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Procedure: enp_crib.pro Purpose: A crib showing how to transform data into the ENP and PEN coordinate systems. E: sat to earth (in-plane) N: east (in-plane) P: north (perpendicular to plane). Defined relative to another coordinate system: P_sat = spacecraft position in geocentric interial coordinate system V_sat = deriv(P_sat) (spacecraft velocity in the same coordinate system.) P_enp = P_sat cross V_sat E_enp = -P_sat N_enp = P_enp cross P_sat Notes: $LastChangedBy: pcruce $ $LastChangedDate: 2009-09-16 15:18:08 -0700 (Wed, 16 Sep 2009) $ $LastChangedRevision: 6741 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/ssl_general/trunk/cotrans/special/enp/enp_crib.pro $
(See ssl_general/cotrans/special/enp/enp_crib.pro)
Procedure: enp_matrix_make Purpose: Creates a set of matrices that will rotate data from the input coordinate system into ENP. E: sat to earth (in-plane) N: east (in-plane) P: north (perpendicular to plane). Defined relative to another coordinate system: P_sat = spacecraft position in geocentric interial coordinate system V_sat = deriv(P_sat) (spacecraft velocity in the same coordinate system.) P_enp = P_sat cross V_sat E_enp = -P_sat N_enp = P_enp cross P_sat Inputs: pos_tvarname: Tplot Variable storing the spacecraft position in an intertial earth-centered cartesian coordinate system(like gei) You can use globbing to pass multiple position vectors simultaneously. ('th?_state_pos') Outputs: xxx2enp transformation matrix Keywords: /pen : reorders the basis vectors so that they transform to and from PEN rather than ENP fail=fail: Will be set to 1 if operation failed, returns 0 if operation succeeded. Will not signal failure if at least one input was processed. suffix: The suffix to be appended to the tplot variables that the output matrices will be stored in. (Default: '_enp_mat' or '_pen_mat') newname: The name of the output matrix. If this keyword is used with multiple input values, the outputs may overwrite each other. So you should only set this keyword if there is a single value for the state input. velocity_tvar: Set this keyword to the name of a tplot variable or variables that store velocities matching the positions. This way the routine doesn't need to calculate the velocity using derivatives Notes: Because velocity is calculated using the derivative of position, there should be a small numerical error at the end points of the time series $LastChangedBy: pcruce $ $LastChangedDate: 2009-09-16 12:37:46 -0700 (Wed, 16 Sep 2009) $ $LastChangedRevision: 6739 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/ssl_general/trunk/cotrans/special/enp/enp_matrix_make.pro $
(See ssl_general/cotrans/special/enp/enp_matrix_make.pro)