;+ ; Procedure: enp_crib.pro ; ; Purpose: A crib showing how to transform data from ENP coordinates to GEI coordinates and vice versa ; ; E: sat to earth (in orbtial plane) ; N: east (in orbital plane) ; P: north (perpendicular to orbtial plane). ; ; Defined relative to another coordinate system: ; P_sat = spacecraft position in geocentric inertial 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: egrimes $ ; $LastChangedDate: 2014-02-11 08:33:06 -0800 (Tue, 11 Feb 2014) $ ; $LastChangedRevision: 14275 $ ; $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/general/cotrans/special/enp/enp_crib.pro $ ;- ;set the time timespan,'2008-03-01', 5, /days ;load some 1-m resolution FGM data for GOES 10 goes_load_data, trange = trange, probes='10', datatype='fgm', /avg_1m ;---------------- ;ENP system ;---------------- ;input position MUST be earth-centered and inertial ;velocity/orbital plane determined using derivative of position. ;If there are not enough points, the result will be inaccurate. Also, may have small error at the tails. enp_matrix_make,'g10_pos_gei' ;accepts newname,suffix keywords, can use globbing on inputs stop ;-------------------- ;ENP->GEI ;-------------------- tvector_rotate,'g10_pos_gei_enp_mat','g10_H_enp',/invert ;invert keyword runs transformation backwards ; rename the new tplot variable copy_data, 'g10_H_enp_rot', 'g10_H_gei' ; set the default options options,'g10_H_gei',labels=['Bx','By','Bz'],ytitle='g10_H_gei' ; plot the field components in GEI coordinates tplot, 'g10_H_gei' stop ;-------------------- ;GEI->ENP ;-------------------- ;this routine interpolate rotation matrices automatically, no need to match cadence ahead of time tvector_rotate,'g10_pos_gei_enp_mat','g10_H_enp' ;accepts newname,suffix keywords, can use globbing on inputs options,'g10_H_enp_rot',labels=['E','N','P'],ytitle='g10_H_enp' options,'g10_H_enp',yrange=[-100,150] tplot,['g10_H_enp'] stop ;----------------------- ;User Provided Velocity, Rather than derivative of position velocity ;----------------------- tinterpol_mxn,'g10_pos_gei','g10_H_enp' enp_matrix_make,'g10_pos_gei',velocity_tvar='g10_vel_gei' tvector_rotate,'g10_pos_gei_enp_mat','g10_H_gei' ;accepts newname,suffix keywords, can use globbing on inputs options,'g10_H_gei_rot',labels=['E','N','P'],ytitle='g10_H_enp' tplot,['g10_H_gei_rot','g10_H_enp'] ;should match stop ;------------------------------ ;User provided Single Orbital Element, doesn't use velocity at all ;------------------------------ ;GOES 10 orbital elements for 2007-12-17 orbital_time = time_double('2007-12-17/01:37:56') orbital_ras = 81.7391D ;right ascension of ascending node orbital_inclination = 2.2461 ;orbital inclination orbital_elements = [orbital_time,orbital_ras,orbital_inclination] enp_matrix_make,'g10_pos_gei',orbital_elements=orbital_elements tvector_rotate,'g10_pos_gei_enp_mat','g10_H_gei' ;accepts newname,suffix keywords, can use globbing on inputs options,'g10_H_gei_rot',labels=['E','N','P'],ytitle='g10_H_enp' tplot,['g10_H_gei_rot','g10_H_enp'] ;Should be small error due to accumultated time-series error orbital elements. ;Occurs at the GEI-POS-Z 0-crossing. ;Should be fixed by interpolated orbital elements. stop ;------------------------------ ;User provided Interpolated Orbital Element, doesn't use velocity at all ;------------------------- orbital_time1 = time_double('2007-12-10/06:52:04') orbital_ras1 = 081.8024D orbital_inclination1 = 2.2298D orbital_time2 = time_double('2007-12-17/01:37:56') orbital_ras2 = 81.7391D ;right ascension of ascending node orbital_inclination2 = 2.2461D ;orbital inclination ;Can have as many orbital elements as you want, not limited to providing elements at only 2 times orbital_elements = [[orbital_time1,orbital_ras1,orbital_inclination1],[orbital_time2,orbital_ras2,orbital_inclination2]] enp_matrix_make,'g10_pos_gei',orbital_elements=orbital_elements tvector_rotate,'g10_pos_gei_enp_mat','g10_H_gei' ;accepts newname,suffix keywords, can use globbing on inputs options,'g10_H_gei_rot',labels=['E','N','P'],ytitle='g10_H_enp' tplot,['g10_H_gei_rot','g10_H_enp'] end