Coherent Ionospheric Doppler Radar

Lead Scientist: Dr. Gary S. Bust, Dr. Trevor Garner, Dr. Tom Gaussiran and Dr. Roy Calfas
Organization: University of Texas at Austin, USA
Objective: To tomographically reconstruct the ionosphere and to provide input to Data Assimilation models

The Coherent Ionospheric Doppler Receiver (CIDR) are radio receivers developed at the Applied Research Lab at the University of Texas designed to measure the line-of-sight relative total electron content (TEC) using the 150 and 400 MHz radio beacons on board LEO satellites. The CIDR system is capable of tracking up to three different beacon satellites with different offsets in frequency at one time including the Navy Ionospheric Monitoring System (NIMS), RadCal, and GFO. In the near future, more radio beacons at these frequencies will be launched on the C/NOFS and COSMIC spacecraft.

CIDR is unique in its ability to monitor three simultaneous satellite passes at data rates up to 1 kHz with an instrument error of less than 0.1 radians of phase. CIDR system chains currently are in operation in Alaska, the eastern United States and Greenland. These chains are all oriented latitudinally. In the next year, a new CIDR system chain will be placed in South America in a longitudinal orientation near the magnetic equator to study equatorial phenomena in association with the C/NOFS 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.

The data produced by a chain of CIDR systems is used to tomographically reconstruct the ionosphere along the satellite track. Depending on the number of ground installations (no less than 4) and baseline, the tomography can reveal the large scale structure of the ionosphere, medium sized structures such as plumes, patches, etc., 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.