# Presentation: 362650

## Apollo 14 Cold Cathode Ion Gage

- General Instrument Description:
- Measures the neutral gas density at the lunar surface
- Range - 2 x 105 to 1010 part./cm3 Nitrogen equivalent (Note:
- the dominant gas in the lunar atmosphere is Ne.)
- Provides the ambient temperature in Kelvins
- Data format is scanned microfilm plots
- Time period covered by data: Feb 1971 to Dec 1973
- Science tasks attempted:
- Looked for sunset/sunrise effects and diurnal density changes
- Looked for sporadic gas bursts at night
- These tasks were generally successful -
- Sunset/sunrise effects were observed (see plot on following page)
- and the expected predawn density increase due to Ar40 was observed,
- however, daytime densities are obscured by high
- background - presumably due to outgassing.
- Numerous bursts were seen at night.

- Freeman - Apollo Dataset Review

## Apollo 14 Cold Cathode Ion Gage

- General Impressions and Issues:
- Overall, the data description, documentation and support documentation are complete and accurate
- There is one error in the A14 instrument overview - In the file a14_ccg_0001/CATALOG/INST.CAT and all succeeding INST.CAT files two sentences in the 2nd paragraph of the Instrument Overview actually refer to the A15 instrument. This is not readily apparent to the untrained reader.
- Note: there is a major error in the A15 documentation. See note on A15 on the last slide.
- Generally, the dataset is suitable for use and science can be done. However, the CCIGs were rendered somewhat obsolete in terms of science by the deployment of the Lunar Atmosphere Composition Experiment (LACE) on Apollo 17. The LACE provided a lunar surface mass spectrometer. Also, the Lunar Orbital Mass Spectrometer (LOMS) provided supplementary data.

- Freeman - Apollo Dataset Review

## Apollo 14 Cold Cathode Ion Gage

- Further issues:
- The quality of the scanned plots is bad. It is generally impossible to
- Make out the printing on the labels on the x- and y- axes. The
- Figure on the following slide is an actual plot. This is not a showstopper.
- The scale marks on the y- axis are often outside the frame and
- therefore cannot be read. More care should have been used in scanning.
- There is frequent arcing during the day that renders some data
- useless including the temperature data.
- I think much of the daytime data are swamped by outgassing.
- I suspect that the true densities are below the instrument threshold
- At night. However, night-time bursts are probably real.
- An A to D converter failed causing a loss of much temperature data
- later in the mission.

- Freeman - Apollo Dataset Review

## A typical plot from the A14 CCIG Dataset. Note 

- A typical plot from the A14 CCIG Dataset. Note
- That the legends are unreadable. This does not
- mean that the dataset is unusable. With a little
- effort it is possible to do qualitative work.

- Temp

- Density

- Freeman - Apollo Dataset Review

## Apollo 14 Cold Cathode Ion Gage

- Further matters:
- Completeness of description - The instrument description is good.
- (It would be nice to know more about when to trust the dayside data
- but this would be a great burden on the PIs.)
- Completeness of dataset - There are data gaps when the CCIG was
- turned off due to arcing during the day. This is unavoidable.
- Data from the later year of operation are missing from the dataset.
- Why?
- Interpretability - The data can be interpreted.
- References - The referencing is adequate.

- Freeman - Apollo Dataset Review

## Apollo 15 Cold Cathode Ion Gage

-   In the Apollo 15 documentation the following files all refer to the A14 instrument:
- DATASET.CAT
- INST.CAT
- INSTHOST.CAT
- MISSION.CAT
- VOLDESC.CAT
-   Likewise, the files: DATA/A15_CCIG_71_MO4674.LBL and DATA/A15_CCIG_71_MO4674.TXT
- all contain Apollo 14 data instead of A15 data.
- Most of the issue comments already made for A14 apply to A15.

- Freeman - Apollo Dataset Review