The passive optical sample assembly (POSA) hardware, scheduled for the flight on orbital flight test 1 is described. The function of the instrument is aid in the assessment contamination hazards to sensitive payloads in the shuttle cargo bay. It consists of an array of passively deployed samples mounted on the development flight instrumentation pallet in the shuttle cargo bay. The directory of samples together with their intended measurements are presented. The plan for POSA data analysis is also given

Linton, R. C.

English

NASA Technical Reports Server

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NASA TECHNICAL
t.. MEMORANDUM
; , NASATM-82407(NASA-TII-_>407) _H_ _ASSIVE OPTIC&L aA_L?- H_1-20go8
_. _Sgg_,L¥ (,.L_OSA) ON S'l'S-1 (RA,_A) 1"7 p
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G3/Tq 41895
THEPASSIVEOPTICALS_P.LEASSEMBLY(POSA)ONSTS-I
By Roger C. Linton
Space Sciences Laboratory
GeorgeC, Marshall Space Flight Center
34arshall Space Flight Center, Alabama
MSFC - Form ]lqo (Rev June 1071)
https://ntrs.nasa.gov/search.jsp?R=19810012339 2020-03-21T13:16:03+00:00Z
_"_ . T_CHN_CAL REPORT STANDARD TITL._ PAC;I_
; _.._pORTNASATM-N°'_2407' 12. GOVI£RNMENI" ACCESSION NO. 8. RECIPIENT'S CATALOG NO.I
: 4. TITLE AND SUBTITLE E. REPORT DATE;
r:. The Passive Optical Sample A._._embly(POSA) on STS-1 March 1981
:_ 6, P_RrDRMING ORGANIZATION C(.,DE
7. ALITNOR(_t) 8, PERFORMING ORGANIZATION REPnRr ;/
Roger C. Ltnton
e PERFORMINGO_ ANIZATIONNAMEANOAOORESS _0. WORKUNITNO.
GeorgeC. MarshallSpace Fllg:,tCenter
I MarshallSpace FlightCenter,Alabama 35812 I.CONTRACTORGRANTNO.• ' 1=. rY_ or REPOR;"a PERIOOCOWRE.12. SPONSORING AGENCY NAME AND ADDRESS
Technica'i Memorandum
' National Aeronautics and Space Adminlstratto_L---
Washington, D.C. 20546 14. SPONSOR=._AGENCYCO.E
15. SUI=PLEMENTARY NOTES
Preparedby Space SciencesLaboratory,Scienceand Engineering
m _ m
16. ABSTRACT
The PassiveOpticalSample Assembly(POSA),scheduledfor flighton Orbital
FlightTest 1 (0FT-I),is an instrumentto aid in the assessmentof contamination
hazardsto sensitivepayloadsin the Shuttlecargo bay. It consistsof an array
of passivelydeployedsamplesmountedon the DevelopmentFlight Instrumentation
(DFI) pallet in the Shuttlecargo bay. Th,s report describesthe POSA hardware,
the directoryof samplestogetherwith their intendedmeasurements,and the plan
for POSA data analysis.
Contamination /__''_ r.__
Passiveopticalexperiment Unclassified Unlimited
0FT-I experiment
w ._ ...................._.......... _ ........... I.,.,.,__ ._................,_,,_.__T_.__._._.:,,_..;._..,.CZ_. "r_° }..}'_
I/
TABLE ()rCONTENTS
Paqe
INTRODUCTION...,..,,...,............,....,.,................. .. 1
DESCRIPTIONOF IIARDWARE.,,..,,....,,,,,....,.................... I
DIRECTORYOF SAMPLES ,.,,,....,,....,.,.,,,....................... 6
. DATA ANALYSISPLAN ,,,,,,,,,,,,,.,,,...,,,....,................... 9
BIBLIOGRAPHY ,,,,,,,,,,,,.,.,,,,.,.,....°,,...................... 12
iii
Li:
LIST OF ILLUSTRATIONS
II Figure Nn. Title
it)
I. POSA mounted nn DFI pallet in carqo bay of OFT-I
(POSA in centerof photograph) .................... 2
2. Close-upview of POSA in c,_rgobay ................. 3
3. POSA configuration.................................5
4. PassiveOpticalSample Assembly .................... 7
LIST OF TABLES
Table No. Title Pa_e
I. PassiveOpticalSampleAssembly (POSA)............. 4
,._. ProjectedSchedulefor POSA Data Analysis .......... II
iv
I_'_: NASA TECIINICAL MEMORANDUM
F INTRODU_TION
[i_: The Passive Optical Sample Assembly (POSA) is a modified versionof one of the instruments included in the Induced Environ ent Contamina-
_, tion Monitor (IECM), an inteqrated technology payload consisting of I0
individual instrument_ sharing a common power and data collection sys-
tem. The IECM, designated for flight on all Orhiter Flight Tests
(OFT's) suGceedinq the first and on Spacelahs 1 and 2, is designed to
• provide verification measurements of Shuttle contaminant emission and
deposit levels durin(l nround operations, ascent, on-orbit, descent, and
postlanding. Despite the severe payload constraints of OFT-I which
• necessitated removal of the IECM from the mission, consensus substan-
tiated a critical need for _t least baseline data pertinent to the eval-
uation of Shuttle contamiHation hazards. The POSA, while less ambitious
in scope than its parent IECM experiment (Passive Sample Array), is now
included on OFT-I to provide some limited contamination verification of
the Shuttle environment so urgently needed by the design and user com-
munities. Figures 1 and 2 show the POSA in the cargo hay of the
Shuttle.
