PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 OBJECT = TEXT PUBLICATION_DATE = 2000-12-22 NOTE = "Description of contents in the CALIB subdirectory." END_OBJECT = TEXT END file: GLLUVS2:[Mariner9.PDS_ARCHIVE.GEN_TEMPLATES]CALINFO.TXT Dec 22, 2000 - KES Nov 14, 2012 - KES Content Description of the CALIB Subdirectory The CALIB subdirectory on this CD-ROM volume contains the calibration files associated with the Mariner 9 UVS data set. These files consist of sensitivity and wavelength calibrations for the two channels (G and F) of the UVS instrument. The data files are in the binary External Data Representation (XDR) format. This format is easily read into IDL. The user should contact the Principal Investigator home institution or associated team authors regarding the most up-to-date calibration knowledge, process and files. The calibration files on this Experiment Data Record (EDR) CDrom are all derived from pre-flight testing and in-flight calibration activities. THE DATA FILES CONTAINED IN THIS DIRECTORY ARE: CALINFO.TXT - this user description F_SENS.LBL - the UVS F-channel sensitivity label file F_SENS.XDR - the UVS F-channel sensitivity data F_WAVE.LBL - the UVS F-channel wavelength label file F_WAVE.XDR - the UVS F-channel wavelength data FFLT_SEN.LBL- the UVS F-channel in-flight sensitivity label file FFLT_SEN.XDR- the UVS F-channel in-flight sensitivity data G_SENS.LBL - the UVS G-channel sensitivity label file G_SENS.XDR - the UVS G-channel sensitivity data G_WAVE.LBL - the UVS G-channel wavelength label file G_WAVE.XDR - the UVS G-channel wavelength data N_SENS.LBL - the UVS N-channel sensitivity label file N_SENS.XDR - the UVS N-channel sensitivity data N_WAVE.LBL - the UVS N-channel wavelength label file N_WAVE.XDR - the UVS N-channel wavelength data EUV_128POINT_CAL.DAT - the updated EUV calibration EUV_128POINT_CAL.DOC - its label file SANDEL_PIXEL_FIX_FPN9.DAT - the EUV 'hotpixel' correction SANDEL_PIXEL_FIX_FPN9.DOC - its label file Plus other helpful files, tube exposure, slit map, other instrument UV calibration data (eg. SUSIM) and deadtime information. HELPFUL HINTS - UVS A) Calculation of the integration time for UVS data 1) Phase 1 Playback data is recorded at the original full data rate of 1008 bits/second. The Playback (UPB) data files contain the instrument data fiducial which contains eighteen (18) bytes of sync, engineering, and status words. (See the UVS Functional Requirements Document GLL 625-205, 4-2034 for a complete description of the fiducial contents.) The data's label file describes the data fiducial and header time value locations. The UPB Spacecraft Clock (SCLK) Start time value, IN THE DATA FILE, gives the exact time of the 1st integration of the spectra contained in that record. The SCLK End time gives the exact time of the start of the last integration contained in the spectra. The label file gives the times for the start of the first record and the start of the last record in the UPB data file. The integration time of the individual UVS datum is given in the command word (see the sequence load files for each orbit load). It is also in the last two bits (right-most, Least Significant Bits) of UVS Status Word #1, given in the ninth byte of the eighteen byte fiducial. An integration value equal to one (01) represents a commanded integration time of six milliseconds (6ms); this is the value used for a great majority of the nominal mission observations. The grating steps after the integration for a total instrument period of 7.6 ms. Each full-rate spectra takes 4.3 seconds or 6.5 minor frames of the SCLK clock; there are 14 spectra in one Rim; 84 UVS periods (readouts) occur in one minor frame. The last 0.3 seconds of each spectra are used to re-configure the instrument before the next spectra. The data record format process inserts a value of -1 when no data were present in the downlink. Also note: the last minor frame of each Rim is always used by the instrument to re-sync the grating drive. Thus, no integrations are performed during this period so the last eighty-four (84) words of each Rim are zero. Be careful to see the Functional Requirement Document for a complete description of instrument timing. 