Data Set Information
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| DATA_SET_NAME |
VL1/VL2 MARS LABELED RELEASE V1.0
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| DATA_SET_ID |
VL1/VL2-M-LR-2-EDR-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview:The Labeled Release (LR) instrument on each Viking Lander operatedthroughout the Primary Mission and continued into the ExtendedMission. The basic analysis cycle for the LR experiment was todeliver a sample of martian soil to one of four test cells, seal thecell and moisten the soil with an aqueous solution of carbon-14labeled organic media. A second nutrient injection was typically doneabout 7-8 Mars days after the first injection. The test cell wascontinuously monitored for the release of radioactive labeled gas asan indicator of heterotrophic metabolism. Viking Lander 1 (VL1)conducted four analysis cycles with two nutrient injections for cycles1, 2, and 4 and three injections for cycle 3. Viking Lander 2 (VL2)conducted five analysis cycles. The first four cycles had twonutrient injections each, and the fifth cycle had one injection[LEVIN&STRAAT1976B; LEVIN&STRAAT1977A; LEVIN&STRAAT1979A].Data collected by the LR instruments included radioactivity countsfrom evolved carbon-14 labeled gas and temperatures of the detectorsand the head-end assembly. Radioactivity was counted for 16-minuteintervals during an analysis cycle, except for several hours aroundthe time of nutrient injection where intervals of 2- to 4-minutes wereused. Detector and head-end temperatures were measured at 16-minuteintervals throughout the cycle.The LR data were originally archived on microfilm housed at NSSDC. LRdata were also available from a set of computer listings in thepersonal archives of Co-Investigator Dr. Patricia Ann Straat. Thedata in this PDS archive were transcribed into digital files fromthese two sources. The Straat listings were the primary source used.The LR experiment included an extensive test program that not onlytested the operating characteristics of the LR instrument, but alsoanalyzed many terrestrial samples for comparison with the Marsresults. These test data are not currently part of the PDS LabeledRelease archive, but much of it has been published in the scientificliterature [e.g., LEVIN&STRAAT1981A; LEVIN&STRAAT1981B;LEVIN&STRAAT1979B; LEVIN&STRAAT1977B; LEVIN&STRAAT1976B].Parameters:The LR data set contains three basic data measurements: radioactivitycounts, detector temperature, and head-end temperature. Measurementsare tagged with the time they were made and are stored in atime-ordered format.RADIOACTIVITY COUNTS: Radioactivity in the LR data set are given ascounts/minute. Counting was generally done over a 16-minute periodand then normalized by the length of the counting interval todetermine the average number of counts/minute within that interval.Each LR instrument had two solid-state beta detectors and could becommanded to use either one or both detectors. In cases where onlyone detector was used, radioactivity values were corrected to valuesequivalent to counting with both detectors. The radioactivityrecorded by the LR detectors included a background signal from theMars environment and from the Radioisotope Thermoelectric Generators(RTGs) that powered the Viking Landers. Background levels weredetermined from radioactivity measurements made prior to the start ofan analysis cycle. Radioactivity values with and without backgroundcorrection are provided for measurements made during the incubationperiod of an analysis cycle.TEMPERATURES: Both detector and head-end temperatures in the LabeledRelease data set are given in degrees Celsius. Temperatures weremeasured every 16-minutes throughout an analysis cycle. Sampletemperatures are less than those recorded by the head-end temperaturesensor because the test cell heaters and temperature sensors arelocated at the top of the test cell above the sample. SeeLEVIN&STRAAT1977A for information on correlating head-end and sampletemperatures.TIME: The primary time tag for the LR data set is known as Marsmission time. It is defined as the number of Earth seconds pastmidnight of Sol 0, where Sol 0 is the day of landing (P. A. Straat,personal communication, 2000). Mars mission time values in thisarchive have been transcribed from the computer listings or microfilm.The LR data files include several other time-related fields that werecomputed from the transcribed Mars mission time values during