First, let's simplify the expression step by step:

${17}^{0}$ = 1 (Any non-zero number raised to the power of 0 is 1).

$a^{-2} = \frac{1}{a^2}$

So the expression simplifies to:

$\frac{ {3}^{3} \div 27 }{1 \times \frac{1}{a^2}}$

Now let's simplify further:

$3^3 = 27$

$\frac{27}{27} = 1$

Therefore, the expression simplifies to:

$\frac{1}{a^2}$