Can I use an ANN to translate image output from one sensor to simulate output from another sensor?
This is very much possible. There is a function which can map the images from the higher resolution pictures to the lower dimensional ones; and a neural network can be trained to learn that function. 

However, to train a neural network to do this you will need thousands of images from both cameras. Then you can feed the pictures taken with your higher resolution camera as the input to the network and then compute the loss of the network at the output with the corresponding lower resolution images. 

If you do not have so many images, there has been work on taking images and applying some sort of filter to change their appearance. These techniques are often called style transfer, you can find some tutorial here and code which I have tried and can confirm works here. It might be hard to get a representative image to use as the style image using your old camera. You can try an average of a few pictures, or a picture of a white background, you would have to try things out, I do not know what would work in this case.

If you share examples of your data we can help you more.