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https://ntrs.nasa.gov/search.jsp?R=19770026638 2020-02-12T07:51:20+00:00Z
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,.
S-191 SENSOR PERFORMANCE EVALUATTON ,^
FINAL REPORT
Job Order 75-2154
(NASA-CR- 151527) S-191 SENSOR PERFORMANCE N77- 335.92 '. ,r
EVALUATION Final Report (Lockheed ^%'-
Electronics Co.,) 76 p HC A05/MF AO iCSCL 14B Unclas
G3/43 49701
Prepared . By
Lockheed Electronics Company, Tnc.
Aerospace Systems Division
Houston, Texas;,; r
' Contract NAS 9-12200
for
^1^^^^G^%^^^^, ^ `Earth Observations Division ^^^ ^^- ^-^k^^ ^^ ;
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a
National Aeronautics and Space Adrninistratwn,^
LYNDON B. JUHNSON SPACE CENTERHouston, Texua
.^June 1975
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LEC-5778 .^-n
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ACKNOWLEDGMENTSt
I would like to acknowledge several individuals for
.. their contributions to this document: Richard D. Juday (J5C) ;!reviewed this document. and gave helpful suggestions and
constructive criticisms. William E. Hensley (JSC) gave
direction and helpful suggestions on the forma and contents.
Especially appreciated in the final days of compilation
of this document were my two programmers; Edward L. Downes
(LEC), who. wrote the 5-191 programs and implemented the LWL3
portion.,. and William V. Argo, Jr. (LEC) who implemented the
SWL portion. of the program. Both showed superior knowledge
in their field of endeavor and were timely in the implemen- jtation and requested variations in the program. ^` a37
I would also like to thank 'the suggestions and ideas
contributed by Peter D. Lloyd (LEC) and Charles E. Campbell '!
,(LEC). They were very_ .helpful in the interpretation of
instrument .anomalies.s
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CONTENTS
Section Page.f
1.0 INTRODUCTION . 1-1
1,
2.0 SWL ANALYSIS. . ^. 2-1
^` ^ 2.1 COMPARISON OF DATA FROM EREP S-191( AND THE BACKUP UNIT S-191.: 2-1 ,. .
2.2 INTERCOMPARISON OF 5-191 LUNAR `'DATA 2 -13
j ^ 2.3 COMPARISON OF LUNAR DATA FROM S-191AND THE LITERATURE 2-21
2.4 PRELIMINARY OFF-BAND RADIATLONCORRECTIONS. .-
2-25
3.0 LWL ANALYSIS. 3-1
3.l AUTOCAL ANALYSIS 3-1
3.2 INTERCOMPARISON OF LWL MARE DATA 3-5
3.3 COMPARISON OF EREP LUNAR DATA TO :_THE LITERATURE . 3-13
3.4 COMPARISON OF EREP 5-19.1 DATA TOATMOSPHERIC. MODEL DATA 3-15 ":
k
4.0 CONCLUSION . 4 -1
r 4
5 .0
iREFERENCES . ',
.,5 -1
^' APPENDIX MEASUREMENTS TAKEN ON LAKE TITICACA INSUPPORT OF SKYLAB EXPERIMENTS
A_
TABLES <,
Table Page;,^.
I S-191 EREP,LUNAR DATA IDENTLFICATION:' 2-4
II TIME FRAMES FOR'RESERVOIR/LAKE DhTA 3-19
.....111
rtr`F
_- --
._ ^..^ n .. .. _._ ... .- -
r
>i
FIGURES
J-
^^
;.
Figure Page r
- 1 Location of Mares used in the 5-191 lunarcalibration 2-3 ^
2 Mare Serenetatis DOY 165 (LC-1) 2-5 ^
3 Mare Tranquillitatis DOY 165 (LC-1) 2-6 .^
4 Mare Serenetatis . DOY 254 (LC°3) 2-7
5 Mare Tranquillitatis DOY 254 (LC-3) 2-8
6 Mare Serenetatis DOY 343 (LC-4) 2-9
7 Mare Tranquillitatis DOY 343.. (LC-4) . 2-10 ^
8 Mare Serenetatis DOY 007 LC-5( ) 2-11
9 Mare Tranquillitatis DOY 007 (LC-S) 2-12
10 Relative radiances of Mare Serenetatis toDOY 165 (LC-1). (Relative. solar irradiance
..correction to DOY.00.7.) n 2-16 _;
11 Relative _radiances of Mare Tranquillitatis toDOY 165 (LC-1). (Rela ve solar irradiancecorrection to DOY 007.) 2-17
12 Relative responsivites normalized toDOY 165 (LC-l). 2-18 ^ ^.
- 13 .Comparison of McCord's data and.EREP data:y
2-23 'i;
14 Off-band correc ion applied to data fromMare Serenetatis. 2-27
15 Responsvties for a 8.972°C referencesource tempera ure. 3-3
16 Responsivities forea -1. 5.24..2.°C referencesource. _ 3-4
17 LWL xadiance data from. Mare Serenetatis 3-6
;,
iv
f....
r
1
'•
^,
s
-.
Figure Fage
}
^`
18 LWL radiance. data from Mare Tranquillitatis 3-7E'
19 Radiance ratio from Mare Serenetatis relativeo to DOY 165 (LC-1) 3-8
20 Radiance ratio from Mare•Tranquillitatis• r
relative to DOY 165-(LC-1). 3-9
21 Heated responsivity ratios used in lunar caldata. 3-11
22 Comparison of Mare Ser^netatis radiance fromLC-1 and equivalent blackbody radiance. 3-12
23 Comparison of radiance data from Marea
Serenstatis SL-4 b S-191 _and Shorthill .( ) Y 3-16
24 Comparison of radiance data from Mare.Tranquillitatis (SL-4) by S-191 and ".Shorthill 3-17 ,
` 25 Location of S-191 pointing direction and ^ground truth data collection. 3-22
9
26 Comparison of S-191 radiance data on MonroeReservoir and radiance predictions by the .;Calfee-Pitts and Anding atmospheric models. 3-23
27 Comparison of S-191 radiance data on theGreat Salt Lake-and the radiance predictionby the.Calfee-Pitts atmospheric model 3-24 .-,
28 Comparison of S-19.1 radiance data on LakeTiticaca and radiance. from a 13.5°Cblackbody 3-25 :;
'^
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DEFINITION OF TERMS
r
DOY Numerical day of year during EREP operation
(May 1973 through February 1974). An example
of this relationship which exists between '
EREP DOY 165 and the Gregorian calendar is
fJune. 14, 1973. There is no redundancy in the.
EREP numbering system; however,. there may be
1 confusion in the chronological order; for
instance lowernumber DOY's from 001 . through.
032 refer to 1.974, while. higher DOY numbers^
refer to 1973.
ECLIPTIC The plane defined by the earth's orb itabout
'r the sun.
EREPi
Earth Resources Experiment Package
Kp K-index. is a measure of transent..geomagnetic.
activity recorded by earth observatory magne- t ^
tometers over a three hour range. The index '^
varies from 0 to 9, with K _ 0 indicating
q^iet`or calm,`while K _ 9 signifies great '
geomagnetic fluctuations. The K-index from
several observations are combined to form..a '^
j worldwide', or planetary index, Kp.3
1^
^_ LUMINANCE The angle of observation (reflection angle)^ LONGITUDE
projected into the phase plane. -(From
figures 3 and 5 in section 3.4 -of ref . 3.) "^Y
f PHASE ANGLE In this. re ort, the included angle describedPI(' by two imaginary lines intersecting at the ^:,_} ri
center of the moon, one passing through the ^ n
K center of the sun and the other through the
point pf.observation.:,;;;;
E _ vi
,a;
- ___- ---__. , __ , --_ _ _,__ -- - r ._ - _ _— ___,__ __ _
._._
:'
S-191 SENSOR PERFORMANCE EVALUATION :`
FINAL REPORT-
f
1.0 INTRODUCTION '
A final analysis has been, performed on the Skylab S-191
spectrometer data received from missions SL-Z, SL-3, and SL-4.
This. analysis follows the plan put forth in LEC-0413-5 on an
Instrumentation Plan for S-191 System Spectroradiometric
Response Determination (SPE-S-191-005).
The purpose of this task. was to determine the repeat-
ability and accuracy of the. S-19i spectroradiometric
internal calibration by correlation to the output. obtained
from well-defined external targets. These included targets4.
-on the .moon and earth as well as deep space. In addition,
the accuracy of the S-191 short wavelength auto calibration '.,^
was flight checked by correlation of the EREP S-1.91 outputs
and the Backup Unit S-191 outputs after viewing selected '
targets -on_ the moon,'
The analysis is divided into two sections because of
general dissimilarities in the data; short wavelength (SWL)
and- long wavelength (LtiVL)
1-1
,^ ^^
..-^..
9^1 I,, 4 _ _ _ __. ___,.. ^. _.
_ _ _ __ ,.
;^
^^2.0 SWL ANALYSIS
The SWL analysis was . first accomplished by comparing. the
_ outputs from several. lunar data takes both from the .EREPf
S-191 .and the Backup Uni S-191. In addition, the EREP 5-191
lunar outputs from. different lunations wer,^ intercompared
in order to establish the relative accuracy aid to determine
if any drift and/or degradation had occuxed in the instru-
merit. Finally, the lunar spectral data was. compared
j to rela ive data in . the . literature and some. preliminary
off-band corrections were made.r
2.1 COMPARISON OF DATA FROM EREP S-191.
.AND THE BACKUP UNIT 5-191
t During the months of November 1973. through March 1974, the
` Backup Unt.S-.191 was operated during appropriate periods ofH
^^ several lunations in conjunction with the EREP"S-191 to obtain
^ data. from three Mare areas on the moon. This Backup . Unit
data was collected primarily at Mt. Capulin, New Mexico and ^'
^' Denver, Colorado. The .reason for collecting the backup
unit data was that there had been some question as to the
pre-flight SWL calibration of the EREP 5-191. Because'of ^"I
this, it .was de iced to ntercompar•e their outputs on a '
^' common target to gaim`additional confidence in ` the flgh ;^
unit's_. calibration.