As the name implies, the POSA instrument is totally passive. It
is a mounted array of five optical samples and three static-charqed
Teflon sheets (electrets). Table 1 provides a directory of the samples
contained in the POSA for OFT-I. All of the samples were subjected to a
series of optical and analytical measurements prior to delivery to
Kennedy Space Center (KSC). The measurements will he repeated in an
identical manner when the POSA is returned to Harshall Space Flight
Center (MSFC) following the flight mission. The degradation of the
optical properties of the optical samples will constitute the basis for
analysis of the severity of the contamination hazards for payloads in
the Shuttle cargo hay, while analysis of the electrets will provide a
means of identifying and specifyinq the relative abundances of the con-
taminants.
DESCRIPTION OF HARD!,IARE
The POSA consists basically of a sturdy, rectanqular holder (fTig.
3). Six cylindrical receptacles (I.09 in. wide, 0.187 in. deep) are
bored at equal spacing along the axis of the holder. Smaller (0.75 in.
diameter) holes in each of the six sample "slots" are counterhored com-
Dletely through the holder so that, when the samples are emplaced, ef-
fluents can reach front and rear surfaces of the samples direct3y. Thi,,
will allow assessment and some comparison of diroctinnality in efflHent
flow.
A retainer plate _lith six circular slots is holted over the sample
holder, allowing maximHm front-surface exposure of the samples while
holding down the oHter edges. Durinq the phases of qround handling,
transportation, and installation when exposHre is net desired, a snlid,
rectangular cover plate with captive screws is provided to protect th_
samples. All hardware is 300 series stainless steel.
FIGURE I. POSA fnoLintedun IIFIpallet in c,_rgobay of OF1-1
(POSA i_l renter of photo qraldl).
FIGURE 2. Close-up view of POSA in cargo bay.
(FWD indicates forward with
respect to the Shuttle.)
__--- - . " " • , , " " _ -,',,', i .................... I.... I
F '
p
, TABLE I. PASSIVEOPTICALSAMPLEASSEMBLY (POSA)
jl Tray 012
Sample I.D. Material
_i A MgF2/AIMirror
I B Gold MirrorC 1810 _ Filter
D CaF2 Window
E Top'.CaF2 Window
Base: Electret#8
F Top: Electret#10
Base: Electret#9
The POSA is mounted to the Development Flight Instrumentation
(DFI) pallet in the Shuttlecargo bay by means of two bolts,one at each
end of the holder;these bolts mate to existing captive nuts under the
IECMmountinq rails of the DFI pallet.
The samplesare subjectto chipping,breaking,or crackingif not
adequatelyprotected. Therefore,Teflon gasketsare placed in each slot
of the holder prior to installationcf the samplesand, in some cases,
on top of the samples as well. Qualificationtestino of the Passive
Sample Array/IECMand analyticalcalculationsfor the POSA have proved
satisfactorymechanicalintegrity.
Identificationof the POSA hardwareand the individualsamples is
providedby means of stampednumbersand letters,on the front surfaceof
the retainerplate.
