NASA PDF RELEASE 2026-05-08 INC. 1973 ⌥ 524 WORDS OCR

NASA-UAP-D005, Apollo 17 Crew Debriefing for Science, 1973

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This document is an excerpt from the Apollo 17 Crew Debriefing for Science, dated January 8, 1973, produced by NASA's Manned Spacecraft Center in Houston. It records a technical briefing by Dick Henry, co-investigator on the Apollo 17 ultraviolet experiment. Henry describes results from UV observations made at high galactic latitudes during the mission, specifically the detection of a spectral signature resembling that of a hot star in regions where no hot stars were known to exist within the instrument's field of view.

The document is notable for Henry's candid acknowledgment that the observed UV spectrum does not fully conform to the leading explanatory theory — that hot starlight from the galactic plane is scattering off interstellar dust — and that extragalactic radiation remains a viable alternative explanation. The record contains no redactions in the excerpted pages. In the context of UAP-related document releases, the significance is not obvious from the text itself; the anomalous UV background described is a recognized astrophysical puzzle and does not reference unidentified aerial phenomena directly.

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Apollo 17 was the ninth crewed U.S. mission to the Moon, and the sixth to land Astronauts on the lunar surface. This document is an excerpt from the Apollo 17 Crew Debriefing for Science on January 8, 1973, in which Dick Henry, co-investigator on the ultraviolet experiment on Apollo 17, discusses seeing results that were unexpected. • Pages 119-120. “One of the most exciting results of X-ray astronomy was the fact that an X-ray background was observed over the sky that nobody had expected, and part of this is the gamma-ray background that Dr. Trombka talked about. In the UV, nobody knows, but you never know until you look. You do have to deal with this background of stars that we know is there. So, we did look at a large number of different points at high galactic latitudes, both north and south. The spectrum that we see is above this dark count. In other words, this abnormally high dark current did not, in fact, interfere with that experiment. The spectrum that we see looks like the spectrum of the hot star; however, we know that there were no hot stars within our field of view. Therefore, the most conservative interpretation, I think, is that what we're seeing is light from hot stars in the galactic plane going up out of the plane and reflecting off interstellar dust. There are certain characteristics of the spectrum, though, that don't fit that theory, and it's at least possible that this is extragalactic radiation. I'm looking forward very much to the detailed computer study of this, but it's going to take a long time.”

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VASA MSC-07632 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION APOLLO 17 CREW DEBRIEFING FOR SCIENCE JANUARY 8, 1973 PREPARED BY SCIENCE REQUIREMENTS BRANCH PLANETARY AND EARTH SCIENCES DIVISION INDEXING DATA DATE 1-8-73 OPR MSC M52 - 07632 PGM APO SUBJECT SIGNATOR NS LOC 080-44F MANNED SPACECRAFT CENTER HOUSTON, TEXAS 951-481238

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HENRY ( CONT ' D) 119 gravitationally holding it together. We though it might be in the form of ionized hydrogen. We looked for Lyman-alpha radiation, red shifted from the ionized hydrogen, and we didn't see any. We set a lower limit, which certainly ex- cludes the possibility that the Coma cluster is held together by this ionized hydrogen. I think that may leave a real mystery as to what is holding the thing together. The fourth point may turn out to be the most interesting thing of all. When you look in the Milky Way, you see a lot of UV coming from the stars, but the question is, what do you see when you look up to the North Galactic Pole or down to the South Galactic Pole. One of the most exciting results of X-ray astronomy was the fact that an X-ray back- ground was observed over the sky that nobody had expected, and part of this is the gamma-ray background that Dr. Trombka talked about. In the U, nobody knows, but you never know until you look. You do have to deal with this background of stars that we know is there. So we did look at a large number of different points at high galactic latitudes, both north and south. The spectrum that we see is above this dark count. In other words, this abnormally high dark current did not, in fact, interfere with that experiment. The spectrum that we see looks like the spectrum of the hot

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120 HENRY ( CONT 'D) star; however, we know that there were no hot stars within our field of view. Therefore, the most conservative inter- pretation, I think, is that what we're seeing is light from hot stars in the galactic plane going up out of the plane and reflecting off interstellar dust. There are certain characteristics of the spectrum, though, that don't fit that theory, and it's at least possible that this is extragalactic radiation. I'm looking forward very much to the detailed computer study of this, but it's going to take a long time. Fifth point: Lyman-alpha hydrogen radiation is a completely separate problem, and Gary Thomas at the University of Colorado and Charles Barthum [?] observed this from OGO-5. We obtained just an enormous amount of data on the Apollo that's going to straighten out this picture and clarify it considerably. This is hydrogen that is inside our solar system. It's sunlight reflecting off this. The hydrogen, Gary Thomas thinks, is hydrogen from interstellar space streaming through the solar system, and he is looking for- ward with great anticipation to getting detailed analyses of that. One more thing: the spectrum of the Earth. I keep saying "we," but these were the guys that were there. We looked at the Earth from outside. A lot of people have observed

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