During the Spacelab 1 shuttle mission, spectroscopic measurements were made of the atmospheric emissions over a broad wavelength range extending from the extreme ultraviolet to the near infrared. Those measurements were made under a variety of vehicle attitude and sunlight conditions. Superimposed on such spectra would be any features associated with the induced vehicle environment and its interaction with solar photons and the ambient neutral atmosphere and plasma. Various anomalies and unexpected features in the spectra from the perspective of possible shuttle-induced origins are discussed. The data indicate a dramatic cleanup of the vehicle environment over the course of the 10-day mission, a strong non-atmospheric red continuum underlying the spectra at night and at large angles to the velocity vector, and a variety of molecular band distributions which are not explained by the present understanding of the atmosphere

Torr, M. R.

English

NASA Technical Reports Server

THE W-VIS OPTICAL ENVIRONMENT OF THE SHUTTLE 
Marsha R. Torr 
Department of Physics, Utah S t a t e  Universi ty  
Abstract .  During the Spacelab 1 s h u t t l e  mission, spectroscopic 
measurements w e r e  made of the  atmospheric emissions over a broad wave- 
length range extending from the extreme u l t r a v i o l e t  t o  
f ra red .  These measurements w e r e  made under a v a r i e t y  o 
tude and sunl ight  condi t ions.  Superimposed on such spec t ra  would be any 
f e a t u r e s  assoc ia ted  with the  induced vehicle  environment and i t s  i n t e r -  
a c t i o n  with s o l a r  photons and the ambient neu t r a l  atmosphere and plasma. 
In  t h i s  paper, w e  d i scuss  var ious anomalies and unexpected f e a t u r e s  i n  
t he  spec t ra  from the  perspect ive of poss ib le  shuttle-induced or ig ins .  
The data ind ica t e  a dramatic cleanup of t he  vehic le  environment over t he  
course of t he  IO-day mission, a s t rong  non-atmospheric red continuum 
underlying the  spec t ra  a t  n ight  and a t  large angles  t o  the  v e l o c i t y  
vec tor ,  and a v a r i e t y  of molecular band d i s t r i b u t i o n s  which a r e  not 
explained by our present  understanding of the  atmopshere 
Introduct ion 
The phenomenon of glows assoc ia ted  with spacecraf t  sur faces  d i r e c t e d  
i n t o  the  ve loc i ty  vector  i s  now widely known. I n  the  case of t he  
s h u t t l e  a t  a l t i t u d e s  near 250 km, these  glows are v i s i b l e  t o  the  naked 
eye a t  n ight  and are read i ly  photographed with hand-held cameras [see 
Banks e t  al., 1983; Mende e t  a l . ,  19831. In  addi t ion ,  it has been 
recognized f o r  many years  t h a t  s e n s i t i v e  instruments d i r ec t ed  i n t o  the 
ve loc i ty  vector  experience an i n t e n s i t y  enhancement that: i nc reases  
s i g n i f i c a n t l y  from the  blue t o  the  red and which i s  due t o  the i n t e r -  
ac t ion  of t he  vehic le  with the  ambient environment [Torr e t  al., 1977; 
Y e e  and Abreu, 19831. These e f f e c t s  a r e  well covered i n  r e l a t e d  papers 
i n  these  proceedings. 
Of major concern t o  those working a t  low l i g h t  l e v e l s  from space 
veh ic l e s  i s  whether these  e f f e c t s  are due e n t i r e l y  t o  sur face  and near 
sur face  glow which can perhaps be avoided by looking a t  angles  other  
than the  ram or  by operat ing a t  much g rea t e r  a l t i t u d e s ,  or  whether an 
extended o p t i c a l  contamination e x i s t s  around the  vehicle .  A clear 
understanding of t he  ex ten t  of t he  induced o p t i c a l  environment i s  of 
importance t o  inves t iga t ions  from space s h u t t l e ,  Space S ta t ion ,  Space 
Telescope, and veh ic l e s  operat ing i n  the  upper atmosphere i n  general .  