Assembly of the POSA for flight (with all componentshaving been
properly cleaned, double-bagged,and brought into a designated clean
room) is straightforward. A Teflon gasket is deposited into each
depression (slot)of the holder. Into each of the first four sample
positionsis depositedan optical sample,front surface up. Two elec-
trets are placed in positions (slots)E and F. A third electret is
added to slot F. The electretsare placed so that particlesare at-
tractedfrom above or below the POSA. The fifth optical sample (CaF2)
is added on top of the electret in slot E. AdditionalTeflon gaskets
are added as needed to fill, hut not overfill,the sample slot depres-
sions. The retainer plate is then placed over the sample holder, the
six (6-32 Phillips-head)bolts dropped into place, lock nuts added, and
all tighLened uniformly to I0 to 12 in. Ibs. (torque). Finally, the
cover plate, with two captive bolts, is placed over the assembly and

t!
1
holted into posii.icm, Th(, I'OSA was delivnred to KSC with t.he m(_untinq
hardware (holt._, washers, spacers) separately haqqed. At KSC, the wash-
ors were added t.othe two nK_unl.inqholt.s,the bolts placed throuqh the
P desiqnated Imles of the POSA, the spacers added, and the P(ISAt.iqhtened
: down t.o the DFI pallet. The cover plate was removed, as scheduled, at
the last cargo hay access on March 17, ]_q..
! DIRF.CTORYOF SAMPLES
t There are six sample positions in the POSA tray to be flown (Fig.
- 4). The selected directory of samples for STS-1, as shown in Table 1,includes:
I
A,--_.t_rrar- Thin film alumin,mlnvercoated with maqnesium
fluoride
11,.Mirror Thin film .hold
C. Filter - Thin film multilayered metallic vacuum ultraviolet
filter
D. Window - Calciiim fluoride (CaF2), transparent tn 1216
F. Window- Calcilmlfluoride (OAF2), uv qrade
F. F.lectret l-lnctricallychar,ledTeflon sheet
The hasic philosol_hyof selection was determined hy the relative
sensitivity of the surfaces selected and the relevance of concern for
similar materials as coi_Iponentsof futur(,STS payloads sensitive to con-
tanlination. In part ictllar, the followinq measurements apply for the
samples in the order previously listed:
A. An ol,tically flat (\/lO) fused silica suhstrate is coated with
1000 _ lhickness alumin_mluhi('h is, in turn, nvercoated with a pro-
tective and reflective-enhancinn ','.50_ thick layer of ma(mesium flu-
oride. The sample is desinnat(,d as .qqt.2/A1. The. suhstrate thickness
is 3;! toni (0.125 in.). lhis l,arlicular composition of thin film mirrm"
I_rovidf, s ihe hit!trust r('llecl,_nc.e in the v,tcIllllll ult.r,tviolei, spectral
ran,le thromlh, or down to, l;']t_ /_ wavelnnqt.h (l_yman ._).
lleasurements of spectJlar, sl,ectrnl reflectance Jre performed in
the waw, lenqth r,_nm, l?(lll in 3(100 ,_ in a reflectom(,ter at the exit
slit of a Seya-Namiok,_ Illl_Ilo('hYom.tior. A hy,h'oqen disch,_rqe lamp is
utilized as the _mn'ce. Addiiion.lll.v, the Ill('aSlll'l,llli, lltS ,ti't' extended
thr(_llqh ;'.5 II w,_vel(,nqih l_y m.,.tsurin.1 lhe .tiffu_e reflect an(-(, in ,t
(_ier-Punkl(, inte,lratinq sl,here t,}cility.
I_. The qold mirror cml_ii;ts of ,_ ,l(l(1 _ thickm,_s lnyer of
p_lr(, nntd (m ,I t_s_,,t silicn s_ll_tr,]i(,. The s_lhstrntes (_f ,_ll mirrors
s(,l(,('ted fro" _se in the I'OSA ,we ideni ic,_l. This s,_ml_le is desi(m,_t(,d
,t,; tile ,_ mirror, t:nth ,,(_ld ,lint tl,ll,IA1 mirrors ,n'e _l,_n(h_r(t c(_ml,on-
e/it s Of st,,Ice opt ical in,;! r_:,_eni at i'on. In i lh, ,,p(,rt rnl r,]nm, of
• . , ........... ...... =
_.--,,x-,,-,--_-= ......- ....... I I I I I II
s,.=,
, "" ,, , ,,, a I I I I ' .................... " II
PI _.
i measurements s(,lect_d, the denradatinn duo tn d_positinn of cnntaminants
i_ detectable for the pr{,senco of a_ littl(, a_ nno i,_no]ayer nf cnn_ami-
nat inn.
i
i Specular, spectral rgflectance of the qold mirror is measured in
i the range 1200 to 3[)00 _ and i_ extende_, for diffuse reflectance
and hackscatter measurements, through 2.5 _ with the Gier-llunkle facil-
ity.
