June 15, 2016

Cleanliness Plan - PA-3

Cleanliness Plan

To describe the approach for defining the measures ensuring compliance with performance requirements with regard to product contamination by particles and/or chemical species.

Two documents are required:

  • Cleanliness Requirements Specification (CRS) setting out the specifications on surface molecular and/or particulate contamination,
  • Cleanliness and Contamination Control Plan (C&CCP) in response to the CRS.

 

A. Purpose

By definition, a contaminant is “any foreign matter that remains on a surface or in a functional environment long enough to degrade its performance or reduce its service life”. In the space industry, the three families of contaminants can be detrimental:

  • particulate contamination (mainly on the ground): this corresponds to particles of visible inert matter (in the micrometre range) which are transported by fluids and build up on surfaces.
  • molecular contamination (can be on the ground, but mainly in flight): this consists of deposits of droplets of varying homogeneity which form after the transportation of molecules in liquid or vapour form.
  • biological contamination: this is caused by viable particles present on surfaces or in the ambient air.

 

Lessons learned from experience have led to increased awareness of the risks of damage and decreased performance in space systems due to chemical or particulate contamination. In this day in age, with instruments becoming more and more sophisticated, and quality and reliability constraints becoming more and more rigorous, contamination control is a necessity and must be applied throughout every stage in the development of a satellite – from the component level to the system level.

For this purpose, a regulatory framework has been instituted, and the risk minimisation rationale involves establishing a cleanliness plan for a given piece of equipment or for the fully integrated satellite, as set out in standard “RNC-ECSS-Q-70-01 Cleanliness and contamination control”. 

This standard defines the cleanliness rules and associated quality control to be implemented during operations within the project’s scope of responsibility, for components that are sensitive to contamination and components in close proximity to them.

In terms of the activities to be carried out, it complies with the cleanliness requirements that apply to the product in question.

B.  Principles of preparation

The Cleanliness Plan is initialised by the project at the end of Phase A and its content is discussed with the Customer to ensure that it is in line with the cleanliness management processes between the project and its Customer. It is finalised at the end of Phase B.

The project's Cleanliness control approach is based on a process comprising the following steps:

  • setting up the project’s Cleanliness organisation,
  • identifying the components that are sensitive to contamination,
  • identifying the sources of contamination,
  • identifying the Cleanliness requirements that apply to the project,
  • establishing an allocated contamination budget for each phase of the project,
  • describing the measures taken to comply with this constraint.

 

Ultimately, the project needs to present an assessment of the contamination of sensitive components, to be compared with the contamination values deemed admissible in the contamination budget.

The aim is to cover the product’s entire life cycle, from the design phase to end of service life – including the procurement, manufacturing, integration, testing, storage and transportation phases.

In terms of the products in question, the Cleanliness scope covers:

  • the design and development of all models (EM, QM, FM and the associated ground support equipment),
  • the production of flight models and any non-flight component that may be in close proximity to flight models.

 

C.  Typical content

1. Purpose

This chapter introduces the general objectives and scope of the project Cleanliness Plan activities.

In particular, it clearly describes the product in question and the project to which it is related.

Example

1. Purpose

This document defines the cleanliness rules and associated quality control to be implemented during “Instrument XXXX” project operations, for components that are sensitive to contamination and components in close proximity to them.

Instrument XXX comprises the following 2 sub-assemblies:

-  - Sub-assembly 1…
-  - Sub-assembly 2…

Laboratory YYY is the prime contractor for instrument XXX. Sub-assembly 1 is produced by this Laboratory and the development of Sub-assembly 2 will be outsourced to company ZZZ.

 

2. Scope

This chapter introduces the activities proposed to manage project requirements, in addition to the people involved throughout every phase of the project.

Example

2. Scope

Unless otherwise specified, this document applies to the instrument components and associated ground support equipment, during the phases within the project’s scope of responsibility (design, procurement, integration, testing, storage, transportation and launch preparation, and in-flight use).

Les The cleanliness requirements set out in this document shall apply:

- for the design of all models (EM, QM, FM and associated ground support equipment),
- for the production of flight models and any non-flight component that may be in close proximity to flight models.

 

 

3. References

3.1 Reference documents

These constitute the bibliography required for the drafting of the Cleanliness Plan.

Example

3.1 Reference documents

RNC-ECSS-Q-ST-70  STANDARD Materials, Mechanical componeents and ProcessesMaterials, mechanical Components and Processes
RNC-ECSS-Q-ST-70-01Cleanliness and contamination control
RNC-CNES-Q-HB-20-522QA manual for monitoring of payload or instrument integration.
   

 

 

Note: RNC-ECSS-Q-ST-70-01 is the essential document.

