A description of rate buffers files for all experiments currently supported by XRONOS follows. The descriptions of records 1 thru 4 are for the so-called ``new" types of file-headers. The old types of file-headers have been phased out in 1986 and they are not supported by XRONOS. To find out whether a particular header is in the old or new format, see record 1 word 55.
Files are binary with records 128 words long. Default variable type for all fields is normal signed integer*2.
The layout of record 1 is common to all instruments
Record 1 ________ Word Description ____ ___________ 1-8 source name (a16,ascii) 9-10 s/c pointing ra, scaled such that 360 degrees = 10**9 (i*4) 11-12 s/c pointing dec, scaled such that 90 degrees = 10**9 (i*4) 13 s/c roll in units of 0.1 degree 14 =1 if slew flag set, =0 otherwise 15 spare 16 type of rates file: =0 for old low-resolution rates file =1 for old msec (luigi-type) " " =2 for new low-resolution rates file =3 for new msec (luigi-type) " " (not supported) =4 for old low-res rates files obtained from arriv. time files this determines which layout of recs 5 onwards applies. 17-18 Bin integration time. It can be specified in the following units, depending on the value of word 29: a) 2**-14 sec (i*4) (word 29 = 0) b) microsec (word 29 = 1) c) sec (word 29 = 2) 19-20 shf key of start of rates file (i*4) 21-22 shf key of end of rates file (i*4) do not use these shf keys for accurate correlation of s/c time with utc. they are ok to an accuracy of 1 second, but for precise correlation use the 'datation area'. 23 experiment number (1,2,3,4,5,6 = L1,L2,ME, GS,SSS,MPC) this determines which layout of record 2 applies below. 24 0 = no correction to bin times has been calculated 1 = barycentric correction has been applied to the data in records 5 and on 2 = barycentric correction has been computed, and the results for various times are stored in records 3 and 4 as described below, and may be interpolated to correct the time of any bin. 25-26 no. of data points/bins, not including special markers for gaps, e-o-f..(i*4) 27-28 shf key of file creation time (i*4) 29 Flag to control the units in which the bin integration time is specified (see words 17-18) the allowed values are: =0 for 2**-14 sec units =1 for microsec units =2 for sec units 30-31 spare 32 power of 2 by which to multiply all c/s in recs 5 onwards of a compressed low- res rates file - not used for other file -types. the program reading the file should multiply all bin values by 2 to this number, to obtain the 'true' values 33 power of 2 by which to multiply all err/sec in recs 5 onwards of a compressed low-res rates file - not used for other file types. 34 power of 2 by which to multiply all deadtimes in recs 5 onwards of compressed low-res file - this is for future use 35-36 average count rate for data in file in units of 0.001 cts/sec (i*4) for all instruments but L1 & L2 (for which units are 1.e-6 cts/sec) 37-38 standard deviation of previous quantity in units of 0.001 cts/sec (i*4) for all instruments but L1 & L2 (for which units are 1.e-6 cts/sec) 39 no. of data gaps in a msec file - not used for low-res 40 set to 1 if real variables converted to hp 9000 ieee standard 41-42 time of centre of first bin in file relative to the datation reference point given in words 43-44 (following immediately) and expressed in s/c clock units. (signed i*4) the ref time of the centre of the 1st bin is therefore: words 43-44 plus words 41-42 (calculated with i*4 arithmetic). 43-48 accurate datation information, for relating s/c clock to utc. no correction for propagation etc is made. contains 3 i*4's: (1) s/c clock of datation reference point, i.e. the ref time of the 1st hk record in units of 2**-14 secs (unsigned i*4) (2) the utc of the datation reference point,i.e. the ground station time of the 1st hk record this i*4 contains the whole number of secs i.e. the shf key (3) the remaining microsecs to complete the utc of the datation reference (between 0 and 999999) 49-54 exactly the same information as given in words 43 to 48, but for a datation reference at the end of the file (the last hk record). only of interest for cases when extreme time accuracy is needed and when it is necessary to measure the speed of the s/c clock. 55 this location defines whether recs 1 to 4 are in new or old format. this listing only describes the new format actually, for which word 55 = 1. old headers can be identified as such by value 0 for word 55. the value 2 means that header is in new format but was derived from old format; some fields may therefore be missing. 56 spare 57-58 source ra scaled such that 360 deg =1.e9 i*4 59-60 source dec scaled such that 90 deg =1.e9 i*4 61-62 no. of 128 word records in file 63 average barycentric correction in units of 0.1 sec applied to file if word(24)=1 64 spacecraft clock correction, the no.of pulses /expected pulses = (0.999999+word(64)*1.d-10) this will only be set if word(24)=1 OR 2. 65 =1 if file is concatenated using conlc 66 spare 67-68 if word(24)=2 contains the no. of msec to be added to the 1st datation time (43-48) in order to correct arrival times to the barycenter (see also word 71). 69-70 as words 67-68 but for the time given by wrds 49-54. 71 residual no of microsec to be added as 67-68 72 residual no of microsec to be added as 69-70 73-74 shf key of observation start (implemented on 19/7/88) 75-76 shf key of observation end ( " " " ) 77-128 spareThe layout of record 2 is different for different instruments.
