"…The primary purpose of the Data statement is to give names

to constants; instead of referring to π as 3.141592653589793

at every appearance, the variable Pi can be given that value

with a Data statement and used instead of the longer form of

the constant. This also simplifies modifying the program,

should the value of π change."

– Fortran manual for Xerox Computers

• When compiled with full optimizations with Microsoft Visual C, the select_ephemeris() function misbehaved to the extent of setting the DEEP_SPACE_EPHEM_FLAG incorrectly on occasion. I traced it to this line (in basics.cpp):

temp = ck2 * 1.5 * (r1r13.0-1.0) / pow( 1.0-tle->eo*tle->eo, 1.5);

which sets 'temp' to INF, despite the fact that ck2, r1, and tle->eo had reasonable values. Changing it to read as follows:

temp = ck2 * 1.5 * (r1r13.0-1.0) * pow( 1.0-tle->eo*tle->eo, -1.5);