Rev.
01q
Dwg. No.
37-11002.18
ECO
37-037
02q
37-11002.18
37-115
03q
37-11002.18
37-249
A
37-15040
37-254
B
37-15040
37-300
Description
Initial release extracted from
CSR
Reformatted, tailored to
instrument team
responsibilities and updated
with new information.
Updated requirements &
bakeout information
Updated based on feedback
from instrument team and
GSFC contamination control
experts
Updated based on feedback
from GSFC. Changed “shall”
statements to “will”
statements since this
document is not a tracked
requirements document.
Added a facilities
requirements section and
included details about
instrument purge.
Author
Approved
ZKhan
8/20/2014
ZKhan
5/11/2015
ZKhan
RFGoeke
6/1/2015
ZKhan
RFGoeke
7/27/2015
TESS
Instrument Contamination Control Plan
Dwg. No. 37-15040
Revision B
27/July/2015
37-15040
i
Date
2/17/2014
Revision B
Table of Contents
1.0
1.1
Purpose ................................................................................................................ 1
Scope .......................................................................................................................... 1
2.0
List of Acronyms ................................................................................................. 1
3.0
Definitions ............................................................................................................ 2
4.0
Applicable and Reference Documents .............................................................. 3
5.0
Contamination Documentation Requirements ................................................. 4
5.1
Deviations .................................................................................................................. 4
6.0
Roles and Responsibilities ................................................................................. 4
7.0
Cleanliness Requirements Development .......................................................... 4
7.1
7.2
7.3
7.4
8.0
8.1
8.2
8.3
9.0
10.0
10.1
10.2
10.3
Contamination Sources for TESS ............................................................................. 5
Derivation of Particulate Cleanliness Requirements ............................................... 6
Derivation of NVR Cleanliness Requirements ......................................................... 7
Contamination Analyses and Laboratory Testing ................................................... 8
Cleanliness Requirements .................................................................................. 8
Sensitive Surface Identification and their Requirements ........................................ 8
DHU Cleanliness Requirements...............................................................................10
Cleanliness Requirements Levied on the Spacecraft and Launch Vehicle ..........10
Facilities Requirements .................................................................................... 10
Design Phase Contamination Control .......................................................... 10
Material Selection .....................................................................................................10
Design and Venting ..................................................................................................11
Purge .........................................................................................................................11
11.0
Fabrication and Assembly Phases Contamination Control ....................... 11
12.0
Integration Phase Contamination Control ................................................... 12
12.1
12.2
13.0
13.1
13.2
13.3
13.4
Cleanroom Facility Requirements ...........................................................................13
Vacuum Bakeout Requirements ..............................................................................15
Test Phase Contamination Control .............................................................. 15
Vibration Testing Requirements ..............................................................................15
Thermal Balance/Thermal Vacuum (TB/TV) Testing Requirements ......................16
EMI/EMC Requirements ............................................................................................17
Performance Requirements .....................................................................................17
14.0
Contamination Control Requirements for Storage and Transport ............ 17
15.0
Cleanliness Inspection and Monitoring ....................................................... 17
16.0
Personnel Requirements ............................................................................... 18
37-15040
ii
Revision B
Preface
This is the TESS Instrument Contamination Control Plan. It describes detailed cleanliness
requirements for the TESS instrument as well as planned actions to meet those requirements.
Revision 01q was an initial draft extracted from the Concept Study Report (Dwg no. 37-16001)
Revision 02q reformatted the content from Revision 01q. Some additions were made based on
a standard contamination control plan template and some sections not relevant to instrument
team were removed. Cleanliness requirements and information about contamination analyses
was also updated.
Revision 03q refined the cleanliness requirements and added details about bakeouts.
Revision A is an update based on feedback from instrument team and GSFC contamination
control experts.
Revision B is an update based on a formal review by GSFC as well as comments from a
Technical Interchange Meeting. Since this is not a tracked requirements document, “shall”
statements have been changed to “will” statements, as appropriate. A facilities requirements
section has been added and more details have been included about the instrument purge.
37-15040
iii
Revision B
1.0 Purpose
The purpose of this document is to define the overall cleanliness requirements for the
design, fabrication, assembly, integration and testing of the TESS Instrument as well as
planned actions to meet those requirements.
1.1 Scope
The cleanliness requirements for the TESS instrument for all mission phases are
addressed, from spacecraft and instrument design, through fabrication, assembly,
integration, and testing, up through launch and on-orbit through end-of-life.
TESS instrument sensitivities and allowable contamination requirements are presented,
along with the planned methods for limiting contamination up to instrument delivery to
Orbital ATK for integration with spacecraft. Plans for analyses, laboratory investigations,
cleanroom and hardware monitoring, are also addressed. Wherever possible, the TESS
program will utilize existing contamination control methods and documentation that have
been developed for other missions.
