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The Galileo Energetic Particles Detector


Galileo EPD Handbook


Chapter 2. EPD Software


Energetic Particle Detector Experiment Flight Software System Documentation (continued)

Source: H. Malcom, July 30, 1982




Major Software Modules


The major software modules that are included in the Galileo EPD software system are listed below:


Real Time Executive
     LEMMS PHA Spectrum Accumulation and Compression
     Real Time Interrupt Handler
     Memory checksum

Ten Real Time Interrupt Interval Service Routines
Data System and Motor Controller Command Queue Loader
Command Decoder and Executor
CMS PHA Input Routine
Rate Channel Data Compression and Packing Routine
Subcommutated Housekeeping Routine


Figure 2.2 shows the hierarchical relationship between the various modules within the EPD software system:



The real time executive, in addition to performing system initialization, accumulates and log-compresses LEMMS PHA spectra and computes a memory checksum of a subset of ROM that can be specified by a group of data system commands. Accumulation of LEMMS PHA spectra and the computation of memory checksums are performed as background tasks--that is, in between tasks when the system is responding to interrupts. The executive, upon receiving an interrupt, saves the state of the software system and transfers control to one of ten real time interval interrupt handlers. The appropriate interrupt handler is determined by a real time interval (TRI) counter that is maintained by the executive.


Each of the ten interrupt handlers carries out the tasks that are scheduled for the corresponding RTI by invoking one or more subroutines for each of the tasks to be performed.



Next: 3.0 Microprocessor System Hardware Overview


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Updated 8/23/19, Cameron Crane


Manufacturer: The Galileo Spacecraft was manufactured by the Jet Propulsion Laboratory, Messerschmitt-Bölkow-Blohm, General Electric, and the Hughes Aircraft Company.

Mission Duration: Galileo was planned to have a mission duration of around 8 years, but was kept in operation for 13 years, 11 months, and 3 days, until it was destroyed in a controlled impact with Jupiter on September 21, 2003.

Destination: Galileo's destination was Jupiter and its moons, which it orbitted for 7 years, 9 months, and 13 days.