, and this time I launched to an inclination of -63.4°, then made some corrections. It came out looking like this, and I included my orbit info window.

so, as you can see, still a huge difference between that and my red, target orbit. But here is my contract.

I haven't corrected my Long to AN yet, but I put a node up to do it, and it was just a minor change. I can't figure out why my orbit is no where near the target orbit when it seems the numbers match.

[eddiew]

As has been said before; ignore the numbers. They don't help, they aren't useful. There aren't any tools in the game to tell you when your numbers are going to match the contract's, so just go by the visuals. You've got to pilot these missions with your eyes, not your instruments.

What you want to do, by the way, is launch when the red orbit line crosses both the launchpad and the centre of the planet, and ascend along that orbital angle - in this case, probably going largely north or south. It won't be perfect, but it should be better

(If you really want to know, the difference is in the longitude of your ascending node, i.e. the point at which both sides of your orbit are in line with the centre of the planet. But since there's nothing in the game to help you aim at this, it's a total red herring...)

[GoSlash27]

Try setting up a radial burn where your orbit crosses the equator using the maneuver node. See if you can get it closer that way.

In the future, you really want your inclination and ascending node sorted out before you set the apoapsis. It costs a little more in the short term, but pays off in the long run.

Best,

-Slashy

[Reactordrone]

It looks like the orbit info is giving inclination relative to north-south rather than the equator so if you want to persist with trying to get the autopilot to do it you might have to subtract the needed inclination from 90°.

[Taki117]

As has been said before; ignore the numbers. They don't help, they aren't useful. There aren't any tools in the game to tell you when your numbers are going to match the contract's, so just go by the visuals. You've got to pilot these missions with your eyes, not your instruments.

What you want to do, by the way, is launch when the red orbit line crosses both the launchpad and the centre of the planet, and ascend along that orbital angle - in this case, probably going largely north or south. It won't be perfect, but it should be better

(If you really want to know, the difference is in the longitude of your ascending node, i.e. the point at which both sides of your orbit are in line with the centre of the planet. But since there's nothing in the game to help you aim at this, it's a total red herring...)

THIS! Don't worry about getting every number exact, the ones you are worried about are AP and PE. Everything else with either fix itself after orbit matching (Like longitude of AN and ARG of PE) or be useless after you launch anyway (Inclination, I'm looking at you). MechJeb can only do so much to help you get to where you need to go, especially since all MechJebs plane changes occur at Kerbins equator, not at the Ascending node of your target orbit. This is because you can't set the target orbit as...well...a target. Time your launch so that you are passing under the orbit (It's ok if you are off by a bit) and go into a circular polar orbit. (It doesn't have to be exactly polar, but it does need to be circular) from there line up the AN and DN of your target orbit, plop a maneuver, and pull Normal/Anti-normal, as well as Radial/Anti-radial and Pro/Retro grade to match orbits. Don't try to launch into such a highly inclined orbit (Not even NASA does it that way) instead set up a series of maneuvers from a stable, low altitude orbit to correct inclination first, then AP/PE.

[eddiew]

I'd actually suggest setting a loosely circular orbit at the desired PE first. The higher you are when you do inclination changes, the less it will cost. Never do manoeuvres below the lowest altitude you need​ to be at

(Far as I can tell, there's often a benefit from burning prograde to get away from the planet, changing inclination at AP, then burning retrograde again at PE to circularise again.)

[StrandedonEarth]

Just because the inclination is the same doesn't mean you're in the right plane. That's why missions to the ISS usually have split-second launch windows, so that they're launching into the right plane for an efficient rendezvous. I find it easiest to ignore the numbers and eyeball it. Play with the maneuver nodes until you get the orbits lined up the same ( you may need multiple burns), going the same direction. Having RCS helps to fine-tune (using the ijklhj keys to translate) the orbit after major burns

[Randazzo]

The first thing I would suggest is to ignore all the data regarding the orbit with the exception of orbital direction (prograde or retrograde) at launch. The obvious exception would be Polar orbits, since if you launch out of plane it will take a tremendous amount of Delta V to match them. Launch at zero. There will be people ho scoff at this, but when you get better at figuring out when to launch, then you can worry about launching into plane.