.'
The re ults of the backup unit data taken is-contained
A
;;
in the final report of MSG-05548(ref. 1). In this report, the^'
Y phase angle* versus radiance at everal different wavelengths^^
See Definition'of Terms, Page vi.
a
7i
+^
3 2-14
1
__
a^,, ^.
^ _^
.y e-.. .. ...r ..., .......
d ^
was developed for Mare Serenetatis, Mare Tran,quillitatis,
and Mare Imbrium.. An illustration of the location of the
Mares and the approximate. field of view of S-191 superimposed
on them is shown in figure L .This data was not individually
solar irradiance corrected but most of the data was collected
in November 1973, .December 1973,. and January 1974 .which is
very close to minimum solar distance and is considered eQuv-
alent to EREP* data taken on January 7, 19.74.
4:Lunar data was collected from six EREP passes. However,
only. four will be used in the .following analysis. LC-2
(Lunar Calibration-2) did not have correlating photography
and LC-6 was a special data. taken .close to full moon where
.radiance versus .phase an^^^.e is a highly non.-linear function..
The four lunar data times and locations, the lunar
phase angles*, and solar irradiance correcton^•factors are3
shown in table I.
Seven scans were usually averaged fora generation-of . the ,
data_ on each Mare if all scans within the time s an were. good.p
' A11 radiance data. was solar distance normalized-to DOY 007* ^ t
(Day of .Year 0.07) for comparison to the S-191 Backup Unit data, -
`3
.
_The comparisons for Mare Serenetatis and Mare Tranquil-
I ltats are shown in figures 2, 3, 4, 5; 6, 7, 8, and . 9. The-;
resu is of this :comparison are very good.-for Mare Serenetatis3
=^
Solar irradiance correction refers to .the calculationof the difference `in irradiance at the. lunar surface as>caused
_n
by seasonal variations n'.the solar dis-tance. See reference Zfor basis- of this calculation. ''
*^ See Definition of" Terms, page vi. '^^
-'^
'r'^
2-2 ..1
r. y^- q
t
^^_ ^:^ _..^T__^ - ^ _ _ ___ --d
191 FOV S(TPERIMPOSEDON MARES
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WAVELENGTH (µm) ;^ ^
Figure 5.— Max'e Tranquilltatis DOY 254 (LC-3). ^'
ii 4
..^ ... ^_ .. ... r.'' M,
_ _ ___ _ .
^, _ 1.__ _____. __^
^ .,, ^- ° .^ ^, ^^ iy^,, ^..r.
t ^:
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WAVELENGTH (am)- - - ---
Fgure 6.— Mare Serenetatis D0Y 343 (LC-4).,: t- _..., _ ^ ._.._ .___ ^. __ ^ ^.^_^,_... _ . , , . _ , ^F-- - _. , , ^, . __ .. _ _ _ __. ._ _^ _.
.. a . . - ^.. ^; _ _ . ati.
.. V_
^ r
.... w.
E
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FHN
o ? 10'wUZQ
Q
JQF-Uwa
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on (LC-4) DUY 343 (one of the days when a large amount of
backup unit data was obtained), plus (LC-3) DOY 254 with
differences on the order of ^ percent. Conversely, Mare
Tranquillitats, in the same day, does not fit the backup
unit prediction very well and is 'generally high by a factor
of 15 percent. A11 EREP data fall within about 15 percent
of the backup unit's prediction; however, no. clear cut phase
angle versus radiance function appears to exist for compar-
ing small phase angle changes on different lunations. Other
factors that. will be described may explain this non-
. correlation,
'^ 2.^ INTERCOMPARISON OF S-191 •LUNAR DATA
Before the moon was selected as an external calibration.
source, an extensive lite-rature search was undertaken to
determine its suitability. The major problem was in matchingi
theillumination geometry for selected areas.. The best
solution lay in selecting uniform Mare areas.. and taking data ar
a approximately -the. same. relative timzs during different
lunations. It was realized that the same precise llumina-
tion geometry is never reproduced; however, the.. phase angle
has been shown empirically (ref. 3) to be an accurate monitor
`# of Lunar brightness.- This is because the moon's eQuatenal ;:'.. .
plane is •inclined to the ecliptic* by l-1/2 degrees . causing
luminance longitude* and selenographc* longitude to be very ,x
nearly the same.
The moon. is-not Lambertan in character and anon-linear -'
relationship develops between phase angle and brightness ati-
,.
^,See De inition o erms, pages vi and vii:. s`
a!.,
., 2-13
w
^^
[?
,f
^^;
,,,
f1
a^
phase angles included within ±5 degrees. A nearly lineari
relationship exists outside these bounds up until the time
that shadowing approaches,
The selection of a proper phase angle is also limited
by the fact that color differences and poTarizaaion begin
>'a to occur at large phase angles.. For this reason,. angles
r',: were chosen close to full moon but outside the non-linear
.portion of . the brightness phase angle relationship..
Several othex variables which may cause second-orderr,
effects were generally ignored in this instrument analysis.
These were:.
1. Variation in the solar constant
,: 2. Amount . of reflected ashen (earth) light impinging
on the moon and reflected back to S-191.
` 3. Luminescence of the.. lunar surface as caused by UV,
', X, and corpuscu ar energy from the-Sun.
^_ -
Luminescence of the lunar surface caused by UV, X
and corpuscular energy from the sun,..however, was
investigated on a cursory basis by analysis_of the
geomagnetic planetary` index Kp* . This was obtained
•for the months and days duxing the lunar cals from
the Journal of Geophysical Research. Thee. values
for the sum of Kp during lunar cats are shown-on
^^ ^
-.
the following page.
:! Sere De inition o Terms, page vi.
u.;ai
;;f
2-14
^:
^k
,^•,
^e= _ _
__^ i.r..,.,n.T^^-
r-
MagneticE K^> condit'i:on
June 14, 1973(DOY 165) LC-1
Sept. 11, 1973
(DOY 254) LC-3
25-1/3 Disturbed
19-1/3 Disturbed Changing.,Sept . . 12 was.-quiet with.E Kp 14
4' Dec. 9, 1973
(DOY 343) LC-4 28 Disturbed
Jan. 7, 1974(DOY 007) LC-S 4=1/3 Very quiet
v
...The interpretation of this tabulation. is that LC-1
and LC-4 would .have the greatest possibility of '^
^:containing luminescing radiation in their S-1.91
,; measurements... Because of the closeness in the,.
^^^
different radiance value measurements and limited
'' -,, number of lunar . cal measurements, further inter-a
pretaton of this effect has not been attempted.
The 5-191. radiance from lunar calibrations. for LC-1,
:' LC-3, LC-4', and LC-S, whose times. are shown. in table I, were -'
all corrected for solar irradiance difference and normalized '
to LC-1 (DOY 163) to determine whatchanges had. occurred.
during the Skylab mission The-curves for Mare Serenetatis
^^ are shown in figure 10 and Mare - Tranquilltats are shown"in = `^;- a_ figure 11. ...The normalized responsivites'used Yn each rad-
' fiance calculation are also plotted in figure 12 so that it
' could be determined approximately how the detectors were
} behaving...
-;'. '
j
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2-15
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1.25i
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wa ^,
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1.t
1.^
1.0
1.
1.(,u.4 U.b U.a' 1.0 I.L I.^F i.b 1.t5l,iJ 2.2 2.4 2.6
WAVELENGTH (um)Figure 11. — Relative radiances of Mare Tranquillitats to DOY 165 .{LC-1).
(Relative solar irradiance connection to DOY 007}
,- y f. ^ _ ....
-=-=r.^.^.,.^.^ .,...u^
,:
L-i,,
^.
f.,,
a
^^
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1.05
1.0.0
w0.95i H
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' 0.8A
0.75
0.73
ITT._.r ___
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q^
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^^... _ _ ...i^ it. -1-..^_ ___ _
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^ _..
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^ i..^,r. _ ^__
__._ ___ -I
_ i ^^^
---
^—{ t
LEGEND_— RESP
^.DOY 254 (PRE—AUTOCAL)
_RESPDOY 1.55
RESPDOY 254 (POST-AUTOCAL)
^ -^^ RESPDOY 165
RESPDOY 343
_ — _RESPDOY 165
___ RESPDOY 007— .^
RESPDOY 1.65
^__ ^,-1—__ I f- I ! I I i I i ^
R ^
_ _ _
lr
I.__._
.- .i. __.._..}_—_—a--
_ _ _ .. ^. .. __.^.....--
t_.^
._.__^^ ^.^'
.. ^.
.
I ^+-------i-
-t ^_^._
___
^^^^--._._..__._ 4 __
_
_
_^.
___^..__`
^^
__
__
__
_.
;_ ^: _
__
^
__ — —
y'
^^^,
I`
^.
i
i
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S
h^
i
i'
p.4 0.,6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8-
^.. .. WAVELENGTH (um) d.
Figure 12: —Relative responsivities normalized to DOY 165 (LC-1).
e.^^--
.. -,..
^T
_ ...—
' y. ,
^_-
aw ^^o
`'^. :min - "`_ — s, ..e.. ^_..... _ s:_:^.^...:.
