B-17 Photo Recon over Japan before Doolittle raid

[kaki3152]

In the book "When the Airlines Went to War" by Robert J. Serling there is a reference to something I did not know and would like to know more:

" The airline's [United] first major commitment to the war effort began one month after Pearl Harbor , when a pair of brand new B-17s ferried in from the Boeing factory in Seattle arrived at United big overhaul base in Cheyenne, Wyoming. The modification orders indicated that they were obviously being prepped for some kind of special mission. UAL's mechanics were told to cram extra fuel tanks into every available space, remove all guns and bomb bay racks and install new racks that would hold photographic equipment. Seven weeks later, in mid February, the two Flying Fortresses left Cheyenne and headed for Alaska...These were the B-17s that flew photo reconnaissance flights over Tokyo preceding Jimmy Doolittle's bombing raid the following April"

I have never heard of B-17 Reconnaissance flights over Tokyo in early 1942. Is this correct?