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GALILEO

The Galileo Energetic Particles Detector

 

Galileo EPD Handbook

 

Chapter 1. Instrument Summary

 

EPD Commands

 

Also see Command Changes.

 

Source: Bob Moore, various dates

 

There are 256 command codes that are allocated to this experiment by JPL, not all of which are used. There are motor control commands and EPD commands.

 

Motor commands can cause the motor to:

 

1. Stop scanning.
2. Start scanning.
3. Set a new interval between steps.
4. Go in and out of the chicken mode. (The chicken mode keeps the telescope behind the shield much of the time.)
5. Have its controller read out its own ROM or RAM to check the memory contents.
6. Go into a modified scan mode. The modified scan mode allows only specified sectors to be scanned. The specified sectors are ground programmable.
7. Go into open and closed loop modes in case there is a problem with the position encoder.
8. Go into an emergency mode in which the motor attempts to go where it is commanded to go using the maximum amount of power available for each step.
9. Go into a fast scan mode in which motor triggers arrive every 2-2/3 seconds.
10. Go to any sector and stay there.
11. Respond to a set number of triggers and stop to debug a possible problem.
12. Make the next sector change CW or CCW.
13. Reset via software or a hardware clear.

 

The EPD commands will:

 

1. Turn the LEMMS power on and off.
2. Turn each of the 8 LEMMS amplifiers on and off.
3. Turn the A detector bias on and off.
4. Turn the J' detector bias on and off.
5. Set the bias at normal or high levels.
6. Turn the CMS electronics on and off.
7. Turn the TOF electronics on and off.
8. Turn the PHA on and off.
9. Turn the motor driver on and off (but not the motor controller).
10. Disable or enable the TOF logic conditions on the rate logic.
11. Turn the CMS analog electronics on and off.
12. Choose the 0 degree or 180 degree end of CMS.
13. Cause the CMS to use the 0 degree and 180 degree ends for alternate logical records.
14. Turn the instrument off and turn on heat generating loads.
15. Program all thresholds for the alarm status monitor function.
16. Override the priority system in the PHA so that it will disable the ROM in the PHA and substitute a canned priority that gets sent up with the command as data.
17. Interchange odd and even definitions for two packets in a logical record so that in case the spacecraft synchronization is not what it is expected to be, the instrument can be resynchronized.
18. Put the motor into an accelerated scan mode where the motor goes faster than normal. Triggers are sent to the motor every 8/3 second to get the motor to step at a faster rate to the sector designated as the end, stay there for 12 seconds and then come back.
19. Load the motor controller memory with one byte of instructions which will allow problems in the ROM to be patched around.

 

Eight-macro commands, which have not been defined yet, will be combinations of the commands that have been discussed. (Only four macros, specified 3/19/81, have been defined to simplify placing the instrument into a normal operating mode.)

 

The following list contains all of the Galileo EPD bus commands. Those commands preceded by an asterisk (*) are interactive commands. Those commands which have a second byte (bits 9-16) in addition to the op-code are data commands. The data symbol which represents the second byte can be one of 256 binary coded levels. Commands with op-codes less than 80 (hexadecimal) are destined for the EPD motor controller; commands with op-codes greater than 7F (hexadecimal) are destined for the EPD data system. Some of the commands which are executed by the data system also affect the motor controller; however, the internal communications between the motor controller and the data system do not involve the CDS bus or the EPD bus adapter. Commands listed with no mnemonic symbol are internal commands that do not involve the CDS.

 

Table 25. Galileo EPD Bus Commands

 

     

