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APOLLO 17 HEAT FLOW THERMAL CONDUCTIVITY RDR SUBSAMPLED V1.0 (PDS)

NSSDCA ID: PSPG-01086

Availability: Archived at NSSDC, accessible from elsewhere

Time span: 1972-12-12 to 1974-12-31

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview

This data set comprises a reduced, subsampled set of the data returned from the Apollo 17 Heat Flow Experiment (HFE) from 12 December 1972 through 31 December 1974. The experiment consisted of two probes placed by the Apollo 17 astronauts in holes drilled in the lunar surface near the Apollo 17 Lunar Surface Experiments Package (ALSEP) site to measure the thermal conductivity. For more information on the experiment and instrumentation see the instrument.cat file in this directory. The data consist of a set of ten ASCII tables with time, temperature differences, and average temperatures readings measured by the thermocouples in the heat flow probes and probe cables. The data have been restored and reformatted from binary data held on magnetic tapes at the NASA National Space Science Data Center (NSSDC) under NSSDC ID of PSPG-00022 (old NSSDC ID 72-096C-01A).

Data

The data for each probe are divided into 5 files. All numbers in the files are of the form E14.7 (e.g. [1.8388079E+10]). The first column in each file contains the time in milliseconds from 24 hours before the beginning of the year in which the mission was launched. (Apollo 17 was launched in 1972, so the time in milliseconds is measured from 00:00 UTC on 31 December 1971. For example, the elapsed time in milliseconds at 01:00 UT on 1 January 1972 would be 90,000,000. The leap year 1972 and the single leap second added on each of 30 June 1972, 31 Dec 1972, and 31 Dec 1973 -- in which the heat flow timing of elapsed seconds would keep counting while the UT clock would be ''stopped'' for a second -- were incorporated into the computed UT start and stop times in this data set.) The files are arranged in chronological order with a few exceptions noted at the end of this description. Files 1, 2, 4, and 5 contain the temperature difference between the upper and lower ends of the bridge (column 2) and the average temperature (column 3) in degrees Kelvin. File 1 is for the upper section gradient bridge (DTGx1, x is the the probe number), file 2 for the lower section gradient bridge (DTGx2), file 4 for the upper section ring bridge (DTRx1), and file 5 the lower section ring bridge (DTRx2). Note that for each bridge, the upper sensor is designated with an 'A' and the lower sensor with a 'B' (e.g. DTG11A and DTG11B), see the INST.CAT file for more details on the naming convention. File 3 contains the heater state (column 2), the reference bridge temperature (column 3), and the cable thermocouple temperatures (columns 4-7 corresponding to TC_1 through TC_4 respectively). The file naming convention is as follows: the first seven characters identify the Apollo mission and the heat flow experiment (A17_HFE); the next two characters identify the probe, P1 for probe 1, P2 for probe 2; finally, the last character before '.tab' gives the file number, 1 through 5. The files contained in this data set are: A17_HFE_P1_1.TAB - Probe 1 upper section gradient bridge DTG11 (approximately 130 cm to 177 cm depth) A17_HFE_P1_2.TAB - Probe 1 lower section gradient bridge DTG12 (approximately 185 cm to 233 cm depth) A17_HFE_P1_3.TAB - Probe 1 heaters and thermocouples A17_HFE_P1_4.TAB - Probe 1 upper section ring bridge DTR11 (approximately 139 cm to 168 cm depth) A17_HFE_P1_5.TAB - Probe 1 lower section ring bridge DTR12 (approximately 194 cm to 224 cm depth) A17_HFE_P2_1.TAB - Probe 2 upper section gradient bridge DTG21 (approximately 131 cm to 178 cm depth) A17_HFE_P2_2.TAB - Probe 2 lower section gradient bridge DTG22 (approximately 186 cm to 234 cm depth) A17_HFE_P2_3.TAB - Probe 2 heaters and thermocouples A17_HFE_P2_4.TAB - Probe 2 upper section ring bridge DTR21 (approximately 140 cm to 169 cm depth) A17_HFE_P2_5.TAB - Probe 2 lower section ring bridge DTR22 (approximately 195 cm to 225 cm depth) Two numbering conventions exist in the literature for the thermocouples. We are using the convention that TC14 designates the thermocouple at the top of probe 1, TC13 is the cable thermocouple closest to probe 1, followed by TC12 and TC11. Probe 2 would have TC24, etc. (Another convention, seen in the Preliminary Science Reports, has the probe thermocouple designated as TC11, followed successively in the cable by TC14, TC13, and TC12.) The data are kept in separate files for each bridge because the measurement times were different. The measurement time intervals for a given sensor would vary over the course of its operation, so it should be noted that the time sequences in the data sets do not necessarily follow a linear pattern. In normal operating mode a 7.25 minute measurement sequence is used to collect the ambient high- and low-sensitivity differential data from the gradient sensors and the thermocouple outputs. The same measurement sequence would be used when the heaters were commanded on for the low conductivity (0.002 W) mode, with the heaters activated in turn for typically 36 hours. For the high-conductivity (0.5 W) sequence, the ring bridge sensors were used and were read every 54 seconds. This mode nominally would last 8 hours. This mode could also be done without the heaters on, with measurements simply being made by the ring bridge sensors. This mode, known as a ring bridge survey, would be used approximately every 6 hours at first and less frequently later in the experiment. However, the data archived here only represent subsampled data, typically at 57 minute intervals. The instrument was turned on 12 December 1972 and the first reading listed from probe 1 is at 03:05:47 UT. The first reading listed from probe 2 is at 03:08:27 UT. Please