archiveproduction (see Processing Section below). The LR data files includetime fields for elapsed time from nutrient injection and elapsed timefrom a specific Sol number. These fields are included to allowdisplay of the data in forms similar to previously published graphs[e.g., LEVIN&STRAAT1979A; LEVIN&STRAAT1977A; LEVIN&STRAAT1976B].Other computed time fields are UTC and local lander time. The Vikingproject used the format of sol number, hour, minute, and second forlocal lander time with times in a sol extending beyond 24 hours. Thisusage is different from the PDS standard for local time. As a result,local lander time is called native time in the LR data files.Processing:All radioactivity, temperature and Mars mission time data in this LRdata set were transcribed by hand into data files. The primary datasource was computer listings supplied by P. A. Straat. The NSSDCmicrofilm was used to recover data for gaps in the computer listings.Personnel at the PDS Geosciences Node transcribed the computerlistings, whereas personnel at NSSDC transcribed the microfilm. Alldata entered by hand was checked for accuracy. However, typographicalerrors may still exist in the data set. See the CONFIDENCE_LEVEL_NOTEfor estimates of the data entry accuracy.All ancillary time fields in the LR data set were computed from theMars mission time parameter. The computation of UTC and local landertime from Mars mission time require the UTC of midnight at Sol 0 andthe number of seconds in a martian day. The intent of including thesetime fields in the LR data set was to provide a means of comparisonwith times in other Viking data sets. As such, the methods used hereto compute UTC and local lander time attempted to reproduce, asclosely as possible, values consistent with values from the Vikingproject. A value of 88775.241 seconds/Sol was derived from analyzinga series of local lander time and UTC values published inCLARKETAL1977. The UTC value for midnight of Sol 0 was estimated fromtimes in CLARKETAL1977 and from acquisition times of Viking Landerimages taken on Sol 0 for each lander [TUCKER1978]. The estimated UTCvalues were 1976-07-19T19:39:54 and 1976-09-03T12:48:45 for VL1 andVL2, respectively. These values are slightly different from thosepublished in ALLISON1997 and ALLISON&MCEWEN2000.Data:The LR data consists of three files for each analysis cycle. Eachtable has an associated detached PDS label. The tables are:(1) Detector temperatures(2) Head-end temperatures(3) Radioactivity counts(1) Detector temperaturesThis table includes fields of detector temperature, Mars mission time,and several derived time fields (see PDS label). Data are sorted inincreasing Mars mission time order.(2) Head-end temperaturesThis table includes fields of head-end temperature, Mars mission time,and several derived time fields (see PDS label). Data are sorted inincreasing Mars mission time order.(3) Radioactivity countsThis table includes fields of raw and background-correctedradioactivity counts, channel number, Mars mission time, and severalderived time fields (see PDS label). The background-corrected fieldwas derived from the raw radioactivity field by subtracting a constantbackground value determined from data collected prior to nutrientinjection. Data collected in single channel mode were corrected todual channel mode (using a constant multiplier) before backgroundcorrection. Data are sorted in increasing Mars mission time order.Analysis Cycles:A number of published papers describe the soil sampling and analysisrationale for the LR experiment, along with the scientific results[e.g., LEVIN&STRAAT1979A; LEVIN&STRAAT1977A; LEVIN&STRAAT1976B]. Asummary of the sampling and analysis strategy information from thesepapers is given here.Viking Lander 1 Cycle 1-----------------------The sample for VL1 cycle 1 was acquired from a smooth patch offine-grained material named Sandy Flats. The sample came from within4 cm of the surface. VL1 cycle 1 was performed autonomously accordingto preflight instructions. Sample Site : Sandy Flats Collection Temperature : -83 deg C Collection Sol : 8 (fresh) Experiment Type : Active First Injection Sol : 10 Second Injection Sol : 17 Purge : 23Viking Lander 1 Cycle 2-----------------------This sample was acquired on Sol 8 (see VL1 cycle 1) from Sandy Flatsand stored in the biology hopper for about 20 sols. Before nutrientincubation, this sample was heated to 160 deg C for about 3 hours tosterilize the sample as a