;docformat = 'rst' ;+ ;Calculate solar angles alpha and beta from EVE ESP quadrant data ; :Params: ; diodes: in, required ; calibrated/dark-corrected diode values. Can be quadrant fraction. These values are normalized before use. ; Array of 4 values, index 0 to 3 match up with quadrant diode names Q0-Q3 ; ; :Keywords: ; alp: out ; Solar alpha angle (E/W) in arcminutes. Positive when center of brightness is east/left of ESP axis ; Bet: out ; Solar beta angle (N/S) in arcminutes. Positive when center of brightness is north/above ESP axis ;- pro esp_quad_to_ab,diodes,alp=alp,bet=bet ;ESP channels (From the right point of view it makes sense) ; +-----+-----+ ; +-----+-----+-----|5 Q0 |6 Q1 |-----+-----+ ^^^^^^^^^ ; |1 366|2 257|3 Drk|-----+-----|8 171|9 304| Solar North--> East/Left ; +-----+-----+-----|4 Q2 |7 Q3 |-----+-----+ ; +-----+-----+ ;channel name ;1 366 ;2 257 ;3 dark ;4 q2 ;5 q0 ;6 q1 ;7 q3 ;8 171 ;9 304 ; ;channel name ;5 q0 ;6 q1 ;4 q2 ;7 q3 ;8 171 ;2 257 ;9 304 ;1 366 ;3 dark ;Normalize diodes to sum to 1.0. This doesn't hurt if the diodes are already normalized. q=total(diodes[0:3]) q0=diodes[0]/q q1=diodes[1]/q q2=diodes[2]/q q3=diodes[3]/q ;Quadrant diode coordinates in E/W (qy) and N/S (qx) directions qx=(q1+q3)-(q2+q0) qy=(q0+q1)-(q2+q3) ;Convert diode coordinates to arcminutes in E/W (alpha) and N/S directions alp_m=68.5752 alp_b=1.45181 bet_m=20.347 bet_b=0.420920 alp=alp_m*qy+alp_b bet=bet_m*qx+bet_b end