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Appendix E. EPD File Structure (continued)

3. Rate Block

Source: T. P. Armstrong, July 24, 1985

The rate block is a spin-synchronous reformatted collection of the count rates in all EPD channels. The fundamental unit of this block is the spacecraft spin, nominally 20 seconds, but with anticipated small variations about this value. The rate block is constructed in a payload fixed coordinate system. The angular sectors are nominally 5.625, 11.25, or 22.5 degrees, are obtained from 1/3, 2/3, or 4/3 second samples which are taken in a time synchronous mode. DECREEP algorithm is described in EPD Proc section 4.3.2. Each rate block will contain the data from one spin (in the case of the highest resolution--20 seconds) at a specified motor step position. A full, unit sphere scan, therefore, requires 7 such records and might be regarded as a "logical record". However, in many operational circumstances, the EPD instrument will not be in full scan. If it is "parked" the logical record would be one spin in duration--appearing as a single physical record.

The rate average is performed in spacecraft payload coordinates. Sector 1 is defined to begin at the time when the zero degree detector axes pass through the Jovian equatorial plane. The 180 degree detector data will be stored in sector 1 one half of a spin later and thus will correspond to the same look direction as the zero degree data. The relationship of the 64, 32, and 16 sector data is

 R16(1) = <R32(1)+R32(2)> = <R64(1)+R64(2)+R64(3)+R64(4)>

where R16, R32, and R64(I) stand for the 16, 32, and 64 sector data, respectively, at the I th sector and < > stands for an average.

ItemName Length
1 Spin Block
Variables:T64(64), T32(32), T16(16)
Contents:

Durations (seconds) of each of the sectors.  This may vary from sector to sector if the spin  rate changes.

Variables: PHIDOT (2)
Contents: Spin rate at beginning and end of spin
Variable: TSPIN
Contents: Duration of this spin
Variable: FNSPIN
Contents: Number of spins in this record
128 4-byte reals


2 4-byte reals
 

1 4-byte real
 
1 4-byte real
2 Motor Block
Variable ISTEP(12)
Type:4 byte integer
Contents:
  1. Step position of this record
  2. Motor mode; 0=parked, 1=scanning
  3. Number of positions in this scan
  4. Direction of scan; +1=increasing, -1=decreasing, 0=turn position
  5. Maximum position in this scan (1-7)
  6. Minimum position in this scan (0-6)
  7. Next expected position (0-7)
  8. Former position (0-7)
  9. Index of this position (1-NPOS, see 3 above)
12 4-byte integers
3 Magnetic Field Block
Variable:BDATA(64,4):
Contents: Magnetic field measurements in despun payload
coordinates at the times of the 64 sectors
of this spin.
   BDATA(I,1) = Bx, nanotessla, for Ith sector
BDATA(I,2) = By, nanotessla, for Ith sector
BDATA(I,3) = Bz, nanotessla, for Ith sector
BDATA(I,4) = No. of samples, for Ith sector
 
4 R64(4,64) Count Rates for 4 Channels
Units:Counts/second
Type:4 byte real numbers (DEC)
  1. EO
  2. EI
  3. A0
  4. A1
 
5 R32(16,32) Count Rates for 16 Channels at 32 Sector Positions.
Units:Counts/second
Type: 4 byte real numbers (DEC)
1. A0Summed
2. A1Summed
3. A2 
4. A3 
5. A4 
6. A5 
7. A6 
8. A7 
9. E0Summed
10. E1Summed
11. E2 
12. E3 
13. F0 
14. F1 
15. F2 
16. F3 
  
6 R16(100,16) Count Rates for 100 Channels at 15 Sector Positions
Units:Counts/second
Type:4 byte real numbers (DEC)
1. A0Summed
2. A1Summed
3. A2Summed
4. A3Summed
5. A4Summed
6. A5Summed
7. A6Summed
8. A7Summed
9. A8 
10. DC0  
11. DC1 
12. DC2 
13. DC3 
14. E0Summed
15. E1Summed
16. E2Summed
17. E3Summed
18. F0Summed
19. F1Summed
20. F2Summed
21. F3Summed
22. B0 
23. B1 
24. B2 
25. CP1 
26. CP2 
27. CP3 
28. CA0 
29. CA1 
30. CA2 
31. CA3 
32. CA4 
33. CM0 
34. CM1 
35. CM2 
36. CM3 
37. CM4 
38. CM5 
39. CN0 
40. CN1 
41. CH0 
42. CH1 
43. CH2 
44. CH3  
45. CH4 
46. CH5 
47. CE1 
48. CE2 
49. CE3 
50. CP1P 
51. CP2P 
52. CP3P 
53. CA0P 
54. CA1P 
55. CA2P 
56. CA3P 
57. CA4P 
58. CM0P 
59. CM1P 
60. CM2P 
61. CM3P 
62. CM4P 
63. CM5P 
64. CN0P 
65. CN1P 
66. CH0P 
67. CH1P 
68. CH2P 
69. CH3P 
70. CH4P 
71. CH5P 
72. CE1P 
73. CE2P 
74. CH3P 
75. AS 
76. BS 
77. CS 
78. DS 
79. EB1 
80. EB2 
81. FB1 
82. FB2 
83. JA 
84. JB 
85. JC 
86. KS 
87. LS 
88. JAP 
89. JCP 
90. KP 
91. Spare 
92. Spare 
93. Spare 
94. Spare 
95. Spare 
96. Spare 
97. Spare 
98. Spare 
99. Spare 
100. Spare 
    
7 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 no. of samples in this average.
 N64(4,64) Array of flags for R64(4,64)
 N32(16,32) Array of flags for R32(16,32)
 N16(100,16) Array of flags for R16(100,16)
  

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Updated 1/13/05, T. Hunt-Ward
tizby@ftecs.com