The NPR News item I Spy, Via Spy Satellite: Melting Himalayan Glaciers discusses use of declassified historical satellite images that include glaciers, and link to the newly published and Open Access article in Science Acceleration of ice loss across the Himalayas over the past 40 years.
It also links to a short pdf fact sheet on the NRO's website Hexagon; America's Eye in Space which contains the image/infographic below.
I don't understand what's being illustrated for the first stage core and the two side boosters. The two boosters look to be very different from each other and have different names, and I can't figure out where the separation of the first stage of the core separates from the second stage. What is actually happening here?