|
|
 |
|
|
Ann. Geophys., 18, 1231-1241, 2000
www.ann-geophys.net/18/1231/2000/
© European Geosciences Union 2000
MIDAS-W: a workstation-based incoherent scatter radar data acquisition system
J. M. Holt1, P. J. Erickson1, A. M. Gorczyca1, and T. Grydeland2
1Massachusetts Institute of Technology, Haystack Observatory, Westford, MA 01886, USA
2University of Tromsø, Tromsø, Norway
Abstract. The Millstone Hill Incoherent Scatter Data
Acquisition System (MIDAS) is based on an abstract model of an incoherent
scatter radar. This model is implemented in a hierarchical software system,
which serves to isolate hardware and low-level software implementation details
from higher levels of the system. Inherent in this is the idea that
implementation details can easily be changed in response to technological
advances. MIDAS is an evolutionary system, and the MIDAS hardware has, in fact,
evolved while the basic software model has remained unchanged. From the earliest
days of MIDAS, it was realized that some functions implemented in specialized
hardware might eventually be implemented by software in a general-purpose
computer. MIDAS-W is the realization of this concept. The core component of
MIDAS-W is a Sun Microsystems UltraSparc 10 workstation equipped with an
Ultrarad 1280 PCI bus analog to digital (A/D) converter board. In the current
implementation, a 2.25 MHz intermediate frequency (IF) is bandpass sampled at 1
µs intervals and these samples are multicast over a high-speed Ethernet which
serves as a raw data bus. A second workstation receives the samples, converts
them to filtered, decimated, complex baseband samples and computes the
lag-profile matrix of the decimated samples. Overall performance is
approximately ten times better than the previous MIDAS system, which utilizes a
custom digital filtering module and array processor based correlator. A major
advantage of MIDAS-W is its flexibility. A portable, single-workstation data
acquisition system can be implemented by moving the software receiver and
correlator programs to the workstation with the A/D converter. When the data
samples are multicast, additional data processing systems, for example for raw
data recording, can be implemented simply by adding another workstation with
suitable software to the high-speed network. Testing of new data processing
software is also greatly simplified, because a workstation with the new software
can be added to the network without impacting the production system. MIDAS-W has
been operated in parallel with the existing MIDAS-1 system to verify that
incoherent scatter measurements by the two systems agree. MIDAS-W has also been
used in a high-bandwidth mode to collect data on the November, 1999, Leonid
meteor shower.
Key words: Electromagnetics (instruments and
techniques; signal processing and adaptive antennas) – Ionosphere (instruments
and techniques)
Full Article in PDF (319 KB) |
|
|
