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Orbiter Instrument Training

Synchronize to Target

Bring up the Orbit MFD and the Synchronized Orbit MFD together. The Sync MFD includes a display for the relative Inclination ( Rinc ). This should be below 1 degree, if it is not you will need to align orbit before you can synchronies. The first thing to be done is to match tables between ship orbit and target orbit so that both ships have similar orbital elements, particularly PeD, ApD and T. See changing orbital shape if you need help here.

If the target is behind your ship you simply want to increase T, the time it takes to complete an orbit, this will give the target time to catch up. On the other hand if you are behind target then decrease T. You can probably guess how you could do this by just using the Orbit MFD, but there is a better more fuel efficient method by using the Sync MFD.

The Sync MFD displays a reference line and the time it takes for ship and target to reach the reference line for several orbits. There are a number of options for where you want the reference line to be placed. Shift [M] will toggle through them. There are two intersect points where the reference line can lie, or you may place it on periapsis or apoapsis of either the ship or target. The last option is for manual placement of the reference line anywhere you like.

Regardless of which option you use, when your ship crosses the reference line you will do a burn until the time for both ship and target to reference line in some future orbit match. This will normally be several orbit laps away. Notice that the reference line is both your start and finish line. The number of orbits for the ship and the target do not need to be the same, only that both vessels meet at the reference line at some future orbit.

If your ship is ahead of the target you will need to increase the time ( T ) it takes to complete an orbit to let the target catch up. This is done by burning prograde when the reference line is crossed. When you are behind target you will need to burn retrograde to decrease ( T ) so your ship will catch up with target. When burning retrograde you must take care that you do not deorbit altogether. Therefore I normally try to launch ahead of my target so my burns will be prograde. Either way works fine just be careful to watch PeD when burning retrograde.

How long should you burn? It is very difficult to watch the numbers for ship to reference (Sh-ToR) and target to reference (Tg- ToR) as you are burning. They are constantly changing and it's nearly impossible to match the two of them. Time of arrival difference ( Dtmin)  is the key to watch while burning It is the difference in time between the ship and the target to cross the "Finish" reference line. You simply need to burn until the Dtmin is zero and the ship and target should arrive at the same time.

Look at the yellow highlighted numbers for Sh- ToR and Tg- ToR they should match when your burn is completed. The yellow Sh-ToR  number indicates how much time in seconds until the final reference crossing. It also indicates how many orbits are left before you synchronize to target. You may show additional orbits in the table by using the shift[N] command.

Which reference option should be used? All of them will work the same. However you must wait until you cross the line to begin your synchronization burn. The manual option allows you to move the reference line to where your ship is now and you may begin burning immediately.

If you are low on fuel you may want to begin the burn at PeD or ApD to get the most bang for your buck. You can also do a smaller burn time and just make more orbital laps before meeting up with target. In this case ship and target will come closest to one another without regard to the reference line.

If everything goes well the target should be within range of the target when you finish your final orbit. The ship, target and "Finish" reference line should all overlap. Target is normally within 200 km distance but our aim is be within 50km. If you are out of range run a second synchronization burn.

When you make your final crossing and the target is within range, it is best to undo the distortion in your orbit caused by the synchronization burn. In other words return to the original orbit where the ships orbital element numbers match that of the targets. Therefore both ship and target are in close proximity and are in identical orbits.

You should be within 50 km now and you can turn off both the sync and orbit MFDs. Prepare for docking by bringing up the Dock MFD and tune radio to docking port. Now open the bay doors or docking port doors. Look at the Docking HUD and rotate your ship until you are pointing toward the relative velocity vector. You should stop your motion relative to target by thrusting toward the vector ball.

Once your velocity is near zero, rotate toward the target and thrust. You should be closing in on the target now. At some point the target may begin to slip away again. Stop all relative motion as describe above and begin thrusting toward target again. Be careful though not to build up to much velocity. Eventually you will come to within 2 or 3km of target and will need to come to a complete stop relative to target. At this point you will begin docking procedures.

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