2.0 List of Acronyms
BOL
CAD
CCE
CCD
CCM
CCIP
CCP
CVCM
DHU
EMC
EMI
EOL
ESD
FED-STD
GSE
GSFC
HEPA
IPA
I&T
LPM
37-15040
Beginning Of Life
Computer Aided Design
Contamination Control Engineer
Charge-Coupled Device
Contamination Control Manager
Contamination Control Implementation Plan
Contamination Control Plan
Collected Volatile Condensable Materials
Data Handling Unit
Electromagnetic Compatibility
Electromagnetic Interference
End Of Life
Electrostatic Discharge
Federal Standard
Ground Support Equipment
Goddard Space Flight Center
High Efficiency Particulate Air
Isopropyl Alcohol
Integration and Test
Liters per minute
1
Revision B
MIL-STD
MLI
NVR
OGR
PAR
PCB
PST
QA
QCM
TML
TQCM
TV
VCS
Military Standard
Multi-Layer Insulation
Non-Volatile Residue
Outgassing Rate
Performance Assurance Requirements (Document)
Printed Circuit Board
Point Source Transmittance
Quality Assurance
Quartz Crystal Microbalance
Total Mass Loss
Temperature-Controlled Quartz Crystal Microbalance
Thermal Vacuum
Visibly Clean Sensitive
3.0 Definitions
An area where the number of 0.5 µm particles per ft3 does not
exceed X
Cleanroom
Room in which the concentration of airborne particles is
controlled to specified limits.
Clean Zone
Defined space in which the concentration of airborne particles
is controlled to specified limits. Clean zones are classified in
accordance with IEST-14644, which describes the maximum
number of particles permitted per cubic foot of air.
Contamination Any unwanted material that causes degradation in the desired
function of an instrument or flight hardware.
Contamination Organized action to control the level of contamination.
Control
Fiber
A particle whose length-to-width ratio exceeds 10:1 with a
minimum length of 100 microns.
Gross
Cleaning hardware surfaces to visual inspection standards
Cleaning
Level x per
The cleanliness level defined by a number and/or letter
MIL-STD
designating the particle distribution and molecular cleanliness,
1246
respectively.
Nitrogen
Pressurized flow of clean, dry nitrogen through a system in
Purge
order to displace impurities and reactive species.
Non-Volatile
Soluble material remaining after evaporation of a volatile liquid
Residue
which usually causes degradation in the desired function of a
lens system, instrument or flight hardware.
Particle
A small quantity of solid or liquid material with definable shape
or mass with a length to width ratio less than 10:1.
Particle Size
Expressed as the apparent maximum linear dimension or
diameter of the particle.
Precision
A cleaning procedure done in a controlled environment to attain
Class X Area
37-15040
2
Revision B
Cleaning
Sensitive
Surface
Solvent
Flushing
Solvent
Washes
Surface
Cleanliness
Level
Swab Sample
Tape Lifts
Vapor
Degrease
Visibly Clean
a specific level of cleanliness. This procedure follows gross
cleaning.
Any surface of flight hardware that must meet a specified
cleanliness level to ensure the minimum performance levels.
Method of cleaning surfaces with a stream of filtered solvent
under pressure, which is directed against a surface to dislodge
and rinse away any foreign material.
A quantitative method of verifying MIL-STD-1246 molecular
cleanliness levels by measuring molecular contamination in a
solvent, which was washed over a surface and collected.
An established level of maximum allowable particulate and/or
NVR contamination ranging from visibly clean to specific MILSTD-1246 levels (e.g., Level 300A, Level 300B, etc.).
A qualitative method of identifying contaminants by analyzing
the residue on a solvent-soaked swab that was wiped over a
surface.
A quantitative method of verifying MIL-STD-1246 particulate
cleanliness levels by measuring particulate contamination on a
sample of tape that has come in contact with the surface one
wants to examine. The method is described in ASTM E1216:
Standard Practice for Sampling Surface Particulate
Contamination by Tape Lift.
Item to be cleaned is exposed to heated solvent vapors that
condense on the part and wash away contaminant.
The achievement of a clean surface as seen without optical
aids (except corrected vision) as measured by a specified
method. Three levels of visibly clean (VC) requirements are
defined in JSC-SN-C-0005C
4.0 Applicable and Reference Documents
The applicable and reference documents mentioned in this TESS Instrument
Contamination Control Plan are listed in Table 1 and Table 2.
Table 1 - Applicable TESS Documents
Document Number
37-10037
Document Title
TESS Contamination Control Plan
Table 2 - Contamination Control Reference Documents
Document Number
MIL-STD- 1246
NASA-RP-1124-Rev-4
GSFC-TLS-PR-7324-O 1
37-15040
Document Title
Product Cleanliness Levels and Contamination
Control
Outgassing Data for Selecting Spacecraft Materials
Contamination Control Procedures for the Tape Lift
Sampling Surfaces
3
Revision B
ASTM E-595
IES-RP-CC-018-89-T
ISO-14644 – 1-7
JSC-SN-C-0005C
MIL-PRF-27401G
Methods of Test, Total Mass and Controlled Volatile
Condensable Materials from Outgassing in a Vacuum
Environment
Cleanroom Housekeeping – Operating and Monitoring
Procedures
Cleanrooms and Associated Controlled Environments
Space Shuttle Contamination Control Requirements
Performance Specification: Propellant Pressurizing
Agent, Nitrogen
5.0 Contamination Documentation Requirements
There are a number of contamination-related documents which will be produced and
periodically updated throughout the TESS Mission development process. These include:
 TESS Instrument Contamination Control Plan [this document]
 TESS Instrument Contamination Control Implementation Plan (CCIP)
 Supporting procedures, guidelines, standards, plans, etc.