A t  t he  F i r s t  Shu t t l e  Glow Workshop a year ago, we reported an i n i t i a l  
da ta  set obtained on the  Spacelab 1 s h u t t l e  f l i g h t  with the  Imaging 
Spectrometric Observatory (ISO). These p a r t i c u l a r  da ta  w e r e  obtained i n  
an observing sequence i n  which the  field-of-view w a s  d i r ec t ed  tan- 
g e n t i a l l y  away from the  Earth and s t r a i g h t  out of the  payload bay (-2 
ax i s )  i n t o  the  v e l o c i t y  vector.  The data  w e r e  acquired on the  dayside 
of the  Earth. From these da ta  it w a s  concluded t h a t  t he  wavelength 
region from 6000 a t o  8000 a w a s  densely populated with a number of 
b r igh t  overlapped bands. These bands w e r e  subsequently t e n t a t i v e l y  
i d e n t i f i e d  as N2(1P) [Torr and Torr, 1985al and w e r e  found t o  s i g n i f i -  
c a n t l y  exceed the  br ightness  of these f ea tu res  expected from the  ambient 
atmosphere. 
98 
https://ntrs.nasa.gov/search.jsp?R=19860003779 2020-03-20T15:59:01+00:00Z
It then becomes of obvious interest  t o  know how these  spectra ob- 
t a ined  looking i n t o  t h e  v e l o c i t y  vec tor  compare with o t h e r s  obtained 
with d i f f e r e n t  viewing geometries and under d i f f e r e n t  condi t ions  of 
s o l a r  i l lumina t ion .  I n  t h e  following sec t ions ,  w e  p re sen t  a v a r i e t y  of 
prel iminary spectra obtained i n  d i f f e r e n t  o r i en ta t ions .  
Results 
Three spectra are shown i n  Figure 1, a l l  taken with the  field-of-view 
of t h e  instrument looking t a n g e n t i a l l y  away f r a n  t h e  Earth and on t h e  
dayside, but with t h e  field-of-view i n t o  the  wake, a t  90° to  the  wake, 
and i n t o  t h e  v e l o c i t y  vec tor ,  respec t ive ly .  The lower panel ( i n t o  t h e  
v e l o c i t y  vector)  i s  t h e  spectrum shown a t  the  workshop a year ago. A l l  
t h r e e  spec t r a  show b r i g h t  bands i n  t h e  red. However, it should be noted 
t h a t  t he  scales on the three spectra are q u i t e  d i f f e r e n t ,  so t h a t  t h e  
i n t e n s i t i e s  are inc reas ing ly  b r i g h t  going from t h e  bottom t o  the  t o p  of 
t h e  f igure.  Thus, t h e  s u r p r i s i n g  a spec t  of t he  da t a  shown i n  t h i s  
f i g u r e  i s  t h a t  t he  ram da ta  are s i g n i f i c a n t l y  "cleaner" i n  t h e  r e d  
po r t ion  of the spectrum. The s e n s i t i v i t y  of t he  instrument drops by a 
f a c t o r  of 3 from 6000 8 t o  8000 8.  Thus, t he re  is  a tendency to amplify 
t h e  noise a t  higher wavelengths i n  converting from counts t o  R/8. How- 
ever ,  t he  i n t e g r a t i o n  per iods  are comparable i n  a l l  three cases. The 
da ta  taken with the  field-of-view looking i n t o  the  wake w e r e  taken on 
the  f i r s t  day of t he  miss ion ,  some 20 hours a f t e r  launch. The data 
taken looking a t  90° t o  the v e l o c i t y  vec tor  w e r e  taken on the second day 
of t he  mission, approximately 40 hours a f t e r  launch. The data i n t o  t h e  
v e l o c i t y  vec tor  w e r e  acquired on day 10 of the miss ion  and followed a 
very extended per iod of t he  payload bay being d i r e c t e d  a t  the Sun 
(almost 24 hours ) .  These r e s u l t s  t he re fo re  suggest t h a t  t he re  w a s  a 
s i g n i f i c a n t  cleanup i n  t he  vehicle-induced environment over t he  course 
of the IO-day mission. 
The data shown i n  Figure 2 w e r e  a l l  taken looking a t  a tangent ray 
a l t i t u d e  of 250 km i n t o  t h e  wake and on the  f i r s t  day of t h e  mission. 