From your 0 degree orbit, do the following:

• Ensure your current orbit is circular
  
• Focus view on Kerbin (or whatever body you are orbiting)
  
• From your map view, locate the AN and DN nodes on the target orbit. (They will be indicated on contract orbits.)
  
• Adjust your view so that both your current orbit and your target orbit each form a straight, flat line. (At the same time..You need this perspective.)
  
• Now adjust your view so that the AN and DN nodes (They each have a little triangle pointer) are intersecting at the same point in your perspective (Both orbits should still be flat lines). The tips of the two pointing icons should just barely be touching, or as close as you can get. Click on this point of your orbit and create a manuever node.
  
• Adjust your inclination from this point. From a circular orbit, the Delta V requirements should be roughly the same on either side (ascending, descending) of the orbital plane. This does require a basic understanding of how to change your inclination.
  
• If you use mechjeb to do this, remember that you may have to do a "negative" inclination change to match the orbit, depending on the node you perform the manuever at.
  
• Using the same perspective trick, you can overlay the Ap and Pe node indicators and plot the changes to your apsides to perfectly match the target orbit.
  

If you follow this procedure (assuming I haven't made it seem entirely arcane), your matching orbits will be perfect after three burns (more if you change altitude in steps). Two disclaimers:

1. You do not necessarily need to circularize your orbit before matching inclination, but remember that trying to change inclination at periapsis and at lower altitudes is much costlier than near apoapsis or high altitude.
   
2. If you choose not to circularize, it will not work for matching apside points. You'll just have to create a node and drag it around until it matches.
   

Edited March 20, 2015 by Randazzo

[michaelhester07]

I'll give you my experience for satellite launches into kerbin orbit.

---===== Launch =====---

1. Any heavily inclined orbit like that has 2 launch windows. Open your map and look at kerbin, then rotate around until the orbit appears flat. Now time warp until the marker for your satellite is nearly lined up. This is one of your launch windows.

2. Pay attention to the direction the rotating dots are on the orbit. This tells you what direction your launch will be.

3. launch. When you get to the point where you'll start your gravity turn click on the velocity indicator on the navball to select "orbit" mode, then line up your orbit prograde to the heading that your final orbit will be. You can estimate the orbit. Your screen shot's orbit would be about 150 degrees if prograde on it goes south, or about 320 if it goes north. Don't let your own prograde altitude on the nav ball drop below 45 degrees until your apoapsis is above 40km.

4. Finish your orbit insertion as you usually would.

---=== Orbit: learning the markers for your current ship ===---

Most of my satellite designs end up with 3000+ delta V in the payload so I can "burn with impunity". If your satellite is designed right then you also have 3000 delta V. We'll use some of it to learn what your markers will do. Find the normal marker (it's the blue marker on the "sky" side of your navball. If you burn towards it you'll rotate the periapsis/apoapsis markers clockwise (as you view kerbin from the north). Find the anti-normal marker, burn towards it. You'll rotate the pe/ap markers counter clockwise. Note that this is reversed if you're in a retrograde orbit (that is an orbit in the opposite direction that kerbin's moons go).

Locate the purple markers. On is to the north, the other to the south.

1. Find the AN/DN on the target orbit. These will not be marked on your orbit. You'll have to eyeball the lineup like you did with the launch window. Burn toward one of the purple markers when you're at DN. If the node's angle decreases keep burning, otherwise burn toward the other marker. Get these angles under 1 degree.

2. Using the information about normal/anti normal you can line up the PE marker with the target orbit's PE. It may be your AP marker. You can do this from any point in your orbit.

3. Now that the PE/AP marker is lined up wait till your ship is at the opposite marker and burn prograde until the marker's altitude is the same as the target orbit marker's altitude

4. Wait till your ship is at the marker from step 3, then burn prograde to set the AP altitude to match the target orbit ap's altitude. Use normal or anti-normal burns to match the marker's location in the orbit.

5. If the contract is not awarded within 10 seconds look for these issues.

- Check your orbit plane (angle is marked on AN/DN of the target orbit) and match it more closely

- Make sure AP and PE are at the correct altitude (you can usually get within 50km)

- Make sure AP and PE are in the correct spot.

