A field spectrometer covering the range 0.4 to 2.5 microns was developed that acquires spectra in 2 seconds at 872 points within the spectrum. The Portable Instant Display and Analysis Spectrometer (PIDAS) can acquire spectra every 8 seconds and stores up to 288 spectra in bubble memory. A hand held display unit allows for display of the current spectrum acquired and superimposed on one of 128 permanently stored library spectra. PIDAS represents a major advance in the technology of field spectral data acquisition and for the first time makes possible the acquisition of enough spectra to characterize the mean and intraclass variance within a LANDSAT MSS or TM pixel

Goetz, Alexander F. H.

Breton 

NASA Technical Reports Server

r? /- 
-/ -35 p I, . . -  
N88- /// L- -? 7 
THE PORTABLE INSTANT DISPLAY AND ANALYSIS SPECTROMETER 
ALEXANDER F .  H .  GOETZ 
13756 
(P  I D A S  ) 
Center f o r  t h e  Study of Earth from Space (CSES)  
Cooperative I n s t i t u t e  f o r  Research i n  Environmental Sciences 
( C I R E S )  
University of Colorado, Boulder, Colorado 80309 
ABSTRACT 
A f i e l d  spectrometer  covering t h e  range 
0.4-2.5 p m  has  been developed t h a t  a c q u i r e s  
spec t r a  i n  2 seconds a t  872 p o i n t s  w i t h i n  t h e  
spectrum. The Por t ab le  I n s t a n t  Display and 
Ana lys i s  Spec t rometer  ( P I D A S )  can a c q u i r e  
s p e c t r a  every 8 seconds and s t o r e s  up t o  288 
spec t r a  i n  bubble memory. A hand-held d i sp lay  
u n i t  al lows f o r  d i sp lay  of t h e  c u r r e n t  spectrum 
a c q u i r e d  and supe r imposed ,  one of  1 2 8  
permanently s t o r e d  l i b r a r y  s p e c t r a .  P I D A S  
represents  a major advance i n  t h e  technology of 
f i e l d  s p e c t r a l  d a t a  a c q u i s i t i o n  and f o r  t h e  
f i r s t  t i m e  makes p o s s i b l e  t h e  a c q u i s i t i o n  of 
enough s p e c t r a  t o  c h a r a c t e r i z e  t h e  mean and 
i n t r a c l a s s  var iance w i t h i n  a Landsat MSS o r  TM 
p i x e l .  
INTRODUCTION 
The need and t h e  idea f o r  t h e  Por tab le  I n s t a n t  Display 
and Analysis Spectrometer ( P I D A S )  developed beginning a t  t h e  
t i m e  of completion of t h e  f i r s t  Por tab le  F i e l d  Reflectance 
Spectrometer (PFRS) (Goetz et al., 1975) .  One of t h e  major 
goals  i n  i n  situ spec t romet r ic  measurements t h a t  has eluded 
u s  u n t i l  now i s  t h e  a b i l i t y  t o  de f ine  t h e  average s p e c t r a l  
r e f l e c t a n c e  c h a r a c t e r i s t i c s  wi th in  one Landsat MSS o r  TM 
p i x e l  and t o  de f ine  t h e  i n t r a c l a s s  var iance w i t h i n  a p i x e l .  
Another major goal  i s  t o  be ab le  t o  make i n  situ s p e c t r a l  
measurements w i t h  a r e so lu t ion  comparable t o  o r  higher  than 
t h e  new c l a s s  of imaging spectrometers such  a s  t h e  Airborne 
Imaging Spectrometer ( A I S )  and t h e  Airborne V i s i b l e  and 
I n f r a r e d  Imaging Spectrometer ( A V I R I S )  . Most l a b o r a t o r y  
instruments do not have adequate s p e c t r a l  r e so lu t ion  beyond 
2 . 0  p m  (Inouye et al., 1987) .  A f i e l d  spectrometer  w i t h  
s u f f i c i e n t  r e s o l u t i o n  i s  a v a i l a b l e  commercial ly  (GER 
Corporation) b u t  t h e  3- t o  4 -minu te  scan time required f o r  a 
s i n g l e  spectrum i s  not i d e a l .  P I D A S  achieves t h e s e  long 
awaited goals  w i t h  t h e  addi t ion  of near-real-t ime d isp lay  of 
s p e c t r a l  r e f l ec t ance .  
8 
https://ntrs.nasa.gov/search.jsp?R=19880004374 2020-03-20T09:21:07+00:00Z
. 
S u p p o r t  f o r  t h e  c o n s t r u c t i o n  o f  PIDAS w a s  o b t a i n e d  f r o m  
t h e  W .  M .  Keck Founda t ion  w i t h  g r a n t s  i n  1983 and  1984.  T h e  
i n s t r u m e n t  w a s  f i e l d  tested i n  J u l y  1 9 8 6 .  
RE QU I REMEN T S 
T h e  main r e q u i r e m e n t  a r i s i n g  f rom p r e v i o u s  e x p e r i e n c e  
w i t h  f i e l d  i n s t r u m e n t s  w a s  f o r  a l i g h t w e i g h t ,  r u g g e d  
s p e c t r o m e t e r  c o v e r i n g  t h e  0 . 4 - 2 . 5  pm r e g i o n  a t  h i g h  
r e s o l u t i o n ,  able  t o  a c q u i r e  and  s to re  complete spectra i n  
severa l  s e c o n d s ,  a n d  d i s p l a y  t h e  r e s u l t s  f o r  i m m e d i a t e  
v i e w i n g .  I n  a d d i t i o n ,  t h e r e  w a s  a need  t o  d i s p l a y  a se t  o f  
s t o r e d  s p e c t r a  f o r  c o m p a r i s o n  w i t h  t h e  f i e l d - a c q u i r e d  
s p e c t r a .  The d i s p l a y  a n d  t h e  a b i l i t y  t o  c a l l  u p  s to red  
s p e c t r a  comprise t h e  l l a n a l y s i s l l  a s p e c t  o f  t h e  i n s t r u m e n t .  
The d i s p l a y  c a p a b i l i t y  i s  a major a d v a n c e  i n  f i e l d  
measurements  b e c a u s e  many o f  t h e  spectral  charac te r i s t ics  of 
s u r f a c e  materials are found i n  t h e  spectral  r e g i o n  beyond t h e  
s e n s i t i v i t y  o f  t h e  human e y e .  P r o p e r  sample l o c a t i o n  a n d  
i d e n t i f i c a t i o n  i s  made p o s s i b l e  by a n e a r  real-time d i s p l a y .  
DESIGN 
I n  order  t o  m e e t  t h e  r e q u i r e m e n t s  d i s c u s s e d  above, it 
w a s  n e c e s s a r y  t o  develop a s p e c t r o m e t e r  w i t h  f e a t u r e s  n o t  
a v a i l a b l e  i n  e x i s t i n g  i n s t r u m e n t s .  I n  p a r t i c u l a r ,  t h e  
i m p l e m e n t a t i o n  r e q u i r e d  t h e  u s e  o f  v e r y  f a s t ,  l i g h t w e i g h t  
r u g g e d  spectrometers a n d  a n  o p t i c a l  h e a d  c o n n e c t e d  t o  t h e  
spectrometers w i t h  o p t i c a l  f i b e r s .  Table 1 l i s t s  t h e  new 
f e a t u r e s  r e q u i r e d  f o r  t h e  d e s i g n .  
Table 1. Des ign  f e a t u r e s  
Hand-held l i q u i d  c r y s t a l  d i s p l a y  
Silica and "exotic" fluoride fibers 
Fast (f/1.2) s o l i d  s i l i c a  s p e c t r o m e t e r s  
S t o r e d  l i b r a r y  o f  spectra 
Spectral  r e s o l u t i o n  g r e a t e r  t h a n  m o s t  l a b o r a t o r y  
2-second data a c q u i s i t i o n  t i m e  
i n s t r u m e n t s  
F i g u r e  1 shows t h e  PIDAS i n  o p e r a t i o n ;  F i g u r e  2 shows 
t h e  major f e a t u r e s  o f  t h e  i n s t r u m e n t .  The r e q u i r e m e n t  f o r  
h i g h  spectral  r e s o l u t i o n  c o u l d  o n l y  be m e t  b y  u s i n g  g r a t i n g  
spectrometers. A great  s a v i n g  i n  w e i g h t  a n d  volume c o u l d  
h a v e  b e e n  a c h i e v e d  b y  u s i n g  c i r c u l a r  var iable  f i l t e r s ,  as 
u s e d  i n  t h e  PFRS, b u t  t h e s e  f i l t e r s  have  a l i m i t a t i o n  i n  
spectral  pe r fo rmance ,  p a r t i c u l a r l y  i n  t h e  v i s i b l e  p o r t i o n  o f  
t h e  s p e c t r u m .  The  A X / X  v a l u e s  i n  t h e  v i s i b l e  a r e  
a p p r o x i m a t e l y  0 .04  and  0 .015  i n  t h e  s h o r t  wavelength  i n f r a r e d  
(SWIR). A t  2 .2  pm t h i s  t r a n s l a t e s  i n t o  a r e s o l u t i o n  of 
9 
ORIGINAL PAGE B 
OF POOR QUALITY 
F i g .  1. P I D A S  d u r i n g  f i e l d  t r i a l s  i n  C u p r i t e ,  Nevada. 
RAIN SHIELD 
SHIELD 
F i g .  2 .  
li 
3 EUEELE a!a @ 
3 
COMPUTER I 
CARD CAGE 
MEMORY 4- CARD CAGE e 
-11 
SPECTROMETERS 
IN PRESSURE TIGHT. 
PURGED HOUSING 
I 
P I D A S  c o n f i g u r a t i o n .  
10 
DPTICAL HEAD b 
KEYPAD 
DISPLAY 
. * P, -d 
approximately 33 n m  o r  a r e s o l u t i o n  60% poorer  than  t h a t  
a v a i l a b l e  from AVIRIS. The s p e c t r a l  r e so lu t ion  of PIDAS i n  
t h e  SWIR i s  def ined by  t h e  4 . 8  n m  sampling i n t e r v a l  and i s  
approximately 10 nm. The sampling i n t e r v a l  i n  t h e  v i s i b l e  
port ion of t h e  spectrum i s  0.88 n m .  
A major design goal  was t o  make t h e  o p t i c a l  head a s  
l ightweight  a s  poss ib l e  which meant t h a t  t h e  spectrometers  
had t o  be separa ted  from t h e  fo re -op t i c s .  Therefore,  t h e  
o p t i c a l  head c o n s i s t s  s o l e l y  of t h e  fore-opt ics ,  a s h u t t e r  
and a chopper, and t h e  incoming energy i s  t ransmi t ted  t o  t h e  
spectrometers by  means of o p t i c a l  f i b e r s .  Figure 3 shows a 
block diagram of t h e  spectrometer  system. The o p t i c a l  
components cons i s t ing  of t h r e e  spectrometers with de t ec to r s ,  
t h e  a m p l i f i e r s ,  and g r a t i n g  d r i v e s  a r e  conta ined  i n  a 
pressure vesse l  shown i n  Figure 4 .  The spectrometer covering 
t h e  VNIR port ion of t he  spectrum cons i s t s  of a camera lens ,  a 
f ixed  g ra t ing  and a 512-element s i l i c o n  de tec tor  a r r ay .  T h i s  
spectrometer  covers  t h e  region 0.425-0.922 p m .  The VNIR 
spectrometer assembly i s  shown i n  Figure 5 .  
The spectrometers f o r  t h e  SWIR por t ion  of t h e  spectrum 
ranging from 0.86 t o  2 . 5  pm posed a more d i f f i c u l t  problem. 
Lead s u l f i d e  d e t e c t o r s  provided the  bes t  compromise between 
s e n s i t i v i t y  and ease  of cool ing .  A disadvantage of l ead  
s u l f i d e  d e t e c t o r s  i s  t h a t  it i s  not  p o s s i b l e  t o  o b t a i n  
mul t ip lexed  a r r a y s  of d e t e c t o r s .  T h i s  means t h a t  each 
de tec to r  r equ i r e s  i t s  own preamplif ier  and analog c i r c u i t r y .  
Unlike t h e  v i s i b l e  spectrometer which contained no moving 
p a r t s ,  it was necessary t o  s t e p  t h e  g r a t i n g  i n  each of t h e  
SWIR spec t rometers  through four  p o s i t i o n s  i n  2 seconds.  
Using 45-element d e t e c t o r  a r r ays  i n  each spectrometer,  360 
channels spaced approximately 4 . 7  nm apa r t  were obtained i n  
t h e  0.86-2.5 pm region.  A very compact Spectrometer design 
was developed employing a s o l i d  block of water-free s i l i c a  
inco rpora t ing  all t h e  o p t i c a l  surfaces i n  one u n i t .  By t h i s  
means, t h e  only alignment required was t o  focus and a l i g n  t h e  
de t ec to r s  and t h e  o p t i c a l  f i b e r s .  T h i s  solid-Schmidt design 
made poss ib l e  a f a s t ,  f / 1 . 2  spectrometer i n  order  t o  acquire  
t h e  maximum s igna l - to-noise  r a t i o .  The f a s t  spectrometer 
design i n  t u r n  placed a requirement f o r  a high numerical 
a p e r t u r e  ( 0 . 5 )  f o r  t h e  o p t i c a l  f i b e r s .  A f u r t h e r  
complication a rose  from t h e  f a c t  t h a t  s i l i c a  o p t i c a l  f i b e r s  
a r e  not  completely water - f ree  and, t h e r e f o r e ,  e x h i b i t e d  
absorption f ea tu res  a t  1 . 4 ,  1 . 9  and 2 . 2  pm. Fluoride o p t i c a l  
f i b e r s  a r e  u s e d  t o  couple t h e  f o r e - o p t i c s  t o  t h e  SWIR 
spec t rometers .  The solid-Schmidt spectrometer  o p t i c s  a r e  
shown i n  Figure 6, and t h e  g ra t ing  d r ive  assembly i n  Figure 
7 .  Figure 8 shows t h e  spectrometer enclosure viewed from t h e  
s i d e  of t h e  SWIR d e t e c t o r s  and t h e  90-channel analog PC 
boards. 
The e l e c t r o n i c s  and da ta  handling a r e  designed around a 
CMOS 8-b i t  processor with s torage i n  bubble memory. The 
11 
ORIGINAL PAGE IS 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
Fig. 3. PIDAS block diagram. 
Fig. 4. PIDAS with cover re- 
moved showing the pres- 
surized container hous- 
ing the spectrometers, 
the hand-held display 
unit and the fore-optics 
head. 
Fig. 5. VNIR spectrometer 
assembly. 
12 
ORIGTNAT P-KGE IS 
S)E POOR QUALITY: 
F ig .  6 .  So l id  Schmidt SWIR F i g .  7 .  SWIR g r a t i n g  d r i v e  
s p e c t r o m e t e r  op t ics .  assembly .  
F i g .  8 .  P r e s s u r e  vessel w i t h  t h e  hous ing  removed 
showing t h e  d e t e c t o r  p r e a m p l i f i e r  b o a r d s .  
processor h a n d l e s  a l l  t h e  i n p u t / o u t p u t  func t ions  and provides 
t h e  data  a c q u i s i t i o n  sequence ,  d i s p l a y  and  memory access. 
The hand-he ld  t e r m i n a l  c o n s i s t s  of a key pad and  a 128- x 
256-element  l i q u i d  c r y s t a l  d i s p l a y .  Software s t o r e d  on a 
prom al lows t h e  d i s p l a y  of e n g i n e e r i n g  data  and  i n d i v i d u a l  
spectra a t  v a r i o u s  m a g n i f i c a t i o n s .  Data f r o m  a 1 2 8 - s p e c t r a  
b u b b l e  memory l i b r a r y  can  be super imposed  upon t h e  c u r r e n t  
data  a c q u i r e d  o r  s t o r e d  i n  t h e  288 spectra da t a  b u b b l e  
memory. The software f e a t u r e s  i n c l u d e  t h e  a b i l i t y  t o  expand 
t h e  scale by  u s e  of g a i n  and  o f f s e t  f u n c t i o n s  s o  t h a t  t h e  
f u l l  8 - b i t  r e s o l u t i o n  can be  d i s p l a y e d .  
PIDAS i s  a s i n g l e  c h a n n e l  i n s t r u m e n t ,  and,  t h e r e f o r e ,  
s p e c t r a  of s t a n d a r d s  and  samples are collected s e p a r a t e l y .  
I n  normal  o p e r a t i o n ,  a spec t rum o f  a s t a n d a r d  i s  collected 
and  encoded  t o  1 2  b i t s .  The most s i g n i f i c a n t  8 b i t s  a re  
s t o r e d  as a r e f e r e n c e  f o r  a l l  subsequent  sample s p e c t r a  u n t i l  
a new s t a n d a r d  s p e c t r u m  i s  a c q u i r e d .  When t h e  sample 
spec t rum i s  a c q u i r e d ,  t h e  i n s t r u m e n t  a u t o m a t i c a l l y  creates a 
13 
r a t i o  of sample t o  s tandard before  s t o r i n g  t h e  spectrum i n  
bubble memory. The advantage of t h i s  method i s  t h a t  no gain 
changes a r e  r e q u i r e d  and s t o r a g e  i s  op t imized .  The 
d i sadvan tage  i s  t h a t ,  p a r t i c u l a r l y  f o r  dark samples,  
d i g i t i z a t i o n  e r r o r  becomes a major f a c t o r  and l i m i t s  t h e  
a b i l i t y  t o  increase  t h e  s ignal- to-noise  r a t i o  by averaging 
sample s p e c t r a .  A summary of t h e  major i n s t rumen t  
c h a r a c t e r i s t i c s  i s  given i n  Table 2 .  
Table 2 .  P I D A S  c h a r a c t e r i s t i c s  
Portable ,  backpack, self-contained, approx. 67 pounds 
Spec t ra l  range - 0 . 4 5  t o  2 .5  p n  
Sampling i n t e r v a l  
Visible  - 0.88 nm ( 5 1 2  channels) 0 . 4 2 5 - 0 . 9 2 2  pm 
Inf rared  - 4 . 7  nm (360 channels) 0 . 8 5 6 - 2 . 4 9 0  pm 
Fore-optics - f / 1 . 2 ,  6 degree c i r c u l a r  FOV 
Spectrometers 
V I S  - Nikon opt ics ,  f /2 .8 ,  512 S i .  
IR-2  - s o l i d  Schmidt, f /1 .2 ,  45 PbS. 
Processor-low power 280 type, 1 6 K  RAM, 8 K  ROM 
D a t a  Memory - bubble, 288 spectra ,  1 2 8  spec t ra  
Hand-held terminal-display 128 x 256 element LCD 
Data acqu i s i t i on  t i m e :  2 s ec . ,  repeat i n t e r v a l :  8 sec .  
sample l i b r a r y  
keypad-custom numeric and command e n t r y  
Data s tored  i n  t h e  bubble memories a r e  downloaded onto a 
floppy d i s c  ac ross  an RS 232 i n t e r f a c e  t o  a P C .  Ba t te ry  
power c o n s i s t s  of t e n  N i C d  D cel ls .  One charge w i l l  r u n  t h e  
instrument f o r  approximately two and a ha l f  hours, s u f f i c i e n t  
t i m e  t o  c o l l e c t  a f u l l  memory load of 288 s p e c t r a .  The 
bubble memories a s  well a s  t h e  b a t t e r i e s  a r e  exchangeable i n  
t h e  f i e l d .  
The i n i t i a l  t a r g e t  instrument weight was 4 2  pounds. The 
present  weight i s  67 pounds; however, it i s  a n t i c i p a t e d  t h a t  
i n  subsequent vers ions of t h e  instrument t h e  weight w i l l  be 
reduced s i g n i f i c a n t l y .  
TEST RESULTS 
I n  t h e  l a s t  year ,  P I D A S  has acqu i r ed  thousands of 
s p e c t r a  f o r  a p p l i c a t i o n s  i n  mineralogy, b o t a n i c a l  s t r e s s ,  
A V I R I S  c a l i b r a t i o n ,  BRDF measurements of snow and i c e  and 
non-destructive t e s t i n g  of a r t i f a c t s  i n  t h e  National Museum 
of Guatemala. Transportation and f i e l d  use have not brought 
about any major instrument f a i l u r e s ,  and it  can be assumed 
t h a t  it w i l l  continue t o  be r e l i a b l e  i n  t he  f i e l d .  
The s igna l - to-noise  c h a r a c t e r i s t i c s  of t h e  instrument 
a r e  shown i n  Figure 9 .  These da ta  were acquired a t  Rogers 
14 
Dry Lake d u r i n g  a n  AVIRIS c a l i b r a t i o n  t e s t .  The l o w  s i g n a l -  
t o - n o i s e  r a t i o  a t  1 . 4  a n d  1 . 9  pm i s  assoc ia ted  w i t h  t h e  
a t m o s p h e r i c  water a b s o r p t i o n  f e a t u r e s .  The e f f e c t s  o f  o t h e r  
m i n o r  water a n d  C 0 2  b a n d s  a re  a l s o  v i s i b l e .  The r a p i d  
v a r i a t i o n  i n  t h e  s i g n a l - t o - n o i s e  v a l u e s  i s  c a u s e d  b y  t h e  
v a r i a t i o n  i n  detector c h a r a c t e r i s t i c s  w i t h i n  t h e  45-element  
a r r a y s .  
PIDAS measurements  i n  t h e  f i e l d  have  been  compared w i t h  
l a b o r a t o r y  s p e c t r a  r e f l e c t a n c e  c u r v e s  o f  t h e  same s a m p l e s .  
F i g u r e  1 0  shows s u c h  a c o m p a r i s o n  f o r  a l u n i t e .  The 
combina t ion -ove r tone  a b s o r p t i o n  f e a t u r e  i n  a l u n i t e  a t  2 .22  p 
has a t r u e  a b s o r p t i o n  band i n  t h e  PIDAS da ta  ( u p p e r  c u r v e )  
b u t  shows o n l y  as a s h o u l d e r  i n  t h e  l a b o r a t o r y  da ta .  The 
Beckman 5240  s p e c t r a l  r e s o l u t i o n  i n  t h i s  r e g i o n  i s  
a p p r o x i m a t e l y  2 5  nm ( I n o u y e  et a l ,  1 9 8 7 ) .  The P I D A S  
r e s o l u t i o n  of a p p r o x i m a t e l y  1 0  nm i s  s u f f i c i e n t  t o  r e p r o d u c e  
e s s e n t i a l l y  a l l  t h e  spectral  f e a t u r e s  of s o l i d s  i n  t h e  0 .4-  
2 . 5  p m  r e g i o n  a n d  h a s  a b o u t  t w i c e  t h e  r e s o l u t i o n  of t h e  
c u r r e n t  a n d  p roposed  imaging spectrometer s y s t e m s .  
500 
30 MEASUREMENTS 
450 OF Bas04 PANEL SOLAR ILLUMINATION 
400 
350 
300 
0 z 
' 250  
m 
c 
ffl 
-4 
? 200 
150 
100 
50 
0 
600 eo0 io00  1200 1400 1600 ieoo 2000 2200 2400 
WAVELENGTH I nm 1 
F i g .  9 .  S i g n a l - t o - n o i s e  as a f u n c t i o n  o f  wavelength  
o b t a i n e d  from 30 s e q u e n t i a l  measurements of 
Rogers  Dry Lake. S/N i s  d e f i n e d  as t h e  mean/ 
s t d .  d e v i a t i o n  f o r  e a c h  wavelength .  
15 
90 
70 
n 
$ 
Y 
W 
0 5 50 
c- 
0 
W 
A 
LL w 
U 
30 
10 
1 
ALUNITE 
, 
1.9 2.1 2.3 2.45 
WAVELENGTH 
(m i cr o met er s) 
Fig. 1 0 .  Reflectance spec t ra  of a l u n i t e  taken by PIDAS 
(upper) and t h e  Beckman 5 2 4 0  ( lower) .  The 
superior  reso lu t ion  of P I D A S  i s  shown f o r  t h e  
absorpt ive f ea tu re  a t  2 . 2 2  p. 
ACKNOWLEDGEMENTS 
The development of P I D A S  could not have taken p l ace  
without t h e  support of many indiv idua ls  a t  J P L ,  among those 
Harry Enmark, P ro jec t  Manager, Bob Irigoyen, P ro jec t  Engi- 
neer ,  and Norm Page, Optics Designer. Arden Albee was t h e  
Cal tech  P r i n c i p a l  I n v e s t i g a t o r ,  Brian C u r t i s s  of Cal tech 
p rov ided  i n v a l u a b l e  suppor t  i n  t h e  l a t t e r  phases  of 
instrument development and developed a l l  t h e  da t a  a n a l y s i s  
software.  P I D A S  i s  covered by U .  S .  Patent #4,560,275 issued 
t o  t h e  Cal i forn ia  I n s t i t u t e  of Technology. T h i s  research was 
16 
s u p p o r t e d  i n  l a rge  p a r t  by  a g r a n t  f r o m  t h e  W .  M .  Keck 
Founda t ion .  
REFERENCES 
G o e t z ,  A .  F .  H .  1 9 7 5 .  P o r t a b l e  F i e l d  R e f l e c t a n c e  
S p e c t r o m e t e r ,  Appendix E i n  & p l i c a t i o n  of ERTS IJU&ISS 
and Image Processlna t o  R e m  Geoba lc  P r W  a n d  
Geoloaic Maggin? i n  N o r t h e r n  A r i z o n a ,  J P L  T e c h n i c a l  
Report 32-1597. 
Inouye,  C . ,  A .  F .  H .  Goetz and S .  S c h u l t z .  1987.  R e f l e c t a n c e  
S p e c t r a  of 156  m i n e r a l s ,  0 . 4 - 2 . 5  pm. J P L  T e c h n i c a l  
Report, i n  press.  
- 
17 


The Portable Instant Display and Analysis Spectrometer (PIDAS)

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server