Fundamental Technologies

Voyager LECP Pages

PHA Priority Scheme for the Voyager LECP Experiment

In discussion of the PHA priority scheme, the shorthand notation

L -> A-B-C

should be understood to mean that if the priority of the channel associated with the PHA data telemetered in the previous interval is L, then the "priority regime" is


This A-B-C priority regime notation indicates that if the priority of the PHA data in the temporary buffer of the current interval is either B or C, then a newly incident, priority A ion will supersede these data and therefore the priority A data will be stored. If a subsequent priority A ion enters, the original priority A ion will remain. Additionally if the priority of the PHA data in the buffer is C and a priority B comes in, then the priority B will stored in lieu of the priority C data. As before, a subsequent priority B will not replace the existing priority B data. All of this is another way of saying that, in the current interval,


means that A has highest priority, B has intermediate priority and C has lowest priority. Note, in the following, that priority 1 channels consist of heavy ions, priority 2 channels are intermediate ions, and priority 3 channels consist of protons and alpha particles.

Three discussions of this priority scheme have been found:

Peletier: Peletier, D.P., et al., IEEE Trans. Nucl. Sci., NS-24, No.1, 797, 1977
Krimigis: Krimigis, S.M., et al., Space Sci. Rev., 21, 347, 1977
Table A7: PHA Enable Conditions from an APL document

Using the shorthand notation the priority schemes given in these three documents may be compared directly:

DocumentPriority SchemeComments
Peletier1 3-2-1
2 1-3-2
3 2-1-3
only even permutations assumed
partially detailed in text
explicitly detailed in the text
Krimigis1   2-3-1
2   3-1-2
3   1-2-3
explicitly detailed in the text
explicitly detailed in the text
explicitly detailed in the text
Table A71   2-3-1
2   3-1-2
  (and 3-2-1*)
3 1-2-3
explicitly detailed in the table
there may be a typo in the table

explicitly detailed in the table

*If the 2,1,1,YES row of the table is replaced with 2,1,1,NO, then Table A7 will agree with the Krimigis description in complete detail. As it stands the table implies that priority 3 data will replace buffered priority 1 or 2 data, but that priority 2 data will replace priority 1 and priority 1 will replace a priority 2.

Q: Is there a typo in table A7, and is Peletier's description wrong? If none are correct, what is the actual priority scheme?

Return to Calibrations and Channel Definitions main page.
Return to Voyager LECP Data Analysis Handbook Table of Contents.
Return to Fundamental Technologies Home Page.

Last modified 5/27/05, Tizby Hunt-Ward