Package gaiasky.util.gaia

Class TransitionScanningLaw

java.lang.Object
gaiasky.util.gaia.BaseAttitudeDataServer<IAttitude>
gaiasky.util.gaia.AnalyticalAttitudeDataServer
gaiasky.util.gaia.TransitionScanningLaw
public class TransitionScanningLaw extends AnalyticalAttitudeDataServer
Implements a smooth transition from Nsl37 to Epsl, or vice versa.

The scanning law used by this AttitudeDataServer is only valid (to required accuracy) in a short (< 0.5 day) time interval when the spin axis is less than a degree of the ecliptic. The revolving phase angle (nu) is written as nu(t) = 0.5 * acc * t^2 (in preceding mode, that is when nu is close to 0) or as nu(t) = PI + 0.5 * acc * t^2 (in following mode, that is when nu is close to PI). Here t is the time in [days] from the reference time (tRef) of this scanning law, and acc is a constant. On initialization, acc is set to a value such that nu(t) according to this law agrees with Nsl37 (for some suitable choice of initial angles) both in value and rate at t = tRef + T, where T is the ramp-up time (if T > 0) or ramp-down time (if T < 0). At t = tRef the revolving phase is exactly 0 (preceding mode) or PI (following mode).

A number of reference quantities can be set as usual by means of setRefTime, setXiRef, setOmegaRef, setTargetPrecRate, and setTargetScanRate from the AnalyticalAttitudeDataServer. Only setNuRef should not be used; it is replaced by setMode(Epsl.Mode). [Nevertheless it is possible to use setNuRef(0.0) instead of setMode(Epsl.Mode.PRECEDING) and setNuRef(Math.PI) instead of setMode(Epsl.Mode.PRECEDING).]

  • Field Details

    • ramp

      protected Duration ramp

    • acc

      protected double acc

    • om0

      protected double om0

    • om1

      protected double om1

    • om2

      protected double om2

    • om3

      protected double om3

    • om4

      protected double om4

    • eps

      protected double eps
      Relative tolerance for exceeding the ramp

  • Constructor Details

    • TransitionScanningLaw

      public TransitionScanningLaw(Duration ramp)
      The constructor is the only way to set the duration of the ramp
      Parameters:
      ramp -

  • Method Details

    • getMode

      public Epsl.Mode getMode()
      Return the Epsl.Mode (preceding or following)
      Returns:
      The mode

    • setMode

      public TransitionScanningLaw setMode(Epsl.Mode mode)
      Preferred method to set the Epsl.Mode (it can also be set using setNuRef)
      Parameters:
      mode - EPSL preceding or following
      Returns:
      This object with the right mode set

    • getRampDuration

      public Duration getRampDuration()
      Return the duration of the ramp

    • initialize

      public void initialize()
      Initialization mainly calculates the acceleration required for the specified ramp

    • getAttitudeNative

      public IAttitude getAttitudeNative(long time)
      Description copied from class: BaseAttitudeDataServer
      Evaluate the attitude in the native time system of the server
      Specified by:
      getAttitudeNative in class BaseAttitudeDataServer<IAttitude>
      Parameters:
      time - - the time elapsed since the epoch of J2010 in ns (TCB)
      Returns:
      attitude for the given time
      See Also: