PDS_VERSION_ID = PDS3 RECORD_TYPE = "STREAM" LABEL_REVISION_NOTE = "2007-09-12 LDP:McLaughlin Created. 2008-06-21 LDP:McLaughlin Resolved liens from the Dec 2007 peer review. 2008-10-16 GEO:Slavney Corrected APOLLO15A1972 reference key ID. 2020-09-18 GEO:White Added authors." OBJECT = DATA_SET DATA_SET_ID = "A15A-L-CCIG-3-ATMOS-DENSITY-PLOTS-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "APOLLO 15 ALSEP/CCIG REDUCED ATMOSPHERIC DENSITY PLOTS V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = "TABLE" START_TIME = 1971-07-31T18:56:00 STOP_TIME = 1973-09-12T17:52:00 DATA_SET_RELEASE_DATE = 2007-12-07 /* Peer-review date */ ARCHIVE_STATUS = "LOCALLY ARCHIVED" PRODUCER_FULL_NAME = {"DAVID WILLIAMS", "FRANCIS JOHNSON"} DETAILED_CATALOG_FLAG = "N" DATA_SET_TERSE_DESC = "Digitized plots of the density of the lunar atmosphere as measured by the Apollo 15 Cold Cathode Ion Gage from 31 July 1971 through 12 September 1973." ABSTRACT_DESC = "This data set contains digitized plots of the density of the lunar atmosphere as measured by the Apollo 15 Cold Cathode Ion Gage from 31 July 1971 through 12 September 1973." CITATION_DESC = "Johnson, F.S. and D.R. Williams, APOLLO 15 ALSEP/CCIG REDUCED ATMOSPHERIC DENSITY PLOTS V1.0, A15A-L-CCIG-3-ATMOS-DENSITY-PLOTS-V1.0, NASA Planetary Data System, 2007." DATA_SET_DESC = " Data Set Overview ================= This data set contains digitized plots of the density of the lunar atmosphere as measured by the Apollo 15 Cold Cathode Ion Gage from 31 July 1971 through 12 September 1973. Data ==== These data are digitized as part of the Lunar Data Project from experimenter-generated, 35-mm microfilm reels containing plots of lunar atmosphere density measurements and instrument temperature as a function of time. Each frame consists of two plots with a common abscissa. The abscissa gives the time of the measurement in the form DDD/HH/MM where DDD is day of year, HH is hour, and MM is minute. All times are Greenwich Mean Time (GMT). The lower plot gives measurements of the equivalent density for a nitrogen lunar atmosphere in particles per cubic centimeter on a logarithmic scale that ranges from 10 E4 to 10 E10 [10 E4 = 10 x (10 to the 4th power) = 100 000.] The upper plot gives the instrument temperature on a linear scale from 0 to 400 Kelvin. Most frames hold 15 hours of data. Note that the ordinate range and scale are identical for all plots, the time scale on the abscissa is the same for most plots (some plots use an expanded scale) but the actual time range is different on each plot. The data are not complete, the instrument was turned off on 18 July 1975, the later data were never received at the NSSDC. In the normal operational mode the basic cycle repeated five measurements (separated by 2.4 s), three measurements (separated by 40 s), and 16 seconds of calibration and auto-zeroing every 2.5 min. Each of the measurements is represented by one point on the graph. In a ground commanded special mode, one measurement was obtained every 2.4 s, with no other measurements being performed. There is no note on the plots indicating which mode the instrument is in. The actual raw signal returned by the instrument was the current measured by the sensors. The sensors were calibrated in pre-flight tests using a pure nitrogen (N2) atmosphere. The values shown on the plots have been converted from the sensor-measured current reading to the equivalent nitrogen-2 atmosphere density using the calibration curves of the appropriate gage and temperature sensor. The results are expressed in terms of the nitrogen-2 concentration which would produce the observed current after correcting for temperature. The response of the instrument depends to a rather modest degree on the composition of the gas, which is not known, but it is assumed the true value will vary from this nitrogen-2 concentration by a factor smaller than 2. The instrument underwent high-temperature arcing during the daytime, often indicated by data dropouts or switching between data modes. Daytime data was also dominated by outgassing, particularly for the first few lunar days. The CCIG was turned off for periods during the lunar day early in its operational history because of this. Sunrise and sunset effects were observed, and bursts were seen at night, particularly at pre-dawn times, which are believed to be real argon-40 events. The NSSDC digitized the original 35-mm microfilm reels of experiment-generated plots, data set PSPA-00099, as part of the Lunar Data Restoration project. See Johnson, et. al (1972A) [JOHNSONETAL1972A], Johnson, et. al (1972B) [JOHNSONETAL1972B], Hodges, et. al (1974) [HODGESETAL1974], and the Apollo 15 Preliminary Science Report [APOLLO15A1972] for more information about the atmospheric density data from Apollo 15. The Apollo 17 Lunar Atmosphere Composition Experiment (LACE) and the Apollo 15 and 16 Lunar Orbital Mass Spectrometers (LOMS) also returned data complementary to the CCIG instrument. For more information about these experiments, see Hoffman, et. al (1973) [HOFFMANETAL1973] and Hodges, et. al (1972) [HODGESETAL1972]. Scanning Procedure ================== The media chosen for storage of the original data was 35-mm silver microfilm. This microfilm was archived at NSSDC and was scanned to produce this digital data set. The actual size of a frame on the microfilm is 19 x 29 mm. The microfilm was mounted on an E-Image Data Scan Pro 300, previewed to allow settings for optimal scanning, and scanned at a resolution of 400 dpi (dots per inch) into tiff format using Photoshop CS2. The original images were black and white negatives, the images were scanned as positives. Each scan captured one frame. The machine is manually refocused every 3 to 5 scans. A resolution of 400 dpi was chosen as the optimal tradeoff between clarity of the plots and scanning time required. Plots scanned at 600 dpi did not show noticeable improvement while requiring roughly twice the scan time. Plots scanned at 300 dpi were not as clear as the plots scanned at 400 dpi. No enhancement was performed on the image after scanning. At a later date the data user may choose to enhance the image or can request the original microfilm using the ID to identify the requisite frames. Each frame was checked as part of the quality assurance (QA) process, frames that were unclear, corrupted, or missing were rescanned. The scanning resulted in banding in many of the images, with bands of lighter and darker background color on the plots. These bands are not on the original plots and are an artifact of the scanning process. (The location of the bands changes with each scan.) The banding appears to have no effect on the readability of the data and is checked in real time as the frames are scanned and then the scans are compared to the originals as part of the QA process for any effect on the readability of the data. The original microfilm reel has many splices where the frames are joined together. These do not affect the data but the locations of the splices have been noted in the index and the label. Occasional short overlaps in the time span have also been found on the microfilm. It is assumed that during the original creation of the microfilm or of the computer printout some of the frames were redone. These instances are noted in the index and the comments in the individual label file. The frame names are in the form AnnA_CCIG_yy_mmmmmmm_fff.tif where Ann is for the Apollo mission (that is, A15), the second A is for the ALSEP experiment CCIG is Cold Cathode Ion Gage, yy is the year of the data (such as, 71 for 1971), mmmmmmm is the microfilm reel ID, and fff is the frame number on that reel. Scans are numbered by position on the microfilm to allow recovery of original analog data if necessary. This data set description was provided by the NSSDC. " CONFIDENCE_LEVEL_NOTE = " Confidence Level Overview ========================= The files were scanned directly from microfilm. The original scans were done with the optimal focus and contrast, but no attempts were made to enhance the digital images. Some images are difficult to read and may benefit from further enhancement by the user. Review ====== This data set was peer-reviewed in December 2007 and was accepted for the PDS archive pending the resolution of liens (completed in June 2008). " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = "MOON" END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = "A15A" INSTRUMENT_ID = "CCIG" END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_MISSION MISSION_NAME = "APOLLO 15" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "APOLLO15A1972" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HODGESETAL1972" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HODGESETAL1974" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HOFFMANETAL1973" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "JOHNSONETAL1972A" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "JOHNSONETAL1972B" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END