SimStart DateTime
SimStart indicates the start time of the scenario. A date and time entry should follow this keyword.SimDuration Duration
SimDuration indicates duration of the scenario. A Duration entry should follow this keyword.LeapSeconds s
LeapSeconds indicates the number of leap seconds to be used. This is the positive integer TAI-UTC. A default value of 37 seconds was used as of Jan 2023. The value is typically not critical as it only affects slowly changing states dependent on terrestrial time, such as the ephemerides of celestial bodies. For example, precession and nutation transformations can be computed with TAI-UTC equal to zero without affecting accuracy. An error in TAI-UTC will have a greater impact on sun, lunar, and planetary ephemerides, although the state of celestial objects changes relatively slowly and is often computed using lower accuracy analytic methods. TAI-UTC is typically only important when inputting (or outputting) GPS time values.EcfEciRate Duration
EcfEciRate sets the rate at which ECF to ECI transformations will be generated. Over the duration of the scenario, precession, nutation, and EOP transformations are compuated at this rate and stored. When required by the eom library, interpolation is used to form the precise transformation at a given time. The modern CIO method allows a rate of 1 set of transformations per day to be suitable for most high precision needs. For computational efficiency, when running Monte Carlo simulations, setting the EcfEciRate to 0 results in the generation of a single set of transformations, eliminating the need for interpolation. A Duration entry should follow this keyword.