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The Galileo Energetic Particles Detector


Galileo EPD Handbook




Appendix E. EPD File Structure (continued)


4. CMS PHA Block

Source: T. P. Armstrong, March 1985


(Note: This is pre-Challenger information.)


This record contains the digitized (0-255) pulse heights and time of flight information from the CMS telescope. It is reformatted and tagged with angle and time information and blocked into large records for convenience. Also attached to this information is the count rate information necessary to normalize the numbers of events in the various priority classes.


There are two types of CMS PHA blocks according to the J/J' flag. The CMS electronics are toggled alternately between the 0 and 180 degree telescope directions. Since this generates entirely distinct rate channels and PHA events, two types of CMS PHA blocks will be accumulated over simultaneous time intervals in the case that J/J' is cycling, or one type will be accumulated if J/J' is not cycling.


CMS PHA blocks are also accumulated separately according to the step position of the EPD instrument. This maintains the angular information of the pulse height information in payload fixed spin coordinates. For a normal stepping sequence which includes all 8 stepping positions, a full set of CMS PHA logical output records would be 8. Further, if the J/J' cycling is in effect, there will be one set of 8 CMSPHA blocks for J and another for J'. Hence, a set of CMS PHA blocks will include from 1 to 16 records.


Item Description Length
1 Spin rate at start 1 4-byte real
2 Spin rate at end 1 4-byte real
3 Number of spins in this average 1 4-byte real
4 Number of full sectors 1 4-byte integer
5 Step position of this record 1 4-byte integer
6 R15(30,16) - Count rates for 30 channels at 15 sector positions
Units: Counts/second
Type: 4 byte real numbers (DEC)
1 CP1
2 CP2
3 CP3
4 CA0
5 CA1
6 CA2
7 CA3
8 CA4
9 CM0
10 CM1
11 CM2
12 CM3
13 CM4
14 CM5
15 CN0
16 CN1
17 CH0
18 CH1
19 CH2
20 CH3
21 CH4
22 CH5
23 CE1
24 CE2
25 CE3
26 JA
27 JB
28 JC
29 KS
30 LS
480 4-byte reals
7 IDQR15(30) - Data presence/quality flags
Units: None
Type: 2 byte integer
  Byte 2  
  0000 Data missing (not on EDR)
  0010 Data missing (wrong subcom pos.)
  0100 Data invalid (motor movement)
  0110 Data invalid (exceed max. rate)
  1000 Data invalid (discontinuity)
  1010 Data invalid (spare)
  1100 Data invalid (spare)
  1110 Data invalid (spare)
  0001 Data valid (nominal)
  0011 Data valid (high threshold)
  0101 Data valid (autocal. fault)
  0111 Data valid (spare)
  1001 Data valid (spare)
  1011 Data valid (spare)
  1101 Data valid (spare)
  1111 Data valid (spare)
  Byte 1 Unsigned integer # of samples in this average
N15(30,16) Array of flags for R15(30,16)
8 NBLOCK - Number of valid PHA events to follow I*4  
9 IEVENT(4,1080) - Up to 1080 repetitions of the digitized pulse heights from a telemetry packet for a total of  17280 bytes.
First index: 1=4 bytes of time information SCLCK
2=Event #1 with bit definitions:
    0-7 = Delta E J
    8-15 = Delta E K
    16-23 = Time of Flight
    24-25 = J ID; 0=Jc, 1=Jb, 3=Ja, 2=unused
    26-27 = Priority; 0=I, 1=II, 2=III, 3=IV
    28-31 = Channel ID:



Next: 5. LEMMS PHA Block


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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.