 Cleanroom Monitoring Logs
 Hardware Cleanliness History Logs
 Testing Results Reports
5.1 Deviations
Deviations from this plan must be properly documented and approved by the TESS
Instrument System Engineer and the Instrument Mission Assurance Manager.
6.0 Roles and Responsibilities
The TESS Instrument System Engineer, Instrument Mission Assurance Manager,
Instrument Contamination Control Lead at MIT Kavli Institute (MKI) and the Instrument
Contamination Control Lead at MIT Lincoln Lab (LL) will be responsible for ensuring that
contamination control measures are implemented throughout the instrument design,
fabrication, assembly, integration, testing, storage and transportation mission phases up
to delivery of the instrument to Orbital ATK for integration with spacecraft.
7.0 Cleanliness Requirements Development
The primary driver for the overall TESS Instrument Contamination Control program is the
need to have a very low background level of targeted species that could degrade
instrument performance (e.g., self-contamination by the TESS instrument or the
spacecraft.) The lens and CCD surfaces are the most critical surfaces for deposited
37-15040
4
Revision B
contaminants. This section details all of the variables that go into defining the TESS
Instrument Cleanliness Requirements.
The Orbital ATK Contamination Control Engineer is responsible for the development of
the spacecraft cleanliness requirements as well as coordination of the TESS cleanliness
requirements with other observatory and instrument contamination requirements.
The NASA Goddard Space Flight Center (GSFC) Contamination Control Engineer is
responsible for the development of project level, including launch environment,
cleanliness requirements and implementation.
7.1 Contamination Sources for TESS
Possible sources of contamination must be identified in order to protect the instrument
from contamination and to effectively clean contaminated components. The following
table lists possible contamination sources at the various development stages.
Table 3 - Contamination Sources for TESS Instrument
Mission
Phases
Molecular
Particulate
Fabrication
Materials outgassing, machining
oils, fingerprints, air fallout
Shedding, flaking, metal chips,
filings, air fallout, personnel
Assembly &
Integration
Air fallout, outgassing, personnel,
cleaning, solvents, soldering,
lubricants, bagging material
Air fallout, personnel, soldering,
drilling, bagging material,
shedding, flaking
Test
Air fallout, outgassing, personnel,
test facilities, purges
Air fallout, personnel, test
facilities, purges, shedding,
flaking, redistribution
Storage
Bagging material, outgassing,
purges, containers
Bagging material, purges,
containers, shedding, flaking
Transport
Bagging material, outgassing,
purges, containers
Bagging material, purges,
containers, vibration, shedding,
flaking
Launch Site
Bagging material, air fallout,
outgassing, personnel, purges, salt
atmosphere
Bagging material, air fallout,
personnel, shedding, flaking,
checkout activities, other payload
activities
Launch/Ascent Outgassing, venting, engines,
separation maneuvers
37-15040
5
Vibration and/or redistribution,
venting, shedding, flaking
Revision B
On-Orbit
Outgassing, UV interactions,
atomic oxygen, propulsion systems
Micrometeoroid & debris
impingement, material erosion,
redistribution, shedding, flaking,
operational events
7.1.1 Self-contamination
Contamination can be transferred to the sensitive surfaces from the rest of the
spacecraft (including TESS instrument) by various methods. Surfaces that may
accumulate particulate and/or molecular contamination and that are not maintained at
their required cleanliness level, are capable of providing contamination that can then be
transported by various methods to contamination sensitive surfaces. Transportation can
take place by contact transfer, by ambient outgassing and recondensation, by thermal
vacuum outgassing and recondensation, and by movement or vibration (for particulate
matter), and for some particularly nasty molecular species, by migration across surfaces
driven by surface tension. For this reason any surface which may transfer contamination
to another contamination sensitive surface must meet the contamination control
requirements of the more sensitive surface or demonstrate that the contamination
transfer will not exceed the contamination requirements of the more sensitive surface.
The first line of defense is choosing materials with inherently low outgassing properties
e.g. those which can be measured using ASTM 595 test. Furthermore, the geometric
design and venting can redirect contaminants or imprison contaminants away from
contamination critical surfaces. Both these topics are addressed in the Design Phase
Contamination Control section.
One final line of defense is maintaining all surfaces at their specified surface and
cleanliness level and outgassing requirements described in Section 8.0.
7.2 Derivation of Particulate Cleanliness Requirements
The TESS instrument particulate cleanliness requirements for optical surfaces were
derived using information from subject matter experts (SMEs) and stray light modeling.
The TESS instrument stray light model was built in FRED Optical Design Software using
a complete CAD model of the lens barrel and lens hood assemblies, with an optical
prescription imported from the lens model. The sensor and sensor electronics were
simplified to a simple square detector, with the light shield imported from the CAD
model. The surface contaminations were defined according to the values proposed by
SMEs. The cleanliness levels on the internal, sealed surfaces (lens barrel, lens surfaces)
were assumed 250, while the cleanliness level on the unsealed surfaces (external lens
surface, inside of lens hood) were varied to establish the requirements captured in Table
4 in Section 8.1. The CCD itself was assumed 150. Stray light performance was
modeled using point source transmittance (PST), which is a ratio of the irradiance on the
detector to the irradiance at the entrance aperture of the system. In this case, the hood
opening is treated as the entrance aperture. In the model, a plane wave with uniform
irradiance filling the aperture was traced through the system and to the detector. The
PST calculation was repeated at multiple azimuths and elevations to provide a
37-15040
6
Revision B
comprehensive system PST. The PST was evaluated against science requirements to
confirm acceptable performance with the specified contamination levels.
