SCULIB_AIRMASS - calculate the airmass for a given zenith distance

Description:

This routine calculates the airmass corresponding to the input zenith distance. The airmass is just sec(Z) until it reaches 2, after which a more complex algorithm developed by Ian Coulson is used (it is described by comments in the code). There may be a discontinuity in returned airmasses around the value 2, I haven't checked.

Invocation:

CALL SCULIB_AIRMASS (Z, AIRMASS, STATUS)

Arguments:

Z = REAL (Given)

zenith distance (radians)

AIRMASS = REAL (Returned)

airmass

STATUS = INTEGER (Given and returned)

global status

Copyright

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