2.2.2 spase://SMWG/Instrument/GIRO/Ionosonde GIRO Ionospheric Sounder Ionosonde 2012-03-21T09:08:00Z The GIRO (Global Ionospheric Radio Observatory) comprises records of subpeak ionospheric characteristics, including altitude profiles of electron density and plasma drift velocity, in the altitude range 90 km to the peak height of the F2 layer, measured by a global ground-based network of active high frequency (HF) radiowave remote sensing instruments, ionosondes. The ionosonde uses stepped- or fixed-frequency probing radio signals transmitted from the ground for propagation into ionosphere, total reflection from an area of matching plasma density, and return to the same or different ionosonde location for detection. The detected echoes are evaluated for their travel time and other characteristics such as amplitude, phase, polarization, Doppler frequency shift, and angle of arrival. The signal travel time is commonly translated to the virtual range to the reflecting area in the ionosphere in the assumption of the signal propagating at the speed of light. Stepped-frequency measurements provide adequate information to compute true range of reflections by accounting for refractive properties of plasma. The ionosonde designs are commonly divided in two classes, (1) a pulsed sounder with stepped frequency that transmits short pulses to detect the echo arrival in the time domain, and (2) a chirp-sounder that transmits a continuous swept-frequency signal to detect its reflections in the frequency domain. The stepped- or swept-frequency sounders produce inherently 2-dimensional data record (frequency x travel time), ionogram. Each element of the 2D ionogram structure holds multiple signal characteristics measured in the ionosonde's receiver channels. Thus acquired information is processed to detect echoes and use their attributes to derive ionospheric characteristics along the propagation path. The fixed-frequency measurement, while using the same concept of radio sounding by total reflection, targets specific plasma densities in the ionosphere, and usually provides higher Doppler frequency resolution by transmitting pulses at the same frequency for several seconds. Simultaneously occurring reflection points in a structured ionosphere are identified by their different echo Doppler frequencies allowing the computation of Doppler skymaps and plasma drift velocity. A heavy investment of time, effort, expertise, and funds continues to be made to produce, collect, quality control, interpret, and store ionograms. It is important that data suppliers and the UML DIDBase developers are appropriately acknowledged in scientific publications that involve analysis of data obtained from the GIRO repositories such as DIDBase and DriftBase. spase://SMWG/Person/Bodo.W.Reinisch PrincipalInvestigator spase://SMWG/Person/Ivan.A.Galkin DataProducer TechnicalContact GIRO (Global Ionospheric Radio Observatory) Home Page http://giro.uml.edu Access to real-time data and software tools en spase://SMWG/Observatory/GIRO Other Sounder Global Ionospheric Radio Observatory spase://SMWG/Observatory/GIRO