# Criteria for accepting or rejecting identifications

## Submission rejected without orbit fitting

### ITF-to-ITF submissions

Please note that the criteria do not apply to NEOCP objects. The MPC will reject ITF-to-ITF identifications without performing any orbit fitting if any of the following is true:

- The submission format is incorrect. See the submission format description.
- The submitted tracklets cover less than 3 distinct nights.
- The arc length covered by the tracklets is less than 3 days.
- The number of nights is 3 and the arc length is larger than 40 days.
- You are trying to submit a two apparition linkage when the second apparition is represented only by a single tracklet regardless of the number of tracklets in the first apparition.

### ITF-to-DES submissions

The MPC will reject ITF-to-DES identifications without performing any orbit fitting if any of the following is true:

- The submission format is incorrect. See the submission format description.
- You are trying to extend the orbit of a one-apparition non-NEO to a two-apparitions non-NEO using only one single tracklet over one night (arc lenght < 0.75 days). Please note that this criteria does not apply to NEOs. See the Recover Page for further explanation.

### DES-to-DES submissions

The MPC will reject DES-to-DES identifications without performing any orbit fitting if any of the following is true:

- The submission format is incorrect. See the submission format description.
- You are attempting to link together two only one-opposition distant objects (q>5.5).

## Submissions rejected with orbit fitting

### ITF-to-ITF submissions

Please note that the criteria do not apply to NEOCP objects.The MPC will reject certain identifications after performing an orbit fit if any of the following is true:

- If the tracklets cover exactly 3 nights, have an arc length < 40 days and RMS > 0.25" and orbit quality is not sufficient (defined below).
- If the tracklets cover more than 3 nights, have an arc length < 10 days and RMS > 0.25" and orbit quality is not sufficient (defined below).
- The orbit fit did not converge.

**Minimum orbit quality definition for 3-nighters:**Covariance requirements on the converged orbit: The 1-sigma range for the orbital elements must satisfy the following: semimajor-axis<0.05 AU, perihelion distance<0.05 AU, inclination<0.5 deg, eccentricity<0.05; and the eccentricity of the orbit must be < 0.5.MPC accepts multi-opposition ITF-to-ITF submissions when:

- for 2-opposition orbits, one apparition must have at least 3 nights, the other apparition at least two nights; or
- for 3-opposition orbits, at least one apparition must have at least 3 nights and another apparition at least two nights; or
- for 4+ oppositions, at least two distinct nights are present on two apparitions.

New apparitions are counted by gaps between subsequent nights being longer than 237 days.

### ITF-to-DES submissions

The MPC will reject certain identifications after performing an orbit fit if any of the following is true:

- The orbit fit did not converge.

### DES-to-DES submissions

The MPC will reject certain identifications after performing an orbit fit if any of the following is true:

- The orbit fit did not converge.