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DIGISONDE-4D
SYSTEM MANUAL
VERSION 1.2.11
5-8 SECTION 5 - SYSTEM SOFTWARE
CHAPTER 1
SYSTEM SOFTWARE OVERVIEW
GENERAL DESCRIPTION
5:1. The purpose of the system software is to automatically operate the ionospheric sounder transceiver sys-
tem to produce displays and product data files of real-time measurements, to report acquired data to remote data
subscribers, provide public access to the local repositories of data, and to allow remote commanding and
maintenance of the sounder.
5:2. The sounder contains two embedded computing platforms, CONTROL and DATA, running in parallel.
Both computers load the software automatically on power-up and operate in the multitasking environment exe-
cuting tasks of different priorities simultaneously. CONTROL platform operations are described in Chapter 2
of this Section. Chapter 3 details system software of the DATA platform.
CHOICE OF SOFTWARE VERSUS HARDWARE IMPLEMENTATIONS
5:3. Current choice of the Digisonde-4D digital signal processing (DSP) architecture balances both special-
ized and generic computing platforms. Development of specialized DSP hardware continues to be part of LDI’s
strategy to build low-power, light-weight, space-qualified radio sounding instrumentation. At the same time, for
the ground-based applications that do not require radiation hardening, inexpensive small-format embedded
computers present a feasible alternative to custom DSP hardware. Digisonde-4D system software reflects the
existing balance between software and hardware DSP solutions. .
5:4. The Control Platform is an embedded computer that manages hard real-time tasks under control of the
RTEMS operating system. The digital receivers are designed to appear to the Control Platform as an IDE hard
disk drive whose contents can be read using a standard HDD driver. The Data Platform is another embedded
PC that performs processing of the acquired sample data to create data products. The Data Platform runs a suite
of processing algorithms ranging from pulse compression to ARTIST ionogram autoscaling and EDP calcula-
tion, and the derivation of ionospheric tilt angles from Doppler skymaps.
5:5. Software components in the signal processing pipeline are designed to accommodate real-time data
stream of varying bandwidth, depending on the selection of measurement program parameters. All internal
communications are protected with the packet queues that dynamically buffer data to wait for the destination
component to become available. Online data visualization engine in DCART uses the mailbox mechanism to
adaptively decimate data that are displayed in real-time.
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