Editing Greisen–Zatsepin–Kuzmin limit (section)

===The Fermi Gamma-ray Space Telescope===
Launched in June 2008, the [[Fermi Gamma-ray Space Telescope]] (formerly GLAST) will also provide data that will help resolve these inconsistencies.
* With the Fermi Gamma-ray Space Telescope, one has the possibility of detecting gamma rays from the freshly accelerated cosmic-ray nuclei at their acceleration site (the source of the UHECRs).<ref>{{cite journal |last=Ormes |first=Jonathan F. |display-authors=etal |date=2000 |title=The origin of cosmic rays: What can the Fermi Gamma-ray Telescope say? |journal=AIP Conference Proceedings |volume=528 |pages=445–448 |doi=10.1063/1.1324357 |arxiv=astro-ph/0003270|s2cid=7461124 }}</ref>
* UHECR protons accelerated (see also [[Centrifugal mechanism of acceleration]]) in astrophysical objects produce ''secondary electromagnetic cascades'' during propagation in the cosmic microwave and infrared backgrounds, of which the GZK process of pion production is one of the contributors. Such cascades can contribute between about 1% and 50% of the GeV–TeV diffuse photon flux measured by the [[EGRET]] experiment. The Fermi Gamma-ray Space Telescope may discover this flux.<ref name="Kalashev2007">{{cite journal |last=Kalashev |first=Oleg E. |author2=Semikoz, Dmitry V. |author3=Sigl, Guenter |year=2009 |title=Ultra-High Energy Cosmic Rays and the GeV–TeV Diffuse Gamma-Ray Flux |journal=Physical Review D |volume=79 |issue=6 |pages=063005 |arxiv=0704.2463 |bibcode=2009PhRvD..79f3005K|doi=10.1103/PhysRevD.79.063005|s2cid=119154125 }}</ref>