The TESS instrument particulate contamination requirements for optical surfaces were
further considered in terms of surface obscuration. For this analysis, the percent area
coverage was used as a measure of surface obscuration. The particulate distributions
used [obtained from MIL-STD-1246C] in the analysis were based on the cleanliness
levels specified above. It was assumed that none of the obscuration due to particulate
contamination was overlapping. So the total percent area coverage was calculated
simply as the sum of the percent area coverage for each surface. The percent area
coverage was evaluated against science requirements to confirm acceptable
performance with the specified contamination levels.
The TESS instrument particulate cleanliness requirements for CCDs were derived using
information from subject matter experts and analysis of surface obscuration. From a
science perspective, up to 0.1% of pixels can be lost without impact to the mission. A
surface obscuration analysis shows that the SME proposed cleanliness level of 150 for
CCDs meets the science requirement.
7.3 Derivation of NVR Cleanliness Requirements
Outgassing requirements for the instruments are derived from the surface requirements
of the spacecraft and instrument sensitive surfaces. During flight the return flux from
outgassing is negligible; therefore, line of sight and reflected contamination is the
primary mechanism for outgassing to affect sensitive surfaces during flight.
The TESS instrument non-volatile residue (NVR) requirements for optical surfaces and
CCDs were derived using information from subject matter experts (SMEs), a molecular
deposition analysis & modeling of loss in optical performance due to NVR. The
molecular deposition analysis was performed using conservative assumptions. The
critical surfaces were given their coldest on-orbit temperature and the other (source)
surfaces were given their hottest on-orbit temperature. The TESS Instrument camera
leans assembly will be operating at -75 +/- 10°C) and lens hoods at -80°C to -145 °C.
The CCDs will be operating between -60 to -80 °C. The focal plane electronics printed
circuit boards (PCBs) will be operating between 0°C to 10 °C. At these temperatures,
any outgassing from organic materials, including the PCBs, will be negligible. So, there
will be potentially negligible condensation of contaminants on sensitive surfaces during
the on-orbit life of the instrument.
Additionally, the loss of optical performance due to NVR was modeled as absorption of
the incoming light by an NVR film on each surface thus resulting in transmission loss
through the lenses to the CCD. The NVR levels used were A/2 beginning-of-life (BOL)
and A end-of-life (EOL) on internal sealed optical surfaces and CCDs. The NVR level on
the unsealed first lens optical surface was varied to establish the requirements captured
in Table 4 in Section 8.1. The transmission loss due to light absorption by NVR was
evaluated against science requirements to confirm acceptable performance with the
specified contamination levels.
37-15040
7
Revision B
Surfaces without a view of a sensitive surface have no derived outgassing requirement
for on-orbit use, however, thermal vacuum testing may force outgassing requirements
due to vacuum chamber reflection of contaminants. In any case, use of low outgassing
materials is required to minimize property changes after exposure to vacuum.
Along with the selection of low outgassing materials for the TESS instrument, a thermal
vacuum bakeout program will be accomplished for the TESS program and is described
in Section 12.2. All flight hardware subsystems will be baked out separately as required
to meet the requirements in Table 4. The hardware will demonstrate that it meets its
outgassing requirement as measured in a vacuum, i.e. <1X10-5 Torr, on a TQCM
controlled to –40 °C.
7.4 Contamination Analyses and Laboratory Testing
Wherever possible, previous analyses and laboratory testing performed for other
instruments will be utilized on behalf of TESS. These analyses and laboratory activities
include:
 Materials evaluation analyses and testing for materials not previously
characterized
 Particulate accumulation and redistribution analyses (using existing analyses)
8.0 Cleanliness Requirements
This section details the cleanliness requirements for the TESS Instrument. Section 8.1
highlights the critical surfaces and provides surface and outgassing requirements the
TESS Instrument. Section 8.3 specifies the requirements levied on the spacecraft and
launch vehicle by the TESS Instrument.
8.1 Sensitive Surface Identification and their Requirements
The contamination sensitive surfaces identified for the TESS instrument include:
 Camera lenses
 CCD arrays
 Internal optical surfaces
Table 4 summarizes the on-orbit cleanliness requirements associated with each of these
identified sensitive elements. In addition, based on the need for maintaining the
cleanliness integrity of the integrated set of sensitive components, the cleanliness
requirements for the non-sensitive TESS surfaces have also been established and are
presented herein. Note that these requirements are the on-orbit beginning-of-life (BOL)
and end-of-life (EOL) cleanliness level requirements. On-orbit is defined as the start of
Science Operations. The TESS Project as a whole is responsible for meeting these
requirements. A contamination budget allocates requirements to various subentities. The
Instrument team at MIT is responsible for instrument contamination control activities only
till delivery of the Instrument to Orbital ATK for Observatory Integration and Test (I&T).
Table 5 lists the contamination requirements that the Instrument team is responsible for
meeting. The following subsections provide more details about these requirements.
