PERFORMANCE EVALUATION

FOR PLANETARY LANDERS OF A QUASI-MICROSCOPE

Ernest E. Burcher, Friedrich 0. Huck, Stephen D. Wall, and Susan B. Woehrle

Langley Research Center ampt ton, va. 23665

1

1 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. MARCH 1977

https://ntrs.nasa.gov/search.jsp?R=19770014460 2020-01-31T02:05:35+00:00Z

TECH LIBRARY KAFB. NM ~. . -

1. Report No. NASA TN D-8370

~ - .

2. Government Accession No. I I -~

4. Title and Subtitle

PERFORMANCE EVALUATION OF A QUASI-MICROSCOPE FOR PLANETARY LANDERS

- 7 . Author(s)

Ernes t E. Burcher, F r i e d r i c h 0. Huck, Stephen D. W a l l , and Susan B. Woehrle

9. Performing Organization Name and Address

NASA Langley Research Center &"ton, VA 23665

. .

12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration Washington, DC 20546

.. - 15. Supplementary Notes

Ernest E. Burcher: Langley Research Center. F r i e d r i c h 0. Huck: Langley Research Center. Stephen D. W a l l : Langley Research Center.

- 5. March 1977

6. Performing Organization Code

8. Performing Organization Report NO.

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506-18-21-02 10. Work Unit No.

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Note 14. Sponsoring Agency Code

Susan B . Woehrle: McDonnell Center for t h e Space Sc iences , Washington Un ive r s i ty , S t . Louis, Missouri 63130.

. . ~ - . . . ~. - .. .

16. Abstract

S p a t i a l r e s o l u t i o n s achieved wi th cameras on lunar and p l a n e t a r y l a n d e r s have been l i m i t e d t o about 1 mm, whereas microscopes of t h e type proposed f o r such l a n d e r s could have obtained r e s o l u t i o n s of about 1 um bu t were never accepted because of t h e i r complexity and weight. The quasi-microscope evaluated i n t h i s paper could provide in t e rmed ia t e r e s o l u t i o n s of about 10 urn w i th r e l a - t i v e l y simple o p t i c s t h a t would augment a camera, such as t h e Viking l a n d e r camera, without imposing s p e c i a l design requirements on t h e camera or l i m i t i n g i t s f i e l d of view of t h e t e r r a i n . Images of n a t u r a l p a r t i c u l a t e samples taken i n b l ack and white and i n c o l o r have shown t h a t g r a i n s i z e , shape, and t e x t u r e are made v i s i b l e f o r unconsol idated m a t e r i a l s i n a 50- t o 5OO-um s i z e range. Such information may provide broad o u t l i n e s of p l a n e t a r y s u r f a c e mineralogy and al low in fe rences t o be made o f g r a i n o r i g i n and evo lu t ion . The mine ra log ica l d e s c r i p t i o n s of s i n g l e g r a i n s would be a ided by t h e r e f l e c t a n c e s p e c t r a t h a t could, f o r example, be est imated from t h e six-channel m u l t i s p e c t r a l d a t a of t h e Viking l a n d e r camera.

.

17. Key Words (Suggested by Authoris)

Opt ic s Imaging P l a n e t a r y missions

_ ~ _ 18. Distribution Statement

U n c l a s s i f i e d - Unlimited

Subject Category 35 - ~ . - - ~

19. Security Classif. (of this report) 20. Security Classif. (of this page)

Unc 1 as s i f i ed Unc las s i f i e d - . ~ -_

* For sale by the National Technical Information Service, Springfield, Virginia 22161

PERFORMANCE EVALUATION OF A QUASI-MICROSCOPE

FOR PLANETARY LANDERS

Ernest E. Burcher, F r i e d r i c h 0. Huck, Stephen D. Wall, and Susan B. Woehrle*

Langley Research Center

SUMMARY

S p a t i a l r e s o l u t i o n s achieved wi th cameras on luna r and p l ane ta ry l a n d e r s have been l i m i t e d t o about 1 mm, whereas microscopes of the type proposed f o r such l ande r s could have obtained r e s o l u t i o n s o f about 1 pm but were never accepted because of their complexity and weight. The quasi-microscope evalu- ated i n t h i s paper could provide in te rmedia te r e s o l u t i o n s of about 10 pm with r e l a t i v e l y simple o p t i c s that would augment a camera, such as t h e Viking l ande r camera, without imposing s p e c i a l design requirements on the camera or l i m i t i n g i t s f i e l d of view of t h e t e r r a i n . Images of n a t u r a l p a r t i c u l a t e samples taken i n black and whi t e and i n co lo r have shown t h a t g r a i n s i z e , shape, and t e x t u r e are made v i s i b l e f o r unconsol idated materials i n a 50- t o 500-pm s i z e range. Such information may provide broad o u t l i n e s of p l ane ta ry su r face mineralogy and a l low in fe rences t o be made of g r a i n o r i g i n and evolu t ion . The minera logica l d e s c r i p t i o n s of single g r a i n s would be a ided by t h e r e f l e c t a n c e s p e c t r a t h a t could, f o r example, be estimated from the six-channel m u l t i s p e c t r a l data of t h e Viking lander camera.