The comparison i n  t h i s  case is  of d i f f e r e n t  s o l a r  condi t ions ;  night ,  
t w i l i g h t ,  and day. In  th i s  case,  r e l a t i v e l y  b r i g h t  band f e a t u r e s  are 
again present  i n  the red po r t ion  of t he  spectrum. Because so many of 
t h e  contaminants are the  same a s  the  spec ie s  occurring n a t u r a l l y  i n  t h e  
atmosphere, t h e  problem is  t o  t r y  t o  determine whether these f e a t u r e s  
are due to  the  ambient upper atmosphere o r  due t o  t h e  vehic le ,  or due t o  
a d i s t o r t i o n  of t he  ambient environment by the  vehic le .  A s  w a s  men- 
t ioned  above, t h e  viewing geometry i n  these  th ree  sequences is tan- 
g e n t i a l  t o  t he  Earth. I n  such a viewing conf igura t ion ,  n a t u r a l l y .  
occurring f e a t u r e s  are considerably amplified because the  s l a n t  pa th  
length  of t he  atmosphere is longer than the v e r t i c a l  d i s t ance  through 
the same emission layer .  The s l a n t  pa th  ampl i f ica t ion  f a c t o r  a t  these  
a l t i t u d e s  would be approximately 30 f o r  atmopsheric f ea tu res .  Thus, t h e  
f e a t u r e s  appearing i n  t h e  nightglow spectrum would correspond t o  v e r t i -  
cal i n t e n s i t i e s  of 1-2 R/8 i f  they are of atmospheric or igin.  However, 
if the  source is  a glowing i n t e r a c t i o n  region surrounding the vehic le ,  
i t s  i n t e n s i t y  would not be expected t o  change i n  t h e  same way with angle 
to  the zenith.  
I n  Figure 3, w e  show a comparison of t h e  250 km tangent ray a l t i t u d e  
nighttime da ta  shown i n  Figure 2, toge ther  with another nightglow spec- 
trum taken with the field-of-view looking within 200 of the v e r t i c a l .  
99 
The s l a n t  path f a c t o r  d i f f e rence  i n  the  obvious atmospheric f e a t u r e s  
such as t h e  O ( l D )  l i n e s  a t  6300/6364 a is  evident. 
major d i f f e r e n c e  between the  two spectra. W e  have been cau t ious  i n  
a s s ign ing  any real s ign i f i cance  t o  underlaying continuum i n  the IS0 da ta  
f r m  Spacelab 1 f o r  var ious  reasons. O u r  observing sequences w e r e  
designed with r e l a t i v e l y  few background measurements and even some of 
these  w e r e  l o s t  due t o  launch delay impacts. I n  addi t ion ,  t h e  veh ic l e  
t e s t i n g  a s soc ia t ed  with the  mission required subjec t ing  the payload t o  
thermal extremes. In  several cases, the re  w a s  t he  p o s s i b i l i t y  t h a t  t h e  
nearest instrument background measurement might not f u l l y  remove a 
changing thermal background component. As a r e s u l t ,  r e s i d u a l  back- 
grounds w e r e  removed from the  da t a  and the ana lyses  have concentrated on 
t h e  l i n e  and band spectra .  However, i n  t h e  case of t h e  near v e r t i c a l  
spectrum shown i n  Figure 3, t h e  continuum apparent i n  t h i s  spectrum w a s  
repeated on seven consecutive n ights ide  passes, a l l  of which had rela- 
t i v e l y  good instrument background cor rec t ions .  We theref  o re  be l ieve  
t h a t  t hese  data (and poss ib ly  t h e  o ther  spectra shown also) i n d i c a t e  a 
s t rong  red continuum with a p a k  i n t e n s i t y  of approximately 30 R/a .  
This continuum cannot be atmospheric i n  i t s  o r i g i n  and i s  obse rved ,a t  
n igh t  looking a t  an angle of almost 90° t o  the v e l o c i t y  vector. 
Figure 4 shows a dayglow s p e c t r a l  survey covering 600 a t o  8000 8. 
I n  t h i s  case t h e  instrument w a s  looking a t  a tangent r ay  he igh t  of 150 
km and a t  an angle of 20° t o  t he  wake. Six consecutive such spec t r a  
w e r e  obtained over a f u l l  o r b i t  with t h e  veh ic l e  s u n l i t .  Considerable 
a n a l y s i s  has  y e t  t o  be done on these da ta  and only a few comments will 
be made here. The red v i s i b l e  wavelengths are dominated by t h e  b r i g h t  
O2 atmospheric bands which are explained by atmospheric sources. 
