Is there a way to recover a .FITS file that got saved to .CSV extension?

Question

I have accidentally saved a .fits file with a .csv extension and now can not open it. This is a very important data for us I wonder if there is anyway to recover it? Thank you so so much for your help!

I've tried to change the extension back to .fits but met the error "1st key is not SIMPLE or XTENSION" when trying to open the fits file.

This is how the beginning of the file looks like when open in notepad

Andor Technology Multi-Channel File 65538 1 65567 0 0 1 1684880276 -60
   0 1e-06 0.009185 0.009185 1   0.009185 1e-07 0 1 50 0 0 0 0 0   
 256 0 4 0 0 0 0 0 0 0 0 0 3.3e-06 0 1 12972 0 1 -999 1 0 1 0 0 -1 4 32
 30000 0 0 1 500 1 1 15.887 550 0 0 0 0 0 0 0 0 0 1 1 9 DU897_EXF   

Answer 1

Based on the file contents Andor Technology Multi-Channel File 65538 this is a SIF file and should be viewable in any SIF viewer.