INTRODUCTION

V i s u a l imaging is g e n e r a l l y accepted t o be of primary importance i n explor- i n g the Moon and the p l a n e t s by landed s p a c e c r a f t , as has been demonstrated by the USSR Luna ( re f . I), Lunakhod ( re f . 21, Venera ( re fs . 3 t o 51, U.S. Surveyor (ref. 61, and Viking ( r e f . 7) missions. Sur face r e s o l u t i o n s that could be obtained w i t h the imaging systems on t h e s e spacec ra f t have been l i m i t e d t o about 1 t o 10 mm. S u b s t a n t i a l improvements i n r e s o l u t i o n could be achieved by the use of automatic focusing techniques ; however, such techniques would s u b s t a n t i a l l y i n c r e a s e t h e complexity of the imaging system (ref. 8 ) . Microscopes w i t h reso- l u t i o n s down t o 0.4 pm have a l s o been proposed (refs. 9 t o 1 1 1 , but have never been accepted f o r a space mission, p a r t l y because of t h e i r complexity, weight, and c o s t . They r e q u i r e e l a b o r a t e mechanisms f o r sample p repa ra t ion and s p e c i a l imaging systems w i t h p r e c i s e focus c o n t r o l .

A quasi-microscope concept was int roduced and analyzed i n r e fe rences 12 and 13 t o br idge t h e gap between t h e r e s o l u t i o n s ob ta inab le w i t h p l ane ta ry lander cameras and t h e much higher r e s o l u t i o n s ob ta inab le only wi th complex

*McDonnell Center f o r the Space Sc iences , Washington Un ive r s i ty , St. Louis , Missouri 63 130.

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microscopes. wi th a u x i l i a r y o p t i c s t h a t do no t impose s p e c i a l des ign requirements on t h e camera or l i m i t i ts normal func t ion t o image t h e surrounding t e r r a i n . Evalua- t i o n s o f t h i s concept are e s s e n t i a l l y l i m i t e d t o t h e Viking l ande r camera (ref. 14) . The camera has an in s t an taneous f i e l d o f view o f 0.12O f o r mult i - s p e c t r a l imaging wi th s i x s p e c t r a l channels i n t h e 0.4- t o 1.0-pm wavelength range, and an ins t an taneous f i e l d of view o f 0.04O f o r broadband imaging wi th f o u r e l e c t r o n i c a l l y selectable focus s t e p s . The depth o f f i e l d ex tends from 1.7 m t o i n f i n i t y , and t h e smallest d e t a i l t h a t can be reso lved is about 1.5 mm (ref. 15).

A quasi-microscope c o n s i s t s o f a p l a n e t a r y l ande r camera augmented

F i r s t -o rde r o p t i c a l ana lyses i n d i c a t e t h a t t h e use of a single l e n s as magni f ie r could y i e l d a r e s o l u t i o n o f about 40 pm, w i t h a depth o f f i e l d of 500 pm f o r each focal p o s i t i o n and an unvignet ted objec t -a rea diameter of 6 mm ( t h a t is, 150 p i c t u r e e lements) ( ref . 12) . Analyses of a more complex a u x i l i a r y o p t i c a l system c o n s i s t i n g o f a f i e l d l e n s i n a d d i t i o n t o t h e magnif ier i nd ica t ed t h a t a t en fo ld improvement could be obta ined i n r e s o l u t i o n , t h a t is, about 4 pm. The corresponding depth of f i e l d would be 11 pm at each f o c a l p o s i t i o n and t h e unvignet ted objec t -a rea diameter would be 1 t o 1.6 mm ( tha t is, 250 t o 400 pic- t u r e e lements ) , depending on t h e s i z e of t h e f i e l d l e n s (ref. 13). Pre l iminary design t rade-off ana lyses by t h e Perkin-Elmer Corporat ion (under NASA c o n t r a c t ) l e d t o t h e s e l e c t i o n of an o p t i c a l system tha t could provide a r e s o l u t i o n of 11 pm as a f avorab le compromise between performance c a p a b i l i t y and des ign com- p l e x i t y . The corresponding depth o f f i e l d was p red ic t ed t o be 32 pm f o r each f o c a l p o s i t i o n ( t h a t is, 128 ym with f o u r focus s t e p s ) and t h e unvignet ted objec t -a rea diameter t o be 4 mm ( t h a t is , 372 p i c t u r e e lements ) . was a l s o added t o l i m i t t h e s i z e of t h e f i e l d l e n s t h a t would otherwise be r equ i r ed t o ob ta in t h i s o b j e c t area.

A r e l a y l e n s

The quasi-microscope design could be f u r t h e r r e f i n e d , e s p e c i a l l y wi th regard t o t h e t o t a l number and th i cknesses of l e n s e lements . However, it appeared prudent t o implement t h e pre l iminary design and t o eva lua te t h e over- a l l performance. The eva lua t ion is d iv ided i n t o two p a r t s : ( 1 ) an o p t i c a l performance a n a l y s i s i nc lud ing r e s o l u t i o n , depth of f i e l d , and f i e l d of view, and ( 2 ) an a n a l y s i s of t h e q u a l i t y and k inds o f information tha t are provided about t h e phys ica l and chemical c h a r a c t e r i s t i c s o f r e g o l i t h material.

