Document title: Documentation sfd for NDADS DE LAPI SATM data Project: DE NDADS Datatype: LAPI Super-EID: DOCUMENT There may be other documents also identified by this super-EID. NDADS filename: LAPI_FORMAT.SFD TRF entry: B46551.txt in NSSDC's controlled digital document library, Feb. 1998. Document text follows: ---------------------- CCSD3FF0000500000001CCSD3CS00004MRK**001 ADIDNAME=NSSD0130; CCSD$$MARKERMRK**001CCSD3KS00002MRK**002 TYPE_OF_FILE: LAPI SATM FILE DATA_SOURCES: DYNAMICS EXPLORER B, LOW ALTITUDE PLASMA INSTRUMENT (LAPI) SCIENTIFIC_CONTACTS: DR. J. D. WINNINGHAM / DR. R. A. HOFFMAN SOUTHWEST RESEARCH INST. CODE 696 P.O. DRAWER 28510 NASA/GSFC SAN ANTONIO, TX 78284 GREENBELT, MD 20771 PHONE: 512-522-3075 PHONE: 301-286-7386 SPAN: NSSDCA::PEM::DAVID SPAN: DE696::U6RAH CCSD$$MARKERMRK**002CCSD3DF0000200000001 FILE_ATTRIBUTES: Fixed length, sequential file RECORD_LENGTH: There are four possible record lengths for a LAPI SATM file. The record length depends upon the number of sensors used and the energy step rate. Also, due to a failure in the telemetry system (day 81227), the amount of LAPI data telemetered was considerably decreased. In order to conserve space and make the file structure easier to use, smaller record sizes were used after that date: a) Before day 81328: 4819 byte records (1205 long words) 16 sensors, 32 steps/second 4307 byte records (1077 long words) 30 sensors, 16 steps/second b) After day 81327: 2515 byte records (629 long words) 16 sensors, 16 steps/second 2259 byte records (565 long words) 30 sensors, 8 steps/second DESCRIPTION_OF_THE_FILE: Each SATM record contains LAPI data from one DE-2 major telemetry frame (8 seconds) of data. FILE_STRUCTURE: STRUCTURE_OF_THE_DATA_RECORD: VI4 = VAX INTEGER*4 VR4 = VAX REAL*4 VL1 = VAX LOGICAL*1 BYTE CONTENTS TYPE VALUE COMMENTS/ NUMBER RANGE UNITS 1-4 DATE VI4 81247 - 83049 yyddd 5-8 TIME VI4 0 - 86400000 milliseconds (time that the 1st measurement of the sweep was completed) 9 FLAG VL1 8,64,72,128, status flag 136,192,200 10-13 Invariant Latitude (IL) VR4 0 - 90 degrees above ~87 fill data 9999999 14-17 Magnetic Local Time (MLT) VR4 0 - 24 hours 18-21 Altitude (ALT) VR4 300 - 1100 kilometers 22-25 Latitude (LAT) VR4 -90 - 90 degrees 26-29 Longitude (LON) VR4 0 - 360 degrees 30-33 Local Solar Time VR4 0 - 24 hours 34-37 L-Shell Value VR4 1 - 100 Earth Radii above 100 fill data 9999999 38-41 Orbit Number VR4 0 - 9000 42-45 GEI Satellite Speed VR4 6 - 10 km/sec 46-49 Solar Zenith Angle (SZA) VR4 0 - 180 radians (was marked as -90 - 90 degrees, 2020Feb12) 50 Dark/Light Indicator VL1 0, 1 true/false 51 Number of Sensors VL1 0 - 30 52-147 Magnetic Field Data VR4 Gauss REAL*4 B(3,8) B(i,j) 8 sets per major frame i=1,3(Bx,By,Bz) 1 set per second j=1,8 (time) 148-163 Geiger-Mueller Tube Data VL1 0 - 255 telemetry bits LOGICAL*1 GM(2,8) GM(i,j) 8 sets per major frame i=1,2(0,90 deg) 1 set per second j=1,8 (time) 164 PPS1 Start Value VL1 1 - 64 165 PPS1 Stop Value VL1 1 - 64 166 PPS1 Skip Value VL1 0,1,3,7,15,31 167 PPS1 Steps Per Second VL1 1 - 64 168 PPS2 Start Value VL1 1 - 64 169 PPS2 Stop Value VL1 1 - 64 170 PPS2 Skip Value VL1 0,1,3,7,15,31 171 PPS2 Steps Per Second VL1 1 - 64 172-179 Shaft Encoder Angle VI2 0 - 255 telemetry value 4 values per major frame 