exec() has been disabled for security reasons

I am trying to initiate my new website in alter vista platform.
I have a backend execution file to generate astronomical information required for my site.

My site don't work and give following error.

Notice: exec() has been disabled for security reasons in /membri/astrowilson/index.php on line 89

Can anyone help me to fix this error.

That function unfortunately is not available for security reasons and we don't plan to make it available in the near future