SYMBOLS

D l e n s diameter, pm

d diameter of p i c t u r e element ( p i x e l ) or r e s o l u t i o n diameter, pm

F F-number or f / D

f f o c a l l e n g t h , m

lp/mm l i n e p a i r s per mm

R o b j e c t or image d i s t a n c e from l e n s , m

2

A& depth of f i e l d or focus , m

m t r ansve r se magni f ica t ion

x wave length , pm

$2 number of unvignet ted p i c t u r e e lements ( p i x e l s ) i n c e n t r a l l i n e scan

Subsc r ip t s :

C camera l e n s

f f i e l d l e n s

0 o b j e c t i v e l e n s

r r e l a y l e n s

P r i m e s denote image space.

SYSTEM DESCRIPTION

Figure 1 p r e s e n t s a s impl i f i ed cutaway view of t h e Viking l ande r camera augmented w i t h the quasi-microscope o p t i c s . i n s e r t e d i n t h e s l o t under t he o p t i c s , i n one o f s e v e r a l p o s s i b l e ways. Per- haps the s imples t way would be t o use a small t u r n t a b l e as fol lows: A su r face sampler, such as t h e one on t h e Viking l a n d e r , could depos i t some material on one s i d e o f t he t u r n t a b l e , and t h e t u r n t a b l e could then be r o t a t e d t o br ing t h e sample under t h e quasi-microscope o p t i c s . As t h e sample is r o t a t e d , it would pass under a l e v e l i n g arm which would smooth the sample t o a t h i n l a y e r compat- i b l e with t h e o p t i c a l depth of f i e l d of t h e quasi-microscope. After the sample has been viewed, the t u r n t a b l e could be r o t a t e d s e v e r a l times u n t i l a brush has cleaned o f f the sample .

The material t o be viewed is

The camera is b a s i c a l l y a radiometer w i t h an opt ical-mechanical scanning mechanism. It f e a t u r e s an a r r a y o f 12 s i l i c o n photodiodes, c o n s i s t i n g of 4 broadband channels with selectable focus f o r h igh- reso lu t ion imaging, 1 broad- band channel f o r r ap id surveys , 6 narrowband channels f o r co lo r and near- i n f r a r e d m u l t i s p e c t r a l imaging, and 1 narrowband channel f o r scanning the Sun. The ins tan taneous f i e l d s of view are 0.040 f o r the fou r h igh- reso lu t ion chan- n e l s and 0.120 f o r t h e o the r channels . A nodding mir ror scans the in s t an taneous f i e lds of view i n e l e v a t i o n from 400 above t o 600 below the plane normal t o t h e o p t i c a l a x i s , and the upper housing r o t a t e s i n azimuth between success ive l i n e scans w i t h selectable frame widths ranging from 2.5O up t o 342.5O. fa l l ing on t h e selected photodiode is transduced i n t o an e lectr ical s i g n a l which is ampl i f ied , sampled, and quant ized f o r d i g i t a l t ransmiss ion . Table I p resen t s a sumnary o f p e r t i n e n t des ign and performance characterist ics.

Light

The narrow window of the camera u s u a l l y h ides behind a p o s t t o avoid unnec- e s s a r y exposure t o d u s t . The dus t pos t would have t o be s l i g h t l y enlarged t o con ta in the quasi-microscope. The a u x i l i a r y o p t i c s could t h u s be wi th in view

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of t h e camera without apprec i ab ly l i m i t i n g t h e camera's f i e l d o f view o f t h e surrounding t e r r a i n . t h e enlarged dus t pos t would limit it by 29O.

The p r e s e n t dus t p o s t l i m i t s t h e f i e l d o f view by 17.50;

F igure 2 ( a ) p r e s e n t s a detailed drawing o f camera and quasi-microscope o p t i c s , and figure 2(b) is a th in - l ens r ep resen ta t ion . The o b j e c t i v e l e n s focuses a magnified image of t h e sample onto a negat ive f i e l d l e n s , and t h e r e l a y l e n s p re sen t s t h i s image i n the form o f ( n e a r l y ) p a r a l l e l l i g h t r a y s t o t h e camera. The camera scans t h i s image wi th a photosensor focused a t ( n e a r l y ) i n f i n i t y . The d i s t ance between t h e camera and quasi-microscope is not c r i t i c a l f o r focus ; however, t h e u s e f u l f i e l d of view w i l l decrease due t o v i g n e t t i n g i f t h e d i s t a n c e between t h e scanning mir ror and quasi-microscope r e l a y l e n s is apprec iab ly increased .

Figure 3 p resen t s a s i m p l i f i e d th in - l ens r ep resen ta t ion of t h e o p t i c s t oge the r with performance equa t ions based on f i r s t - o r d e r geometric ana lyses . (See ref. 13. ) Performance p r e d i c t i o n s t h a t r e s u l t from s u b s t i t u t i n g proper va lues i n t o these equat ions are summarized i n table 11.

SYSTEM EVALUATION

Op t i ca l Performance

Any l ine-scan camera such as t h e Viking lander camera is b a s i c a l l y an o p t i c a l sampling system wi th a s p a t i a l frequency response which, un l ike t h e time frequency responses of e l e c t r o n i c s , is d i f f i c u l t t o shape. It is important t o d ivo rce t h e image q u a l i t y degrada t ion t h a t is imposed by o p t i c a l performance l i m i t a t i o n s of t he system from t h e a d d i t i o n a l degradat ion t h a t is introduced i f s p a t i a l d e t a i l is undersampled. That is , t h e angular r e s o l u t i o n of t he camera is unavoidably l i m i t e d by t h e t rade-off requi red between camera ins t an taneous f i e l d of view, s e n s i t i v i t y , and depth of f i e l d ( refs . 6 and 121, whereas t h e sampling i n t e r v a l can be somewhat independent ly selected ( refs . 16 t o 19) . It is, t h e r e f o re , advantageous t o eva lua te t h e quasi-microscope wi th a l a b o r a t o r y fascimile camera t h a t f e a t u r e s a v a r i a b l e sampling i n t e r v a l i n a d d i t i o n t o a camera l e n s and photosensor a p e r t u r e t h a t are i d e n t i c a l t o those of t h e Viking lander camera.

F igure 4 shows a test se tup of t h e l a b o r a t o r y facsimile camera augmented w i t h the quasi-microscope. Unless otherwise s p e c i f i e d , a l l r e s o l u t i o n measure- ments were made with a h igh- reso lu t ion (0.040) photosensor a p e r t u r e and ( n e a r l y ) s u f f i c i e n t sampling i n t e r v a l s (0 .020) .

Resolut ion c a p a b i l i t y is g e n e r a l l y b e s t s p e c i f i e d as sine-wave modulation t r a n s f e r func t ion ( M T F ) . Since sine-wave targets were not a v a i l a b l e , square- wave or t r ibar targets are t h e next best a l t e r n a t i v e . Therefore , t h e Nat iona l Bureau o f Standards (NBS) r e s o l u t i o n test c h a r t shown i n f i g u r e 5 was selected. When photographica l ly reduced t o 7.5, t h e c h a r t p rovides t r ibars ranging from 3.5 t o 24 lp/mm, and when reduced by 25, tribars range from 12 t o 83 lp/mm; thus , t h e range of s p a t i a l f r equenc ie s of i n t e r e s t is adequately covered.

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Figure 6 p re sen t s an average curve of s e v e r a l t r i b a r frequency response measurements. The l i m i t i n g r e s o l u t i o n is about 11 lJm ( t h a t is, 22 W / l p or 45 lp/mm), which is i n c l o s e agreement wi th t h e f i r s t - o r d e r o p t i c a l a n a l y s i s p r e d i c t i o n summarized i n table 11. The r e s o l u t i o n is p r imar i ly l i m i t e d by t h e photosensor a p e r t u r e s i z e r a t h e r than by quasi-microscope b l u r r i n g or by camera sampling, as i n d i c a t e d by t h e t h r e e p i c t u r e s o f t h e NBS c h a r t shown i n f i g u r e 7. F igures 7 ( a ) and 7 ( b ) , which were obtained wi th t h e facsimile camera a t sampling i n t e r v a l s o f 0.04O and O.O2O, r e s p e c t i v e l y , show t h a t sampling i n t e r v a l s broader than 0.02O reduce i m a g e q u a l i t y . Figure 7 ( c ) , which w a s obtained wi th a f i l m camera wi th o p t i c s similar t o those of t h e facsimile camera, shows t h a t improve- ments i n t h e angular r e s o l u t i o n of t h e camera w i l l l e ad t o h igher s p a t i a l reso- l u t i o n s wi th t h e quasi-microscope.

The usab le o b j e c t area ( t h a t is , quasi-microscopic f i e l d o f view) was determined by count ing t h e number o f unvignet ted p i x e l s (about 360) a long a diameter of a computer p r i n t o u t of t h e i m a g e , and mul t ip ly ing t h i s number by t h e diameter of a p i x e l i n t h e o b j e c t f i e l d ( t h a t is, by 11 pm). The r e s u l t i n g diameter is about 4 mm, which is aga in i n c l o s e agreement with t h e p r e d i c t i o n s l i s t e d i n table 11.

Two square-wave targets were used t o measure t h e s p a t i a l frequency response as a func t ion of defocus ( t h a t is , quasi-microscopic depth of f i e l d ) a t 25 lp/mm (40 pm/lp) and 40 lp/mm (25 pm/lp). cover a depth of 0.4 mm over t h e 4-mm-diameter area. o f ' t h e square-wave s p a t i a l frequency response a g a i n s t d i s t a n c e from t h e in-focus plane. These r e s u l t s i n d i c a t e t h a t t h e square-wave response f o r 40 lp/mm d e t a i l remains above 5 percent over a depth of f i e l d of about 0.13 mm per focus s t e p , and f o r 25 lp/mm over a depth of f i e l d o f about 0.32 mm. The u s e f u l depth of f i e l d of t h e quasi-microscope is t h u s apprec iab ly larger f o r de t a i l s l i g h t l y above t h e quasi-microscope r e s o l u t i o n l i m i t than t h e geometric depth of f i e l d p r e d i c t i o n . (See t a b l e 11. )

The targets were mounted a t a 60 s l o p e t o F igure 8 p r e s e n t s p l o t s

The r e s o l u t i o n could be increased wi th a quasi-microscope designed f o r h igher magni f ica t ion , but only a t t h e expense of a decreased o b j e c t f i e l d and/or an increased o p t i c a l complexity. A more a t t r a c t i v e approach t o i n c r e a s e reso- l u t i o n would be through an inc rease i n t h e angular r e s o l u t i o n of t h e camera. An inc rease i n angular camera r e s o l u t i o n by a c e r t a i n f a c t o r (up t o about 3) would inc rease t h e r e s o l u t i o n obtained wi th t h e quasi-microscope by n e a r l y t h e same f a c t o r , whereas t h e o b j e c t f i e l d would remain t h e same. (See refs. 12 and 13.)

