An ionosonde is a special radar for the examination of the ionosphere. The transmitter sweeps all or part of the HF frequency range, transmitting short pulses. These pulses are reflected at various layers of the ionosphere, at heights of 100–400 km, and their echos are received by the receiver and analyzed by the control system. The result is displayed in the form of an ionogram, a graph of reflection height (actually time between transmission and reception of pulse) versus carrier frequency.

This dataset collection contains ionosonde data from the UKSSDC:
-Ionosonde station data
-Raw Data from Digital Ionosondes for COST-271 Action Effects of the Upper Atmosphere on Terrestrial and Earth-Space Communications
-Bulletins
-Raw Digital Ionosonde Data Tapes
-Digitised bulletins
-Digitised films
-Scanned version of paper ionograms
-Scaled paper Ionosonde Data Bulletins