37-15040
8
Revision B
Table 4 - On-Orbit Instrument Cleanliness Requirements
Component [sensitive
elements in Italics]
On-Orbit Cleanliness Requirements [per
MIL-STD-1246C]
Beginning of Life (BOL)
End of Life (EOL)
External L1 Surface
550A
600B
Internal Optical Surfaces
250A/2
250A
Internal Lens Barrel
VC-HS + UV
VC-HS+UV
Internal Lens Hood
550A
600B
CCD
150A/2
150A (TBC)
Focal Plane Electronics
VC-HS + UV
VC-HS+UV
Harness
VC-HS + UV
VC-HS+UV
External Camera Surfaces
550A
600B
Table 5 - Cleanliness Requirements As Delivered for Observatory I&T
Component [sensitive
elements in Italics]
Cleanliness
Requirements as
Delivered for
Observatory I&T
External L1 Surface
350A*
Internal Optical Surfaces
250A/2*
Internal Lens Barrel#
VC-HS + UV
Internal Lens Hood
350A*
CCD
150A/2*
Focal Plane Electronics#
VC-HS + UV
Harness#
VC-HS + UV
External Camera Surfaces
350A*
*Non-volatile Residue (NVR) will be verified by
performance, or witness plates analysis.
Particulate requirements will be verified by VC-HS + UV
at various magnifications, as described in the CCIP.
#
NVR cleanliness for these components will be covered
by bakeout specifications as described in Section 12.2.
37-15040
9
Revision B
8.2 DHU Cleanliness Requirements
Since the instrument DHU is located inside the spacecraft, its cleanliness does not
impact the sensitive surfaces of the instrument. However, the following particulate
cleanliness requirement is levied on the DHU. NVR cleanliness for the DHU will be
covered by a bakeout specification as described in Section 12.2.
Table 6 - DHU Cleanliness Requirement
Project Phase
Cleanliness
Requirement
Delivered to Instrument
team from vendor
VC-2 [per JSC SN-C0005]
8.3 Cleanliness Requirements Levied on the Spacecraft and
Launch Vehicle
The project-level TESS Contamination Control Plan (37-10037) places cleanliness
requirements on the spacecraft and launch vehicle.
9.0 Facilities Requirements
In order to meet the cleanliness requirements described in Section 8, facilities where the
TESS Instrument is processed (including Observatory I & T and launch processing)
need to provide a noncondensing atmosphere, i.e. the temperature and humidity are
controlled to remain above dew point.
10.0 Design Phase Contamination Control
Contamination prevention is a basic design consideration and will be examined
throughout the development process.
10.1 Material Selection
Informed and enlightened materials selection is crucial in order to limit contamination
sources. In order to control contamination and protect sensitive surfaces, the use of
minimal contaminating materials and the use of covers and protective shields must be
considered. Manufacturing materials, when organic in nature, should be low outgassing,
non-shedding and non-flaking. All materials selected for the TESS instrument which are
37-15040
10
Revision B
organic in nature will meet the NASA-RP-1124-Rev-4 outgassing requirements as a
minimum criteria.
In addition all efforts will be made to select materials that meet the following
qualifications based on the results of the ASTM 595 test:
 1% Total Mass Loss (TML)
 0.1% Collected Volatile Condensable Material (CVCM)
For questionable materials, or materials where data does not exist, it may be necessary
to test outgassing characteristics as per ASTM E595 test.
10.2 Design and Venting
The instrument will be designed such that outgassing products are vented away from the
TESS instrument inlet and to insure sensitive surfaces are not contaminated. Instrument
vents will be located and directed to minimize the potential to contaminate critical
elements.
10.3 Purge
The instrument will be equipped with a purge manifold and purge ports on the cameras
to enable a nitrogen purge of the cameras. Nitrogen purge will take place during
integration and test phases and during launch operations up to fairing encapsulation.
The purge system will use Grade B, Type 1 nitrogen per MIL-PRF-27401G. The inlet
flow rate to the purge manifold is designed to be 5.7 LPM.
11.0 Fabrication and Assembly Phases Contamination Control
Fabrication and assembly of TESS components may take place in uncontrolled
environments during the early purchasing phase (> Class 7 environments), however,
these operations should take place in a Class 6 environment whenever possible for all
TESS Instrument components except the DHU. DHU is being fabricated and assembled
at vendor facility and vendor is responsible for contamination control. The information in
this section applies to for all TESS Instrument components except the DHU.
During all fabrication and assembly phases and associated storage/transportation
periods, contamination control measures will be instituted. Surfaces will be kept clean,
and if any debris is generated during the manufacturing process it will be
cleaned/vacuumed off.
During assembly, mating surfaces will be cleaned to meet their cleanliness requirement
prior to attachment. All interior volumes will be cleaned thoroughly and verified prior to
final assembly and attachment. Isopropyl alcohol, or a 3 to 1 mix of IPA with deionized
water may be used as a solvent.
37-15040
11
Revision B
All ground support equipment will be kept visibly clean during assembly. Any cables,
harnesses, etc. will be cleaned and/or sealed in cleanroom approved bagging material
before attachment to flight hardware, and vacuum baked prior to instrument integration
to meet contamination control requirements of instrument sensitive surfaces. To limit the
duration of the instrument and observatory vacuum bakeouts, GSE equipment should
meet their outgassing certification and be part of the chamber pre-test certification of the
chamber background outgassing, prior to instrument thermal vacuum testing.