The r e l a t i v e s p e c t r a l t r ansmi t t ance was determined as t h e r a t i o of t h e s p e c t r a l rad iance of a lamp imaged d i r e c t l y t o t h a t o f t h e lamp imaged through t h e quasi-microscope onto. . the en t rance s l i t of a monochromator. The measure- ments were made a t 0.05-w i n t e r v a l s over t h e wavelength range 0.4 t o 1 .1 w by us ing a f i l t e r t o block t h e second-order d i s p e r s i o n s of t h e monochromator grating. The abso lu te t r ansmi t t ance w a s measured a t a s i n g l e wavelength (0.9 pm) as t h e r a t i o of t h e s i g n a l measured d i r e c t l y wi th a co l l imated l i g h t beam t o t h e s i g n a l f o r t h e l i g h t beam through t h e quasi-microscope. The r e su l - t a n t abso lu t e s p e c t r a l t r ansmi t t ance curve is p l o t t e d i n f i g u r e 9.

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Minera logica l Analysis

The quasi-microscope provides a new t o o l f o r p l ane ta ry exp lo ra t ion , both f o r i d e n t i f i c a t i o n and f o r examination of c o n s t i t u e n t materials composing p l ane ta ry r e g o l i t h s , wi th r e s o l u t i o n s normally obtained only i n the l abora to ry . The a n a l y s i s presented i n t h i s paper is l i m i t e d t o t h e range and q u a l i t y o f information t h a t could be obta ined about t h e ino rgan ic c h a r a c t e r i s t i c s of r e g o l i t h material, a l though t h e concept may a l s o have b i o l o g i c a l a p p l i c a t i o n s .

F igure 10 p r e s e n t s b lack and whi te images o f f i v e geologic materials. The samples and t h e i r composition are summarized i n table 111. The images were obta ined with t h e camera 0 . 0 4 O i n s t an taneous f i e l d of view, by us ing i n s u f f i - c i e n t ( 0 . 0 4 O ) and n e a r l y s u f f i c i e n t (0.020) sampling i n t e r v a l s . The images show t h a t small de ta i l s are b e t t e r reso lved w i t h nea r ly s u f f i c i e n t sampling, and t h a t t h e increased data r equ i r ed should g e n e r a l l y be worthwhile. Figure 11 p r e s e n t s co lo r images of t h r e e of t h e f i v e materials. The images were obtained wi th t h e 0.12O ins t an taneous f i e l d o f view and ( n e a r l y ) s u f f i c i e n t (0.06O) sampling i n t e r v a l s . Information about g r a i n s i z e s , shapes, and c o l o r s t h a t can be e x t r a c t e d from these images provides c l u e s about ( 1 ) t h e s i z e d i s t r i b u t i o n of g r a i n s produced by igneous ( i n t r u s i v e and e x t r u s i v e ) processes or by shock metamorphism; ( 2 ) the s i z e d i s t r i b u t i o n r e s u l t i n g from s o r t i n g and abras ion during t r a n s p o r t by wind, water, or b a l l i s t i c processes ; (3) c o n s t i t u e n t min- eral components deduced from cleavage and f r a c t u r e p a t t e r n s ; ( 4 ) t he degree of chemical and phys ica l a l t e r a t i o n deduced from t h e degree of roundness and g r a i n s p h e r i c i t y ; and (5) an estimate of minera logic composition obtained by an examination of co lor . For i n s t a n c e , g r a i n morphologies and t e x t u r e s of t h e material i n figure 10 are well def ined . The l a b r a d o r i t e can be d i s t ingu i shed by i ts h igh r e f l e c t a n c e and p a t t e r n of c leavage from t h e two pyroxenes, a u g i t e and hypersthene. The two pyroxenes, which comprise t h e dark g r a i n s , are d i f f i - c u l t t o d i s t i n g u i s h by t h e i r morphology and t e x t u r e a lone . The co lo r image ( f ig . I l ( a ) ) , however, permi ts a u g i t e and hypersthene t o be more r e a d i l y d i s - t inguished , t h e a u g i t e as golden green , and t h e hypersthene as reddish brown.

The h ighly i r r e g u l a r and rounded s u r f a c e s of t h e material i n f i g u r e 10(b) t e n t a t i v e l y i d e n t i f y it as a h igh ly altered material. Aggregated g r a i n s and p i t t e d s u r f a c e t e x t u r e s tend t o suppor t t h i s conclusion e The reddish-brown co lo r of t h e sample ( f ig . 7 ( b ) ) a ids t o d e f i n e t h e sample as l imoni te or g e o t h i t e .

The f i n e gra ined and dark material i n f i g u r e lO(c) can perhaps be recog- nized as t h e presence of a large percentage o f mafic minera ls , l i k e pyroxene and o l i v i n e . Only minor amounts of a l i g h t e r minera l , such as f e l d s p a r , are observed. This is a c l o s e approximation t o the composition of t h i s sample, a p e r i d o t i t e . Again, as with t h e mor i te sample, co lo r images ( f ig . 11) would he lp t o d i s t i n g u i s h between t h e mafic minera ls .

