Galileo Spacecraft Pages
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.
|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
|480 4-byte reals|
|7||IDQR15(30) - Data presence/quality flags
|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.
Next: 5. LEMMS PHA Block
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Updated 10/14/04, T. Hunt-Ward