,, _
The interpretation of these curves is rather complex;
however, several things become evident. The first is that
there is no discernible relationship between phase angle
and radiance levels for these small phase angle differences
during different lunations. SecAndly, Mare Tranquillitatis
radiance data from LC-1 does not appear to correlate with
the other three lunar calibrations. It would be very-easy
to say, because of .the poor VTS* photography on LC-1, that
the instrument was not really pointing at Mare Tranqullitatis
during the times identified._ However, it is believed that
the instrument was pointed properly and that the differences
were caused by {1) a relatively poor uniform target..and (2)
a human-factors problem. The first item is apparent when
comparing the three well-identified lunar calibrations in
Mare Tranqullitatis to .these . same calibrations on Mare
Serenetats. There is a great. - deal more deviation at most
wavelengths. The. SL=3 astronaut apparently did not cause
5-191 to "look" at the same position on Mare Tranquilltats3
^.s ^,id the SL-4 astronaut. This is witnessed. by 'a greater
deviation between DOY 254 (LC-3) and DOY's 343 (LC-4) and `
007 (LC-• 5)
The human-factors' roblem is caused b the-fact thap y ,^
the SL-2 astronaut was instructed only to look at large, uni- i t •
_-form, dark areas on-the moon. The poor'LC-1'VTS photography = ^^^;
indicated that he was looking at Mare Tranquillitatis. Mare__
Tranquillitats subtends .approximately 2-1/2 milliradians ^^
and it is probable teat several l milliradian (field of view
of S-191) variable radiance areas exis within this total ,,area.. Withthe previously mentioned set of instructions`,
^^ ;:
,See De ^.nition of Terms,: page vii. ,'^
•,2-19
^. ^._ ^.^ ^ .^ ra^r^ - ,^_^
^...,A._....,.r^.......,.. ....... _... __.
.-.__^rt.
,,..- ^
..,..v.,,.++^--^^..^ :.^^^'.^7t...:._=,_.ate..._. ww. ^ - .._._... ^, ..._.,. ._ .:...
-
``
kl
•4 ^ 5
},^ the SL-2 astronaut most robabl scked thp y p' e darkest area-
within Mare Tranquill^tatis. However,_when it became known
^'^, to the SL-3 and SL-4 astronauts that Mare Tranquill.itats
;, - was the target., it is suspected that they "centered" on Mare,r
Tranquillitatis, which contains a rather bright protuberance,i
near the center, thus explaining the difference. in LC-1. Mare
Serenetats, which only subtends about 1-l/2 milliradians,
does not allow for these variations and will be used. as the
standard in further analysis.
^^ The plot of normalized Mare Serenetatis data hould have.
'r. canceled out most detector anomalies unless. they occur ^`
`'rbetween autocal and data take time anal . show only lunax changes, ^`
":1
lamp changes, and optical path (including external mirror}F
z`'
^` changes. ;^
,^i^ A general .. trend can. be detected in the normalization, `'
;' First, the deviation from the mean in the 0.7 through 0.9 um^,
,,^; and l.S through 1.75 um bands is less thanabout. ± 1-1i2 per.-
^' zt. cent for LC-3, LC-4, and LC-5. This is very close for over
;_ 100 days-difference in mission time and indicates, along ^^ '
with the ,statistical flow of the curves, that lunar spectral
^;,, radiance differences f`or slightly different phase . angles are'' r;.'' not readily detectable from these .limited samples.
z,
i4
Several remaining spectral 'regions in the Mare Serene-
i}f.,
tabs normalized curve have high deviations. Several instru-
,;^ ^ ment anomalies could cause these-deviations,' Some of the-r
;, possible ones are as follows:^
,; 1. 0.4 0 4.5 ^m region —silicon drift at low outputssis •
;:'
`` between autocal and data take and slight lamp drift
•'^, between autocal to autocal.;^fii
• T:.'.
-._,
)ri - ^- ^0
- ` _
d W
-^..-+
p
2. 1.0 to 1.1 um region —silicon drift at low outputs ^-
between. autocal and data .take. '^3
3. 0.9 to 1.5 um region —.cal lamp does not repeat ^ '
peak wavelength output after each turn-on, possibly
because of insufficient'warmup time,
4. 1.9 to 2. ^.8 um region —possible thermal. effects a
in cal lamp.. envelope.
f
r Further work would be needed to determine and sort out?
^` the-specific causes of these high deviations, _if indeed
^ there is enough: lunar ca ibration data .for a good statistical
evaluation:
!' 2.3 COMPARISON-OF LUNAR DATA FROM S-191j AND THE LITERATURE^ -
:! 3
:i
j
^ -The most. appropriate comparison to the literature is
Ewith McCord and Johnson's (ref. 4) relatve^spectral reflec-
tance curve on Mare Serentats. McCord-and-Johnson took
data from a standard area in Mare Serenetatis (18...7°N,
21.4°E) of approximately 15 km diameter' with 52' narrow band^
>.1 -`^^
ntexference filters covering ,the 0.3 to 2.5 um region.,.^^
The measurements were made .through telescopes at Cerro j
Tololo Inter-American Observatory and Mt. Wilson. Observatory.
The relative spectral flux from the lunar . area was measured
(j^ through each o£ the filters, as well as the'flux fromi. standard stars. This data from the standard stars were
^4
^.:,,^
^,; 2-21
_.
,^
f
:...
.^
p
.., _ __ __ .^,.-. r-,__. _.,.-,.-^ .. _ . ._ a -,. ,,. ____
f }
^,t{
:. {
-; used to calibrate the instrument and atmosphere. Several
ratios were established to obtain the relative . spectral
J measurements. These were:
relative spectral measured spectral tabulated spectral
p reflectivity of = flux of Mare Serenetatis x flux of standard stars
Mare Serenetatis measure spectral tabulate spectral`^ flux of standard stars fluxof sun..
fihe tabulated_ flux of the standard stars were obtained
from t:he works of Oke (ref. S) and Oke and..Schild (ref. 6)
'^^ and tabulated solar fluxes from Labs and Neckel (ref . 7) .;:
" ; ; Some data in these curves was missing due to the lack of
information on standard stars in the near infrared. "'
McCord and. Johnson also ratoed the flux from. the
standard area of Mare Serenetatis to other. areas on the
moon including an area in Mare Tranquillitatis encompassing
the Apollo 11 banding site (Tranquillity Base).
The spectral reflectivity of returned Apollo 11 dis-
turbed surface fines were measured by-Adams and Jones '(ref.` "F"
8). McCord and .Johnson, by proper reverse rationg of Adams
^; and Jones data were ab e to develop the ec{uivalent spectral ^^
measurement for Mare Serenetatis. The comparison to their
'^ telescope measurements was 'excellent if .not remarkable,. _-
"" _and-led them to conclude Ghat the spectral measurement of
'_ - small. samples of dstrubed material are indeed representative
' of the larger undisturbed area telescope measurements . in
,: addition, they concluded that the spectral areas in which
`' they were unable to make measurements'(because of unavaib-
ability of 'standard star data).could be'described by the
:.
^,
^._ 2-22
^'^
_.,; ,.
Y 10z
'i7E..^.OQ
F-'4
W
E^o
Qw
^ EN. ^
o
^
NHOy
>Q>7
w ^ Z 10'^ W
U^^ ^
aZ
a'N 0a
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^;a
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t[
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curve derived from the measurements of Adams and Jones. k
(ref. 8). Phis derived curve for Mare. Serenetatis by
McCord and Johnson is the basis of comparison to S-191..3
_^ The conclusions of McCord and Johnson that large ^7
undisturbed lunar areas can be spectrally represented by
disturbed lunar soil samples is also supported by independent
measurements. O'Leary and Briggs (ref. 9) compared spec-
trometric measurements. of Apollo 11 soil . fines t^^ earth-based.
and lunar-orbiter measurements of Mare Tranquillitatis and
found excellent agreement.
In making a relative comparison, the McCord data was'
changed from relative spectral reflectance to relative spec-
tral radiance by multiplication with tabulated .solar spectral
irradiance (ref 7). The comparison . can then be made directly
by normalizing McCord's data a selected S-191 wavelengths.
From figure 2, concerning Mare Serenetatis . , it is assumed
that 0.85 and 1,55 um are the most stable wavelengths for
S-191. Normalizing McCord's data at these wavelengths and
.plotting against. Mare Serenetatis from LC-1 is shown in
figure 13. '^
The^`e is contradiction in relative radiance in compar-,,;
ng McCord's curve and the S-191^curve-on Mare Serenetatis
at s icon and lead sulfide (PbS) wavelength The silicon
appears to jut out of the curve on Mare Serenetatis and does
not have the smooth rounding of the McCord . data, PbS behaves,;
much like McCord's data at the .center wavelengths and. deviate<s
considerably `at the spectral tail.
^`_Z_24 -
-< ,.^
_:
^, _.-.
:^
^,^^{-{
¢,^;
I.
ri'^
'^
i„!,
^^^ ...
If PbS has an accurate relative calibration and McCord's
data is an accurate description of 1 milliradian field of
view subtended at Mare-Serenetatis, then silicon output is
t 1 20 t h' h C 1 h' 1approxlma e y percent oo ig onverse y, t is. is a so ^ ,
true if silicon is assumed to be more accurate.
' Both S-19 .1 data.:and McCord's data. have secondary calf-
°± bration backing their validity; therefore, we can . only say
that the .differences must be in the areas on which data was
.ttaken.
u.
` Z.4 PRELIMINARY OFF-BAND RADIATION CORRECTIONS
,,
A computer program has been written by LEC and run. on
the Univac 1.110 computer for calculation of of-band radia-
Lion in the S-191.* The . program uses SO41-2 raw data . tapes..
;`! to generate radiance data either 'as described in PHO=TR-524
(ref. 12) or with an off-band correction factor applied. Thert
program will also ..average data over several spectral scans'.
(The PHO-TR-524 type . radiance-data is a simple case. where k
off-band radiation is considered equal to zero`.).,
The program::bascally implements the responsivity and _^
^:; radiance iterations a^ described in MSC-05528, (ref 13,
^' pages 7-5n through 7-5Q).,^
^;^. _ _,
Thee only.:dfference is that off-band transmission
T off (A) in equations {70) and (13} is assumed to be constant..