The materials i n figures 10(d) and 10(e) are d i f f i c u l t t o d i s t i n g u i s h , a l though they have d rama t i ca l ly d i f f e r e n t minera logies . Both samples appear t o c o n s i s t of rounded b r i g h t grains, but t hose i n f igure 10(d) are f e l d s p a r c o n s t i t u e n t s of a l a t i t e , and those i n f i g u r e 1 0 ( e ) ape q u a r t z c o n s t i t u e n t s of a vo lcan ic t u f f breccia. Perhaps t h e only d i s t i n g u i s h i n g c h a r a c t e r i s t i c is the

6

higher b r igh tness o f t h e q u a r t z g r a i n s . e a s i l y solved, and co lo r images a lone would not e n t i r e l y c l a r i f y the d i f f e rence .

T h i s problem o f i d e n t i f i c a t i o n is no t

The problem o f unique i d e n t i f i c a t i o n of sample mineralogy could be par- t i a l l y circumvented by u t i l i z i n g t h e Viking l ande r camera's six-channel mul t i - s p e c t r a l c a p a b i l i t y t o produce s i n g l e p a r t i c l e r e f l e c t i v i t y s p e c t r a (ref. 20) . The p resen t c a p a b i l i t y ex tends from 0.4 t o 1.1 pm, and has the p o t e n t i a l t o provide important information about the presence o f t r a n s i t i o n metals (Fe, T i , and C r ) and t h e na tu re of their valence s ta tes and bonding character i n sili- cates, oxides , and hydroxides. (See ref. 17 . ) Such s i n g l e c r y s t a l s p e c t r a , f o r i n s t a n c e , would a l low one t o d i s t i n g u i s h between hypersthene, a u g i t e , and Fe-bearing o l i v i n e , s i n c e t h e d i s t i n c t i v e Fe+2 t r a n s i t i o n absorp t ion band char- a c t e r i s t i c a l l y s h i f t s from 0.85 pm (hypersthene) t o 0.95 p m ( a u g i t e ) t o 1.03 t o 1.05 pm ( o l i v i n e ) . range t o 2.5 pm by use o f PbS d e t e c t o r s would g r e a t l y enhance t h i s c a p a b i l i t y .

The p o s s i b l e ex tens ion o f t he Viking l ande r camera's s p e c t r a l

CONCLUDING REMARKS

The pre l iminary quasi-microscope design t h a t was evaluated i n t h i s paper c o n s i s t s o f a five-element o b j e c t i v e l e n s , a one-element f i e l d l e n s , and a six-element r e l a y l e n s . The o p t i c s fit i n t o a s l i g h t l y enlarged dus t pos t o f t h e Viking lander camera without apprec iab ly l i m i t i n g t h e camera f i e l d o f view of t h e t e r r a i n .

The quasi-microscope can provide a r e s o l u t i o n o f n e a r l y 10 llm over a 4-mm-diameter area i f t h e o b j e c t is i n exac t focus . The e f f e c t i v e depth o f f i e l d is about 0.13 mm f o r 25 F.lm/lp de ta i l and 0.32 mm f o r 40 llm/lp detail . Increased r e s o l u t i o n could be obtained w i t h h igher quasi-microscope magnifica- t i o n at the expense o f a decreased o b j e c t f i e l d and/or an increased o p t i c a l complexity. The r e s o l u t i o n is p r imar i ly l i m i t e d by t h e photosensor a p e r t u r e of t he camera; an inc rease i n t h e angular r e s o l u t i o n of the camera up t o a f a c t o r of three would provide a corresponding i n c r e a s e i n quasi-microscope r e so lu t ion without decreas ing the o b j e c t area.

The o p t i c a l r e s o l u t i o n s p o s s i b l e w i t h the quasi-microscope are normally obtained only i n the l abora to ry . By u t i l i z i n g m u l t i s p e c t r a l t echniques wi th h igh r e s o l u t i o n monospectral imagery, a great deal o f information can be obtained about r e g o l i t h o r i g i n and modi f ica t ion by phys ica l o r chemical pro- cesses. Much o f the important a n a l y s i s done a t the Lunar Receiving Laboratory a t Lyndon B. Johnson Space Center involved microscopic a n a l y s i s o f s o i l s ; much of t h a t type of a n a l y s i s could be accomplished by inc lud ing a quasi-microscope on the next p l ane ta ry lander .

Langley Research Center Nat iona l Aeronaut ics and Space Adminis t ra t ion Hampton, VA 23665 November 9 , 1976

7

REFERENCES

1 . Selivanov, A. S.; Govorov, V. M . ; T i tov , A. S.; and Chemodanov, V. P.: Lunar S t a t i o n Telev is ion Camera. Cont rac t NAS 7-100, R e i l l y T r a n s l a t i o n s , 1968. (Avai lab le as NASA CR-97884.)

