The Millstone Hill Incoherent Scatter DataAcquisition System (MIDAS) is based on an abstract model of an incoherentscatter radar. This model is implemented in a hierarchical software system,which serves to isolate hardware and low-level software implementation detailsfrom higher levels of the system. Inherent in this is the idea thatimplementation details can easily be changed in response to technologicaladvances. MIDAS is an evolutionary system, and the MIDAS hardware has, in fact,evolved while the basic software model has remained unchanged. From the earliestdays of MIDAS, it was realized that some functions implemented in specializedhardware might eventually be implemented by software in a general-purposecomputer. MIDAS-W is the realization of this concept. The core component ofMIDAS-W is a Sun Microsystems UltraSparc 10 workstation equipped with anUltrarad 1280 PCI bus analog to digital (A/D) converter board. In the currentimplementation, a 2.25 MHz intermediate frequency (IF) is bandpass sampled at 1µs intervals and these samples are multicast over a high-speed Ethernet whichserves as a raw data bus. A second workstation receives the samples, convertsthem to filtered, decimated, complex baseband samples and computes thelag-profile matrix of the decimated samples. Overall performance isapproximately ten times better than the previous MIDAS system, which utilizes acustom digital filtering module and array processor based correlator. A majoradvantage of MIDAS-W is its flexibility. A portable, single-workstation dataacquisition system can be implemented by moving the software receiver andcorrelator programs to the workstation with the A/D converter. When the datasamples are multicast, additional data processing systems, for example for rawdata recording, can be implemented simply by adding another workstation withsuitable software to the high-speed network. Testing of new data processingsoftware is also greatly simplified, because a workstation with the new softwarecan be added to the network without impacting the production system. MIDAS-W hasbeen operated in parallel with the existing MIDAS-1 system to verify thatincoherent scatter measurements by the two systems agree. MIDAS-W has also beenused in a high-bandwidth mode to collect data on the November, 1999, Leonidmeteor shower.Electromagnetics (instruments andtechniques; signal processing and adaptive antennas) – Ionosphere (instrumentsand techniques)
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