.with - .wavelength and is taken outside the integral. A seriesrY
^;,.
'^
User s- escriptons ave een written. V. .Argo, Jr.wrote' the'SWL-poxton (ref '10) and E. L. Downes, the LWL por-
,;;
tion {ref 11)^^
T ^-f
2-25
;Y^• K”
^-
_ m _..
^ ^._.,
f of factors P were used in parameteriaing T of^(^) = 10^ 4 F; ^;
^^ comparisons were made for DOY 007. The results of these
^^ calculations -for F - 0.2^ and 0.00 are graphically shown `^f ^;,_ ^^ - in figure l4 relative to McCord's data at 0.855 um.- ;f'.
s.
• The graphical method is rather subjective in this
determination. of off-band radiation since the two curves
do not fit well at the longer silicon responsive wavelengths.
^'
A relatively good: fit is obtained at 0.45 through 0.5 um at
this F factor, however. ^.
ztIi
j ^
^;...
-t
i ^,,F
^i. 7 4r
,^. i
?. ^ ..
^ !,
^
f
t^
.`,y-
I '
;:
,.,T
;^;
,.^-
-^
2-26i
<-
__ ,x
-'
from Mare Serenetatis•
Z-27
1
0U2tW^THf ^
n=
10-2^
_y r
o -"t , j ^ _f
• - .i
'i !- MARE SERENETATIS DOY 007
- - . ; ^1 ^ OFF-BAND _ F n 0.0 ( OFF-BAND )
` -+
--- ^t -OFF-BAND ^F=0.240
:: I- ^:^^ ^: :::.:I:.. .. ._. _
Mc CORD'S DATA NORMALIZED
.. .:._-^ : --= AT 0.855 um^ 7 + - -1
^ ^ ^ r
` i _
II
i T^-^ - -t `
ait ^ r~
raw w^ T
♦
f^
-t - - ^ }
-_ 4 ^ -..^_,r-T- -...^ :^.. ^.
.,.,
3.0 LWL ANALYSIS ,'
^^
_ The LWL analysis consists of ntercomparing the radiance ^
values of the 4 lunar calibrations listed in table I and then ^ r
comp axing the most appropriate o.f those lunar cals to the
literature. Additionally, lake/reservoir data measurements
^by 5-191 were. compared to apparent radiance predictions from
thesesame lakes/reservoirs by atmospheric programs.
One of the problems experienced with the LWL was the non-
colinearty in the responsivty calculations from the heated
and ambient autocals. This problem will be discussed before
` proceeding with . the LWL...analyss.
"^
;-3.1 AUTOCAL ANALYSIS - ^ ,9
'.
,..,
Preliminary analysis had been accomplished in MSC-05528
°' (ref 13, pages 7-5Q through 7-5n), which showed that. the
responsvity required to zero the S-1.91. aperture . radiance
when looking at deep space was roughly a function. of the1
reference temperature setting, especially at the lower end ^,
of the ` LWL 5-1.91.. spectrum. This- gave indications of being, ,
<i
an off-band; problem.
The`5-191. program which calculates off-band radiation
was used to'compute the heated and ambient.'responsvites
to-determine if there existed a unique off-band solution at
which the re ponsivties would converge. The results of
these calculations were not encouraging because convergence
began at assumed spectrally constant values of Tof f(^.) but
did not' approach a unique solution at reasonable values of - ^ '.
^^^ 3-1
a
3
. ^: ^t
_ .
^-^^.
^.,. ^-....^- ^ . , ..s_ __
`^
^,*".
^:^r
^,r
^.
Toff(`), .e;, values from 0.0001 through 0.001 (with the -'^ -
.i
^^
assumption that. T off is independent of wavelength).4
^
In order to study the problem more .closely ., the 5-191.^
program was used to compute ambient and heated responsvities^: .
for DOY 223 and DOY 254 according to PHO-TR-524 (ref ,12,^..":Y page 4- 12) . These two days were representative of all refer-
ence temperature settings during mission auto calculations
" except one. These reference temperatures were 8:.972°C and
^` -15.242°C. The results. of these calculations are plotted in
figures 15 and 16, As can be seen, .the responsivities are t
inearly colinear from 10..5 through 14.5 um but diverge appxe-
ciably at the band ends... These center wavelengths respon-;.
9
sivities are the most accurate for use in radiance ^ °^
': computations. ,^
The cause of this divergence in responsivity is not f
presently _known. Parametric evaluations of errors in ^
system physical constants and off-band calculations have
not yielded acceptable solutions. In addition, the respon- '^
,^. " sivities at -1..:5.242.°C reference setting are more nearly ?; ^^a
^` convergent than. those at 8.972°C, which wouldseem to rulet
'Y
^' out any knd__of background noise limitation. If the heated ^' s
cabs were not being monitored-correctly, then the 'question
^aarises as to why some spectral re'sponsivities are colnear '"
'; k^,,while others are. not. ''
,f
F_
More specific answers would rec{ure considerably more
responsvity data reduction with the S-191 program ahch
^', has only recently come on-line. However, the termination
of the sensor performance evaluation leaves these questions
unanswered, and the final ana ysis will be evaluated on the-
"F:^^
basis of available time and data. .r
;," 3-2
-
:.Y
^^UV
N
(fu
5000
^1
i
{
!; 4500
4000E
_j^, s
Y
LL!
{: ai 3500^^ ^h
E
^ 3000^ Q
^^ ^ 2b00
f 'J
I^ ^
^.'
>
Z
^. 2000is
^
I ^
ZO 1500a
r
i
1000
^.
^'
E
5.00
^, WAVELENGTH IN u m
' f. AMBIENT AUTOCAL HOUSEKEEPING DATA )r
Time {GMT)Htd{°C) Amb(°C) Dic(°G) Ref(°C) Det{°K)
Start Stop
223:15:30:31.99 223x15:30;38.501 18.789 18.463 23.:.378 8.972 85.704
Y HEATED AUTOCAL HOUSEKEEPING DATA
i
-Time (GMT)Htd(°C) Amb(°G) Dic(°C) Ref(°C) Det{°K)
Start Stop:.
223:.15:31:40=064 P23:75:31:46.613 49.099 18.165 23.462 8.972 . 85.495
Iis
figure 15. —Responsivties fora 8.972°'C reference source temperature.
.;,''
3-3
_– — -'``
_ -^ _
` I -5 _ ..... __._.. ...___ _ _
5500
5000
4500
i
4000E
fa
i W
^ 3500
U
3000
Q3200
JO_Z
^. 2000H
ZO 1500arnw
1000
.500
WAVELENGTH W a m `I ..,,,
AMBIENT AUTOCAL HOUSEKEEPING DATAv
)
i
<i
" HEATED AUTOCAL HOUSEKEEPING DATA
i'
A
6 -^
Figure 16. ^- Responsiviti/,a for a -15.242° G reference. source.
:...^ 3-4
?me (GMT).Htc(°C) Amb(°C) Dic(°0) Ref(.°C) Det('K)
Start Stop
254:14:D0; 00. 583 254:14:00:07,085 50.546 23.221 24.781. -15.242 86.260
Time (GMT).Htd( °C) qmb(°C) Di c(°C) Ref(°G) Det{°K)
Start Stop
254:14:00:40.533 254:14:00:47.036 4'9.044 23.98_ 24.866 -15.242 86.191
_ ___ _ _ _ _ _ A .. _... _._ _ ^. _. __...-. _ ^ ._, w--
.'_ _
^, u,
^ ._._. ,^ _ T_ __. 1 1. __I..
i_..^^,x.__ ._ __ _ _— -- - — -- .a ^ _ .^^.f_ __ _. I ^^a_.^- Y
r;
3.2 INTERCOMPA^tISON OF LWL MARE DATA
f^ j
`' The same time. periods ntercompared in the SWL were
also compared in the LWL. The data on the .moon have all ' w.
been calculated using the heated . autocal responsivti^s
because these temperatures are closer to that of the moon
than the ambient temperatures.
The radiance data collected on Mare Serenetatis is
shown in figure 17 and Mare Tranquillitats in figure 18.
Again, it can be noted that Mare Serenetats is a much better
behaved target than is Mare Tranquillitatis. LC-S has a
.serious. anomaly between 8.2 and 10 um and is low by about
10-15 ` percent at 9.5 um. This correlates to the SWL data }
on LC-5 as a drop in relative radiance from .4 to .S5 um ^
can be noted in figure 10 on Mare Serenetatis. `'
The exact extent of this anomaly can be studied more.
closely in figures 19 and 20 which are normalized radiances
of Mare Serenetatis and Mare Tranqullitatis to da a on
DOY 16S (LC-1).
Low data. in the LWL suggests 4 possible problems; .
(1) the nstrumen was-not pointing properly, (2) internal
^'. changes occurred in the instrument, (3) the..lunar target
changed, or (4) -the external mirror or the vicinity around
5-191 became degraded or contaminated.
Mare Tranquillita is (DOY 007) in figure 20 also. shows
this anoma7.y which_ eliminates the possibility that the
instrument was not pointed: properly. -In order to prove that
instrument internal values had. not changed, a-normalization
R.J.