C. The vacuum ultraviolet filter is composed of a multilayer thin
i film composition deposited on a magnesium fluoride substrate. The fil-
ter transmits a 225 X bandwidth of liqht centered at 1810
wavelength. Peak transmission at II_lO _ is 21 percent. Such fil-
ters are common components of vacuum ultraviolet instruments flown in
space. The transmission is hiqhly sensitive to contamination. The
filter is opaque to all wavelenqths of light in the range 0.12 to 2.5
except, of course, for the "narrow" bandwidth, as desiqned.
Measurements of the filter include front-surface specular, spec-
tral _eflectance and direct transmission in the wavelength range 1200 to
3000 A.
D.. The calcium fluoride "window" is dimensionally identical to
the mirror suhstrates; both sides are optically polished. Transmission
extends through the ultraviolet. Such windows are commonly used as com-
ponents in spacehorne optical instruments, and the degradation of opti-
cal performance due to contamination can severely degrade the perform-
ance of the elements they are emplaced to protect.
Measurements of front-surface specular, spectral reflectance and
direc_ transmission are performed in the _mvelenath ran qe 1200 to
3000 A. In addition, the sa,ll)les of this type are subjected to
backscatter measurements in the Gier-Dunkle facility.
E. The CaF2 sample is optically polished on beth sides (2.54 col
dianleter, ,.o_ r. nlm thick). This sample is transparent to light throuqh
the wacuum L_Itraviolet to a mannitude decreasinq to zero helmv
Because of hardness, resistance to water, uv-induced damage, and,
of course, favorable transmission properties in the vacuum ultraviolet,
calcium fluoride windmm are commonly used as components of spaceborne
optical instrumentation (particularly as window,s for environmentally
sensitive detectors).
Measurements of frnnt-surf,_ce specular, spectral reflectance and
(iirec_ tr,_nsmission .lr_-' I_orformed ill tile _.lilvelr, nqlh ranqe 1200 t.n
3000 A.
F. The elecir_,tq arC, made nf Teflnn-polytoirafluor_,t.hylene,
(.C2114)n. Ileciret s are dieleri rics with a permanent surface i
Ctlarne thai ,!iv_,s timm i,rnl,erti_m ,lnaloqollS in iqa,_tl_,ts b.V attracting
8
b!,,/
i,
charged particles and ions t_ their surface, From X-ray microprobe_
; analysis of the effluents collected on the Teflon electrets, enerqy
measurem_.nt._ are made in the X-ray enerqy ranqe from (I.7C17 tn 30 Ko.V
P _C).170 keY (i,e. fluorine to silver). Thu._ an elemental analysis and! _ ' , .,
r an estimate of the. ahundance nf the elements are ohtained.i
Three electrets are included in the POSA for (_FT-I. One is placed
,, under Sample E, the calcium fluoride "window." For this electret, the
L ion-attractinfl charged surface is oriented 180 denrees from the direc-
, tion the CaF2 samples faces, providing a measure of the directionality
of effluent flow. The other two electrets are placed in sample slot "F"
of the POSA holder (one facing "up" and the other facing "down") for
I directionality analysis,
The preceding measurements were performed on the samples prior to
installation in the Shuttle, and they will he repeated _n an identical
manner after the fli,lht to asses_ the contamination hazards of the STS
cargo-bay envir,'}nment. '
DATA ANALYSIS PLAN
The inclusion of a variety of optical surfaces and electrets in
the F'OSA for STS-I offers a correspondinq variety of "sticking" proba-
hilities for contaminants. Each of the samples in the POSA was chosen
for its relative sensitivity to optical deqradation by deposition of
contaminants as well as inherent relevance to future STS payloads.
Measurements of the optical properties of the samples made prior to
installation of the POSA on OFT-I will be compared to identical measure-
ments on the samples after the fli.qht. Analysis will he directed toward
understanding the mechanisms of degradation as well as identification of
the contaminants themselves. The inclusion of electrets in the POSA
will enhance the probability of collectinq and retaininn contaminants
and, further, will provide a basis for chemical identification hy esti-
mating elemental ahundan_e.
' The plan for rOSA data analysis is subdivided int'o the followinq
major phases:
I. DIirinq pro-installation measurements of the optical properties
of the five optical samples and back qround microprobe measurements of
the three electrets, personnel will handle the samples vHth clean-room
procedures, incl_dinn ,qloves.
