Slitless spectrograph for upper atmosphere chemical release

Cooper, C. D.

English

NASA Technical Reports Server

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C. Dewey C o o p e r  
P h y s i c s  Departmenr 
The 1 J n i v e r s i t y  of G e o r g i a  
A t h e n s ,  Georgia  
C o n t r a c t  NASI -1672 
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https://ntrs.nasa.gov/search.jsp?R=19650011734 2020-03-16T23:52:01+00:00Z
I. ABSTRACT 
A s l i t l e s s  spectrograph was designed and cons t ruc ted  
using an 1800 groove/mm r e f l e c t i o n  g r a t i n g  and an F/0.87 
camera l ens  of 76mn f o c a l  l eng th  t o  provide a d i spe r s ion  
of 70 A / m .  This instrument gave e x c e l l e n t  s p e c t r a  for 
upper atmosphere chemical r e l e a s e s  during t h e  F i r e f l y  I11 
s e r i e s .  The s l i t l e s s  spectrograph i s  being used by Georgia , 
Tech a t  t h e  present  t ime under Contract  NASI-1671. 
11. INTRODUCTION 
The search  f o r  means t o  measure w i n d s  of t h e  upper 
atmosphere l e d  q u i t e  n a t u r a l l y  t o  t h e  s t u d y  of chemical 
r e l e a s e s  t h a t  could t a p  energy s t o r e d  i n  t h e  ionosphere 
and thereby produce v i s i b l e  clouds which could be t racked  
a t  n igh t .  S p e c t r a l  information from t h e s e  clouds can be 
used t o  d e t e r n i n e  t h e  presence of var ious  atomic o r  mole- 
c u l a r  spec ie s  which a r e  present  i n  t h e  upper atmosphere. 
The t a s k  assigned under t h i s  c o n t r a c t  was t o  provide 
spec t rographic  coverage f o r  t h e s e  chemical r e l e a s e s  during 
t h e  ex ten t  of t h e  con t r ac t .  High r e s o l u t i o n  s p e c t r a l  
coverage was t o  be provided w i t h  an a u r o r a l  s l i t - t y p e  
spectrograph which was the  proper ty  of t h e  A i r  Force 
Cambridge Research Center.  However, a s l i t  -type spec t ro -  
graph is r a t h e r  s t r o n g l y  l i m i t e d  i n  a p p l i c a t i o n  where 
t h e  s p e c t r a l  source i s  a very weak luminescent d i s t a n t  
cloud. One of t h e  ob jec t ives  of t h e  program was t o  develop 
a f a s t  s l i t l e s s  type spectrograph t h a t  w m l d  record s p e c t r a l  
information from t h e  Luminescent clouds t h a t  were expected, 
- 2  - 
111 . ACCOMPLISHJ-ENTS 
A .  S l i t l e s s  Spectrograph 
A study of s l i t l e s s  spectrographs which use t r a n s -  
mission g r a t i n g s  showed that 600 was the maximum number 
of grooves per  mm t h a t  could be used on a blazed t r a n s -  
m i s s i o n  g ra t ing .  A blazed r e f l e c t i o n  g r a t i n g  was r e a d i l y  
a v a i l a b l e  wi th  1800 grooves pe r  mm. 
A g r a t i n g  wi th  1800 grooves/mm w i l l  g ive t h r e e  times 
t h e  s p e c t r a l  d i spe r s ion  which can be obtained wi th  a 600 
groove/rnm g r a t i n g .  A s l i t l e s s  spec t rograph  produces a 
s e p a r a t e  image of t h e  Light source f o r  each of t h e  wave- 
lengths  present .  For a d i s t a n c e  l i g h t  source ,  one cannot 
increase  t h e  s p e c t r a l  r e s o l u t i o n  by u s i n g  a longer  f o c a l  
l e n g t h  camera l e n s  s i n c e  t h i s  inc reases  t h e  s i z e  of t h e  
. .  rTLib <i,ci--~se - -  - - - & -  =-;-a nv=exren+-e en? f r o m  r image L L I  A.USa6L Y * - -  
obta in ing  g r e a t e r  s p e c t r a l  r e s o l u t i o n  even though g r e a t e r  
d i spe r s ion  can be obtained by inc reas ing  t h e  f o c a l  length.  
The above f a c t o r s  were considered and a slitless 
spectrograph was designed us ing  t h e  fol lowing components: 
Bausch and Lomb r e f l e c t i o n  g r a t i n g  w i t h  1800 grooves/mn, 
Super Farrand F/0.87 l e n s  wi th  a 76 mm f o c a l  l e n g t h ,  
and a 70 mm Bea t t i e  Coleman fllm magazine with d a t a  
chamber. 
The spec t rograph  was cons t ruc ted  so t h a t  t h e  zero  
s p e c t r a l  o rde r  of t h e  g r a t i n g  could be superimposed just 
above t h e  s p e c t r a l  images. This  provided a method of 
determining wavelengths. A photograph of t h e  spec t rograph  
i s  shown i n  Fig: 1. 
I 
- 3- 
The s l i t l e s s  spectrograph proved t o  be very e f f e c t i v e  
i n  recording f a i n t l y  chemi-luminescent clouds i n  t h e  upper  
atmosphere. Representat ive s p e c t r a  obtained wi th  our 
spectrograph of chemical r e l e a s e s  which were observed 
d u r i n g  t he  F i r e f l y  I11 program sponsored by A i r  Force 
Cambridge Research Laboratory a r e  included i n  Fig. 2. 
I n  t h e s e  spectrograms t h e  s p e c t r a  a r e  spread h o r i z o n t a l l y  
and t h e  zero  o r d e r  image appears above t h e  s p e c t r a .  The 
spectrogram labe led  Dana shows a continuum which is produced 
by an aluminum re l ease .  The two images a t  396% and 3 9 4 U  
have been i d e n t i f i e d  a s  t h e  resonant l i n e s  of aluminum. 
The spectrogram labe led  Netty was produced by an ace ty l ene  
r e l e a s e .  Here again a continuum is  present  but s t rong  
CH and t h e  Swan bands of C2 a r e  e a s i l y  i d e n t i f i e d  even 
though t h e  clouds s i z e  is very l a rge .  The spectrogram 
l abe led  Ruby shows t h e  r e so lu t ion  which i s  poas ib le  f o r  
po in t  l i k e  clouds.  This chemical r e l e a s e  contained cesium 
and sodium, On t h e  o r i g i n a l  f i l m  t h e  fol lowing atomic l i n e s  
were i d e n t i f i e d :  6 2 1 3  C s ,  6010A Cs, 5845A Cs, 5896A N e ,  
5890A Na, 5670A Ne, 5688A N e  and 5683A Na. The two sodium 
yel low l i n e s  which a r e  only 6A a p a r t  a r e  a c t u a l l y  reso lved  
on t h e  spectrogram. These spectrograms show t h a t  t h e  
s l i t l e s s  spectrograph is a wel l  designed instrument which 
perf o m s  wel l  i n  recording t h e  s p e c t r a  of chemi-luminescent 
clouds i n  t h e  upper atmosphere. 
L 
. . . 
B.  S p c c t  r-oyrap’tiic coverapc f o r  NASA bJaLlc)ps S t a t i o n  r e l e a s e s  
of  C S 2  311 1 ! ) I ) (  ( ’ f I3)4 on 1 .Tune 1962 and 2 4  Sept e 1963. 
a .  Eqii i pment used .  
1. The a u r o r a l  s l i t - t y p e  spec t rograph  which used 
an F/0.87 camera lens  and provided a d i spe r s ion  
of LOO A/mm was i n  opera t ion  f o r  t h e s e  launches.  
2 .  The s l i t l e s s  spec t rograph  descr ibed  i n  Part A 
above was in  operat ion f o r  t h e s e  launches,  
b .  Data obtained 
No luminescent c louds were observed f o r  t h e  
CS r e l e a s e s .  The P b ( C H Q ) &  r e l e a s e  was scheduled 
f o r  r e l e a s e  a t  113 seconds a f t e r  launch a t  about 
1 1 5  km a l t i t u d e .  Photographs by P r o f ,  Edwards of 
Ga. Tech ind ica t e  t h a t  t h e  r e l e a s e  occurred near 
80 seconds a f t e r  launch a t  an a l t i t u d e  of  approxi-  
mately 8 2  km, O u r  spectrographs were not opened 
a t  t h i s  t i m e  and it  i s  very doubt fu l  i f  s p e c t r a  
could have been recorded because t h e  r e l e a s e  was 
n o t  v i s i b l e  t o  t h e  observers  a t  t h e  spec t rographic  
s i te .  
C .  Future Spectrographic  Coverage. 
The s l i t l e s s  spectrograph developed under t h i s  
con t r ac t  proved t o  be a va luab le  i n s t r u m e n t  f o r  record ing  
s p e c t r a  from chemical r e l e a s e s  i n  t h e  upper atmosphere. 
A t  our r eques t ,  t h e  spec t rographic  work under t h i s  c o n t r a c t  
w a s  t r a n s f e r r e d  t o  Contract NASI-1671 with Georgia Tech. 
They can bes t  provide t h e  t e c h n i c a l  s e r v i c e s  needed f o r  
opera t ing  t h e  spectrograph i n  t h e  f i e l d .  
ill 
Fig. 1 
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5585A 5156A 4737A 4315A 
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N e t t y  - A c e t y l e n e  
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5893A 
Ruby - MPEC 
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Spectrographic coverage and data reduction of nasa chemical release.  studies directed toward design and development of new spectrographic instrumentation  final report

Spectrographic coverage and data reduction of nasa chemical release. studies directed toward design and development of new spectrographic instrumentation final report

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