2) Phase 2 Realtime Science data (RTS) has been summed over time in the on-board Command Data Subsystem (CDS) computers. These are the files in the URT directories of each orbit on this CD. A description of the summation is given in the Instrument Modes section of the UVSINST.CAT file on this CD. The fiducial is the same as that in the Playback mode; it is summed along with the spectral data so that to interpret the engineering data it must be divided by a factor equal to the number of spectra in one RTS summed Rim, always equal to seven (7), times the number of summed Rims. Thus, True Value = Returned Value/(7 * summed Rims). The number of summed Rims is given in the header data as part of the science data of each Phase 2 RTS data record and is described in the data's label file - see header word 33, the 'commanded summation period (in RIMS)'. This sum duration can be verified with header word 19 minus word 12, the actual values. The Spacecraft Clock (SCLK) Start and End times given in the RTS (URT) files give the exact time of the 1st integration of the first count in the first spectra of the summed data, and the time of the Rim start following the last spectra that is actually summed. Thus, if the SCLK values are 3682277:00:0 and 3682280:00:0 the duration of the summation is three full Rims. One full Rim is used by the CDS to readout the UVS Summation Buffer, or Rim 3682280:00:0 in this example. The next summation period begins on the next Rim start, or 3682281:00:0 in the above example. The summation duration is always an integral number of Rims in UVS RTS mode. Remember to adjust for the 84 zero words at the end of each Rim. The first seven words of the UVS fiducial contains the 'sync' value of 255. You may verify the summed period by checking these values. The onboard summation buffer is long enough to accomodate two UVS spectra, with fiducials; this allows alternating spectra to sample different wavelengths, when commanded to do so. The first fiducial in a RTS buffer normally contains a grating flyback (from the last spectra of a Rim to the first spectra of the next Rim) and is therefore less reliable as a Starting Wavelength engineering value than the Starting Wavelength derived from the second fiducial. Toward the end of the GEM mission, the reported Starting Wavelength grating position began to differ from the commanded position. The team does not fully understand the condition at this time but appears to be related to degredation of one or both of the diodes in the grating drive mechanism, either due to radiation or age. However, proper operation appears to have continued through the nominal mission and into the GEM with occasional wavelength offset 'ghosting'. Altogether improper operation begins to occur during some observations late in the GEM period with total grating commandability failure by orbit 22. No data files are provided after the grating failure. UVS Status files list the Starting Wavelength values and whether they agree with the commanded wavelength. See the files named UVS_RTS_xxx_STATUS.LIS where xxx is the orbit number; these give time and status for every RTS data file in that orbit. B) Log-decompression of the UVS F-channel data If you intend to use the UVS F-channel data then there are several additional pieces of information you need to know. One is that the F-channel is log-compressed. To decompress you will need one of two software programs: either the version for UVS full-instrument-rate Playback - for individual, non-summed spectra, or the Phase 2 RTS 'summation buffer' version. These programs are both IDL programs and are given below. --------- PRO DECOMP,DATA_IN,DATA_OUT ;full-rate/PB version ; ;the following routine is used for full-spectral, Playback or full-rate ; (1008 bits/sec) F-channel count decompression Z=DATA_IN ;written by William McClintock ZC=Z AND "017 ; before Nov,90 ZX=(Z AND "360)/16 NP=FIX((ZC+16)*2.^(ZX-5)+2.^(ZX-6)) DATA_OUT=NP RETURN END ; pro phase_2_decompressor,vin,vout ;Phase 2, summation buffer version ;From: LYA::PRYOR 22-JUN-1996 19:45:42.22 ;To: SIMMONS,STEWART,BARTH ;CC: PRYOR ;Subj: a phase 2 f decompression routine to play with and test ;assumes you have already divided out the number of integrations ;given compressed vector vin with values like 13.3 (not just 0,16,32,40,..) ;it will return vout vout=vin-vin ;to get same size array of 0's ; ;background info ;given a 15 bit number, get the 8 bit number F channel returns ; N X C ;N=15 bit fixed point binary number ;X=4 bit binary power of 2 exponent ;C=4 bit fraction (1 bit hidden) ;in=indgen(2^14)+1 ;alog2=alog(in)/alog(2) ;my Calculus book, p. 328 ;outx=fix(alog2+1) ;outc=fix(in*2.