3.2 Applicable documents

All documents applying to the drafting of the Cleanliness Plan.

Example

3.2 Applicable documents

xxxxxxxProduct Assurance Plan for Instrument XXX
yyyyyyyCustomer’s Product Assurance Specification
zzzzzzzGuide on best practices in a laboratory clean room environment
wwwwWWWWWWWWWW
   

 

 

3.3 Glossary

This paragraph provides the acronyms used in this document.

Example

3.4 Glossary

PAProduct Assurance
QAQuality Assurance
AIT or AIVAssembly, Integration and Testing or Verification
MCMolecular Contamination (in g/cm2)
PCParticulate Contamination (in ppm)
CVCMCondensed Volatile Condensable Material
DMMPLDeclared Material & Mechanical Parts List
DPLDeclared Process List
ELEvent log
LBLog Book
ppmparts per million
EM QM FMEngineering, Qualification and Flight Model
MLIMulti Layer Insulation
AITPAssembly, Integration and Test Plan
IQAPIntegration Quality Assurance Plan
PAMProduct Assurance Manager
IQAMIntegration Quality Assurance Manager
AIVMAssembly Integration Verification Manager
RMLRecovered Mass Loss
   

 

4. Organisation of Cleanliness activities

4.1 Inputs

This paragraph specifies the inputs for the Cleanliness Plan activities.

Example

4.1. Inputs

As input for the Cleanliness activities, the project will take into account the specimen description and identify the components that are sensitive to contamination and the sources of contamination, by examining the following elements:

- the MCP list,
- the examination of on-board technologies (detectors, radiators, propulsion systems, etc.),
- the mission’s environmental factors,
- the description of the project’s AIT/AIV environment and sequence.

 

The project will have at its disposal the PA specification applying to it, and the MTA specifying the thermal testing environment, in particular.

Finally, the project will implement the various measurement means (outgassing, contamination) and cleanliness check means that are available.

 

4.2 Outputs

This paragraph specifies the expected output of the Cleanliness Plan activities.

Example

4.2. Outputs

As output of the Cleanliness activities, the project will provide the following elements:

- summary of cleanliness requirements for sensitive components with regard to the expected performance parameters,
- subcontractor cleanliness plan with milestones (KIP, MIP, other),
- safety plan (management of cleanliness-related flight and non-flight components),
- design choice elements: orientation plan for the Instrument’s MLI vents and location of heaters for outgassing,
- contamination budget forecast taking into account the entire AIT AIV profile (manufacture, test, integration, storage, transportation),
- cleanliness assessment approved by the Instrument Project Manager .

 

4.3 Organisation

This paragraph specifies the responsibilities of the persons responsible for the activities set out in the Cleanliness Plan.

Example

4.3 Organisation

Those taking part in the Cleanliness activities are: the project manager, the system manager, the equipment managers, the PA manager and the AIV manager. The contamination expert is consulted for key points.

The table below lists the responsibilities for each group of activities described in the Cleanliness Plan.

 

Cleanliness ActivitiesPAMAIVMProject Manager & ArchitectsEquipment manager
Definition of requirements   X<0}
General information from PAX   
Processing of anomaliesXXXX
Design  XX
Material selectionX   
Process selectionX   
Equipment deliveryX  X
Equipment inspectionX   
Equipment cleaningXX X
Equipment bakeout X  
Work in clean roomXX  
Specimen monitoringXX  
Testing constraintsXX  
Prohibited activitiesXX  
Handling & storageXX  
Diagram X  
Contamination budgetX   
Contamination budgetX   
Start-up in orbit  X 
      

 

 

4.4 Assumptions 

This paragraph sets out the assumptions on which the budget forecast is based.

Example

4.4 Assumptions 

- After cleaning, PC on sensitive components is negligible.
- Surface MC is measured on contamination specimens.
- Airborne MC is not taken into account.
- Compliance with best practices in terms of cleanliness makes it possible to control the risk of contamination of sensitive components. These best practices are known and applied by the personnel involved in the activities from the design phase through to delivery of the instrument, or for the satellite cleanliness plan, until launch preparation. These best practices for activities in a clean room environment are set out in [DAzzzzzzz].
- No contamination modelling required at the Instrument, Platform or Satellite levels.
- The environment taken into account for the flight phase is described in document RNC-ECSS-Q-ST-70-01 Annex D2, sections D2.1.3 for the natural & induced environment and D2.2.3 for the transportation of contaminants in space.
- Contamination relating to expected environments (without anomaly) is estimated at:

PhasePCMC
Surface protected by cover10 ppm0
Transportation phase10 ppm (standard value) 
Vibration test25 ppm (standard value) 
Thermal vacuum test25 ppm (standard value)3.10-6 g/cm2 for one year
ISO 8 (100,000)275 ppm / day (*)2.10-6 g/cm2 for one year
Launcher fairing on ground (5000)32 ppm / day (*)Negligible
Fairing during firing170 ppm (standard value)Negligible
ISO 5 (100)2 ppm / day4.10-7 g/cm2 for one year
Flight environmentNegligiblevalue TBD based on lessons learned

(*): values to be divided by 5 for vertical sensitive surfaces

 

 

5. Identification of sensitive components

All components requiring special precautions with regard to a risk of contamination are considered to be ‘sensitive' to contamination, even if the admissible contamination values are high.

Possible cases of sensitivity to moisture shall be taken into account.

The admissible contamination values indicated are those which are, at the end of the mission, compatible with the mission objectives.

5.1 Sensitive components

Components that are presumed to be sensitive are listed.

For each sensitive component, the allowable PC and MC values are provided, along with the references from which they were taken.

 

Example

5.1 Sensitive components

The sensitive components that have been identified are primarily the following:

- optics,
- the SSSS sensor of Sub-Assembly 1,
- thermal control coatings and radiator shields,
- mechanisms,
- as a general rule, connectors when they are not plugged in.

 

The allowable contamination values for sensitive components are indicated below:

For the SSSS sensor, according to DRxxxx

- PC: ‘Cumulated exposure time in a class 100.000 room shall be less than 20h. Alternatively less than 100 particles larger than 1 micrometer must accumulate on the first optical surface.’
- MC  < 0.6 10-6 g/cm2.

 

5.2 All other non-sensitive surfaces

For all surfaces that are not presumed to be sensitive, the admissible PC and MC values are also provided.

Example

5.2 Any other surface deemed not-sensitive

For other components deemed not-sensitive, the following allowable values shall be taken into account:

- PC < ‘visibly clean’
- MC < 10-6 g/cm2.

 

 

6. Identification of the sources of contamination

For general considerations on sources of contamination, refer to document RNC-ECSS-Q-ST-70-01 - Cleanliness and contamination control - Annex D, § D.2.1 Typical contaminants and their sources.

As this list is not exhaustive, other sources can be considered on a case by case basis, whether for the payload instruments or at the satellite level. Sources of cross contamination shall also be taken into account in the case of multiple stores.

Example

6. Identification of the sources of contamination

This involves taking into account PC and MC of the following components, for example: 

-  MLIs,
-  structures,
-  composite panels,
-  solar panels,
-  sensors,
-  FM harnesses,
-  etc.

 

7. Description of Cleanliness activities

This section lists all of the requirements to be taken into account with regard to cleanliness aspects and defines how the project complies with them in terms of setting up activities, persons responsible and ensuring traceability.

The requirements are derived from the Product Assurance specification that applies for the supply of equipment and their integration (identified in the example below in REQ-PA-xxx format) and specific additional Cleanliness requirements (identified in the example below in “REQ-PROP- xxxx” format).

 

Example

7. Description of Cleanliness activities

7.1 General information from product assurance

7.2 Processing of anomalies

7.3 Design 

7.4 Material selection 

·  REQUIREMENTS

…REQ-PA-xxxx

Materials’ resistance to vacuum pressure with thermal vacuum outgassing tests as per RNC- ECSS-Q-ST-70-02 §5.5.3 (RML < 1.0% and CVCM < 0.1%).

REQ-PROP-yyyy

In close proximity to a component sensitive to molecular contamination, the selection criteria for vacuum outgassing of materials becomes RML < 0.1% and CVCM < 0.01%.

REQ-PROP-zzzz

The covers that protect sensitive components against contamination and the contamination specimens will be identified as ground support equipment in the list of materials.

RESPONSIBILITIES

Materials, Mechanical Parts, Processes QA Manager

Thermal architect and MTA for requirements on fixation of MLIs

TRACEABILITY

 Validated DMMPL.

 

7.5 Process selection

7.6 Delivery of equipment containing sensitive components

7.7 Equipment inspection

7.8 Equipment cleaning

7.9 Equipment bakeout

7.10 Work in a controlled-environment area

7.11 Specimen monitoring

7.12 Cleanliness constraints during testing

7.13 Activities prohibited in proximity to sensitive surfaces

7.14 Handling, transportation and packaging, storage

7.15 Diagram of steps within the project's scope of responsibility

7.16 Contamination budget

7.17 Contamination assessment

7.18 First start-up in orbit

 

8. Conclusion

Summary table of cleanliness requirements and allocations.

 

Activities / documentation

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