TESS subsystems will be maintained at their specified cleanliness level throughout the
fabrication process. Inspections will be performed by trained personnel. Cleanliness
requirements during subsystem fabrication are as follows:










During manufacturing operations such as machining, welding and soldering
contaminants should be cleaned off of the hardware by wiping and/or vacuuming.
Lubricants and cutting oils (i.e. oils and greases) should be cleaned off as soon
as possible after the manufacturing operation using appropriate solvents.
All machined parts will be precision cleaned prior to assembly, as per LL PS-321, or equivalent process.
Prior to priming or painting a surface it should be free of particulate or molecular
deposits and be inspected at a visibly clean level.
If an area becomes inaccessible during fabrication it will be cleaned and
inspected to the specified cleanliness level for that surface before becoming
inaccessible.
Upon the completion of a fabrication operation, the components will be subjected
to a gross cleaning procedure involving solvent washes and particulate removal,
yielding a surface meeting required cleanliness levels. Parts with less than 1
square foot of area may be grouped together into one NVR rinse for verification
purposes. The fabricated components will then be bagged to negate
contamination effects.
Parts, surfaces, holes and so forth will be cleaned with isopropyl alcohol (IPA)
moistened wipes.
Wiping should be in one direction only and each pass should be with a clean
area on a wipe or using a new wipe for each pass. In some instances wipes will
be ineffective and swabs moistened with alcohol may be used. Cleaning will
continue until all surfaces meet their specified cleanliness level upon inspection.
Any cleaning of painted surfaces will be done with the approval of the TESS
Instrument System Engineer.
Prior to any final assembly, all surfaces will be vacuumed giving special attention
to holes, crevices and riveted regions.
Assemblies will be visually inspected with a blacklight for external oil or grease
deposits, and if any are found, the areas will be wiped with IPA moistened wipes,
using a clean wipe area for each pass and wiping in one direction.
12.0 Integration Phase Contamination Control
Nitrogen purge of the instrument cameras will take place during integration phase.
37-15040
12
Revision B
12.1 Cleanroom Facility Requirements
Integration of the TESS instrument, including integration of subsystems (not including
DHU as DHU is integrated directly with spacecraft) will take place in a class 6 (or better)
cleanroom facility. Certain operations may take place in a non-cleanroom environment
providing the hardware is recleaned after the operation. Integration of the instrument
with the spacecraft may occur in a class 7 (or better) environment, however, the TESS
sample pathways and QMS will remained sealed unless the air cleanliness environment
is class 6 (or better). Table 7 describes the cleanroom classes used in this document.
Regular monitoring of the cleanroom, GSE, and flight hardware will be accomplished,
Table 7 - Selected airborne particulate cleanliness classes for clean
rooms and clean zones [from ISO-14644-1]
schedule provided in the TESS Instrument CCIP.
The instrument subsystems shall be delivered to the cleanroom in a clean, doublebagged condition. Exterior surfaces shall be verified as meeting the requirements in
Table 5 upon receipt at the cleanroom, and if required, cleaned and re-verified to that
level before any further I&T operations with that hardware takes place.
During down-times when hardware is not actively being worked on, and overnight and
weekends, hardware will be kept covered with an approved cleanroom certified, antistatic bagging material. Bagging materials and drapes will be contamination and
electrostatic discharge (ESD) approved.
To prevent electrostatic discharge (ESD) damage to any of the electronic components
precautions beyond contamination control measures are required. This may mean using
anti-static packaging films for sensitive parts. In addition, ESD approved garments and
grounded wrist straps, will be worn, testing the wrist straps conductivity before each
entry into the cleanroom. When personnel are within 1 meter of the ESD sensitive
hardware, they will connect their wrist strap to an approved grounding strap. Additionally,
the room temperature will be maintained at 70±5°F and the relative humidity will be
maintained at 30 to 50%. Quality Assurance will determine the ESD sensitivity of the
hardware.
The following list highlights the planned contamination procedures to be implemented
during integration activities:
37-15040
13
Revision B
1. The most sensitive hardware will be placed closest to the HEPA filters in the
cleanroom and less sensitive hardware will be kept downwind from the more
sensitive hardware (if possible).
2. Parts from a less controlled fabrication and assembly area will be cleaned to the
appropriate cleanliness level of the hardware to which it will come in contact, or if
it will not be near flight hardware to a visibly clean level or sealed in cleanroom
approved bagging material prior to entry into the clean room.
3. The room temperature will be maintained at 70±5°F and the relative humidity will
be maintained at 30 to 50%. If at any time environmental conditions are not
within these values, it will be reported to the TESS Instrument System Engineer
and the TESS Instrument Reliability and Quality Assurance Manager, to
determine the appropriate corrective action. All work will stop on the hardware
and it will be secured under appropriate cleanroom and ESD bagging material
until this corrective action has been determined.
4. The cleanroom will include an air particle monitor, and a group of contamination
witness plates which will be evaluated on a periodic basis (as detailed in the
TESS CCIP.)
5. All non-flight hardware surfaces will be cleaned to Visibly Clean Sensitive
throughout integration activities. A solvent rinse may be used to verify the
molecular levels meet the budgeted requirement. All flight hardware will be
maintained at the appropriate cleanliness level for the specific piece of hardware
involved (as specified in Section 8.0.)