2 . Sel ivanov, A. S.; Govorov, V. M . ; Z a s e t s k i i , V. V . ; and Timokhin, V. A. (Morr is D. Friedman, t r a n s l . ) : Chapter V. P e c u l i a r i t i e s of t h e Construc- t i o n and Fundamental Parameters o f t h e ltLunokhod-l Te lev is ion Systems. Lockheed Missiles & Space Co. Trans l . (From Peredvizhenaia Labora to r i i a na Lune - Lunokhod-1 , Acad. Sci. SSSR Press (Moscow), 1971, pp. 55-64.)

3. F i r s t Venus Photo Returned by Venera-9. Aviat . Week & Space Technol. , vol . 103, no. 17, O c t . 27, 1975, p. 15.

4. Brown, David A . : Data Show Venus Young Evolving P lane t . Aviat ion Week & Space Technol., vol . 103, no. 18, Nov. 3, 1975, pp. 19-20.

5. Sov ie t Venera Ins t rumenta t ion Deta i led . Aviat ion Week & Space Technol. , vo l . 103, no. 20, Nov. 17, 1975, p. 52.

6. Surveyor P r o j e c t S t a f f : Surveyor P r o j e c t F i n a l Report . P t . I: P r o j e c t Descr ip t ion and Performance - Volume I. Tech. Rep. 32-1265, Jet Propul- s ion Lab., C a l i f o r n i a I n s t . Technol. , J u l y 1 , 1969. (Avai lab le as NASA CR-105302. )

7. Mutch, T. A . ; Binder, A. B . ; Huck, F. 0 . ; Lev in tha l , E. C . ; Morr is , E. C . ; Sagan, Carl; and Young, A. T . : Imaging Experiment: The Viking Lander. I c a r u s , vo l . 16, no. 1 , Feb. 1972, pp. 92-110.

8 . Huck, F r i e d r i c h 0 . ; and Lambiotte, J u l e s J . , Jr.: A Performance Analysis of t h e Optical-Mechanical Scanner as an Imaging System f o r P lane ta ry Landers. NASA TN D-5552, 1969.

9 . Greene, V. W . ; Landgren, D. A . ; Mull in , D. D . ; and Pe terson , R . E . : Micro- s cop ic System f o r Mars Study Program. Rep. No. 2326 ( J P L Cont rac t 9501231, Elec t ron Div., Gen. M i l l s , Inc . , August 30, 1962. (Avai lab le as NASA CR-51538. )

10. Loomis, Alden A. : A Lunar and P lane ta ry Petrography Experiment. Tech. Rep. No. 32-785, Jet Propuls ion Lab., C a l i f o r n i a I n s t . Technol., Sept . 1 , 1965. (Avai lab le as NASA CR-64917.)

1 1 . Soffen, Gerald A . : Extraterrestrial O p t i c a l Microscopy. Appl. Opt., vo l . 8, no. 7 , Ju ly 1969, pp. 1341-1348.

12. Huck, F r i e d r i c h 0.; S i n c l a i r , Archibald R . ; and Burcher, Ernest E . : F i r s t - Order Op t i ca l Analysis of a Quasi-Microscope for Plane ta ry Landers. NASA TN D-7129, 1973.

8

13. Wall, Stephen D.; Burcher, E rnes t E . ; and Huck, F r i e d r i c h 0.: O p t i c a l Analysis o f a Compound Quasi-Microscope f o r P l a n e t a r y Landers. NASA TN D-7414, 1974.

14. Huck, F. 0. ; McCall, H. F.; P a t t e r s o n , W. R . ; and Taylor , G. R. : The Viking Mars Lander Camera. Space Science Instrum., vo l . 1 , no. 2 , May 1975, pp. 189-241.

15. Huck, F. 0 . ; and Wall, S. D. : Image Q u a l i t y P r e d i c t i o n : An Aid t o t h e Viking Lander Imaging I n v e s t i g a t i o n on Mars. Appl. Opt., vo l . 15, no. 7 , Ju ly 1976, pp. 1748-1766.

16. Katzberg, Stephen J . ; Huck, F r i e d r i c h 0.; and Wall, Stephen D. : Photo- s enso r Aperture Shaping To Reduce Al i a s ing i n Optical-Mechanical Line-Scan Imaging Systems. Appl. O p t i c s , vo l . 12, no. 5 , May 1973, pp. 1054-1060.

17. Huck, F r i e d r i c h 0 . ; and Park, Stephen K . : Formulation o f t h e Information Capaci ty o f t h e Optical-Mechanical Line Scan Imaging Process . NASA TN D-7942, 1975.

18. Huck, F r i e d r i c h 0.; and Park, Stephen K . : Optical-Mechanical Line-Scan Imaging Process: Its Information Capaci ty and Ef f i c i ency . Appl. Opt., vo l . 14, no. I O , Oct. 1975, pp. 2508-2520.

19. Biberman, Lucien M . , ed.: Percept ion o f Displayed Information. Plenum Press, I n c . , c.1973.

20. Park, Stephen K . ; and Huck, F r i e d r i c h 0.: A Spectral-Reflectance E s t i m a - t i o n Technique Using M u l t i s p e c t r a l Data From t h e Viking Lander Camera. NASA TN D-8292, 1976.