^^ 3-5
. rokt
__ : , —
r;;
4.6
4.4
4:2
- 4.0
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HTD(°C) AMB(°C) .REF(°C) DIC(°C} DET(°K)
DOY 165 23.017 22.798 ..8.972 25..294. 85.$43
DOY 254 29,595 23.029 41.047 23.632. 86.399
DOY 343 29.041 .16.501 .41.047 2.1...357. 86.747
DOY 007. .28.568 16.161 41.047 24.896 87.302
^, 4.6
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HTD(°C) AMB{°C) REF(°C) DIC(°C) DET(°K)
DOY 165 23.055 22.798 8..972 25.251 85.843
DOY 254 29.992 22.952 41.047 23.632 86.399
DOY 343 29.634 16.426 . 41.047 21.315 86.747
DOY 007 29.199 16.124 41...047 .20.896 87..302
.. _ _. . ..^
i'
' 1..25. ^
1.24
• 1.23 ,
1.22',^, 7.21
1.20_. 1 .19
• 1.18
1.171.161.151.14
1.13.1.121.11
0 1 .10
a1.09. DOY 343
'
^ T.08 DOY 1651.0T
1.06 DOY 007
0 1.05_
DOY 165 ;,1.04 DOY 2541.03 ^ _ DOY 1651.02
1.01
1.00.99
.98,_
,97
9 6 ,t , j _..95 __- ,.94 MARE SERENETATIS
,93
.92
.91
.90 4 ,.^ , _ ^:
.896
^ 8 9 10 11 12 13 14 15 16WAVELENGTH (um)
.Figure 1,9. - Radiance ratio .from. Mare Serenetatis relative to DOY'165 (LC-1).
3-8
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._ _ _ _ - -- .-
_F w.tt _ ^ ^.^.^
- t.zi1.201.19
1.181.171..161.15
1.14^ 1.13
I 1.12i 1.11
1.101.091.08
} 0.1.071.06
^; 1.05^; 1:04
I ¢ 1.030 1.02
^ ^ 1.011.00.99.98.97.96.95.94.93.92.91
.90
. 89
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j
was made on heated responsivities used in LC-1, LC-4, and
LC-5 to the heated responsivity calculated for DOY 254
(LC-3). The results are shown in figure 21. No appreciable
,_ internal changes occurred in S-191 on DOY 007-. The pons-
bility that the spectral exitance of the Mares changed
' appreciably between. LC-1, LC-3, LC-4, and LC-S is not a
likely occurrence.
"` Therefore, it is assumed that some sort of contamina- ,.
tion/degradat_ion occurred in the external mirrors or in the
near vicinity of Skylab. This is supported`by the SWL anal-
ysis as serious degradation occurred in the 0-.45 to 0.55 um
region on Mare..Serenetatis data on DOY 007.
'. The data in figure 19 on Mare Serenetatis appears fo ^. '
"tail up" at the. spectral ends relative to DOY 165. One of ^
' the reasons attributed to thsis that. DOY lfi5 is the only
lunar cal in whicl-i the.. reference source setting was constant.
- during the auto. cal and the data. take. Because of slight
saturation at a few wavelengths during this first lunar cal,
the flight plan was .changed. for the follow-on lunar cals so
^ that..: the reference source was changed after . the auto cal
' from -15.242°C to 41.047°C before lunar data-takes. This -- ''r
was great. for non-saturation, but poor for calibration.
Because. the"reference source setting was not changed on LG-1,
' it is considered to be the most accurate description of LWL
relative radiance of Mare- Serenetatis. _A plot. of Mare -
^;Serenetatis in figure 22 on DDY 165 versus the. radiance` of
a 370°K and.. 380°K blackbody shows very good agreement except
at apparent absorption bands centered at 8.2 and 9-.4 um
^^ 3-10 -
_:.
J
Fp.
y
G
1.. _
x .
:^ _
__ _-._ _ _ _ _ _ __ _ _ _
.; _... _ ; ;, .. ti.,; ;^. ,.
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1.09 : --_ -- _ ^ ^_ .___^- ^ _.T '^____-^+r _HTD. RESP. DOY 165.
-^
^^_i
HTD. RESP. DOY 254 i^
1 .08 --RELATIUE TO DO^^_
^^
^. ^._-_ _iI ^
^
HTD. RESP. DOY 007 ^:fG^-_
1.07 .k--
^
^_._-.^;.__ _... -- -F-- -- - ___ - -
`
HTD.
HTD.
RESP. DOY 254
RESP. DOY 343
^
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_ _ _ _ - - - .:- 4 _,.^_ _:_- - ^ ^
—HTD. .RESP:. DOY 254
!^ i
Eo t t ^ ! ; ' ;
,
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^^---^-- i^
_--__i HTD. RESP.o
{
i_ '^ DOY 254 = 1.DO Ih,
^`i
^ ^!1
.97 .,, HOUSEKEEPING DATA .i ii
r
.96 I-:
. 95 --
94 ^ -
. 93 ^- .
HTD(°C) AMB(°C) REF(°C) DIC(°C) DET(°K)
DOY-2:54 49.044 23..336- -15.242 24.866 86.191
GOY 343 48.880 T5.403 -15.353 20.979 86.469
DOY 007 `48.826, 15.030 -15.353 20.603 87.024
DGY 165 49.154 22.760 8.972.. 25.423 85.634
1 ^ ^;,
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^ 3
N _Z 2.6WQ 2.4
2.2
2.0
l.p
16
1.4
1.2
l.0
^.. ___ ^.___^.___ _ ___._T_-^ -^
^ ^^
E-- _^.
._! —
I
MARE SERENETATIS
DOY 165 (LC-1)
^,p,.o^^^
3,O o'1
^OC^B `
6^gc^o
Oy
--_T_ ^^...:6 ^
7 ^ ^ 8 9 10 11 12 13 14 15 1 6
^ ^. z.,-.^. ..,_ . -^ _ _ _ _
m L;,
^.^,
'. ,r
.'
'^
Mare Tranquill,itatis, in figure 18, shows the same low
readings from. 8.2 through 10 ^m on D0Y 007 as does Mare
Serenetatis. In addition, a much greater spread of radiances
is encountered from one location to the next. This is
attributed to Mare Tranquillitatis'being a much larger and.
less uniform target than Mare Serenetatis. In addition,
i'^are Tranquillitatis is closer to the lunar equator and may
be affected by solar specular radiation. This may explain
the. higher. readings. on DOY 343 (a partial .lunar eclipse
occurred on D0Y 344). On LC-1 (DOY 165), the reading is high
- . compared to Mare Serenetatis; it :was speculated in the SWL
analysis that this was caused by looking at a dark area`
within Mare Tranquilltatis. This is confirmed by the LWL
measurement. There was also saturation of LC-1 at wave-
lengths between ll.l through 11.9 um. A change or reduction'
in the peak between the two absorption bands at 8.2 and
9.4 um is also noted on DOY 254.. , , ,;
' 3.3 COMPARISON OF EREP . LUNAR DATA TO THE LITERATURE -+
A comparison can be made to the litera ure because F;
Shorthill (ref 14) performed visible and thermal scanning of
the moon in 1963 and 1964. A ^Tzry small field - of-view
optical scanner. was t?sea and the output in the thermal band ^ 'r^j
was plotted into a thermal contour map of the moon for
different Mare analyses. Shorthll ' s instrument used a
large bandpass, as compared to S-:191,''and collected energy.
^ from about 9.6 through 12.2 um.
^ An-accuxate comparison would require convolution of the
C energy under the S-1 .91 spectral radiance curve: from 9.6 I.
through: 12.2 um and comparison to Shorthll ' s measured area „^:^
-^
f1
3 -13 max;
h
. ;^
. _ _ ^.._
w . _ a,^..:: .,^, i .^- ^,r.^.^^__.._._._»._,x^
r
` ^ ^ ^^
t 4
I`;
4^
4^.
r^ •
I-
4
.
' (1 milliradian 5 = 191 ..coverage) averaged temperature values.-
^^ Because of the time limitation fore.. completing this report,
the overall system spectral response curve is considered '
!^° Iflat over the bandpass of Shorthill's instrument (ref 14,
page 9) which is a close approximation.
^ G.
A plot of Shorthill's area a^reraged Mare thermal data
'"'^' versus phase angle gave what appeared to be some physical
'^ ('
discrepancy or error in the data. However, from measure-
^'merits by EREP over different Lunations, this-discrepancy `
^^^A.
also. appears. Taking phase angle alone as a measure
i ^ of physical quantities on the moon from one luna-
tion to the next is not a complete description of the
^ optical properties of the moon. For this reason, amore
jcomplete match in the infrared would be at the same. solar
distance and illumination angles. Shorthill took thermal
data on the moon in`December of 1964 prior to a total
^^ eclipse of the moon: (ref 14, page 85). EREP also took dataE
in December 1973 before a partial eclipse of . the .moon. A
calculation was made on this data and the comparison as
follows:
k Mare `Serenetats .Mare Tranquilltatis '^^ '^'° 18°E* 7°N, 30°E* ^,2 7 N ; ,-
4Shorthill's data 8 ^ 6 ^
. - 12/17/1964 ;,
i20H 16.2M UT 27.26° 172.49° 16,94° 114.02°
EREP data12/09/1973 ^>:
OOH 25M UT 28.19° I64.853° 20.41° 110.34°
` Whexe 6 is the solar illumination angle from zenith w
and ^ is the azimuth of the sun direction from the .north^-__;_ .
Approximate selenograp is coor^cinates at center o Mare'. ;.,,
.:
,,3-14
^, H'°?7
rL'
.. ,,,. ^.. ^., _ _s.,r--^. , _ __ _ __- -- ^_..
.-
..,;. ^_^^. ___ , . T.^. _ _. _
meridian that passes through the Mare (^ is'+ clockwise,
- counterclockwise). As can. be seen the solar illumination
angles are closely matched on Mare Serenetatis and slightly
y under 4° difference on Mare Tranquillitatis, The earth
direction in close also as the. phase angles are -14.77° for
"' EREP DOY 343 (LC-4) and.-17° 52' for Shorthill's measure:-
ments. Solar irradiation. is very nearly the same (both data
'^-' takes were in December) assuming the solar constant has not
,:varied during 9 years.
The results of this comparison are shown in .figures 23
and 24. Radiance values measured by S-191 are 10 to 15 per-
cent lower than Shorthill's measurements and are about
10 percent below his error bounds..
3.4 COMPARISON OF EREP 5-191 DATA. TO
ATMOSPHERIC MODEL DATA.
' The last part of the LWL analysis involves comparing
the radi'a.nce ;predicted by atmospheric programs coming from -^ 1
j lakes/reservoirs to than measured by the S-191.f^. ,
The atmospheric program at JSC (ref 15) w:as basically ^ 1^^ a
developed by Dr. Calfee of NOAH with Dr David Pitts of JSC ^
adding selected features. The program assumes^up to 30 homo-
geneous layers* of atmosphere with each having a :constant
pressure and constant temperature. The program deve ops line-
^' by-line data for about 7.5 , 250 lines. of cari^on dioxide, water, ''
methane, .ozone :,` and nitrous. oxide into spectral emission and 'a
transmission-data for each layer. Each of the layers are ,^
,
^^\`t
Only l0 were use in-our ana ysis.
3-15
^q'P »
Y.0
4.4
4.2.
4.0
3.8M
1'^ 3.6x^ 3.4
^ 3.2NN '
3.0
W N^ a 2.8O+ 3
2.6wU
2.40^ 2.2
2.0
1'. 8
l,(
1:4
1.2
1.0
i
Ii
I
I
i
,;
^,
i
HTD(°C) ANB(°C) REF(°C) DIC(°C) DET(°K)^
DOY 343 29.041 16.501 41.047 21.357 86.747
n}
^^
^[
Ii;
I{
1
I'
^{
ik
HTD(°C) AMB(°C) REF(°C) DIC( °C) DET{°K)
DOY 343 29.634 16..426 41.047 21.315 86.747
r:
4_
__ __
4^
^^
4.6
4.4
k.
4.^
4.0
3.8
•M 3.b0" 3.4
^.iw 3.2^'
^; 3.0w ^Y F 2.8V Q
^ 3Z.6z,
z
2.4
^^
2..2
2.0
1.8
_T.6
1.4
1.2
10b 7 8 9 10 11 12 13 14 15 16
WAVELENGTH (um)
Figure 24: —Comparison of radiance data. from . riaxe Tranquillitatis{SL-4) by 5-191 and Shorthll (ref 6, page 85).
_._ _.^ r
,. ^..
...^.L..^.._^:^
^'ii
t
i
1
f
_ n_p
^...
.n---^^
r
i^ '
then applied to water surface radiance data to develop
apparent radiance as viewed from space. This apparent radi-
: ance data can then be compared directly to the measurements
' of S-I91.
,__ '
The Calfee-Pitts atmospheric program requires, as input,
the water surface temperature and radiosonde data. including.
I
altitude, temperaturE, pressure and dewpoint-depression.
i
Early: in the plan for Sensor Performance Evaluation,
i was decided that lake/reservoir sites of opportunity
would be chosen rather than planned, pre = instrumented sites.
Under these conditions lake surface temperatures would
;probably be accurate for . relatively long peri^bds between
lake temperature measurements and 5-191 overflights while ^^ 'd
radiosonde data would not necessarily remain stable unless
iweather conditions remained constant. .With these limta-
Lions in mind, a selection of best Lake/ . reservoir data. was
made. Table II contains these selections.
The surface temperature for Monroe Reservoir was made.
on the- day of the . S-191 flight by a Purdue Universit^T
Principal. Investigation team . .. Their xeport indicated: that ^^,. .., 7the reservoir was a veryconstant 25° C except in the shat-
ows along` the sides. ^ ';
h Radiosonde data was not available from Monroe Reservoir.
rHowever, radio-sonde data was available from three stations
which lay about 200 miles from each. other in a triangle
^^ Y
around Monroe Reservoir .. These. are Peoria, Illinois, Salem,
?, Sllinois, and Dayton,` Ohio. Thee radiosonde data from these j
^^^: three stat-ions were co1'lected from the National Weather♦ 1
Service on the .day of the S-I9l overflight and were taken ^
3-18
.^_, .^,^ _:Y...^.. ate_ _... 'r.rY.3$i^rJ
LOCATION/MISSIOn
Monroe Reservoir/S
Lake Titicaca/SL-4
-Great Salt Lake/SL
wH
__ . _ _ _ _ _,
_^
^`+
TART L^ TT TTT.f L' T!TI AT,fL^O' T7 (1T1
f
j ^^'
at 161:12:00:00. All data were plotted and showed minor
differences, indicating .that a front had probably cleared ^,
the area. The Salem, Illinois data was finally selected as
- the radiosonde data to be input into the Calfee-Pitts '
.program.^
^' The temperature of the Grea Salt Lake was monitored by
a Martin-Marietta .team (ref 16, page 11) and was reported to
be between 4.5° and 6°C at approximately 41° 15' 00" N longi-
tude and 112° 45' 00" W-longitude. Thus was a position the
S-191 was looking at during the S-191 overflight times
described. in-table II. Radiosonde data was also . available
through the National Weather Service. at 029:12:00;00 and was^i- taken at the International Airport in Salt Lake City, Utah....
s
The last lake data was from Lake Titicaca. This data '^^
is important. because Lake Titicaca is-a.t-12,-520 feet and `.
is above most of the atmosphere... The comparison of S-191
to the lake temperature would-exclude an atmospheric program.
A comparison was also . desired of 5-1.91 output to Lake ,;
Titicaca with. an atmospheric program. However', obtaining
a suitable radiosonde sounding was not possible. The most
appropriate one would. have been . at LaPaz, Bolivia, at he .^
J. F. Kennedy International hirpor^t which is at 13,398 fee
This-airport'is only a few miles from the lake and is '° -'
located in the same wEather system. The airport collects
- radiosonde data but not on a regular basis, According tog
the U.S. National Weather Service,_.January 29, 1974 was not
one of those days. However, the National Weather Service
did send data from the closest reporting station located in
,^
Chile, about 400 miles to the south.. However,these data
were not e considered adequate.''-^
ti
9
^ 3 - 2 0';
^_
. -., . ,.,
- .__..
—_ ..,a
_^.
', The temperature of Lake Titicaca was monitored by a
U.S. government team* at almost the precise time of 5-191 ^
overflight and was 13.5°C. Figure 25 shows the. look posi-
tion and time of 5-191 data take at the Lake.. It also
- shows the position. and time of the U.S. government team's ^^'•
temperature measurements. •
^- Plots of all three of these data.. takes are shown in
ifigures 2fi, 27, and 28. Additional atmospheric data is
plotted in ,figure 26 on Monroe Reservoir and was provided
through the .courtesy of Dr. David C. Anding of Service Appli:-
cations, Incorporated, in Ann Arbor, Michigan. His model
- odel exce tinput :data was the same as in the Calfee Pitts-m p
that no ozone lines were assumed. The S-191 data was cal-
culated with. both the ambient and heated responsivites withj,
J
the ambient ca culation fitting thee. models best.
One anomaly is evident,in the 5-191 data and that is a
broad and large absorption .band cen eyed at 9.4 um. This
^^ band includes. the `.ozone lines, but may be .too broad to be `: '
ozone alone.• This absorption band appears in the lunar :data ,
j as well, where it had been. theorized to be a Reststrahlen
'; absorption band of aquartz-like-constituent of the moon. `•
^^^ ':
However, this absorption band. may. be partia ly instru-
ment anomaly. The emissivity by the internal blackbody cal
source coatings do-not give any indication of absorption bands:.
!- at 9.4 um (ref 17, page 28). Zn addition, no silicon monoxide
(which peaks around 9,4 um) coating was applied to the exter--^
; nal mirrors according to: Block Engneexing.` - '^ a
The lunar data indicated.: an increase in the.. absorption
level of the band throughout the lunar data take-. -Between
. -aSee appendix A
^-21
- -- r^;fri^_
^.r--,.._ _ _ -^.
- la
a
n H n r .. r. / • ^ 75LG7 ^DY^ Gr+ 7J'ir<x " ^
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F 13 7,7 141675 •^l ^' , ^ ^ `^. talaqu
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,.M^::<°::-::::-- i : .-,: `:: ,"
TURE 1.3.5 C r jt
r r 'au^ rmna - .....:'?^, _ WATER _TEMPERA -0
hra.^`a^wr^ ;:;:^._ t ' ^' 0 2 7 :19 :18:0 0.::> ;
::>:.:^::_^...-. ..,::;:: .:.._:^.^: _•' 68° 42' W, 16° 15' 5 r.^;....:.:::.:: ..
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+
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(:':'-^^^' Q/^!^.t^ arallas7l^ t•c..y^i'^`
'^ I ^^• (..^1 -onpo . 1 ^ fi ^` r • . ^ ••• :.:•i:<:•:?::S J'AIGACHI ! 'y^ ^ .^ '1
^` ^' r .f1 i ` •••.^,^. '•- S _' rp ^ Pucaroni^ ^i r l
` ^ ^ 1^ \^,,^•-.^^^ ^ "tioe-Ref
^: •' ` ff '^ ''-L^i`^ - 'S ^ ^ •^ - -^^'1 lAPnco '-1^ °^ to PRa ► LA F 1G, ^ ^'
w , r llooe , f ` ^_ " ^S ^.Y^O ,^` ^^' tl. ^ ^.----'.-mil \' .:. \^ j.. ^\\ r ^ fA,A,es ^_ •-^-.._:.:'C" - - •;1 --
'-`. ^ 1 ,—J ^ ^\:! ^ C ::v.•. .::::^^:^ Ali NAC M ^': \ ^ J. f. KErM:IEDY IN r^•
? ^ ` ^ / •/f 160 JA 1^, Dcsayu aero^ • •• '•.. - - 3777Pa ^^nrr,t ^tn+ tii
f _^- ^- ^^ ' jt-'-,`' •-\,. ^_ r^.'^, \^u.^ruLi LOOK DIRECTION I .