^(5-outx)-16) ;out=16*outx+outc ;decomp,out,in2 ;works, so I understand it ; ;levels used in the compression scheme are levels=[0,16,32,40,48,52,56,60,64,66,68,70,72,74,76,78,indgen(176)+80] decomp,levels,counts ;counts will be the min counts assoc'd with a give ;n step ;now, in phase 2 packets, after dividing out the times, you will ;get things like 18.3, etc. ;What to do? ;assume the brightness is almost steady: ;then 18.3 is formed from a linear combination of 16's and 32's ;registered in the box ; x*16+(1-x)*32 = 18.3 where x=fraction of each that was registered ;so what we will do is given a value v ;find level1 and level2 that bound it (and the corresponding decompressed ;count1, count2) for j=0,n_elements(vin)-1 do begin for i=0,n_elements(levels)-2 do begin if (vin(j) ge levels(i)) and (vin(j) lt levels(i+1)) then begin level1=levels(i) & count1=counts(i) level2=levels(i+1) & count2=counts(i+1) ;vin(j)= x*level1+(1-x)*level2 now solve for x x=(vin(j)-level2)/(level1-level2) ;then form the corresponding linear combination of counts vout(j)=x*count1+(1-x)*count2 goto, next_one endif endfor print,'fell thru a crack' & stop next_one: endfor ;;stop return end --------- C) Off-axis scattered light The UVS instrument was carefully tested for off-axis scattered light rejection. The UVS/EUV instrument paper, [HORDETAL1992], provides the point source transmittance curve. D) UVS Dead-time correction When the count rates are high in the F-channel data, a dead-time correction is used to offset an instrumental electronic historicis. The UVS/EUV instrument paper, [HORDETAL1992], contains a description of the standard dead-time correction and provides an algorithm for the user. A slightly different correction, which fits the ground calibration data points better, was used for data analysis. The new algorithm for this correction is T1=1.3145E-9, T2=2.E-36, and CT=CO/(1-T1*CO^1.5-T2*CO^6) where CO is the instrument counts and CT is the corrected counts. E) In-flight calibration data Data files on this CDrom which pertain to in-flight, nominal mission calibration are given below. The Hendrix reference documents the in-flight calibration and the FFLT_SEN.XDR contains the in-flight F-channel calibration. UVS G01A_URT_STRCAL01.DAT;2 G02C_URT_CROSSCAL.DAT;2 C03C_URT_CROSSCAL.DAT;1 C03C_URT_E4UCAL01.DAT;2 E06A_URT_CROSSCAL.DAT;1 G08A_URT_CROSSCAL.DAT;1 C09B_URT_STRCAL01.DAT;1 C10B_URT_11XCAL01.DAT;1 E11A_URT_CALDRK01.DAT;1 E11A_URT_CALDRK02.DAT;1 E11A_URT_STRCAL01.DAT;1 EUV G02C_EUV_CROSSCAL.DAT;1 C03C_EUV_CROSSCAL.DAT;1 E06A_EUV_CROSSCAL.DAT;1 G08A_EUV_CROSSCAL.DAT;1 C10B_EUV_11XCAL01.DAT;1 Additional in-flight calibrations occurred throughout the Galileo Europa Mission (GEM). Look for these on the UVS/EUV GEM CDroms. F) Changes in sensitivity over the mission The UVS sensitivity is has been measured with star calibration and cross-calibration (with EUV) observations throughout the mission. The UVS sensitivity has not changed, as of orbit C22. G) UVS software The UVS software is all written in the IDL (Research Systems Inc) language and is verified to IDL V5.0.3. It has been run on a Vax platform; some has been run on a Unix platform. No difference has been found. See the SOFTWARE/UVS directory for the programs. The Vax uses Logical Names and directory structures that are not the same as the Unix platform. Care should be taken to edit the software if you are using a Unix platform. Vax data directory references have been removed from the software (as best as possible.) Most of the analysis software searches for desired data files by a specific file naming convention (see the notes on this in the two instrument catalog files) so the user MUST rename the data files to the names given in the .LBL file for the desired data file. Some of the software for calculation of geometry parameters uses the Navigation and Ancillary Information Facility's SPICE Toolkit. Links and Logical Names may be found to these programs, and the SPICE Kernels (archived on a separate UVS/EUV CD). Unless a non-8.3 file name formated CDROM is used, you WILL need to rename the files according to the cross-reference list found on that CD. HELPFUL HINTS - EUV A) The most useful EUV data files The EUV instrument uses a complex matrix for data collection in the downlink limited environment of Phase 2. It is highly dependent on the commanded configuration, ie related to the number of detector scans, the sky position and the wavelength binning schemes. The method is described in the EUVINST.CAT file. The team suggests you make use of the reduced data files formatted in an IDL "save file" format; these data files present the deconvolved data matrix for the entire orbit. The EUV EDRs are preserved here in the event of data loss at the Principal Investigator's institution. An IDL Structure for the raw EUV EDR data files is available in the SOFTWARE directory in GLLEUVRT.PRO. Software to read the original files, make the "save file", and to display the orbit files is given in the SOFTWARE/EUV directory on the archive CDROM. The files contain data that has been corrected for 1) sky-observation parameters (location and number of detector scans effects the sky-box size), 2) sequenced wavelength binning ("superpixel" schemes are used to optimize the wavelength resolution in some detector ranges and to use larger bins in other wavelengths, depending on