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The Galileo Energetic Particles Detector


Galileo EPD Handbook


Chapter 1. Instrument Summary


Telemetry and Operation Changes (continued)


Rate Channel Generation


The challenge in the redesign is not so much how to operate the two sides at once, but how to fit the resulting data into the existing telemetry limitations.  The limitations come in two forms: the number of rates that can be accumulated in hardware and the number of telemetry channels available for sending the data back to the ground.  We feel that we have worked out suitable solutions for both of these problems.


CMS Rate Logic Board


The primary hardware limitation is the way that the rate channels are defined on the CMS Rate Logic Board.  After extensive analysis, we have concluded that it is not possible to safely implement the amount of rework that would be required to the present flight board.  We have therefore redesigned the board such that the new channel definitions are implemented in the circuit definitions.  A new board will be built according to this design; the old board will remain as is.  Sufficient parts are available for this new board, and work has recently begun on its fabrication.


Although the new board implements a number of new logic definitions, the basic layout remains unchanged from the old design, and, in fact, we plan on rewiring the old EM CMS Rate Logic Board for the proof of concept phase.  The electrical circuit design and board wire-run list will remain unchanged for all the parts implementing the channel definitions and timing on the prime side.  Due to the similarity of design, we expect few problems with this approach.


Rate Channel Assignments


There are several rate channels which will be eliminated from the old design in the proposed changes:


CE1, CE2, CE3 Electrons
CP1, CP2, CP3 Protons
CA0, CM0, CH0, CA2, CM2, CH2 Jc Channels
JcS, LS Jc and L Singles


In their place, we are adding a number of new rate channels:


TP1, TP2, TP3 Protons
TA1, TA2 Alphas
TO1, TO2, TO3, TO4 CNO
TS1, TS2, TS3, (TO1) Sulfur
TH1 Heavies (Iron and up)
TAC Counts, START Counts, KTS New TOF sensor singles


Note: All underlined channels are in the main array.


Rate Channel Definition Matrix


These new rate channels will be defined by a number of new discriminators. There will be 5 discriminators running off the KT analog signal (KT0-KT4) and 4 discriminators running off the derived analog mass signal (M0-M3). The rate channel definitions will look as follows:



The channel TH1 will not have an upper mass boundary.  Likewise, the 3 proton channels, TP1, TP2, and TP3, will not have a lower mass boundary, but will require the additional condition that a valid TAC Event signal was generated (thus avoiding counting events which only triggered the energy discriminators).



Continue: Rate Channel ID Codes


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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.