For the EXOSAT ME:
Record 2 (for ME) ___________ This contains information that is specific to the me: Words Description _____ ___________ 1 instrument (ar=1,xe=2 , both = 3) 2 record type (a2, ascii) e.g.'e3' 3 start detector number selected(1-8) 4 stop detector number selected (1-8) 5 start b/g det no. (1-8) 0 if no b/g sub 6 stop " " 7 start bin number (1-128) 8 stop " " " 9-10 spare 11 collimator efficiency (10**4 = 1.0) 12 spare 13 background correction method 0=none 1=auto, 2=by file, 3=yes 14-16 bg correction file name [if meth=2] (a6) 17 minimum wait time (htr3 only) 18 deadtime correction factor [only if dt:ca] scaled such that 10**3 = 1.0 19-20 hk cts/sec such that 100 =1 cts/sec (i*4) 21-22 spare 23-24 lc correction additive constant (10**3=1.0) 25 =1 if cts are deadtime corrected else 0 for no correction or 2 for time dep correct. (note that in type 1 rate buffers the correction is applied (due to the integer representation), even if there are some old rate buffers for which word (25)=1 26 spare? 27 start channel number (as opposed to bin number) channels numbered 0..255 28 end channel number as opposed to bin number 29-33 spare 34 no. of on-source dets 35 no. of bg dets used 36-128 spareFor the EXOSAT GSPC:
Record 2 (for GSPC) -------------------- Words Description ------ ------------ 1 instrument ( = 4 , meaning gs) 2 app. program no. 3-4 spare 5 bl lower value 6 bl upper value 7 start channel 8 stop channel 9-10 spare 11 collimator efficiency scaled such that 10000 = 1.0For the EXOSAT LE:
Record 2 (for LE) ------------------ (New layout implemented on 22-8-86 on hp2) Words Description ----- ----------- 1 instrument(=5 for both le1 and le2!!) (le1 & le2 can be distinguished from record 1 word 23) 2 obc ap number (from which it can also be deduced whether le1 or le2 is used) if>100 then this location contains (ap no)*100+submode workspace param. 3 filter wheel position number (as in telecommand readout) 4 minimum wait time (units of 2**-5 secs) 5-10 spare 11&12 normalisation that has been applied to all data points in file; to remove the effect of the normalisation, all points may be divided by this value. it is encoded as 2 i*2's which should be interpreted as follows: rec(12)/3000.0*10.0**rec(11) i.e. like an exponent & mantissa. typical value is in fact 1.0!! 13 minimum fractional exposure that a bin must have before it is filled * 10000 14 lcurv version # (iver*100+imod) 15 1000 * correction factor corresponding to mean fractional deadtime 16-29 spare 30 =1 if dead time corrected for sample rate 31 =1 if corrected for telemetry available 32 =1 if bg subtracted 33 =1 if source only =0 if bg only 34 =0 generally (normal counts in file) =1 for 'existence profile' (bins=0 or 1) =2 for exposure time profile (bins = between 0.0(empty)&1.0(fully exposed)) words 35 to 60 or words 61 to 65 may specify pixels included in file 35 number of source boxes (up to 3) 36 number of background boxes (up to 3) (only 2 allowed for in old format) 37-40 low x, low y, high x, high y, srce box 1 (linearised raw x's and y's) 41-44 same for bg box 1 45-48 same for source box 2 (spare if no box 2) 49-52 same for bg box 2 (spare if no box 2) 53-56 same for source box 3 (spare if no box 3) 57-60 same for bg box 3 (spare if no box 3) 61 source x coordinate 62 source y coordinate 63 radius of source box 64 radius of inner bkgnd box 65 radius of outer bkgnd box 66 srce box area/bkgnd box area * 10000 67 bkgnd non-uniformity correction factor applied * 10000 68-128 spareFor the Einstein SSS:
Record 2 (for SSS) ------------------- (implemented on 20/7/89) Words Description ------ ------------ 1 instrument mode 2 spare 3-4 shf time of last defrost 5 start channel 6 stop channel 7-8 opto rate scaled 10000=1.0 9 rateFor the Einstein MPC:
Record 2 (for MPC) -------------------- (implemented on 23/8/89) Words Description ------ ------------ 1 start channel 2 stop channel 3 l cut-off (scaled 10000=1) 4 b cut-off (scaled 10000=1) 5 anticoinc. cut-off (scaled 100=1) 6 sequence no.For the HEAO-1 A-1:
Record 2 (for A-1) ------------------- (implemented on 1/9/91) Words Description ------ ------------ 1 instrument (=10 A-1) 2 spare 3-10 catalog name (a16 ascii) 11-12 galactic latitude (10^9 units) 13-14 galactic longitude (10^9 units) 15-16 first major frame in file 17-18 second major frame in file 19-22 first instrument mode 23-26 second instrument mode 27-30 third instrument mode 31 total number of mjf's 32 lower energy range (keV x100) 33 upper energy range (keV x100)The layout of records 3 and 4 is common to all instruments:
Records 3 and 4 ---------------- Contains 256 arrival time correction values if word(24) of record 1 is set to 2. In which case the differences wrt to a linear relation between arrival time correction and time are given. The following gives the formulae for reconstructing the arrival time corrections which should be added to the times in the file: correction values are val(j) let t1=time of 1st datation (rec 1, words 43,48) t2=time of 2nd datation (rec 1, words 49,54) i1=correcn to be added in msec at t1 (rec1, words 67,68) i2=correcn to be added in msec at t2 (rec1, words 69,70) m1=residual correction in microsec at t1 (rec1, word 71) m2=residual correction in microsec at t2 (rec1, word 72) then c1=i1+m1/1000.d0 (correction in msec at t1) c2=i2+m2/1000.d0 (correction in msec at t2) dt=(t2-t1)/255.d0 (interval between 256 correction vals) grad=(c2-c1)/(t2-t1).d0 cval(j)=c1+grad*dt*(j-1) (linear value) tcor(j)=cval(j)+val(j)/1000.d0 tcor(j) gives the time correcn in msec at times corresponding to t1+(j-1)*dt for j=1,256For TYPE 0 RATE BUFFERS the layout of records 5 to n is:
Records 5-n (if file type =0 i.e. old low-resolution files ) ___________ Each record contains 16 bins of data. each bin consists of: Word Description ____ ___________ n day no. n+1,n+2 time of day (msec) (i*4) n+3 scaled dead time (i*2) (0-10000) n+4,n+5 counts/sec (r*4) n+6,n+7 error (cts/sec) (r*4) where n=1,9,17,..121 for bins 1,2,3,..16 n+8 -1 on last day no. to indicate endFor TYPE 1 RATE BUFFERS the layout of records 5 to n is:
Records 5-n (if file type = 1, i.e. old msec file) ___________ 256 8-bit intensity samples with 0-252 giving the cts/integration interval, 253 indicating end of file, 254 indicating >252 cts/ integration interval and 255 a data gap.For TYPE 2 RATE BUFFERS the layout of records 5 to n is:
Record 5-n (if file type=2 i.e new low-resolution files) ___________ word n = cts/sec as semi-log scaled i*2 word n+1 = err/sec as semi-log scaled i*2 if err = -1 this means bin is completely empty, i.e. it lies completely within a data gap if err = -2 this means end of file (and the accompanying counts/sec is not to be interpreted as a bin) if err = -3 this means that the accompanying countrate couldnt be converted to semilog without overflow. I.e. 64 bins per rec, and the time of a bin is implied by its offset in the file. Numbers are scaled by a common power of 2 as given in rec 1 of the file. Direct access to any time in the file is thus possible. No deadtimes.For TYPE 4 RATE BUFFERS the layout of records 5 to n is:
Records 5-n (if file type =4 i.e. old low-resolution files obtained from ___________ arrival time files) Note that in this case the data are unbinned and each time represents the arrival time of each photon. For each photon the following information is given (16 photons/rec): Word Description ____ ___________ n day no. n+1,n+2 time of day (msec) (i*4) n+3 scaled dead time set to 10000=1 in this case n+4,n+5 counts/sec, set =1 in this case n+6,n+7 error (cts/sec), set =1 in this case where n=1,9,17,..121 for photons 1,2,3,..16 n+8 -1 on last day no. to indicate end
The photon arrival time (PAT) rate buffers are binary files (with 128 words/rec) created by the EXOSAT LE automatic analysis and database software. A PAT file is divided in PAT-subfiles, each containing the data of one detected source in the field of view. The first header record, partially displayed when a XRONOS applications is executed, contains the following basic information:
Word Description ---- ----------- 1-2 'PAT ' (a4,ascii) identifies a PAT-rate buffer 3 N, number of PAT-subfiles present (if N is negative the photons in each subfile are time ordered) 4 total number of records in the PAT-rate buffer 5+(N-1)*4 (=M) start record number of the N-th PAT-subfile M+1 to M+3 N-th PAT-subfile name (a6,ascii)The maximum number of PAT-subfiles is 31. To select the N-th subfile use the fsN input file option (see sect. 10.3, input file options). The first 2 records of each subfile are the header records for each detected source and use the same layout of normal EXOSAT LE rate file header records. Note some header information in PAT-subfiles and, in general, photon arrival time rate buffers is irrelevant. This is:
Note that XRONOS applications by default work out and apply EXOSAT ME dead time correction to count rates (if not applied yet) and to errors on count rates (to reconstruct exactly the expected variance from a constant source) of ME rate buffers; this will work only if all the relevant infos are contained in the ME rate buffer header. Otherwise a warning message is produced and input file option ma should be used to correct count rates and errors for a dead time correction constant and/or option dv to correct the error bars for the dead time effects on the variance (see Eq. 2.21 in Lewin et al. 1988 Sp. Sc. Rev., 46, 273, with tau=5.5e-6 s for HTR3 and HTR5, tau=4.88e-4 for PULS and PULS2, and tau=2.44e-4 for all other ME data types).