Field

Op-Code Data

Symbol Value Field Description 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
25MTRG 00 Motor controller trigger 0 0 0 0 0 0 0 0  
25RESC 01 Resume scanning 0 0 0 0 0 0 0 1   
25NOSC 02 Cease scanning 0 0 0 0 0 0 1 0  
25ALT 03 Alternate step rate on 0 0 0 0 0 0 1 1  
25ALTR 04 Alternate step rate off 0 0 0 0 0 1 0 0  
  05   0 0 0 0 0 1 0 1  
25CHK 06 Enter chicken mode 0 0 0 0 0 1 1 0  
25CHKR 07 Exit chicken mode 0 0 0 0 0 1 1 1  
  08 Call up motor TM byte 1 0 0 0 0 1 0 0 0  
  09 Call up motor TM byte 2 0 0 0 0 1 0 0 1  
  0A Call up motor TM byte 3 0 0 0 0 1 0 1 0  
  0B Call up motor TM byte 4 0 0 0 0 1 0 1 1  
  0C Call up motor TM byte 5 0 0 0 0 1 1 0 0  
25RROM 0D Readout motor ROM 0 0 0 0 1 1 0 1  
25RRAM 0E Readout motor RAM 0 0 0 0 1 1 1 0  
25MCTR 0F Motor controller soft. reset 0 0 0 0 1 1 1 1  
25MSC 10 Modified scan on 0 0 0 1 0 0 0 0  
25MSCR 11 Modified scan off 0 0 0 1 0 0 0 1  
25LOP 12 Enter open-loop mode 0 0 0 1 0 0 1 0  
25LOPR 13 Exit open-loop mode 0 0 0 1 0 0 1 1  
*25EMG 14 Enter emergency mode 0 0 0 1 0 1 0 0  
*25EMGR 15 Exit emergency mode 0 0 0 1 0 1 0 1  
  16 Motor fast scan on 0 0 0 1 0 1 1 0  
  17 Motor fast scan off 0 0 0 1 0 1 1 1  
25GO0 18 Go to sector 0 0 0 0 1 1 0 0 0  
25GO1 19 Go to sector 1 0 0 0 1 1 0 0 1  
25GO2 1A Go to sector 2 0 0 0 1 1 0 1 0  
25GO3 1B Go to sector 3 0 0 0 1 1 0 1 1  
25GO4 1C Go to sector 4 0 0 0 1 1 1 0 0  
25GO5 1D Go to sector 5 0 0 0 1 1 1 0 1  
25GO6 1E Go to sector 6 0 0 0 1 1 1 1 0  
25GO7 1F Go to sector 7 0 0 0 1 1 1 1 1  
25CW0 20 CW end-sector=0 0 0 1 0 0 0 0 0  
25CW1 21 CW end-sector=1 0 0 1 0 0 0 0 1  
25CW2 22 CW end-sector=2 0 0 1 0 0 0 1 0  
25CW3 23 CW end-sector=3 0 0 1 0 0 0 1 1  
25CW4 24 CW end-sector=4 0 0 1 0 0 1 0 0  
25CW5 25 CW end-sector=5 0 0 1 0 0 1 0 1  
25CW6 26 CW end-sector=6 0 0 1 0 0 1 1 0  
25CW7 27 CW end-sector=7 0 0 1 0 0 1 1 1  
25CCW0 28 CCW end-sector=0 0 0 1 0 1 0 0 0  
25CCW1 29 CCW end-sector=1 0 0 1 0 1 0 0 1  
25CCW2 2A CCW end-sector=2 0 0 1 0 1 0 1 0  
25CCW3 2B CCW end-sector=3 0 0 1 0 1 0 1 1  
25CCW4 2C CCW end-sector=4 0 0 1 0 1 1 0 0  
25CCW5 2D CCW end-sector=5 0 0 1 0 1 1 0 1  
25CCW6 2E CCW end-sector=6 0 0 1 0 1 1 1 0  
25CCW7 2F CCW end-sector=7 0 0 1 0 1 1 1 1  
25TRG0 30 Respond to 0 triggers 0 0 1 1 0 0 0 0  
25TRG1 31 Respond to 1 trigger 0 0 1 1 0 0 0 1  
25TRG2 32 Respond to 2 triggers 0 0 1 1 0 0 1 0  
25TRG3 33 Respond to 3 triggers 0 0 1 1 0 0 1 1  
25TRG4 34 Respond to 4 triggers 0 0 1 1 0 1 0 0  
25TRG5 35 Respond to 5 triggers 0 0 1 1 0 1 0 1  
25TRG6 36 Respond to 6 triggers 0 0 1 1 0 1 1 0  
25TRG7 37 Respond to 7 triggers 0 0 1 1 0 1 1 1  
25ENFS 38 Enter full scan 0 0 1 1 1 0 0 0  
25ENLS 39 Enter limited scan 0 0 1 1 1 0 0 1  
25SCW 3A Set direction clockwise 0 0 1 1 1 0 1 0  
25SCCW 3B Set direction CCW 0 0 1 1 1 0 1 1  

 

Continue

 

 

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Updated 1/2/19, Cameron Crane

QUICK FACTS

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.