6. Parts which are machined, welded or riveted will leave the cleanroom for this
activity and will be inspected and re-cleaned, if necessary to meet its required
cleanliness level, before re-entry. The results of a solvent rinse and tape lift will
be required for hardware with MIL-STD 1246 surface level requirements, prior to
re-entry.
7. TESS subsystems provided to the instrument will be delivered to the cleanroom
in a clean condition. The external surfaces of these instruments shall be cleaned
and verified as meeting hardware cleanliness levels prior to shipment. In
addition, these subsystems will undergo vacuum bakeouts at the supplier facility
to reduce outgassing levels within the instrument.
8. Upon receipt, the TESS subsystems will be re-inspected and verified for
contamination specifications, as part of the receiving inspection.
9. Personnel working in the cleanroom will wear appropriate cleanroom clothing (full
“bunny” suits), shoe coverings, facial masks, nitrile gloves. When working with
solvents polyethylene gloves will be worn.
10. Ground support equipment (GSE) required for testing will be cleaned with IPA to
a visibly clean level, and bagged before going into the cleanroom. Surfaces
which will contact the spacecraft will meet the flight hardware requirements.
11. Oils, greases and other similar agents which may be contamination hazards will
not be used during integration without the permission of the TESS materials
engineer and contamination engineer.
12. Joints or crevices will be covered during integration to minimize the build up of
contaminating debris. Rivets, bolts, nuts and so forth will be cleaned to remove
any type of contamination such as lubricants and machining oils prior to I & T.
Fasteners which are lubricated will be cleaned with an appropriate solvent prior
to being used during integration. Areas which become inaccessible for cleaning
will be cleaned and inspected prior to that time, and be bagged following that
time.
13. All integration GSE, testing equipment, etc., will meet the visibly clean level.
37-15040
14
Revision B
14. If a subsystem or piece of flight hardware is removed for testing, or some other
reason, it will be reverified to its specified cleanliness level before it can reenter
the cleanroom.
15. The instrument support team is responsible for cleaning and maintaining their
respective hardware during instrument integration and testing between specified
cleanings. If the hardware has become contaminated, please inform the TESS
Instrument System Engineer to schedule a precision cleaning.
12.2 Vacuum Bakeout Requirements
Along with the selection of low outgassing materials for the instrument a thermal vacuum
bakeout program will be accomplished for the program. In general:






Materials, parts, and subsystems will be evaluated on a case-by-case basis to
assess the need for vacuum bakeouts in order to meet the NVR requirements
captured in Table 5. An outgassing rate (OGR) requirement will be established for
each bakeout based on part composition and SME recommendations.
Thermal vacuum bakeout of the instrument cameras will be conducted at Lincoln
Laboratory in chambers with pressures less than 10-5 torr. Outgassing rate at the
bakeout termination will be established for each subassembly. If termination rate
is not established, units are baked till outgassing rate (OGR) change is less than
5 %/hour.. The outgassing will be monitored with TQCM kept at -40°C and RGA.
For all bakeout certifications, TQCM will be kept at -40°C and hardware will be
maintained at 2°C below the maximum hot survival temperature
DHU (all electronics) will be baked out with termination OGR 20 ng/s/kg with
TQCM at -40 °C
MLI will be baked out with outgassing rate at termination of 10-12 g/s/cm2
The CCIP will contain further details of the bakeout schemes for various parts of
the instrument.
13.0 Test Phase Contamination Control
The instrument will be subjected to a number of testing operations. If a particular test
requires the removal of bagging, the personnel who come in contact with the instrument
must wear cleanroom clothing, gloves, etc. If solvents are used, polyethylene gloves
must be worn. Post testing cleanliness inspections of external surfaces will be performed
to assure that surface cleanliness levels have not been exceeded.
Nitrogen purge of the instrument cameras will take place anytime the cameras are not in
a cleanroom environment or bagged.
13.1 Vibration Testing Requirements
TESS Instrument will be subjected to a number of system level testing operations. DHU
will be tested by the vendor. Contamination control of other Instrument subsystems
during vibration is described in this section.
37-15040
15
Revision B
Accelerometers and any other required instrumentation will be installed inside the
cleanroom prior to bagging. The test conductor or designee will work with the
contamination control technicians to route the required test cables out of the bag.
TESS Instrument will be double bagged when it leaves the cleanroom for transport to the
vibration testing facility, and will remain double bagged until just before it re-enters the
cleanroom.
Testing facilities will be held at 70±5°F temperature and 30 to 50% humidity conditions.
Post testing, cleanliness inspections of external TESS Instrument hardware will be
performed to assure that surface cleanliness levels have not been exceeded. A full
TESS Instrument cleaning will be performed if the surfaces are shown to be out of spec.
(At times the vibration testing can shake loose particles which had been as of yet
undetected.)
13.2 Thermal Balance/Thermal Vacuum (TB/TV) Testing
Requirements
All tests will be monitored with a combination of the following instrumentation:
 Temperature controlled quartz crystal microbalances (TQCMs),
 Cold fingers
 Scavenger plates
 Residual gas analyzer (RGA)
In addition, cold plates will be used in strategic locations as required to minimize
contamination from known high outgassing sources.
