Protocol for submitting orbital observations to the IAU

[Celesty]

I will greatly appreciate anyone who knows the protocol for accurately recording an orbit for the IAU. I will be looking for 3 points at least.
Do I do this several times a day, a week, a month or only gather 3 points once? I know it depends partly on the route of the planet but when the IAU ask for 3 location points does it mean of one orbit which is then detailed? This seems insufficient but perhaps it's the time involved for proving different potential orbits of greatly varying lengths. Is there an advised table to write the coordinates? What form does this take? What form do the units take? Which points on the orbit do I take?
Thank you kind people.

 

[sbrothy]

I know I've mentioned it before but there's a lot of help available on the website Atomic Rockets.

 

[mfb]

An orbit has 6 degrees of freedom, observing the direction of an object has two parameters. That means you need at least three observations to have any sort of chance to determine an orbit. If these three observations are close together then they are largely redundant - the object will move approximately in a straight line so you can predict one measurement from the others and you only have two useful measurements. If these observations are too far apart, it's not clear if they are all the same object.
Typically discoveries are based on two or more observations close together for a very rough initial orbit estimate, and then more measurements at larger time differences to determine the parameters more precisely. Ideally this orbit lets you search for the object in older images to increase the time span between first and last observations as much as possible.

 

[Filip Larsen]

In practice you would also want to employ statistical orbit determination, that is, with 4 or more direction observations you can use the over-determination to give an estimate for the uncertainty of the derived orbit parameter values. As the number of observations go up over time the uncertainty will typically converge towards the level that is indicative for the observation instrument precision and other noises as well as biases such as perturbations from the major planets.

When fitting for high eccentric orbits (like comets) it is often necessary to use multi-body calculations that include the perturbations of the major planets in order for the fit to maintain accuracy over longer time, like several periods. For planetary orbits (moons, satellites) it will usually be necessary to include non-spherical effects of the gravity potential. For instance, for low Earth orbits it is essential to include at least the J₂ perturbation (oblate Earth) to model the fast drift that several of the orbital parameters are affected by.