The set of available orbit types is dependent upon the central body about which the orbit will be created. Sun synchronous orbits have the property that their nodes maintain constant local mean solar times. These orbits are designed to utilize the effect of the Earth's oblateness, causing the orbit plane to precess at a rate equal to the mean orbital rate of the Earth around the Sun. The orbit repeats the ground coverage cycle and passes overhead at approximately the same local mean solar time for each revolution. The ground trace may be caused to repeat every day or to interweave from day to day before repeating. Sun Sync orbits with repeating ground traces are useful when identical viewing and lighting conditions are desired at different times to detect changes. ![]() Orbits with repeating ground traces are useful when identical viewing conditions are desired at different times to detect changes. With this option, you can create any orbit you wish. Molniya orbits also have a long dwell time in the extreme latitude regions of the Northern Hemisphere. This keeps the perigee of the orbit in the Southern Hemisphere. Molniya orbits are also critically inclined. Molniya orbits are highly eccentric, meaning that there is a large difference between the altitude at apogee and the altitude of perigee. The satellite will pass overhead at the same local mean solar time for each revolution and has a perigee which remains at a fixed latitude.Ī satellite in a stationary orbit will remain fixed in the sky above the specified fixed longitude. The orbit uses a retrograde inclination of 116.565 degrees. The line of apsides does not change over time.Ĭritically Inclined Sun Synchronous orbits combine the features of both basic types of orbits. The orbit types are as follows: Satellite OrbitĬritically Inclined orbits maintain perigee at a fixed latitude. The Orbit Wizard can also be used modify an existing satellite by highlighting the satellite in the Object Browser to expose the Satellite menu and select Orbit Wizard. ![]() When you are using the Insert STK Objects panel in conjunction with the New Scenario Wizard, the Orbit Wizard may be chosen as an option for initializing a new satellite object. The configurable options available will depend on the orbit type selected. The Orbit Wizard is a satellite-level tool designed to assist you in creating any one of several standard orbits, or designing your own satellite orbit. This process also applies when writing a STK ephemeris where the Spacecraft.Epoch is converted to the UTC time system before being written to a STK ephemeris file as the "ScenarioEpoch". This results in the Spacecraft.Epoch property reporting the equivalent TAI Julian date of the UTC epoch in the STK ephemeris. Note: Once a STK formatted ephemeris is parsed, the "ScenarioEpoch" is automatically converted from the UTC to the TAI time system by FreeFlyer. The STK Ephemeris "ScenarioEpoch" is written using the Gregorian UTC time system (dd mmm yyyy hh:mm:ss.s). When FreeFlyer ingest a STK formatted ephemeris, it assumes the "ScenarioEpoch" is defined using the UTC time system with a MJD GSFC reference date. STK is a registered trademark of Analytical Graphics, Incorporated. ![]() FreeFlyer writes a STK v3.0 formatted file. The STK Ephemeris is an ASCII file with the format defined by the STK Users Manual. See the Working with Ephemerides guide for more information about creating and importing an Ephemeris file. When the data is stored in a file, FreeFlyer or Analytical Graphics' Satellite Tool Kit can import the data and perform calculations on the trajectory information. ![]() The STK Ephemeris allows you to store the state of the Spacecraft at each time step during the mission to a file. This format can be used for both input and output of Spacecraft orbital data. The STK® Ephemeris File is an ephemeris-file format for use with Analytical Graphics Inc.’s Satellite Tool Kit®.
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