r.b. goldstein dec. 1978
based on  1. code written by rdr in feb 76
2. tm 391-240 by c. christensen
3. notes prepared by david band  - uses shield factor

ndish - set up from kkp(78) by plnorb
0 no dish
1 mvm dish
2 pvo dish

eps  earth-probe-sun angle in radians
ad   effective area of dish in 3 directions
icode:
.le.0     error
.gt.0     number of coordinate system used
1         earth, s/c, sun
2         s/c (internal)
note - presently only icode=0 and 1 are used

find the region (rgn)
1    0<eps<phiz
2    phiz< eps <pi/2
3    pi/2 < eps < pi-phiz
4    pi-phiz < eps < pi