If you have not yet read the radiation
primer, you are invited to do so.
David Groves, PhD, has
shown that the x-ray environment of space would quickly render any
photographs unusable. [Bennett and Percy, Dark Moon,
Dr. Groves' study contains a number of serious errors.
Although Dr. Groves gives figures for the x-ray dosage to which he
submitted his test films, he does not in any way show that this is the
expected amount of x-ray energy that exists anywhere in cislunar space
or on the lunar surface. This key omission makes Dr. Groves' study of
Dr. Groves used a Bronica ETRSi 120 roll film camera in his tests.
He does not explain why he did not use a Hasselblad EL/500 or EL/700
camera, the type of camera supplied to NASA for use in the Apollo
missions. It is still manufactured by Hasselblad and suitable period
examples of which can be obtained easily from second-hand dealers.
Use of a dissimilar camera limits the extent to which Dr. Groves'
results can be applied to Apollo photographs.
Further, Hasselblad claims they added additional protection to the
film magazines. Dr. Groves does not document any similar changes he
may have made to the film magazine of his test camera. Nor does he
comment upon the possible effect of any of those modifications.
Dr. Groves' inattention to the specifics of the Apollo camera design
questions his ability to accurately simulate the effects of x-rays on
Dr. Groves first took pictures of a standard color chart, then
bombarded that film with x-rays. Then he used standard procedures to
develop the film and observe the results. He found that the images
were significantly fogged in some cases, and completely obliterated in
more extreme cases.
He provided absolutely no shielding around the film during its
exposure to the x-rays. It is unclear whether he left the film inside
its magazine as the Apollo astronauts would have done. Since the
Hasselblad magazines were modified to provide thicker material for the
casing, and the film was kept in the magazines during the entire
mission, it is not clear whether Dr. Groves' procedure constitutes an
What is clear, however, is that Dr. Groves exposed the film to
x-rays thousands of times more intense than what occurs in space. He
used a linear accelerator to bombard the film with an 8 MeV (million
electron-volts) beam of x-rays. X-ray astronomers say the x-rays from
celestial sources radiate at energy levels of less than 5 keV
(thousand electron-volts). The measurement of x-ray energy is similar
to the rating of light bulbs by wattage. The difference between five
thousand electron volts -- ambient x-rays in space -- and eight
million electron-volts -- Dr. Groves' experiment -- is obviously
very large. This factor alone invalidates Dr. Groves' study as an
accurate depiction of the ambient x-ray conditions in space.
Energy level is quite important. Not only do more energetic
x-rays fog film to a greater extent, they also penetrate various
substances to a greater extent. This makes the question of shielding
very acute. 3 keV x-rays, for example, will not even penetrate air
for more than a dozen centimeters.
Dr. Groves exposed his film to x-rays more than a thousand
times more energetic than occur in space.
The experiment subjected the film to three levels of exposure, all
at the absurdly intense 8 MeV energy level. The levels are given in
the study as "25 rem", "50 rem" and "100 rem". Those who have read
the primer and studied the nomenclature
of radiation will immediately realize that this is the wrong unit.
"Rem" applies only to absorbed radiation in human tissue. It
is completely inapplicable to radiation absorbed by photographic
film. The appropriate unit of measure for this study would be either
"rads" or "Grays". It so happens that for x-rays 1 rad is equivalent
to 1 rem, but Dr. Groves' apparent misunderstanding of the concepts of
absorbed dose is very much out of place in a study purporting to give
an expert opinion on radiation exposure.
If we graciously correct Dr. Groves' error of nomenclature and
assume he means exposures in rads, we are still faced with two further
questions. First, how was absorbed dose computed? It is notoriously
difficult to measure the amount of radiation actually absorbed by any
Second, the 25-100 rads to which Dr. Groves exposed the films is
quite excessive. It would take nearly six years in a
spacecraft in cislunar space -- barring any serious solar events -- to
absorb 25 rads of dosage from all sources combined, not just from
Dr. Groves' study contains far too many egregious errors to be
considered predictive in any way of the behavior of Ektachrome film
under the conditions experienced during Apollo space flights. He has
employed levels of radiation far in excess of what can be defensibly
claimed for ambient x-ray radiation in cislunar space.