Why didn't the head of NASA want to look at the Aries 3 site?

The Head of NASA didn't want to confirm that Mark was alive, especially, since he didn't intend to allow the Ares crew to return for him. He didn't even want the crew to know that Mark was alive.

Teddy Sanders did not want to allow Venkat Kapoor to take pictures of the Ares 3 site because all satellite pictures taken by NASA must be released to the public. The rest of the world was just getting over Mark Watney's death, and showing his body might bring that back up, in which case, more blame would be directed to NASA. Teddy finally allows Venkat to take the pictures, although neither are thinking that Mark would actually be alive. Venkat just wants the pictures to try and help secure funding for more Mars missions. Once they take the pictures, however, Mindy Park discovers Mark is still alive.