Coherent Ionospheric Doppler Receiver (CIDR)

The Ionospheric Tomography Network of Egypt (ITNE) is a chain of UHF/VHF radio receivers designed to measure the Doppler shift in 150 and 400 MHz beacons on board low-Earth-orbiting (LEO) satellites. ITNE uses Coherent Ionospheric Doppler Receivers (CIDR), which are radio receivers developed at the Applied Research Lab at the University of Texas. A linear combination of these Doppler shifts yields the difference in the Total Electron Content (TEC) between adjacent samples. These measurements can be integrated to determine the relative (to an unknown integration constant) TEC profile along the path of the beacon satellite.

A CIDR system installation consists of the CIDR receiver, a control computer (which is provided with the system, typically a laptop) and two antennas (one for CIDR, one GPS). The antenna installation requires a good all-sky view with minimal or no obstructions. 100-meter cables are provided as well. An internet connection allows each individual CIDR system to be accessed by the science team remotely. The internet connection will also be used to download satellite track information (so that the system may plan which satellite passes it can observe and record) and the collected data is uploaded to archives for use by the science team. If there is a broadband connection, individual satellite passes can be remotely monitored via a web interface.

CIDR data can be used to tomographically reconstruct the ionosphere along the satellite track. Depending on the number of ground installations (no less than 3) and baseline, the tomography can reveal the large scale structure of the ionosphere, medium sized structures such as plumes and patches, and very fine structures using a short baseline configuration. In addition, the CIDR data can be used as an input to data assimilation models for reconstructing the ionosphere on a global or local scale.

For information on ITNE and the CIDRs used in it, please see
T. W. Garner, T. L. Gaussiran II, J. A. York, C. M. Slack III, D. M. Munton, and A. M. Mahrous, Ionospheric Tomography Network of Egypt: A new receiver network in support of the International Heliophysical Year, , Earth, Moon, and Planets, Volume 104, Numbers 1-4/April, 2009, pp.227-235 doi:10.1007/s11038-008-9286-3. (click )