cycle dependence could account for the fact that the Gemini astronaut~
(1965-1966), although alerted to look for this "high airglow," did
not see it.
The Aurora
'nle ~lercury and Gemini orhi ts were confined within geographlc lat-
itudes of 32°N and 32°5. Since the auroral zones are at geomagnetic
latitudes of 67°N and 67°5 it would seem unlikely that auroras could
be seen by the astronauts. 1I0wever two circumstances were favorahle
for such sightings. Fir!'t, the "dip" of the horizon at orbital hei,;ht5
rllt~ tne viewed ho1'i:on at a consiJcrable distance from the suh-satellite
point. For example at a ~ntelli te height of 166km. (perigee for (;'1'-4)
the dip of thE' hod zon i~; about t 3° and at a height of 297 km. (apogee
for Gl-4) it is about IJ~ Second, the auroral zone, being controlled
by the geomagncLLc fielJ, is inclined to parallels of geographic lat-
itude as iilt.strateL! in Plate IS. Nighttime passes over the castern
United States or over sOllthern Australia bring the spacecraft closest
to the auroral zone. On several occasions auroras were seen in the
Australia-New :ealanJ region. Plate 16 (Fig. 32-7 of NASA SP-121) shows
a reproduction of a sket:h made by the Gemini 7 crew. An auroral arch
is seen below the a3rglow layer.
The Vis ibili ty of Stars..
Satellite orbits ' the full astronomical panoply. This was dee;ueuly not the
cas(;'. All the AJ1lCrjl~an astronauts have expresscu themselves Illost force-
fully that JllriJ1~ satel lite daytime, Le., when the sunjs above the
horizon, they CL'uld not ~ce the stars, even the brighter ones. Only
on Cl fCh' occa~ lons, if thc' low sun was complete ly oceul ted by the space-
craft \~crc SOl\le bnght stars noted. Theinubility to ohserve the
stars as anticipated is ascribed to two reasons; (1) the satellite ~in
dO\~ 5urfac('s ~.cattt:'n'd light from the obliqut' SUll or even from the
cycle dependence could account for the fact tln~ the (;('mini nstronaut,
(1965-1966), although alerted to look for this "high airgloll;," did
not sec it.
The Aurora
The ~1ercury and Gemini orbits were confined within geographlc lat-
itudes of 32°N and 32°5. Since the auroral zones are at geomagnetic
latitudes of (i7°N and 67°S it would seem unlikely that auroras could
be seen by the astronauts. lIowever two circumstances were favorahle
for sllch sightings. Fi r~t, the "dip" of the hori zan at orbi tal hei "hts
pl1t~ tlH' vim"eJ IH1l'i :on at a con:·,iJerable di stance from the suh-satell ito
point. For e:,ample at a sCltelli tl' height of 166km. (perigee for (;'1'-4)
the dip of thE' horicon i e· ahout l3° and at a height of 297 km. (apoo,ee
for G'l . ':; jt ! ,; about 1 r Seconll , the aurora 1 zone, bei ng contro 11 cd
by the geomagnlclc fielJ, is inclined to parallels of geographic lat-
ituJ~ as jll~strated in Plate IS. Nighttime passes over the eastern
UnitC'd States or over southern I\ustralia bring the spacecraft closest
to the :luroral lone. On several occasions auroras were seen in the
;\1.lstralia-New :ealand region. Plate 16 (Fig. 32-7 of NASA 51'-121) shows
a reproduction of a sket::h mado by the Gemini 7 crew. An auroral arch
is seen below the ajrglow layer.
The Visibility of Stars.
Satellite orbits <Ire <It a minimum h('ight of about 160 km, \~hen'
the "sky" above is not the famil i ar blue a~ it; s from the earth's
~lIrfacl'. Since the ~11lall fra~tion of the atmosphere abo'le the ;;pClce-
.:raft produce,; a vc],y 101' :1n10unt of scattering, even in full slinlif;ht,
it was antidpdted that the day sky from (l .~piicecraft would therefore
display the fu11 astronomical panoply. This was decidedly iwl; the
caSl'. All the Amcri(:an a~trol1auts have exprcsseu themselves most force-
fully that JlIrin~ satellite tlaytime, Le., when the slInis ahove trw
hori ZOI1, they could not sec the stars, eVCll the hrll;hter ones, Only
on a fel,' occas lons, 1 f the' low slIn w:t<; callip tete ly occulted by the ~pace
craft "erc sOll\e bnght 5tars noted. The inubility to ohserve the
~tar5 as anticipated is ascribeJ to two reasons; (1) the satellite win-
do" sllrfac"'~ ~,cattt'l'cd light from the obliquc SUll or ('ven from the