^ '. ^ ': ^ fi r" ^ ^- - - S-191-
'! r .^ Hoocultan q 125 ff . { _ `
^` ^ J -`^^ \ i `'^^% ^y .027 19 18 14 ,:^r i /t/ ) f^ ^ r. ^.J ^^il' ,^ ^ r y JESUS DE MACHACAr .^... [. ^ l .e ^ \?^ ^\ ^/
}^^J ^f ^ ^0.LJ RTa'. ! f it -o Cruz .•^^ \ ^ u ' ^ f^ f! ^ ^. ^ ,.r ^ . 1.. c• j• , . • ... " .
,17008 ^ ^'^^^ .. ^..-^1 !•^' ^'. ^^ ^jT^\ ; J l ^ _ r ^- ' _
E: ^ , a^r^.ri ^ ^
TAI, ^ r e^`~ P
/ 111 0 ^ ^^,.c 1^\ /^ \ ,^ •+^ ^ .
`- _ ^ ^ isommo^ \Q/^., ^ _. 1 .1,^..J ♦ ♦ Mach ate'- f ^ \
709 ^ eD
^,J•r !\^ '_'./ ^
r^/a
â
,^•Mfr.`^t^j•.^^L^ZACARA `-.r ^J" fli
,rl 1^^` !! ^ ^•I/^ \ ^ ^ ^/ / ^7^41Ft^- !SEESr ' ^^_., t • }* ^ `•-^^*}..-.-.-r-rTr3^.^ri"T-rFrt-r-*m rrr,^•r't^rl'I (Tr rY rT-r!-TmTT^-rTT'%r''-r-r•-•—•_
^^.
u ;.
Fgure:.,25. —Location of 5-191 pointing directionand ground truth data collections.
,., .. ^ _. .v. ^.._^......... ^ ^.
...... +_^ :_ ti^. ^ _.
..., ., : y.^ ^ ter,•_ •. ,.^^t'
.r...m.s.^_.urv.,,6..wiw zAi au...a..v.ic':• r..d. ..a...^..u..u.•.aL..uiaauu.ai^aYYJ>_.u.v.ac.nu::_Siiirvzu.• - '••. -^•• f i. "^--:v^•.aY.s^.:;.,a-s..a .. ...:.^ mac:.. :^.•: .: - pM' __..vwr... ...... s.^au•. ^..ma a:..u.uu-.a..._ .sf
I ^ I // III I/ tKtr nuu^tRttriiv^ UHIH L/I V \^^-^ I2x10.-4
'1x10.-4
— CALFEE-PITTS MODEL OF RADIANCE DATA ^ SALEM, ILL
-- ANDING MODEL -0F RADIANCE DATA j RADIOSONDE DATA
-- 5191 (HTD RESP) RADIANCE DATA
10x10_q.
9xT0-4
8x10-4
7xT0`4
s
6x10-4NNUN 5x10-4
W 31 Z
`'^ W 4x10-4UZQ►-r
^ 3x10-4
i,
Eu
i I ► I ^ I ^ 1 iO 6 7 8 9 10 11 12 13 14 15 _
WAVELENGTH (um)^ ^
_ Figure 26, — C.omparison of S191 radiance data on Monrne Reservoir and radiance }?' predictions by the Calfee-Pitts and ArLding atmospheric models. '.;:
e
_
S
_ _ _ ;
HTD(°C) AM8('C) REF(°C) DIC(°C} DET{°K}
.GREAT SALT LAKE 15.326 14.841 16.732 20.436 87.714
AMB AUTOCAL 15.974 15..602 -15.273 22.106 88.047
029:17:49:02.690029:17:49:09.183
9x10 '
8x10._4
'^ 7x]0-4
i E
6x10-4N.: ^'v
w ^ 5x10-4NJ^ 3
~" 4x10-4wUZQ3x10.-4
2x104
1x10'4
0
i`
^' r
^;^;
^w
3'
p
1
Y
i
,:,
^'^6 7- 8 9 10 11 12 13 14 15 s,
^E
WAVELENGTH (um)
^'
Figure 27. -Comparison of S191 radiance data on the Great Salt Lake and.the radiance;pred,ction by the Calfee-Pitts atmospheric model.
{
l
,: ...__ ,.
e^^
^'i.,Yy _ ^
•V"m...._ ..,wm....-w.^.^..«_.,.< .^..-,.
-ws.^+a.n[[^.i »miff'.::.,.... ^, ^.._.,.
_._.,.. .... ..,i^,,...:.uu.^...._.
HTD(°C) AMB(°C) REF(°C) DIC(°C) DET(°K)
LAKE TITICACA 22.752 19.409 16.800 22.534 87.580
AMB AUTCCAL
027:19:20:OJ.385027:19:20:07,841
34.247 19.685. -15.321 23.378 87.580
t.:1i^,
I !
i^
^:
^^'
ij
i}iI:
ii
7x10-4
^ 6x10`4
wF—N
r ^ 5x10-4
W '..N
N ^cn 3
4x10-4WUZQr-^
^ 3x10'4
2x10_4
t. _
1x10-4
f _ ,
^..
^^
^ i i ii i ^ ^ ^ ^ ^ r ^^
_- - _._.—.._.
f_.. _
^ ._ _.
f
ground calibration and DOY 161 (Monroe Reservoir data. take),
it is not known what type of contamination may have been
applied to the external mirrors. It is suspected that
contamination may be partially causing the absorption. level ^
whose peak occurs at 9.4 um. _;
It should also be mentioned that Monroe Reservoir is
the most optimum data . take on any of the lake/reservoirs.
The reference source temperature .was not changed . between
auto cal and data take,. and the ambient. temperature of the
cal source at 18.463°C was lower and close to that. of the
relatu'e1y warm reservoir at 25°C. In addition, S-1.91 data
was taken very .close to nadir and close to the beginning
of the Skylab mission.
The data from the Great Salt. Lake is shown in figure 27. '
S=191 data is approximately 10 percent lower than model
prediction. It is not known what is causing these differences.,
however,. the .list of possible variables is duite long. These.;f,`-
a:r e : j
1. The reference source setting during the auto cal
was -15.242°C and. 16.732°C during the data take. f `';4`
2. The ambient source was 14.841°C and higher than ^;
the. colder lake. temperature of 5°C during data take.
^In addition, other instrument temperatures were,^
.dune: high relative to lake. temperature.
.. 3. Detector temperature was high at 87.719°K during..
the data take : $ _
w
4, Lake was about 10° off nadir during ` . data_. take.. ^
5. Weather conditions. were poor., however, the lake }
was clearly visible in VTS imagery.
3-26to ^r
',.
_. Isr. ,^,
'.,
^{
.
^jj
'
6. Progress of externallmrror contamination was not ///
known.... It .appears from lunar data. that. any data
taken after DOY 343 .may be quite marginal especially..
^^ in the 9.4 um region and deterioration at 10 through
11 um became noticeable .on DOY 007.
^ Additional data would be necessary.:to reduce the number
of variables and identify the differences between the model `.
prediction and the S-191 output..
The S-191 Lake Titicaca data is shown in figure 28 and
does . not show good agreement to a backbody curve at 13.5°C. -
A list of variables can also be developed: ;^ ^:-,'
1. .The reference source setting during the auto cal
was. -15.353°C and 16..800°C during the data take.=^
2. The ambient temperature was 19..409°G, and the Take
temperature was lower at .13.:5°C during the data ,:
i take.. Additional temperatures within the instru-
meat were higher than the lake. temperature.....
^ 3. Lake was about'20° off nadir during data take...
4. Detector temperature was high at 87.580°G during ^^'
data take. a
S. Weather conditions were poor and cloudiness pre- '.^:
isvailed over the site.
6.'
Progress; of S-191 external. mirror .contamination.. _=
was. not .known. ^ -^^`^: 7. -The method of lake temperature monitoring is not^.
known. °^{
_^^^
:a,.i
_3_ 27
__ :^ ..___. __. :_ ^,^
^- _•.--_
i
^^^f
^ 4.0 CONCLUSLON
i
^ In the shortwave length (SWL) portion of the spectrum,
^ the repeatability of S-191 while viewing Maxe Serenetatis
^ was better than 5 percen for wavelengths .65 through
.85 um and l.> through 1.75 um. A11 other wavelengths were
^ better than 13_percent, except for. the ends of the silicon
band, .4 through 45 um, and 1.05 through 1.10 um. These
wavelengths are generally unreliable in output.
i
An absolutecalibration was made against. the Backup-
.Unit while viewing the Lunar Mares.. The. most reliable i
^ measurements were made on Mare Serenetatis and .compare
within less. .than 13 percent overall at the wavelengths
chosen for the: backup unit calibration. DOY 254 (LC-3) anal
DOY 343 (LC-4) compare to within less than S percent to the ^'
`^ backu^^ unit data at the selected wavelengths. `^
;;' The l^ngwavelength (LWL) data_on Mare Serenetatis is ,;
repeatable through DOY,343 (LC-4) between 8.5 and 14.5 um to
.within 5 percent. On DOY 00.7 (LC-5), a serious absorption -
anomaly appeared a:^d wa centered at 9.4 um. The band ends ` ; 't `.I ! I g
' of the LWL from 6 through 8 . S }im 'and 14.5 through 1S . 4 um ^ ^' i
appear to-be affected by reference, source.. setting. If ` the i ^
reference source setting is higher during data take than the 1
auto cal, then-the band ends of the radiance data tend to:;
„ roll up...
4
An absolute comparison was made between 5-191 Lunar-
Maxe data: .and that developed by Shorthll (ref 14),. S;-191, ^.
s ^:
was calibrated using aresponsivty calculated from tl^e
heated cal source,. The e heated cal source was about SO^C ^ a
4-1
. ip?r w
(3.32°K) and was .lower in apparent blackbody temperature than
the. moon, which is^approximately 370 to 400°C. Comparison
showed S-191 to be approximately 15 percent lower than
Shorthill's measurements.
