  This white paper discusses the current landscape and prospects for
experiments sensitive to particle dark matter processes producing photons and
cosmic rays. Much of the gamma-ray sky remains unexplored on a level of
sensitivity that would enable the discovery of a dark matter signal. Currently
operating GeV-TeV observatories, such as Fermi-LAT, atmospheric Cherenkov
telescopes, and water Cherenkov detector arrays continue to target several
promising dark matter-rich environments within and beyond the Galaxy. Soon,
several new experiments will continue to explore, with increased sensitivity,
especially extended targets in the sky. This paper reviews the several
near-term and longer-term plans for gamma-ray observatories, from MeV energies
up to hundreds of TeV. Similarly, the X-ray sky has been and continues to be
monitored by decade-old observatories. Upcoming telescopes will further bolster
searches and allow new discovery space for lines from, e.g., sterile neutrinos
and axion-photon conversion. Furthermore, this overview discusses currently
operating cosmic-ray probes and the landscape of future experiments that will
clarify existing persistent anomalies in cosmic radiation and spearhead
possible new discoveries. Finally, the article closes with a discussion of
necessary cross section measurements that need to be conducted at colliders to
reduce substantial uncertainties in interpreting photon and cosmic-ray
measurements in space.