- Make sure your satellite meets the contract requirements (I've had this problem... get to the right orbit but realize I didn't have a goo canister on the satellite)

If you can master the satellite contracts they're the highest profit margin in the game for Kerbin's SOI.

[RW-1]

Just put a new satellite on the launchpad and timewarp until you are almost below the desired trajectory. Then launch directly into the desired orbit (e.g. going north if the dots on the closest side are going up, south if they are going down - just use common sense), trying to correct inclination while early in the launch (where it's cheap). Once you're in an orbit with the correct inclination, matching the contract orbit is just a matter of pushing around Ap and Pe.

This.

forget numbers, launch and turn so that it comes close to the contract orbit. then circularize and maybe make small aN or dN adjustments, and if you went the correct direction (pro/ret) then you'll get it.

[bakanando]

This is one of many situations where the lack of displayed information is completely unhelpful.

As everyone else said, wait until the target's orbit An/Dn are just over the KSC and launch then. Do notice that if it is the Ascending node you have to launch to +63.5, but if it's the Descending one you should launch towards -63.5 or the orbit will still be wrong. It is just matter of matching Ap/Pe and some adjustments to inclination (Normal or Anti-Normal) to match planes if you are a little off-mark.

[Randazzo]

Maybe this will help

[impyre]

Quite simply, inclination by itself isn't enough to fully describe an orbit. Your inclination is the angle that your orbit makes with the equatorial plane. Think of it like a disc. Once you have an inclination, your orbital plane changes (and can be rotated around). This rotation is where the longitude argument comes into play, the longitude of ascending node is the longitude at which your orbit will cross the equatorial plane (and is presumably written with respect to the parent body's prograde vector). Imagine taking your orbit and rotating it around the north pole, this is the adjustment of the longitude of your ascending node. Adjusting this is a very difficult task, which is why at launch you must take care to match the target plane (not just its inclination).

tl;dr

I'm not sure if I'm describing this well, so I'll give one more example. If you think of a satellite dish, pointed up at an angle and imagine the rim of the dish as an orbital path... the angle that the dish makes with the ground is its inclination. If this dish were attached on a post which allowed the entire thing to rotate, this rotation would be like changing the longitude of the ascending node... if it were pointing east, and then rotated to point south this would represent a change of 90 degrees in the longitude of ascending node.

- - - Updated - - -

Here's what I do, I'm too lazy/impatient to wait for the correct time to perform the most efficient launch (directly into the correct orbit)... so I simply launch on a low equatorial orbit (as if going anywhere else really), then burn so that my apoapse rests on the ascending/descending node of the target orbit. Once at apoapse I burn to match inclination and raise my orbit until it crosses the target orbit's periapse or apoapse. Once there I use a combination of prograde/retrograde/radial burns to match my target orbit perfectly. It's a bit more complicated, but it's not terribly inefficient (just marginally inefficient). The reason I use this method is because it really reduces the guesswork and potentially difficult piloting that can go with trying to launch directly into the desired orbit. It makes it relatively easy to eyeball.

[Starchaser]

Well, I waited until the orbit crossed by the launch center, doing several other contracts instead. Tonight I am going to try it again. Wish me luck. Thanks for all the people who tried to help, I'll let you know how much sank through my lead lined skull

Edited March 23, 2015 by Starchaser
corrected verb tense

[Destroyer713]

On the off-chance you still need help, 5th Horseman made a couple of videos that give excellent advice on doing satellite contracts within Kerbin's SOI.

In your case, he details a Kolynia orbit in the second half of the second video there, but I'd watch both videos completely just because of how helpful they can be.

[Starchaser]

Well. I'm not sure here.

and

It seems like I'm right on. Not awarding me the contract. I'm orbiting the right way and the only probe requirements were power and an antenna. I need to go to work. Saving it here I guess.

[Deutherius]

It seems your orbit is good enough. You can see the objectives of the contract in the contract window, being checked as they are completed. Which are remaining unchecked in your case?

[Starchaser]

Meeting the orbit. I am 0.1° off AN and DN, 2 km off on the apo and 5km off on the peri. How minimal is minimal?

The burn is so small to correct the peri that I am afraid I can't hit shift then x quick enough.

I might not have time to get on tonight and correct it though