Early Tennis Racket pictures are not rare; there are hundreds, if not thousands of them. The Luftwaffe started to taken reconnaissance pictures of Stalingrad one year before the battle. The earliest photos I have seen are from the fall of 1941.
Here is a small sample just for you from August 27, 1942. It has been reduce by 75% of the original quality and size. I scanned original is over 54 Mb.
Russ
www.fireonthevolga.com