Diane, here is some information that I hope will be helpful to you. If not in your actual quest for the information you seek, but for a broader understanding of some of the experiences your father endured.
Donald W. Hoock enlisted in the US Army March 10, 1941 in Syracuse New York. His civian occupation prior to enlistment was "Opticians, lens grinders, and polishers". From the National Archives database here;
The following link has a short history of your father's unit written by LtCol C.T. McEniry, 197th A.A. B.N. (S.P.) Commander, and a more detailed history of "A" Battery of the 197th. Althou your father is not listed as assigned to "A" Battery, many of their exploits were shared along with the rest of the Battalion.
Stanford University holds the "Garth R. Newton Papers" which includes "Unit history, orders, letters, and certificates, relating to activities of the 197th Anti-Aircraft Artillery Automatic Weapons Battalion in France and Belgium during World War II. Photocopy." These papers may have some additional information that may be of use to you.
Some of the accounts of landing on Omaha Beach by the 197th on D-Day can be read at the following link. Here is one quote from that source;
"The 462nd AW Battalion began coming ashore around 0900, and the 197th AW Battalion (Self-Propelled) started coming ashore on Easy Red about the same time. The 197th was one of the finest battalions the branch has ever seen."