Astronaut Scientific Debriefings, 1962-1963

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Sunrlse was observed at about 1m later, while the observation was going on.
It follows that the airglow is visible even when the twilight band is very
strong.
An attempt to observe it in the day is certainly indicated.
In this
connection, it should be noted that Capt. V. I. Grissom reported a grayish band
at the top of the blue sky layer.
(Pesults of the Second U. S. Manned Subqrbital
Space Flight,
NASA, GPO (1961). le remembers this layer as narrow and grayish
i n color, representing an actual i ncrease in intensity.
He poi nted out the
approximate position of the layer on one of Lt. Cdr. Carpenter's photographs
at the height of 1.7 degrees above the horizon.
Grissom may have observed the
daytime airglow.
Carpenter did not note any structures, either vertical or horizontal,
in this layer.
He did not observe it completely around the horizon but believes ·1 l
to be continuous all the way.
It does not appear possible that this layer can
actually absorb starl:ight.
Any layer at this level capable of absorbing a
noticeable fraction of the light (25i or more) would also scatter light strongly;
it would therefore be a very prominent object on the daylight side.
In fact, it
is not definitely visible on the photographs of the day side.
Thl s i s entirely
i. n agreement with Lt. Cdr. Carpenter's impression, namely that the decreased
visibility of stars passing through the layer was a contrast effect.
A remarkable feature of this observatton is the discrepancy between
the eye estimates of 8',.10° for the alti tudes above the hori zon, on the one
hand, and the results of timed observations on the other.
The latter i ndicates
altitudes of 2° to 36 .
The latter are clearly correct; f or example, Carpenter
noted that when one ann of his reti cle was at an angle of 45°, it covered the
space between the horizon and the bright band.
The crossann is 1.21 centi meters
i n length and it is a distance of 26.2 centimeters from the astronaut's eye.
At an angle of 45°, i t subtends a vertical angle of about 2°.6.