night. It appeared to him to 1)(' several c.:egrees above the sohd
eat'til ~lIrfaL'e
quart!'r of the fi C' ld of vi cw out of the wi nunlv'
anJ this slll'pr;"cd 1110. r thought I wa~; looking
at clo'H.ls all the till.':) until I saw stars down at
the bottom or underneath the glowing layer.
night. Tt apl'C'al'C'J to him to be several ":egrees above the solid
c'' and the
solid enrth surface is b<:rely discernible (Plate 14); as a matter of
fact i t i~, eas jeT to use the airglow layer than the earth edge as a
reference in making sextant measurements of angular elevations of
staTS.
Ground-based studies of the night airglow show that It is com-
posed of a number of separ:lte and distinct layers. The layer visihl
to the astronauts is a narrow one at a height of about lOll km. which,
seen tangentially by the astronaut!'. is eflsily visihle. (It can be
seCll from the eart~'s surface only marginally but is easily mea~ured
with photometers.)
At a height of ab~ut 250 km. there is another airglow layer which
is especially prominent in the tropics. It is probable that airglow from
this higher level was seen on two occasions. Astronaut Schirra
(~1:'-8) !'eported a faint luminosity of a patchy nature whl Ie south of
~\adaga5car. looking in the general direction of India (NAS,I\. ::;1'-12,
page 53, 3 October 196~) us follo~s:
A smog-appellring layer was l'viucnt Juring
the fourth r[l!,s "h i Ie 1 "a~;n tlrifting flight
on the n.ight :;idc. almost at :'12" south latituue.
I Wl.lultl ~ay Clilt tlii·; 1[1ycr repte~entctl about '
qunl'tPI' of the fil'ld of vi ow Ollt of the wi nuolv'
ant! this slIl'pr;,'icd 111(). r thought 1 was looking
at clo'H.is all the til],(, until I saw stars down at
the bottom or Ilildelneath 'the glowing layer.
( (