N2(1P) bands i n  t h i s  region might a l s o  be explained by atmospheric 
processes.  The W2 emissions are anomalous and are discussed i n  another 
paper i n  t hese  proceedings. Throughout t he  spectrum the re  are f e a t u r e s  
f o r  which w e  do not y e t  have i d e n t i f i c a t i o n s .  
Hopfield bands have a highly anomalous v i b r a t i o n a l  and r o t a t i o n a l  dis- 
t r i b u t i o n  (F igure  5 ) .  It is  l i k e l y  t h a t  t h i s  i s  an atmospheric phenome- 
non, but w e  do not y e t  understand the  e x c i t a t i o n  mechanism [Torr and 
Torr, 1985333, and have found the sane fea tu res ,  s i m i l a r l y  anomalous, i n  
t h e  nightglow [Torr e t  al.,  19851. 
However, t he re  i s  a 
The 
+ 
The N2 Lyman-Birge- 
Conclusions 
I n  t h i s  paper we have presented a number of spectra measured from 
Spacelab 1 under a v a r i e t y  of conditions.  The da ta  i n d i c a t e  a s i g n i f i -  
c a n t  reduct ion  of t h e  i n t e n s i t y  of f e a t u r e s  i n  t h e  red por t ion  of t h e  
spectrum over the course of t he  mission, which could be assoc ia ted  with 
a s i g n i f i c a n t  reduction i n  t h e  vehic le  outgassing Over t h e  10 days of 
t h e  mission. The nighttime da ta  ind ica t e  a s t rong  underlying red con- 
tinuum (30 R/B) a t  large angles  t o  t h e  v e l o c i t y  vector.  
genera l  show evidence of h ighly  anomalous N2 and N: band systems. A t  
t he  p re sen t  t i m e  w e  cannot account f o r  these  i n  terms of our c u r r e n t  
understanding of t h e  atmospheric/ionospheric processes. I n  addi t ion ,  
t he  spectra conta in  a number of f e a t u r e s  which we  cannot y e t  i d e n t i f y .  
Thus, e i t h e r  w e  do not understand some very fundamental aspects of the  
terrestrial atmosphere, o r  t h e  s h u t t l e  environment comprises an extended 
i n t e r a c t i o n  region i n  which var ious  c o l l i s i o n  processes are occurring i n  
l a r g e  numbers. 
The spec t r a  i n  
100 
Acknowledgment. This work w a s  supported by NASA Contract NAS8-33992. 
References 
Banks, P. M., P. R. Williamson, and W. J. R a i t t ,  Space Shut t le  g l o w  
Mende, S. B., 0. K. Garriott ,  and P. M. Banks, Observat ions of op t i ca l  
emissions on STS-4, Geophys. R e s .  LeGg:, 10, 122, 1983. 
Torr, M. R., and D. G. Torr, A preliminary spectroscopic assesscnent of 
the Spacelab l /Shut t le  op t i ca l  environment, J. Geophys. Res. ,  90, 
1683, 1985a. 
Spacelab 1, Geophys. Reee-->$&t_,-, submitted, 198513. 
tangent ray height ,  ZeophKs. R e s .  L e t t . ,  submitted, 1 9 8 5 ~ .  
t i o n  of airglow observations with the Atmosphere Explorer S a t e l l i t e ,  
Planet. Space Sci. ,  25, 173, 1977. 
Birge-Hopfield band nightglow from Spacelab 1, J. Geophys. Res., 90, 
observations, 10, 118, 1983. 
Torr, M. R., and D. G. Torr, The N2 Lyman Birge Hopfield dayglow from 
Torr, Y. R., and D. G. T~rr, A spectral survey of the dayglow a t  150 km 
Torr, M. R., P. B. Hays, B. C. Kennedy, and J.C.G. Walker, In te rca l ibra-  
Torr, M. R., D. G. Torr, and J. W. Eun, A spec t r a l  search for  Lyman- 
4427, 1985. 
U e e ,  J. H., and V. J. Abreu, V i s i b l e  glow induced by spacecraft- 
environment in te rac t ion ,  Geophys. Res.  L+t2, =, 126, 1983. 
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Fig. 5. Fa r  u l t r a v i o l e t  spectra of t h e  dayglow for a 150 km tangent  
r ay  height .  The s i x  consecut ive spec t r a  correspond t o  changing 
l a t i t u d e  and solar zen i th  angle  cohdi t ions  [from T o r r  and Torr ,  
1985333. 
106 


The UV-VIS optical environment of the shuttle

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