note the heat flow instrument was turned on while probe 2 was being inserted into the borestem, temperatures recorded only minutes after drilling was completed. On 18 February 1977 an anomaly occurred in probe 2 at the 230 cm level. The instrument was commanded off along with the other ALSEP experiments on 30 September 1977. The heaters were turned on and off in the low power (0.002 W) mode in January 1973 as follows, with the heater designation followed in parentheses by the depth of the heater, the date and time the heater was turned on, and the date and time the heater was turned off, in UT. For probe 1: H11 (130 cm, 3 Jan. 05:58 - 4 Jan. 18:00); H12 (177 cm, 14 Jan. 00:03 - 15 Jan. 11:48); H13 (185 cm, 21 Jan. 00:03 - 22 January 12:31); H14 (233 cm, 8 Jan. 06:21 - 9 Jan. 16:02). For probe 2: H21 (131 cm, 5 Jan. 05:18 - 7 Jan. 06:07); H22 (178 cm, 16 Jan. 12:06 - 18 Jan. 00:05); H23 (186 cm, 23 Jan. 00:31 - 24 Jan. 12:30); H24 (234 cm, 10 Jan. 05:59 - 11 Jan. 17:59). On 25 January at 18:00 UT H14 was turned on at high power, 0.5 W, and was shut off at 20:30 UT. The nominal data returned from the mission comprised a series of measurement times, 8 series of temperature differences for each sensor bridge pair (4 from each probe), 8 series of average temperatures for each bridge pair, 8 series of cable thermocouple measurements, and a series of temperature measurements from the electronics box. The original data were sent to NSSDC written on four 7-track magnetic tapes (one for each probe) at 800-bpi by an IBM 1130 Model 2415 tape unit. The data were in 32-bit floating point binary and were separated into 5 files in standard IBM 1130 floating point two-word format. Programs were written to read these tapes and translate them into fixed-width, flat ASCII tables at the NSSDC. The Apollo 17 tapes cover the time span from 03:05:47 UT 12 December 1972 to 22:05:17 UT 31 December 1974. The nominal density on the tapes is about one point (logical record) per hour, although some samples were done at a much lower time resolution. A reformatting process was applied at NSSDC in June 2005 to the Apollo 17 Heat Flow Experiment tapes to produce a set of five data tables for each of the two different probes associated with the instrument. All data from a given probe are together in one 'file' as archived in the original data sets noted above. Each 'file' as mentioned in the documentation for the original data set is actually a group of physical records that make up only a part of the original archived file. The physical records are written blocked, with 100 logical records per physical record. Where the data did not fill a complete physical record at the end of a group, the original data had zero values inserted to fill out the 100-logical-record physical record. The logical record size (in 4-byte words) is either 3 words (for files 1, 2, 4, and 5) or 7 words (for file 3). To make the data easier to use, NSSDC separated these groups of physical records into separate files (in the usual meaning of a file) by selecting the appropriate physical records from the archived data file. Thus each original binary archive file resulted in five new ASCII data files, matching the descriptions of the 'files' as described in the original data set documentation. In some cases, the number of physical records in the 'file' was found to be one less than indicated in the documentation. The new output files are written in ASCII, unblocked, and the records containing only fill values have been deleted. In the NSSDC processing program written by H. K. Hills, a physical record of binary data was read in, then the order of the four-byte words in the record was inverted, making the records advance in chronological order (instead of last to first as in the original archived data set). Then the byte order (within a 4-byte word) was inverted to put the bytes together properly in the VAX word (because of the way the VAX handles input tape records). Then the sign, mantissa, and characteristic of the values were selected as bit strings and moved into their own separate computer words, after which the value of each data word was computed. In cases where the input word value was zero, the output value was set to a flag value of -9999 (or -9.999000E03). The logical three-word records or seven-word records were written out in ASCII directly to disk files with no blocking. Trailing filler records of zero values were deleted. These new ASCII data tables have the records in nominal chronological order (i.e., the inverse of the order on the original tapes), but there are exceptions where the time of a given point is slightly less than the time of the previous point. The error occurs in the 6th to the 8th significant digit of the time. No such time irregularities were seen in most files, but there were numerous such cases in A17_HFE_P1_3.TAB. No attempt was made to remove these time discrepancies. There are also occasional anomalous temperature readings or data spike errors in column 3 (TEMP), which may be a result of telemetry errors, tape writing or reading anomalies, or other minor faults. These errors are in most cases very obvious, and we have not attempted to remove the anomalous readings. We note that in general the use of heat flow data is for the study of long-term trends, and the preferred way of dealing with these anomalous data in most cases would be to ignore them.

These data are available on-line from the Planetary Data System (PDS) at:

https://pds-geosciences.wustl.edu/lunar/a17a-l-hfe-3-thermal-conductivity-v1/a17hfe_0001/

Alternate Names

  • A17A-L-HFE-3-THERMAL-CONDUCTIVITY-V1.0

Discipline

  • Planetary Science: Geology and Geophysics

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Marcus G. LangsethData Provider
Dr. Kenneth PetersGeneral Contact
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