180-211 Sensor Identification VL1 0 - 29 >29 error or no sensor 212-[x] Science Data VL1 0 - 255 telemetry bits Telemetered Counts [y]-[z] PPS data VL1 0 - 255 telemetry bits [x] [y] [z] step rate # of sensors 32 16 4307 4308 4819 16 30 4051 4052 4307 16 16 2259 2260 2515 8 30 2131 2132 2259 DESCRIPTION: LAPI SATM contents DATE: YRDAY, where YR is the last two digits of the year, and DAY is the Julian day. TIME: Beginning of time in milliseconds for a major frame FLAG: BYTE VALUE COMMENT 3 8 bad sensor id 5 64 sensors do not compare with previous major frame (excluding field-aligned detectors) 6 128 time gap between records >= 9 seconds For a combination of errors, the flag values are added (i.e. 8 + 64 = 72) INVARIANT LATITUDE (IL): Invariant Latitude in degrees MAGNETIC LOCAL TIME (MLT): Spacecraft Magnetic Local Time in hours ALTITUDE (ALT): Spacecraft Altitude in kilometers LATITUDE (LAT): Spacecraft Latitude in degrees LONGITUDE (LON): Spacecraft Longitude in degrees LOCAL SOLAR TIME (LST): Spacecraft Local Solar Time in hours L SHELL: ORBIT NUMBER: Orbit Number of the pass GEI SATELLITE SPEED: Spacecraft Speed in Kilometers/Second calculated from the GEI velocity vector. SOLAR ZENITH ANGLE (SZA): DARK/LIGHT INDICATOR: NUMBER OF SENSORS: Possible values of 8,16, or 30. MAGNETIC FIELD DATA: REAL*4 B(3,8). First array index indicates (1)Bx, (2)By, or (3)Bz. Magnetic Field calculated from DE-2 Magnetometer Telemetry. GEIGER-MUELLER TUBE DATA: LOGICAL*1 GM(2,8). First array index indicates (1)0 degree, (2) 90 degree. PPS1 START VALUE: Starting energy step level for PPS #1 (typically 1) PPS1 STOP VALUE: Ending energy step level for PPS #1 (typically 61) PPS1 SKIP VALUE: Skip value for PPS #1 PPS1 STEP VALUE: Steps per second for PPS #1 PPS2 START VALUE: Starting energy step level for PPS #2 (typically 1) PPS2 STOP VALUE: Ending energy step level for PPS #2 (typically 61) PPS2 SKIP VALUE: Skip value for PPS #2 PPS2 STEP VALUE: Steps per second for PPS #2 SHAFT ENCODER ANGLE: LOGICAL*1 SEA(4). Multiply by 0.00614921 to calculate angle in radians. This contains the telemetered values of the shaft encoder angle (scan platform) on which the detectors were located. SENSOR IDENTIFICATION: LAPI has 30 sensors(0-29) of which 15 (even numbered) are electron detectors and 15 (odd numbered) are ion detectors. SENSOR NUMBERS PITCH ANGLE ELECTRON ION (DEGREES) 0 1 0+ 2 3 180- 4 5 30 6 7 172.5 8 9 7.5 10 11 45 12 13 112.5 14 15 97.5 16 17 165 18 19 60 20 21 135 22 23 105 24 25 15 26 27 180+ 28 29 0- SCIENCE DATA: LOGICAL*1 TM_COUNTS(4096) OR LOGICAL*1 TM_COUNTS(3840) for file date before 81328 LOGICAL*1 TM_COUNTS(2048) OR LOGICAL*1 TM_COUNTS(1920) for file date after 81327 This array will contain the telemetered counts for the LAPI electrostatic analyzers. In order to determine the actual counts from the telemetered counts, use the lookup table provided below. TM ACTUAL TM ACTUAL TM ACTUAL TM ACTUAL VALUE COUNTS VALUE COUNTS VALUE COUNTS VALUE COUNTS 0 n/a 64 64.5 128 1054.5 192 16894.5 1 n/a 65 68.5 129 1118.5 193 17918.5 2 0 66 72.5 130 1182.5 194 18942.5 3 n/a 67 76.5 131 1246.5 195 19966.5 4 1 68 80.5 132 1310.5 196 20990.5 5 n/a 69 84.5 133 1374.5 197 22014.5 6 2 70 88.5 134 1438.5 198 23038.5 7 n/a 71 92.5 135 1502.5 199 24062.5 8 3 72 96.5 