The Galileo Energetic Particles Detector

Galileo EPD Handbook

Chapter 1. Instrument Summary

CMS Rate Channels - Post-Challenger Information

Source: Critical Design Review, December 1987

Changes to existing circuit boards:

Description of New Hardware Tasks

• Process KT detector signal
• Control high voltage converter
• Switch HVPS power by command
• Route new signals through polytwist
• Process events
• Add additional RAM to data system
• Change J'C aperture into J'B

Figure 1-23. Proposed configuration changes for new EPD CMS subsystem

Spacecraft interface

• No new wires or signals required for new configuration
• Additional load on main spacecraft 15 voltage bus for HVPS
  1. EPD is on the protected spacecraft bus
  2. Fuse protected (redundant)
  3. Relay switched by protected command
  4. Possible EMI/EMC interaction; measured by testing at JPL SAF

Analog filter board rework

• Functional description of changes
  1. KT signal processed by old L and JB amps
  2. JB' and KB' signal into old JC' and KC' amps
  3. JB bias, KT bias
  4. Calibrator signal into TOF channel (TCAL)
• Mounted inside new TOF box
• Parts questions: none
• Functional testing results: no major problems; difficulty switching KT bias
• Known outstanding design issue: select proper K bias network
• Scope: Add 7 components, remove 15; add 7 lines, remove 11

Figure 1-24. Functional Block Diagram of Analog Filter Board

CMS analog electronics

• Basic board operation
• Functional description of changes
  1. KT signal processed by old JC' amps
  2. Discriminator input routing changed
  3. Mass channels defined by KT and T (not K)
  4. Valid event logic definitions changed
  5. Calibrator signal into TOF channel (TCAL)
• Component packaging: unchanged
• Parts questions: none
• Functional testing results: no major problems; more rate testing, etc., necessary
• Known outstanding design issues: TCAL signal not sent to rate logic or PHA
• Scope: Add 2 components, remove 14; add 20 lines, remove 16

Figure 1-25. CMS analog electronics chain

CMS rate logic (new version of previous design)

• Functional description of changes
  1. New rate channel definitions for KT x T
  2. Elimination of CE, CP, and JC channels
  3. New ID code format
• Component packaging: minor changes
• Parts questions: limited accumulator hybrids
• Functional testing results: no problems
• Known outstanding issue: calibrator mux assignments must be modified

Low voltage power converter

• Basic board operation
• Functional description of changes
  1. Relay (K71) to switch 15 volts for HVPS
  2. Old "JA00" command line used to command K71
  3. Filter replaces divider on "K bias board"
  4. 3 volt dummy loads removed - zenors added
• Component packaging: minor changes
• Parts questions: none
• Functional testing results: no problems
• Known outstanding design issues: none
• Scope: Add 10 components, remove 4; add 4 lines, remove 10

Next: CMS Rate Channels - Pre-Challenger Information

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