Geiger Tube Telescope
- id: INS-006
- kind: charged-particle detector
- flown_on: Pioneer 10, Pioneer 11
- confidence: believed-correct
The Geiger Tube Telescope was James Van Allen's charged-particle instrument from the University of Iowa, flown on both Pioneer 10 and Pioneer 11. At Jupiter it made the first direct measurements of the planet's radiation belts — vastly more intense than Earth's — knowledge that shaped the shielding of every outer-planet mission since.