136 1566.5 200 25086.5 9 n/a 73 100.5 137 1630.5 201 26110.5 10 4 74 104.5 138 1694.5 202 27134.5 11 n/a 75 108.5 139 1758.5 203 28158.5 12 5 76 112.5 140 1822.5 204 29182.5 13 n/a 77 116.5 141 1886.5 205 30206.5 14 6 78 120.5 142 1950.5 206 31230.5 15 n/a 79 124.5 143 2014.5 207 32254.5 16 7 80 130.5 144 2110.5 208 33790.5 17 n/a 81 138.5 145 2238.5 209 35838.5 18 8 82 146.5 146 2366.5 210 37886.5 19 n/a 83 154.5 147 2494.5 211 39934.5 20 9 84 162.5 148 2622.5 212 41982.5 21 n/a 85 170.5 149 2750.5 213 44030.5 22 10 86 178.5 150 2878.5 214 46078.5 23 n/a 87 186.5 151 3006.5 215 48126.5 24 11 88 194.5 152 3134.5 216 50174.5 25 n/a 89 202.5 153 3262.5 217 52222.5 26 12 90 210.5 154 3390.5 218 54270.5 27 n/a 91 218.5 155 3518.5 219 56318.5 28 13 92 226.5 156 3646.5 220 58366.5 29 n/a 93 234.5 157 3774.5 221 60414.5 30 14 94 242.5 158 3902.5 222 62462.5 31 n/a 95 250.5 159 4030.5 223 64510.5 32 15 96 262.5 160 4222.5 224 67582.5 33 16 97 278.5 161 4478.5 225 71678.5 34 17 98 294.5 162 4734.5 226 75774.5 35 18 99 310.5 163 4990.5 227 79870.5 36 19 100 326.5 164 5246.5 228 83966.5 37 20 101 342.5 165 5502.5 229 88062.5 38 21 102 358.5 166 5758.5 230 92158.5 39 22 103 374.5 167 6014.5 231 96254.5 40 23 104 390.5 168 6270.5 232 100351 41 24 105 406.5 169 6526.5 233 104447 42 25 106 422.5 170 6782.5 234 108543 43 26 107 438.5 171 7038.5 235 112639 44 27 108 454.5 172 7294.5 236 116735 45 28 109 470.5 173 7550.5 237 120831 46 29 110 486.5 174 7806.5 238 124927 47 30 111 502.5 175 8062.5 239 129023 48 31.5 112 526.5 176 8446.5 240 135167 49 33.5 113 558.5 177 8958.5 241 143359 50 35.5 114 590.5 178 9470.5 242 151551 51 37.5 115 622.5 179 9982.5 243 159743 52 39.5 116 654.5 180 10494.5 244 167935 53 41.5 117 686.5 181 11006.5 245 176127 54 43.5 118 718.5 182 11518.5 246 184319 55 45.5 119 750.5 183 12030.5 247 192511 56 47.5 120 782.5 184 12542.5 248 200703 57 49.5 121 814.5 185 13054.5 249 208895 58 51.5 122 846.5 186 13566.5 250 217087 59 53.5 123 878.5 187 14078.5 251 225279 60 55.5 124 910.5 188 14590.5 252 233471 61 57.5 125 942.5 189 15102.5 253 241663 62 59.5 126 974.5 190 15614.5 254 249855 63 61.5 127 1006.5 191 16126.5 255 258047 PPS DATA: LOGICAL*1 TM_PPS(512) OR LOGICAL*1 TM_PPS(256) for file date before 81328 LOGICAL*1 TM_PPS(256) OR LOGICAL*1 TM_PPS(128) for file date after 81327 This provides the telemetered value corresponding to the energy for a step inside a particular sweep. In order to obtain the energy from the telemetered pps value, use the table below. Also provided is the electron efficiency factor for the various energy levels. This is used in the flux calculations discussed in a later section. TM ENERGY Electron TM ENERGY Electron VALUE (eV) Efficiency VALUE (eV) Efficiency 0 31,143.75 0.26453 32 313.27 0.88931 1 26,993.75 0.28030 33 271.21 0.89889 2 23,381.25 0.29687 34 234.64 0.90742 3 20,250.00 0.31418 35 203.02 0.91488 4 17,531.25 0.33226 36 175.66 0.92133 5 15,212.50 0.35076 37 152.24 0.92678 6 13,206.25 0.36988 38 132.03 0.93138 7 11,425.00 0.39015 39 114.19 0.93531 8 9,900.00 0.41084 40 98.931 0.93852 9 8,581.25 0.43209 41 85.700 0.94118 10 7,425.00 0.45416 42 74.188 0.94337 11 6,465.00 0.47674 43 64.256 0.94514 12 5,568.75 0.49949 44 55.656 0.94658 13 4,831.25 0.52243 45 48.281 0.94774 14 4,187.50 0.54578 