In the following grid of 25 odd digits (1, 3, 5, 7 or 9):
abcde
fghij
klmno
pqrst
uvwxy
we can find 24 different 5-digit prime numbers arranged along the lines of the grid either forward, backward, up, down or in both directions along both diagonals.
It turns out that a=y and e=u. Obviously any rotation or reflection of the grid will satisfy these conditions, so arrange it so that abcde (interpreted as a 5-digit number) is as small as possible.
The (nano) magnetic cache is at:
37° 21.ABC N
122° 06.DEF W
where:
A = c
B = v
C = h
D = s
E = g-e
F = p
Some skill at computer programming may be necessary to find those correct coordinates.
Good luck!

You can validate your puzzle solution with certitude.
Congratulations to Nylimb for being first to solve and to TeamOttlet for being first to find!