J2 Periapsis Precession
Evaluate first-order secular J2 argument-of-periapsis precession for supplied mean elliptic elements in km and seconds.
Description
An oblate central body's J2 term causes secular argument-of-periapsis precession.
An oblate central body's J2 term causes secular argument-of-periapsis precession. The first-order rate changes sign with inclination and vanishes at the model's critical inclinations.1
Evaluate first-order secular J2 argument-of-periapsis precession for supplied mean elliptic elements in km and seconds.
When to use J2 Periapsis Precession
Use this tool to evaluate first-order secular J2 argument-of-periapsis precession for supplied mean elliptic elements in km and seconds.
Prepare the orbital state or model parameters in one reference frame. Confirm compatible distance/time units and the stated angular and gravitational-parameter conventions.
How to use J2 Periapsis Precession and understand its results
- Prepare the orbital state or model parameters in one reference frame. Confirm compatible distance/time units and the stated angular and gravitational-parameter conventions.
- Enter mu, semimajorAxis, eccentricity, referenceRadius, j2, inclinationDegrees using the field table and calculation rules, then run the tool.
- Read radiansPerSecond, degreesPerDay. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| mu | Gravitational parameter, using the same distance and time units throughout; km³/s² for km and seconds. | number | Required |
| semimajorAxis | Semimajor axis | number | Required |
| eccentricity | Eccentricity | number | Required |
| referenceRadius | Reference radius | number | Required |
| j2 | J 2 | number | Required |
| inclinationDegrees | Inclination degrees | number | Required |
Enter positive μ, a and reference radius, eccentricity 0≤e<1, nonnegative J2 and inclination 0–180 degrees. Use km and seconds for the displayed radians/second and degrees/day outputs. The helper computes K and multiplies by the inclination factor; zero J2 produces zero drift.
K = 1.5 J2 sqrt(μ/a³)[R/(a(1−e²))]²; periapsisRate = K(5cos²i−1)/2 Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| radiansPerSecond | Radians per second | number |
| degreesPerDay | Degrees per day | number |
{
"input": {
"mu": 1,
"semimajorAxis": 2,
"eccentricity": 0,
"referenceRadius": 1,
"j2": 0.01,
"inclinationDegrees": 0
},
"output": {
"radiansPerSecond": 0.0026516504294495534,
"degreesPerDay": 13126.611889570608
}
}Limitations and assumptions
This uses mean elliptic elements in a first-order secular approximation. Higher harmonics, drag, other bodies, osculating variations and uncertainty are omitted.
Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use J2 Nodal Precession: Evaluate signed first-order J2 nodal precession for supplied mean elliptic elements in km and seconds. For a complementary task, use J2 Critical Inclination Proximity: Compare inclination with both first-order J2 critical inclinations, rather than a rounded 63.4-degree reference only.
References
-
J2 Periapsis Precession — tool.io
Similar or alternative tools
- J2 Nodal Precession
Evaluate signed first-order J2 nodal precession for supplied mean elliptic elements in km and seconds.
- J2 Critical Inclination Proximity
Compare inclination with both first-order J2 critical inclinations, rather than a rounded 63.4-degree reference only.