control for comparison to VL1 cycle 1results. Sample Site : Sandy Flats Collection Temperature : -83 deg C Collection Sol : 8 (stored in hopper for 20 sols) Experiment Type : 160 deg C control First Injection Sol : 29 Second Injection Sol : 35 Purge : 37Viking Lander 1 Cycle 3-----------------------The VL1 cycle 3 sample was also acquired from Sandy Flats close to thesite of the first VL1 sample (cycles 1 and 2). The sample came fromwithin 4-5 cm of the surface. This analysis was a long activeincubation (about 50 sols), where the sample received three nutrientinjections. Sample Site : Sandy Flats Collection Temperature : -21 deg C Collection Sol : 36 (fresh) Experiment Type : Active, long incubation First Injection Sol : 39 Second Injection Sol : 55 Third Injection Sol : 80 Purge : 89Viking Lander 1 Cycle 4-----------------------This sample was collected during the Extended Mission from the sameSandy Flats area as the previous VL1 samples. It was collected on Sol91 and stored in the Biology hopper in the dark, open to the Marsatmosphere, and at temperatures between 10 and 26 deg C until analysisstarted on Sol 230. The original intent for this cycle was to collecta fresh sample, but concerns by the surface sampler team aboutpossible damage to the sampler arm changed the scenario. The twonutrient injections for this sample occurred about 3 hours apart. Itwas calculated that enough nutrient remained in the reservoir for thetwo injections [LEVIN&STRAAT1979A]. Sample Site : Sandy Flats Collection Temperature : -71 deg C Collection Sol : 91 (stored) Experiment Type : Active First Injection Sol : 232 Second Injection Sol : 232 Purge : N/AViking Lander 2 Cycle 1-----------------------This sample was collected from a crusty to cloddy material in an areaknown as Beta. The material came from within 3.5 cm of the surface.VL2 cycle 1 was performed autonomously according to preflightinstructions. Sample Site : Beta Collection Temperature : -23 +/- 5 deg C Collection Sol : 8 (fresh) Experiment Type : Active First Injection Sol : 11 Second Injection Sol : 18 Purge : 24Viking Lander 2 Cycle 2-----------------------The VL2 cycle 2 sample was collected from the same area of Beta as forVL2 cycle 1 sample. It was a fresh sample collected on Sol 28. Thesample was heated in the test cell at about 50 deg C for 3 hoursbefore the nutrient was injected. The sterilization process wasintented as a control for comparison to cycle 1 results. Sample Site : Beta Collection Temperature : -23 +/- 5 deg C Collection Sol : 28 (fresh) Experiment Type : 51 deg C control First Injection Sol : 34 Second Injection Sol : 38 Purge : 47Viking Lander 2 Cycle 3-----------------------This sample was acquired from under a rock called Notch Rock. Therock was pushed aside to expose the soil. The pushing occurred about1 hour after sunrise and the soil was exposed to low angle sunlightfor approximately 37 minutes before delivery to the biology sampleprocessor. The intent of this sample was to analyze soil that wasprotected from ultraviolet radiation for a long period of time. Thisanalysis performed a long incubation of nearly 90 sols with twonutrient injections.Radioactivity data was collected in single channel mode for part ofthe beginning of this cycle. Data were corrected to dual channel modeby multiplying by a factor of 1.95 prior to nutrient injection and afactor of 2.06 after the first injection. Sample Site : Beneath Notch Rock Collection Temperature : -66 deg C Collection Sol : 51 (fresh) Experiment Type : Active, long incubation First Injection Sol : 53 Second Injection Sol : 60 Purge : 140Viking Lander 2 Cycle 4-----------------------This sample was collected from the same general area as the samplesfor VL2 cycles 1 and 2 in the Beta location. The material for thissample mostly came from the top 5 cm of the surface. The sample mayalso contain material disturbed during the cycle 2 sample acquisition.The sample was heated to 46 deg C for about 3 hours before nutrientwas injected. Sample Site : Beta Collection Temperature : -84 deg C Collection Sol : 145 (fresh) Experiment Type : 46 deg C, control First Injection Sol : 147 Second Injection Sol : 161 Purge : 171Viking Lander 2 Cycle 5-----------------------The original intent for VL2 cycle 5 was to incubate a fresh sample atsub-freezing temperatures to more closely simulate the actual Marssurface conditions. A previously used test cell was required for thiscycle because all four test cells