The TESS instrument level thermal vacuum test will be performed in a TV chamber. The
chamber will be maintained at a class 6 environment or better. Cleanroom garments will
be worn while working within the chamber. The thermal vacuum test will be monitored
with a series of TQCMs and with the aforementioned monitoring instrumentation. All
temperature transitions will be controlled to minimize contamination.
Prior to thermal vacuum testing, the instrument will be cleaned and verified as meeting
cleanliness requirements found in Table 5, then transported to the thermal vacuum
testing chamber.
Prior to loading the hardware into the chamber, the chamber background and ground
support equipment outgassing levels will be measured and verified in a pre-test thermal
vacuum certification, to meet the chamber certification levels for allowable installation of
the instrument into the chamber. These levels will be based on chamber configuration
and will be established in the TB/TV test plan (typically < 10% of the required flight
hardware TQCM rates corresponding to the flight hardware outgassing rates.
Following thermal vacuum testing, the cleanliness of the TESS instrument will be visually
inspected. The structure will be double bagged for transport to its cleanroom integration
facility, or another testing facility. External instrument surfaces will be inspected and
verified as meeting surface cleanliness requirements found in Table 5.
37-15040
16
Revision B
13.3 EMI/EMC Requirements
The instrument DHU will be EMC tested by vendor in vendor facility. The instrument
cameras will be tested by the instrument team. Only the qualification camera unit will be
EMI tested, the flight units will not. The TESS instrument cameras will be bagged in
ESD safe but EMI transparent material. TESS instrument cameras will be double
bagged for transport between the I&T cleanroom and the EMI cleanroom. Whenever
possible, the TESS instrument cameras will be bagged or draped in cleanroom approved
bagging material.
13.4 Performance Requirements
During performance requirements testing, all instrument subsystems will be kept at
cleanliness levels specified in Table 5 and Table 6. If not in a cleanroom environment,
instrument subsystems must be bagged.
14.0 Contamination Control Requirements for Storage and
Transport
The TESS instrument will be double bagged during storage or transportation.
Subsystems and subassemblies which do not have any special requirements for
handling and storage prior to integration will be cleaned to a cleanliness level of visibly
clean and bagged unless integration or test activities prohibit it. All systems will be
stored in an air-conditioned area with controlled access. The instrument will be double
bagged with approved bagging material (Llumalloy or equivalent) at all times unless
integration and test activities prohibit it. The instrument will be double bagged and
transported in a shipping container. The shipping container will be cleaned before
transportation. Temperature and humidity will be monitored in the shipping container.
15.0 Cleanliness Inspection and Monitoring
Cleanliness Inspection methods which may be used for the TESS program are witness
plates, particle counters, black and white light inspections, washes, swab sampling and
tape lifts. Descriptions of these techniques are as follows:



Witness Plates: Witness Plates are used to determine NVR levels, particulate
levels and fallout rates. Witness plates collect passively during cleanliness
monitoring procedures. Witness plates should be placed as close as possible to
contamination sensitive areas, to obtain the most accurate particulate readings.
Particle Counters: Particle counters are used to monitor cleanrooms.
Light Inspections: Visual Inspection is done periodically using black (UV) light
or white light, per JSC-SNC-005C. Visibly clean, using white light, is the absence
of all particulates and non-particulates visible to the normal unaided eye (except
corrected vision). UV inspection light sources are no less than 100 watts and
37-15040
17
Revision B

located no more than 50cm from the inspected item. During UV inspection, light
from other sources should not be more than 5 ft-candles. If visual contamination
is evident, the hardware will be cleaned and then re-inspected under the same
light conditions. If during UV inspection there is any evidence of fluorescence the
item/surface will be re-cleaned. If re-cleaning does not reduce the fluorescence, it
must be determined whether the fluorescing material is a contaminant or the
substrate surface.
Solvent Washes/Wipes: A surface which is to be inspected is washed or wiped
with an approved IPA or other appropriate solvent and the solvent and residue is
collected. This collected residue or rinse is then subjected to a quantitative and
qualitative analyses and the type of contaminant residue is chemically identified.
Cleaning of flight hardware, GSE, and cleanrooms will occur on a scheduled basis and
as required by activities. The Contamination Control Implementation Plan (CCIP) or
specific facility maintenance plan will present the planned cleaning and monitoring
schedule for each facility. As a general goal, the cleanroom facility should be inspected
for contamination concerns daily. The facility should also be cleaned at least once a
week (including mopping of the floor) to insure proper clean operation of the facility.
16.0 Personnel Requirements
Contamination Control and Cleanroom Practices training will be conducted for all
personnel involved in the fabrication, assembly, integration, testing, transportation,
storage and launch site activities of the TESS instrument as well as the rover and
observatory. Areas which will be studied in the training sessions are as follows:
 Definition of contamination and how it affects the TESS mission
 The importance of maintaining contamination control in all the program phases,
that is, fabrication through to Observatory Integration and Test.
 A review of the instrument sensitivities
 Review of the instrument contamination control plan and related contamination
documents
 Specific techniques for cleaning, inspection, and packaging
 Monitoring techniques in the cleanroom and in the shipping containers.
 Cleanroom dressing procedures and rules for working in a controlled cleanroom
area.
37-15040
18
Revision B