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.

[Gianluca]

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