2. Followinn retrieval of the rOSA from the Shuttle cargo hay
after the fli!lht mission, the unit will he douhle-haqned and returned
(hand-carried) to MSFC for analysis.
3. At MSFC, in a laminar-flow class IC),(I00 clean-hooch environ-
ment, the protective cover will he removed and a thoroLIqh visiial inspec-
tion of the samples in the rOSA tray will he performed. Personnel
handlin(l POSA hardware will wear clean-room qariilents and tlse clean-room
nloves in all phases of handlinq.
!!
4, Photonraphs of the POSA will he taken fnr comparison Iiith
those taken prior to KSC delivery,
5. The five optical samples and the three electrets will he re-
moved from the POSA ha:'dware.
6. Individual, clos_-up photographs nf the samples themselves
will he taken.
7, The electrets will he subjected to X-ray microprobe analysis.
8. The optical samples will be subjected to measurements of
reflectance, transmittance, and backscattering efficiency in a manner
identical to that iised in the pre-installation sequence,
9. The optical denradation will be determined hy computing the
percentage change in each of the optical properties, computed as a per-
rentage of the measured difference, if any, divided by the original
value--all as a functio:_ of wavelength.
I0. The microprobe analysis of the eleczrets is expected to reveal
information concerning the nature of the collected contaminants. A
measurement of the relative elemental ahundance will be performed. An
excellent opportunity for assessing at least one aspect of the direc-
tionality of carqo bay effluents will he presented throunh analysis of
the relative abundances from electrets oriented 180 degrees apart in thePOSA.
II. A final analytical tool available for this analysis of the
optical samples will he the scanninfl electron microscope (SEM) facility
in the Space Sciences Laboratory at MSFC. It is nocessary that this be
the final phase of measurement because of lhe necessity nf depositing a
conductive paste to the samples for analysis with this instrument.
Table 2 summarizes a projected sched_le fnr data analysis of thePOSA.
A "quick-look" report c_f the initial results obtained will he
available within 2 weeks of delivery of the POSA to MSFC. Jhe extended
analysis, with concl_sions, _ill he available for distribution (in NASA
Technical Memorandilm format) _Jithin 6 weeks.
I0
Ii, IAI_,I.I- 2. PROJIICTLI) SC.III:IIIIJL[FOIl P(_SAI_ATA ANALYSIS
i
I' l'a_____k i stimated Tim_ R_,q, lre.d Lflcati(m/l-acil its.,
I Retrieval of POSA, 2 days KSCt-
_: installation of
_,, cover plate, douhle-
haqqinq, shipment to
MSFC
, Initial postfliqht I day SSI_/MSFC
inspection (visual), Laminar-flow clean
includin_lphetor]raphs bench
Optical measurements FS64/MSFC
and Seya/Namioka mono-
X-ray microprobe 2 weeks chromator; Beckman
analysis of samples PK-2 integratinq
sphere
Electrml microscope 3 days S[M Facilities:
phnto_iral_h, microprohe I C43/MSF("
analysis of samples I-S731MSIC
l]
-L_ .................................
I_
IL
BIBLIOGRAPHY
!
i Miller,Edgar R., and Decher,Rudolf (eds.):An InducedEnvironment! ContaminationMonitor for the Space Shuttle. NASA TM-78193,
, August 1978.
Pillai,P. K. C., and Shriver,Edward L.: Electretsand Their Applica-
tions in ContaminationStudies. NASA TR R-457,December1975.
Susko,Michael:ElectretsUsed in MeasuringRocketExhaustEffluents
from the Space Shuttle'sSolid RocketBoosterDuring Static Test
! Firing,DM-3 NASA TM-78216,January1979.b" • (
12
!i.
_:L'
i'
APPROVAL
i:
, Ttt[ PASSIV| OPTICAL SAMPL[ ASS[MBLY (POSA) (1N SIS-1
. By Roger C. Linton
The information in this report has been reviewed for technical
content. Review of any information concerninq Department of Defense or
nuclear enerqy activities or programs has been made by the MSFC Security
Classification Officer. This report_ in its entirety, has been deter-
mined to he unclassified.
%_ILL[R
Chief, Optics Physics Branch
-) ?
P.UDOLF DECII[IV
Chief, Space./Physics Division
Director, Space Scienc(_sLaboratory
l].
____ . .... , , , ,,i, ,• I -ii


The Passive Optical Sample Assembly (POSA) on STS-1

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