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The Galileo Energetic Particles Detector


Galileo EPD Handbook




Appendix E. EPD File Structure (continued)


5. LEMMS PHA Block

Source: T. P. Armstrong, April 1985


The LEMMS PHA data are acquired in a cycle of 91 SCLK counts (91 packets of 2/3 second in length). During this 60 2/3 second interval 11 spectra from the A detector, one from E and one from F are acquired. Each spectrum consists of 47 energy channels accumulated in 2/3 of a second (12 degrees of rotation at the nominal spin rate). The shortest logical record interval for this data is 60 2/3 seconds. A logical record will consist of a variable number of physical records. There will be three records in the format listed below for each step position which occurs in this time interval. The groups of three records will have LEMMS data from Detectors A, E, and F. If all possible motor positions were present in the interval, there would be 24 physical records per logical record interval. Each physical record has approximately 12 k bytes.


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 Detector flag: 0="fill," 1=A, 2=E, 3=F 1 4-byte integer
7 PHA(47,32) Detector A, E, or F Pulse Height Spectrum
Units: Counts per second
Type: 4 byte real numbers
First Index: Energy bin from 1 through 47
Second Index: 32 repetitions to cover the 30 possible sectors of a spin 
8 IPHADQ(47,32) Data presence and quality flag for item 6
Type: 2 byte integers
Contents: Bit 0-7 Unsigned integer no. of samples
  8 spare
  9 spare
  10 spare
  11 spare
  12 spare
  13 spare
  14 spare
  15 data presence, 1=yes, 0=no
9 RA30(9,33) Count rates for detector A, E, or F
Units: Counts/second
Type: 4 byte real numbers
First Index: Channel
1. A0 E0 F0
2. A1 E1 F1
3. A2 E2 F2
4. A3 E3 F3
5. A4 EB1 FB1
6. A5 EB2 FB2
7. A6 spare spare
8. A7 spare spare
Second Index: 1 thru 32 is synchronous accumulation corresponding to LEMMS PHA spectrum
10 IDQ(9,33) Data presence/quality flags
Units: None
Type: 2 byte integer
Contents: 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



Next: 6. Rate Calc 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.