IMP-8 pha file consists data records of one 4-day interval, with the last record indicated by a negative interval number. Data records are fixed-blocked by a factor of 3. Physical records are 4656 bytes in length. Logical records are 1552 bytes(388 words) in length and represent one album of data.

WORD CONTENT 1 Universal time at start of album(tenths of seconds of year) 2 S/C clock at start of album(low order 6 bits zero) 3 Pseudo-sequence count-negative at 400 BPS, positive at 1600 BPS 4 Halfword 1 Day of year Halfword 2 Perigee count 5 Milliseconds of day 6 Longitude geocentric(deg.) 7 Latitude " 8 Longitude geomagnetic(deg.) 9 Latitude " 10 Ro(earth radii) (C.U.L.) 11 Radial distance from center of earth(km) 12 GSEx Satellite position in geocentric solar ecliptic coordinates(km) 13 GSEy " " 14 GSEz " " 15 GSMx Satellite position in geocentric magnetospheric coordinates(km) 16 GSMy " " 17 GsMz " " 18 GEIx Sun position in geocentric equatorial inertial corrdinates(AU) 19 GEIy " " 20 GEIz " " 21 L, McIlwain parameter(earth radii) 22 B, Magnetic field strength(gamma) 23 Lsep, Satellite-earth-sun angle(deg.) 24 Year of recording 25 Halfword 1 Data quality flag Halfword 2 Time quality flag 26 Halfword 1 Number of 4-day interval(negative if last record of this interval). Halfword 2 Day of next perigee 27 Milliseconds of day of next perigee 28 Right Ascension Spin vector in celestial inertial coordinates(deg.) 29 Declination 30 Halfword 1 Year Halfword 2 Day of year Time of orbit date 31 Milliseconds of day 32 Byte 1 Al Trend check flag =0 if all Al rate readouts in album satisfied the trend check or were undetermined =# rejected otherwise Byte 2 B Trend check flag, Byte 3 C Trend check flag Byte 4 A1.-B.-C Trend check flag 33 Byte 1 (A&B)1.-B.-C Trend check flag Byte 2 (A&B)2.-B.-C Trend check flag Byte 3 A1.B.-C Trend check flag Byte 4 (A&B)1.B.-C Trend check flag 34 Byte 1 (A&B)2.B.-C Trend check flag Byte 2 DI Trend check flag Byte 3 E Trend check flag Byte 4 F Trend check flag 35 Byte 1 G Trend check flag Byte 2 DI.EI.F Trend check flag Byte 3 DI.EI.-F.-G Trend check flag Byte 4 DI.EI.F.-G Trend check flag 36 Byte 1 (DI&EI)l.EI.-F.-G Trend check flag Byte 2 (DI&EI)2.EI.F.-G Trend check flag Byte 3 Spare Byte 4 Spare 37 CNT - Al events 38 CNT - B events 39 CNT - C events 40 CNT - A1.-B.-C events 41 CNT - (A&B)l.-B.-C events 42 CNT - (A&B)2.-B.-C events 43 CNT - A1.B.-C events 44 CNT - (A&B)l.B.-C events 45 CNT - (A&B)2.B.-C events 46 CNT - DI events 47 CNT - E events 48 CNT - F events 49 CNT - G events 50 CNT - DI.EI.F events 51 CNT - DI.EI.-F.-G events 52 CNT - DI.EI.F.-G events 53 CNT - (DI&EI)1.EI.-F.-G events 54 CNT - (DI&EI)2.EI.-F.-G events [Words 37-54: Bits 0-3 = (16-n) for n = 1,...,16 = 15 for n = 0 Bits 4-31 = Sum(cnt(i)) for i=1,n and n=l,...,16 = only bit 4 on for n = 0 where n is the number of counts data readouts(cnt) within an album. Only readouts with the trend check satisfied(not undetermined or rejected) are included in the sum. 55 Halfword 1 - APP 6, Leakage current, Page 0 Halfword 2 " 1 56 Halfword 1 " 2 Halfword 2 " 3 57 Halfword 1 - APP 36, MED temp., Page 1 Halfword 2 " " Page 3 58 Number of LED or MED PHA points padded. 59 Halfword 1 - Number of LED PHA points with Ll=R(T4=1) Halfword 2 - Number of MED PHA points rejected because event type was -F and F pulse height was >1 or because event type was F and F pulse height was = 0. 60 Halfword 1 - Number of LED PHA points with pulse heights forced to zero because LED was off. Halfword 2 - Number of MED PHA events of word 59, Halfword 2 that were forced to be rejected(by setting F pulse height to zero and event type to F event) because MED was off. 61 Halfword 1 - Number of A.B.-C events with T2,T3 = 0,0 Halfword 2 - Number of A.B.-C events with T2,T3 = 0,1 62 Halfword 1 - Number of A.B.-C events with T2,T3 = 1,0 Halfword 2 - Number of (A&B)2.A.B.-C events with T2,T3 = 0,0 and (A&B)2.A.B.-C rate used. 63 Halfword 1 - Number of (A&B)2.A.B.-C events with T2,T3 = 0,l and (A&B)2.A.B.-C rate used. Halfword 2 - Number of (A&B)2.A.B.-C events with T2,T3 = 0,0 and A.B.-C rate used. 64 Halfword 1 - Number of (A&B)2.A.B.-C events with T2,T3 = 0,l and A.B.-C. rate used. Halfword 2 - Number of (A&B)2.A.B.-C events with T2,T3 = 1,0 (neither rate used). 65 Halfword 1 - Number of (A&B)l.A.B.-C events with T2,T3 = 0,0 and (A&B)l.A.B.-C rate used. Halfword 2 - Number of (A&B)l.A.B.-C events with T2,T3 = 0,l and (A&B)l.A.B.-C. rate used. 66 Halfword 1 - Number of (A&B)l.A.B.-C events with T2,T3 = 0,0 and (A&B)2.A.B.-C rate used. Halfword 2 - Number of (A&B)l.A.B.-C events with T2,T3 = 0,1 and (A&B)2.A.B.-C rate used. 67 Halfword 1 - Number of (A&B)l.B.-C events with T2,T3 = 0,0 and A.B.-C. rate used. Halfword 2 - Number of (A&B)l.B.-C events with T2,T3 = 0,1 and A.B.-C. rate used. 68 Halfword 1 - Number of (A&B)l.B -C events with T2,T3 = 1,0 (no rate available). Halfword 2 - Spare NEXT 5 Halfwords (repeated 128 times) Halfwords 1-2 LED Data Point Halfwords 3-5 MED Data Point 388 WORDS TOTAL