had been used. A surface sampleranomaly during the sample acquisition attempt on Sol 195 prevented thecollection of a fresh sample. Thus, a sample collected on Sol 145 wasused for VL2 cycle 5. The sample was stored for 84 sols prior tonutrient injection. The 0.5 cc sample was placed on top of about 1.2cc of unused sample dumped into the cell from previous acquisitionsplus about 0.5 cc of material from VL2 cycle 1.The LR instrument froze prior to nutrient injection during a powershutdown. It is possible that nutrient delivery lines or valves mayhave ruptured due to freezing. In addition, only a small amount ofnutrient (0.64 cc) was calculated to remain in the reservoir. Thus,it is not clear whether a complete nutrient injection was delivered,although as least a partial delivery is likely [LEVIN&STRAAT1979A]. Sample Site : Beta Collection Temperature : -84 deg C Collection Sol : 145 (stored) Experiment Type : Soil-on-soil in used cell First Injection Sol : 229 Purge : N/A
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| DATA_SET_RELEASE_DATE |
2001-07-15T00:00:00.000Z
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| START_TIME |
1976-07-22T09:54:23.000Z
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| STOP_TIME |
N/A (ongoing)
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| MISSION_NAME |
VIKING
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| MISSION_START_DATE |
1975-08-20T12:00:00.000Z
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| MISSION_STOP_DATE |
1983-02-01T12:00:00.000Z
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| TARGET_NAME |
MARS
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| TARGET_TYPE |
PLANET
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| INSTRUMENT_HOST_ID |
VL1
VL2
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| INSTRUMENT_NAME |
LABELED RELEASE MODULE
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| INSTRUMENT_ID |
LR1
LR2
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| INSTRUMENT_TYPE |
BETA DETECTOR
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| NODE_NAME |
Geosciences
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| ARCHIVE_STATUS |
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview:The sources for the LR data were microfilm stored at NSSDC andphotocopies of Co-Investigator P. A. Straat's original computerlistings. The P. A. Straat computer listings were used as the primarydata source with the microfilm data used to fill in gaps. Themicrofilm contained images of computer pages with variable quality.The data transcribed from the P. A. Straat source were entered twice.The two versions were compared and corrected to ensure that the twoversions exactly matched. For the microfilm data source, informationwas manually entered by one person and then checked by a differentindividual.For VL2 Cycle 3, there was some data that were available in bothsources. A comparison of about 2000 radioactivity readings revealed a0.25% error rate (5 values total) in NSSDC's keypunch and qualitycontrol process. The errors found included a single digit miskeyed,two digits reversed, or fractional digits replaced with zeroes. It ispossible that the error rate is similar for data values where themicrofilm is the only source. The NSSDC microfilm remains availablefrom NSSDC for access by future users.Data Coverage and Quality:Steps were taken to insure that this data set is complete and containsas few errors as possible. However, there are several data gaps.Most data gaps are on the order of one or two sampling intervals, butsome are on the order of Sols. It would appear that these data werenever taken or lost in transmission.The data set contains a few spikes of spurious readings. These areusually obvious as a single data point that is very much larger thanthe values prior to and after the spike.
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| CITATION_DESCRIPTION |
Levin, G.V., VL1/VL2 Mars Labeled Release V1.0, VL1/VL2-M-LR-2-EDR-V1.0, NASA Planetary Data System, 2001.
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| ABSTRACT_TEXT |
Labeled Release (LR) Viking Lander data.
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| PRODUCER_FULL_NAME |
P. G. VALKO
JOSEPH H. KING
PATRICIA ANN STRAAT
GILBERT V. LEVIN
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| SEARCH/ACCESS DATA |
Geosciences Web Services
Geosciences Online Archives
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