Mean Anomaly Periapsis Time
Map a wrapped elliptic mean anomaly to time since the latest periapsis in the supplied period unit.
Description
Elliptic mean anomaly increases uniformly with orbital time in a two-body model.
Elliptic mean anomaly increases uniformly with orbital time in a two-body model. Wrapping it to one revolution gives elapsed time since the latest periapsis, discarding whole prior cycles.1
Map a wrapped elliptic mean anomaly to time since the latest periapsis in the supplied period unit.
When to use Mean Anomaly Periapsis Time
Use this tool to map a wrapped elliptic mean anomaly to time since the latest periapsis in the supplied period unit.
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 Mean Anomaly Periapsis Time 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 meanAnomalyDegrees, orbitalPeriod using the field table and calculation rules, then run the tool.
- Read wrappedMeanAnomalyDegrees, timeSincePeriapsis. 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 |
|---|---|---|---|
| meanAnomalyDegrees | Mean anomaly degrees | number | Required |
| orbitalPeriod | Orbital period | number | Required |
Enter a finite mean anomaly in degrees and a positive period. The tool wraps positive or negative angles into [0,360) and returns the wrapped angle and time since periapsis in the period's unit. Whole-turn anomalies represent zero elapsed time.
elapsed = wrap(meanAnomaly,360)/360 × orbitalPeriod Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| wrappedMeanAnomalyDegrees | Wrapped mean anomaly degrees | number |
| timeSincePeriapsis | Time since periapsis | number |
{
"input": {
"meanAnomalyDegrees": 450,
"orbitalPeriod": 100
},
"output": {
"wrappedMeanAnomalyDegrees": 90,
"timeSincePeriapsis": 25
}
}Limitations and assumptions
It does not return an absolute epoch or count past revolutions. Mean anomaly must not be confused with true anomaly, which is generally not uniform in time.
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 Elliptic Mean To True Anomaly: Solve elliptic Kepler equation with bounded bisection and convert to wrapped true anomaly; angles are in degrees. For a complementary task, use Keplerian Orbital Period: Compute a two-body elliptic orbital period from semimajor axis and total gravitational parameter, not a fixed planetary lookup.
References
-
Mean Anomaly Periapsis Time — tool.io
Similar or alternative tools
- Elliptic Mean To True Anomaly
Solve elliptic Kepler equation with bounded bisection and convert to wrapped true anomaly; angles are in degrees.
- Keplerian Orbital Period
Compute a two-body elliptic orbital period from semimajor axis and total gravitational parameter, not a fixed planetary lookup.