LED data point 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Halfword 1: G T1 T2 T3 T4 A A A A A A A A A A Halfword 2: B B B B B B B B B B P P G = 0 for High gain = 1 for Low gain T1 = a6 bit at accumulation time(1/2 sequence before readout) = 1 (A&B)2.A.B.-C or (A&B)2.A.-B.-C events if HIGH GAIN during 2nd through last readouts on page 0, all readouts on page 1, and 1st readout on page 2. = 0 [A.B.-C or A.-B.-C events if HIGH GAIN] during 2nd through last readouts on page 2, all readouts on page 3, and lst readout on page 0. If LOW GAIN event, event type is (A&B)l.A.B.-C or (A&B)1.A.-B.-C (a6 is irrelevant). T2 and T3 are used for B events only. T2 = 1 if no rate readout that would have counted this PHA event was available. T3 is used only if T2 = 0. Otherwise T3 = 0. T3 = 0 if the rate readout was > 0. = 1 if the rate readout was = 0 T4 = 1 if Ll = R and Ll has not been forced equal to R due to LED being off. = 0 otherwise

MED data point 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Halfword 1 G M - T1 T2 T3 D D D D D D D D D D Halfword 2 - - - - - - E E E E E E E E E E Halfword 3 G M - - - - F F F F F F F F P P G = 0 for High gain = 1 for Low gain M = 0 denotes a multiplication factor of 10 1 " 50 T1 = a4 bit at accumulation time(1/2 sequence before readout) = 1 during 2nd through last readouts of snapshot 0, all readouts of snapshot 1, and lst readout of snapshot 2. = 0 during 2nd through last readouts of snapshot 2, all readouts of snapshot 3, and lst readout of snapshot 0. T1 is only set if T2, T3 (event type bits) = 0, 1 T1 T2 T3 EVENT 0 0 0 DI.EI.F.G 1 0 1 DI.EI.-F.-G 0 0 1 (DI&EI)1.EI.-F.-G 0 1 0 DI.EI.F.-G 0 1 1 (D&E)2.EI.-F.-G

IMP-8 Trend check Consider two readouts of a rate N1 and N2 in sequences S1 and S2 respectively (S2>S1). If N1 or N2 is padded or if S2 not equal S1 + Ns (where Ns = the number of sequence between readouts of that rate), then the trend check is undetermined(T = 1). If S2 = S1 + Ns and 1/15 < N2'/N1' < 15 where N1' = max(N1,1) N2' = max(N2,1) then N2 is accepted by the trend check(T = 0). Otherwise, the trend check rejects N2. If N2 is rejected by the trend check, it will still be used as N1 in the trend check of the next readout of that rate.