Additionally, S-191 lake and reservoir data was. com-
pared to .atmospheric model data.of these same lakes and
reservoirs. These data comparisons were quite contradictory.:
Monroe Reservoir at close to ambient. temperature. (25°C) com-
pared well with 5-1.91 (except at the 9.4 }^m absorption band)
while the colder lakes did not.
The LWL data needs considerably more analysis before it,
can be better understood. Due to design shortcomings, and
..instrumentation shortcomings, it may never be possible to
provide software fixes . for a well calibrated output over the
whole LWL b-and.. The LWL .deep. space data may hold the 'key
to improved instrument calibration.
^_ 1. ^s -_ ^ - - ,^ _ .. 4_ .,_ . _ ^^
5.0 REFERENCES
__
1. MSC-0:5548, Appendix D "Absolute Radiance of Three Lunar ^ ,!Mares," pp. D-1 through D-18.
_ a
2. Robinson, N.; Solar Radiation. Elsevier Publishing.Company, 1966, p. 31.
3. -Haynes, E. L,, et al: Lunar Scientific Model. JPL -Document #900-278, Jet Propulsion Laboratory,Change 2, becember 7, 1971, volume I, Sec..3.4, p. 15.
4. McCord, Thomas B., Johnson, Torrence V.: Lunar SpectralReflectivity (0.30 to 2.50 Microns) and Implicationsfor Remote Mineralogical Analysis. Science, vol, 169, ^^August 28, 1970, pp. 855-858.
5. Oke, J. B.; Astrophys. Journal 140, 689 (1964).
6. Oke, J. B.; Sch^ld, R. E.: The Absolute Spectral EnergyDistribution ^,^f Alpha .Lyrae. The Astrophysical Journal, - '.161, pp.- 1015-•1023, September. 1970.
7. :Labs, G.; Neckle, H,; Z. Astrophys. 69, 1 (1968).,, i
$. Adams, J. 33.; Jones, R. L Science 167, 737 (1970). ^^ a
9. O'Leary,.B.; Briggs, F.: Journal of Geophysical ^'Research, vol. 75 No. 32, p. b532, November 10, 1970.
}10. Argo, W. V., Jr.; User's Guide; Investigation of 5-191 t -'
Skylab Short Wavelength Data.. LEC-5910, May 19 .75. t
ll. Downes, E. L.; Users' Guide'Skylab 5-191-Spectrometer' '':LWL_Data Analysis Program. LEC b377,-,June 1975.
^;
12. Earth.Resources Production Processing ReQuirements for ^^EREP Electronic Sensor, PHO-TR-524, Rev. A, Ch. 2,October 18, 1974.
,^
13. MSC-05528, Earth Resources Experimental Package (EREP)Sensor Performance Report, Vol. II (S-.191), Engineer-ing .Baseline, - SL-2, SL-3, and SL-4'Evaluation,September 6, 1974.
k
i
I ^h
14. Shorthill, R. W.; Saari, J. M.: Isothermal and.Isophotc Atlas of the . Moon, NASA CR-855, Septem- .ber 1967.a ^ ~
15. Pitts, D. E.; et al: Atmospheric Transmission, ComputerProgram CP. NASA TM X-581.37, December 1.97.4{JSC-09063).
16. MSC-05543, Earth Resources Experimental Package (EREP),Ground Truth Data for Test Sites (SL-4), April 30,1974..
17. Gunn, Keith, S-.191 Data Analysis Preliminary Report onLong-Wavelength Responsivty Problems, LEC-3784,.June 1974..
^3
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Addendum;;
r
Further work on S-191' LWL data was carried out. after^. ^ , w ^^
the completion of the attached docume ,^. This work was con- ^
cerned with reduction of data to determine what residual
.radiance the instrument was measuring when looking at deep
.space. In addition, an interpretation of this data relative
to lunar .data was desired.
One anomaly that. was very prevalent in the Lunar. data
was a tendency to sag in the 11 through 15 um band when com-
'' ared to a blackbod .curvep y (see figure 22 in the main text).
Deep space data also had a tendency to zero at about _10.5 um.
For these reasons., it wa decided. to plot portions of a
highl,ycontrolled data take during lunar. calibration one
(LC-1) when . all ..data, i.e., autocal, lunar cal, and deep
-space were taken over ashort. time span (less than. 6 minutes).
at the same reference temperature 8.97.2 °C. In order to com- ^^
pare Mare Serenetatis against deep space, a blackbody
radiance curve was subtracted from Mare Serenetatis radiance
data . so that .the difference would zero at 10.5 um. The black-
'' body temperature satisfying this condition was at 374.5°K.
The results are shown in figure 1. i^
This is a rather remarkable. comparison, in that the
10 through 15.4 um band appears like . the outline of an ink
blot in he Rorschach test in psychology.
^,
.
Interpretation of this data can be made from the curves.
The 10.5 through 14.8 um range shows positive radancefor
:, deep space and-a negative radiance difference for e Mare
Serene,tatis. Since responsvity calculations are vexy
^;
r^ A_Z
^^
1
165:15:42:24.05
165:15:42:30.616
165:15:41:26.00165:15:41:33.44
HTD AMB REF DIC DET
Mare Serenetatis 23.017 28.798 8.972 25.394 85.843
Deep SpacF 23.055 22.798 8.9721 25.251 85.843
3 x 10-4
"^'— ^ l` - ^- 165:1 5: 46: 20 .918_ `' '`
^ 1 65. 15:46.27.468 -?-. ... `. ^ . i t' -fs ^^^ _•
1 x 10 - - _ -- - - -..2 y _ ..:^,"'a--'y,'.'°.--±.,
^. y ^ 3 ^ t• i.
pit,z
-i -^^
0 .-.^,._,_^.• .^ g
-4_ _
^ .i .^ '_ Luc `:': .i ^ I '`I; H
-1 x 10 : ^--- .._ ....^ _ ^ - _ -..- _ ^ ..--t -^ cn
^ } _ i DEEP SPACE DATA (LC-1) n
3
-2 x 10-4
^ -^ - ^ i - tr-- ^ - 1—^ (MARE SERENETATIS RADIANCE ^',- ,_ .: --^-- -- \
i... t .. _:r .. ^ ^
y-4 ` ^ ^_:_.i-- _ - ^ : I ^ 374.5°K BLACKBODY RADIANCE)
- 3 x 10 - j- - - - -^-r--^ - -- 11 - c^
. - , - -^ : --- - - - - - t--
6 .. 7 _^^^ _. 8 :..._. 9 :^.-.. 10 i 11 ^ i 2 c . 13 '• 14 .i .,-r 15 ^ ^l .) 16 2 -WAVELENGTH IN (um) r
HTD Autocal 49.154 22.760 8.972 25.423 85.634
1. Both calculations made with HTD autocalresponsitivities
2. Data takes and autocal had 8.972°Creference source temperature
Figure A-l.— Comparison of Mare Serenetatis against Deep Space.
'" c
._
-_ _ t._ ^._ _. _ _- -x -:- -,,,-
nearly colinear for heated and ambient cal sources in this
spectral region., the instrument is behaving nearly normal
-internally up to the external mirrors.. The positive radi- E
anc^a for deep space would indicate a greater emissive pro-
perty for the external mirrors. than is. developed in the
-radiance calculations. This is in keeping with previous
assessments in the attached report, .and. may be caused by
tarnishing or contamination on the external mirrors. (This
is entirely possible since no known coatings. were ever ^^
applied). The negative radiance difference for Mare
Serenetatis minus the blackbody curve would therefore be
caused by"the extra emissive properties_of the externa
mirror acting as an absorber for .the "hotter" lunar
.radiance. ''-a
It is suspected that the moon acts very nearly. like a
blackbody, except at the 8,2 and 9.4 elm centered absorption
bands which are real as no appreciable absorption occurs in
these bands when. the. instrument looks at deep space.
The spectral regions from 6 through 10.5 um and 14.8..a
^ ;
through 15..4 um have crossover points and these are caused ^,
by a combination of things, the mirror contaminant and
improper modeling of the dichroic in the PHO-TR-5Z4 equations
(ref . 12)'• r
Improper modeling of the dichroic has been investigated
before, but on1.y in the context of parametric studies. on the:
PHO-TR-524 equations. These studies showed that responsivty
colinearity (for ambient and heated autocal) could not be
achieved by changes in the dichroic parameter va ues. What
is `-being suggested here is that the equa ions be changed and
a
A-4
_.^a'^
-`
the instrument be re-modeled to account for dichroic trans-
mission. In the present PHO-TR-524 equations, this is
ignored. Transmission through the dichroic and dispersion
of the energy out of the optical path would explain the
higher responsitivities calculated for the heated cals at
the band ends..-The responsitivities which axe nearly
colinear could also be explained by the fact that the
dichroic is acting. close to the present model at some
wavelengths.
Final Conclusions on LWL Data '
,^Present users of LWL data must be wary of data at the
band ends and also of data from subjects considerably,^
different in temperature from. that of the instrument.. Deep
space. data should be especially avoided in any analysis
without further instrument correction.
The S-191 output can be corrected to give more accurate
readings on radiance data if further time and resources
are alloted for its completion. This. would .not. be
possible except .for a program (ref, 11) by E.L. Downes -i
which would supply the software tools for this investigation. '^
iThe suggestedp,rocedure in .this investigation would be
to remodel the dichroic equations to account. for transmission
losses. The correctness of `the model would be an iterative
' procedure in which the ambient and heated autocal respon-
stvities were colinearzed. Next, deep space data would
be used to properly determine the reflectance and emttance
of the external mirrors. The adjusted model would then>be
i used to test the lunar .data for its closeness to a blackbody
except for the known absorption bands.
A-5
Yom. _ _ _ .^i