the target and desired science) and 3) for the detector pixel sensitivity variation ("hotpixel" correction). The EUV sensitivity calibration factor is not included in these files but the hotpixel correction is included. The software programs provide some additional details. All software is written in IDL. Some routines, especially the time conversion programs, utilize the NAIF Toolkit routines and kernel files, such as LEAPSECONDS. The kernels are all contained on a separate UVS/EUV archive disk and the software is available from the NAIF group. (Nasa's Navigation and Ancillary Information Facility is a Planetary Data System group at the Jet Propulsion Lab.) You may need to establish several logical reference directory tags. See the SOFTWARE/EUV directory for these programs. B) How to determine EUV integration times During Phase 2 operations the EUV instrument was used only in Real Time Science (RTS) mode: a buffer matrix within the EUV instrument was used to sum sky-sector versus wavelength data. Wavelengths were binned to maximize spectral resolution at explicit wavelengths and reduced resolution at other wavelengths by the use of a Fixed Pattern Noise Table (FPNT). See the instrument file (EUVINST.CAT) in the CATALOG directory for a detailed explanation of this operation mode. The EUV summation was controlled by the same CDS algorithms as those for the UVS instrument so that only full RIM periods were summed. The Start and End RIM clock values are given with the data sets. The Start RIM is the time of the first EUV integration and the End RIM is the last full RIM that was summed. The Phase2 FPNTs are given in the SOFTWARE directory in the file named PHASE2_FPNS.DAT . C) EUV calibration Calibration is discussed in the instrument template and a sensitivity table is provided there. The EUV was calibrated at both the Arizona facility and at the LASP facility. In-flight cross-calibration with the UVS instrument, particularly at Lyman-alpha, yielded a third sensitivity. The Tucson and LASP sensitivity measurements did not agree. A paper comparing Galileo EUV calibration with the Voyager UVS calibration was prepared which stated that the Galileo EUV calibration was within 15%. Also, the EUV sensitivity appears to have changed during the mission, based on the Earth1 and Earth2 star/cross-calibration activities and subsequent cross-calibration. Details are not currently specified except that the Lyman-alpha region has probably changed more than other wavelengths. A recently submitted paper by Ajello, et al, (to Icarus) on Jupiter Aurora analyzed data using a 128-pixel interpolated array based on the the Tucson calibration from Sandel compared with a VLISM (Very Local InterStellar Medium) spectrum. This interpolated array is in the calibration directory, named EUV_128POINT_CAL.DAT . In addition to the EUV sensitivity calibration, there is a "hotpixel" correction. This correction was established at Tucson and it normalizes the pixel sensitivity across the 128 detector pixels. See the files SANDEL_PIXEL_FIX_FPN9.DOC and SANDEL_PIXEL_FIX_FPN9.DAT . The in-flight cross-calibration data files are shown in the list above. D) Torus geometry A Galileo UVS/EUV observation visualization software tool (GGGS, Galileo Geometry and Graphics Software) was utilized to create Io Torus geometry parameters for the analysis of the EUV (and UVS) Torus data. These data files are the 'xx.SL4' files given in the GEOMETRY/EUV directory. The GGGS program uses the NAIF Toolkit and Galileo SPICE kernels to generate these .SL4 files. Documentation of the kernels used for any specific .SL4 file is found in its associated .LOG file. E) Sky sampling position, z-axis position and rotor rotation rate. During the nominal and extended missions, the spacecraft Z-axis position and the rotor rotation rate were sampled regularly. During cruise these values were often sampled at five RIM resolution. During encounter periods the accuracy frequently improved to once a minor frame (2/3 sec). During pre-Jupiter cruise periods, however, both the knowledge of the Z-axis position and the rotor rate were often judged from non-navigation readout information, such as Cold Turn Sequence real-time commanded data rates and Star Scanner pointing tables. A separate file of this knowledge is provided on the pre-Jupiter archive volumes. For the Jupiter Mission period and beyond, the Rotor Kernels supply this information. The xx.SL4 file incorporate this z-axis knowledge in the geometry file deter- minations. A table of the predicted z-axis positions for each orbit load sequence, as determined on predicted Star Scanner stars, is given in the Z-AXIS.DAT file in the GEOMETRY directory. F) Changes in sensitivity over the mission See item C) above.