9

TABLE I.- PERFORMANCE AND DESIGN CHARACTERISTICS OF V I K I N G LANDER CAMERA

Character is t ics

Ins t an taneous f i e l d of view, deg

Frame w i d t h , deg E leva t ion Azimuth: min

max

F i e l d o f view, deg E leva t ion

Azimuth

Photosensor Aperture diameter, d mm Distance from l e n s , R C , mm c:

Geometric depth of focus ,

In-focus o b j e c t d i s t a n c e , k c , m

Geometric depth o f f i e l d ,

A k c , mm

A R ~ , m

P i c t u r e elements pe r l i n e , 52

B i t s per p i c t u r e element ~.

10

Survey

0.12

61.44 2.5

342.5

"lor and I High r e s o l u t i o n i n f r a r e d

0.12

61.44 2.5

342.5

~

0.04

20.48 2.5

342.5

100; from 40 above t o 60° below hor i zon ,

342.5; i n m u l t i p l e s o f 2.5O s t e p s selectable i n 10' increments

0.12 54.5

1.38

3.7

1.7 t o OJ

5 12

6

0.12 54.5

1.38

3.7

1.7 t o OJ

512

6

0.040 55.3, 54.8, 54.4, 53

0.47, 0.46, 0.46, 0.1

1.9, 2.7, 4.5, 13.:

1.7 t o

5 12

6

TABLE 11.- PREDICTED QUASI-MICROSCOPE PERFORMANCE BASED ON

FIRST-ORDER OPTICAL ANALYSES

Performance parameter

Diameter of pixel in object field, do, Fcm

Geometric resolution, Fcm/lp (1ph”m

Geometric depth of field, Akc, Fcm

Diameter of unvignetted object field, mm

Number of adjacent con- tiguous pixels per object field diameter,

Camera imaging mode

High-resolution

11

22 (45)

32 per focus step or

128 with four focus steps

4.1

372

Multispectral

33

66 (15)

96

4.1

124

11

TABLE 111.- SUMMARY OF GEOLOGIC MATERIALS

Figure ~ ~ ~~

Sample designation

Limonite

Peridotite

10(e>

Latite

Tuff Breccia

Mineralogic composition

Mixture of 1/3 labradorite, 1/3 augite, 1/3 hypersthene, crushed

~ 9 0 % limonite, crushed

~ 8 0 % augite, minor olivine and hypersthene; crushed

Plagioclase plus potassium feldspar, minor mafics; crushed

Quartz sand and minor feldspar, from Pinacates volcanic field, Mexico

~ ~~~ _ _ ~

12

, /

/ 0

/

Window

Photosensor a r r a

\ \ \ \ \ \ \ \ \ \ \ \ \ \

\ \

Figure 1.- Simplified cutaway view of Viking lander camera with quasi-microscope optics.

13

Folding

I Field lens

I 3 ing mirror

Camera lens

I

Image plane- - I + Objective lens

Object plane -+- I

(a) Detail.

21.0

lFoldlng

141.31 r Relay lens f = 53.7

ig m i

mirr-.

--

Camera lens

F15.6 D, = 9.5

Df = 14.88 I I!

I I i i

38.09 is Objective lens f = 30.0 Ff2.0

Object plane

(b) Thin-lens representation.

rror

Figure 2.- Camera and quasi-microscope optics. ( A l l dimensions are in mm.)

object obiactive plane lens

field relay

lens lens

camera image

lens plone

0 TRANSVERSE MAGNIFICATION:

r,' r : 1, 1,

m: momrc: -

THE FOCAL LENGTH OF THE RELAY LENS I S SELECTED TO BE EQUAL TO THAT OF THE CAMERA LENS; HENCE, P,= P:

0 RESOLUTION:

0 GEOMETRIC DEPTH OF F I E L D :

A!, AL, : - m2

WHERE I, IS THE DEPTH OF FOCUS IN THE CAMERA IMAGE PLANE GIVEN BY

2&'dc AIc I - Dc

0 NUMBER OF ADJACENT UNVIGNETTED PIXELS PER LINE SCAN THROUGH CENTER OF OBJECT:

Figure 3.- Thin-lens representation of camera and quasi-microscope optics with performance equations based on first-order geometric ana lys i s (from ref. 13).

15

16

12

17

48

111 28

20

e R E S O L U T I O N T E S T CHART

Figure 5.- NBS r e s o l u t i o n tes t

14

1952

cha r t .

17

:

Spatid frequency, Ip/mm

Figure 6.- Tribar frequency response of quasi-microscope and camera.

4

,

(a) Laboratory facsimile camera with 0.04' sampling intervals.

.'. :-

(b) Laboratory facsimile camera with 0.02' sampling intervals.

17

20

14

(c) Film camera.

Figure 7.- Images of NBS resolution test chart obtained with the quasi-microscope.

ru 0

Square-wave frequency response

\

/ \ / \

A!," Figure 8.- Square-wave s p a t i a l frequency response as funct ion of ob jec t

d i s t a n c e from f o c a l p lane .

'"I .9

I .8

1 I 1 1 I I 1

Figure 9.- Absolute s p e c t r a l transmittance of quasi-microscope.

( a ) Basalt. ( b ) Limonite.

0.020 samples

0.04' samples

( c ) Peridotite. ( d ) Lat i te . ( e ) Penacates 3. L-76-298

Figure 10.- Black and white images of geologic materials.

( b )

F i g u r e 11.- Color images of g e o l o g i c materials.

( C >

L-76-299

N W

i b t

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