46 41.913 0.94868 15 3,625.00 0.56951 47 36.306 0.94945 16 3,121.25 0.59419 48 31.306 0.95009 17 2,701.88 0.61792 49 27.163 0.95059 18 2,338.75 0.64148 50 23.569 0.95100 19 2,025.00 0.66468 51 20.444 0.95133 20 1,753.13 0.68747 52 17.763 0.95159 21 1,520.00 0.70946 53 15.444 0.95181 22 1,319.38 0.73061 54 13.463 0.95199 23 1,141.25 0.75147 55 11.688 0.95214 24 984.38 0.77179 56 10.156 0.95227 25 853.13 0.79045 57 8.844 0.95237 26 738.69 0.80815 58 7.719 0.95245 27 639.56 0.82472 59 6.706 0.95252 28 553.63 0.84014 60 5.875 0.95258 29 480.31 0.85414 61 5.138 0.95263 30 416.75 0.86697 62 4.525 0.95267 31 360.13 0.87897 63 n/a n/a PROCESSING_DATA: CONVERTING COUNTS TO FLUX: a) Differential Number Flux (J): J = C / (GF * eff * del_T * del_E) where: C - counts per accumulated interval GF - Geometric factor = 2.16E-4 cm**2 sr (for LAPI 5 x 20 degree detector) = 1.36E-5 cm**2 sr (for LAPI 5 x 5 degree (+/- 0 & 180) detectors) eff - efficiency factor = 0.65 for ions from look-up table for electrons, function of energy (see PPS table above) del_T - accumulation interval = 1.27E-2 sec (64 steps/sec) = 2.83E-2 sec (32 steps/sec) = 5.96E-2 sec (16 steps/sec) del_E = width * E (where E is the center energy of the step) SENSOR # width SENSOR # width 0 0.32 15 0.24 1 0.26 16 0.31 2 0.32 17 0.25 3 0.23 18 0.33 4 0.33 19 0.22 5 0.19 20 0.32 6 0.33 21 0.26 7 0.20 22 0.34 8 0.34 23 0.24 9 0.23 24 0.39 10 0.34 25 0.25 11 0.27 26 0.32 12 0.34 27 0.20 13 0.21 28 0.35 14 0.33 29 0.25 b) Differential Energy Flux Differential Energy Flux = J * E * 1.602E-12 (ergs/eV) where: J = Differential Number Flux E = center energy of the step c) Phase Space Density Phase Space Density = A4 * J / E where: A4 = 1.616E-19 for electrons = 5.448E-13 for ions J = Differential Number Flux E = center energy of the step d) Geiger-Mueller Tube Data FLUX = (decommutated counts) * 517.2 in units (#/cm**2 ster sec) where: ACTUAL PITCH ANGLE OF A DETECTOR: Pitch Angle = arc cos ( SIGN * sin(theta) * ( cos(delta + lambda) * sin(phi) - ( sin(delta + lambda) * cos(phi) ) + cos(e) * cos(theta) ) ) where: SIGN = +1 if geomagnetic latitude < 0 = -1 if geomagnetic latitude >= 0 B = SQRT ( Bx**2 + By**2 + Bz**2 ) B2 = SQRT ( Bx**2 + By**2 ) sin(theta) = B2 / B cos(theta) = Bz / B sin(phi) = Bx / B2 cos(phi) = By / B2 e = 85 degrees for 0+ and 180+ detectors = 95 degrees for 0- and 180- detectors = 90 degrees for all other detectors (non field-aligned detectors) delta = detector angle lambda = shaft encoder angle - 90 degrees TIME GAPS: There are occasionally time gaps between major frames. This is due to the fact that bad major frames were not written to the SATM files. Care should be taken in checking for time gaps when analyzing the data. The FLAG variable in the file will indicate when there is a major frame time gap. The processing software will also sometimes throw out bad sweeps, leaving a time gap in the flux and count arrays which are generated. One should check for time gaps when doing any kind of analysis which requires consecutive times. (See VOLDESC.SFD for further information about processing software.) FORMAT_APPLY_SCOPE: This format applies to all the data files, i.e. those that can be named (using wildcards, and "/" to denote directory levels) /LAPI/8*/*.SATM . /* EOF */