Perigee and Apogee of a Conic Section - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Software Libraries (/forum-10.html) +--- Forum: HP Prime Software Library (/forum-15.html) +--- Thread: Perigee and Apogee of a Conic Section (/thread-9675.html) Perigee and Apogee of a Conic Section - Eddie W. Shore - 12-11-2017 12:59 PM Introduction The program CONICAP determines three characteristics of a conic section: Eccentricity: E = 0, circle 0 < E < 1, ellipse E = 1, parabola (this case is not covered) E > 1, hyperbola Periapsis (Perigee): The point on the conic section where it is closest to a primary focus (which is designated at one of the two foci F or F’). Apoapsis (Apogee): The point on the conic section where it is furthest away from a primary focus. Note for a hyperbola and a parabola, the apogee is ∞. The inputs are the lengths of the semi-major axis (A) and the semi-minor axis (P). For a hyperbola, input A as negative. HP Prime Program CONICAP Code: EXPORT CONICAP(A,P) BEGIN // EWS 2017-12-10 // Fundamentals Of Astrodynamics // ABS(A)≥P LOCAL E; E:=√(1-P/A); PRINT(); PRINT("Perigee: "+STRING(A*(1-E))); IF A≥0 THEN PRINT("Apogee: "+STRING(A*(1+E))); END; PRINT("Eccentricity: "+E); IF E==0 THEN PRINT("Circle"); END; IF E>0 AND E<1 THEN PRINT("Ellipse"); END; IF E>1 THEN PRINT("Hyperbola"); END; END; Examples A = 8, P = 3 (Ellipse) Perigee 1.67544467966 Apogee 14.3245553203 Eccentricity 0.790569415042 A = -8, P = 3 (Hyperbola) Perigee 1.38083151968 Apogee N/A Eccentricity 1.17260393996 Source: Roger R. Bate, Donald D. Mueller, Jerry E. White. Fundamentals of Astrodynamics Dover Publications: New York. 1971. ISBN-13: 978-0-486-60061-1