ASTM E2900-19

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2900 − 12 E2900 − 19
Standard Practice for
Spacecraft Hardware Thermal Vacuum Bakeout
This standard is issued under the fixed designation E2900; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice establishes methods for thermal vacuum bakeout of spacecraft and spacecraft components.
1.2 This practice defines the equipment, environment, and certification criteria for each type of bakeout.
1.3 The methods defined in this practice are intended to reduce component outgassing rates to levels necessary to meet mission
performance requirements of the contamination sensitive hardware. Times, temperatures, and configurations contained in this
document have been found to provide satisfactory results. Experienced operators may find that other, similar times, temperatures
and configurations have provided satisfactory results. If deviations from these criteria are deemed appropriate, they should be
detailed in the bakeout report.
1.4 This practice describes three bakeout methods: Method A, using prescribed time and pressure criteria; Method B, using
prescribed QCM stabilization rate criteria; and Method C, which measures the QCM deposition rate.
1.5 Determination of the acceptable molecular outgassing, selection of the bakeout method, and determination of the specific
test completion criteria are the responsibility of the user organization.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E1546 Guide for Development of Fire-Hazard-Assessment Standards
E296 Practice for Ionization Gage Application to Space Simulators
E834 Practice for Determining Vacuum Chamber Gaseous Environment Using a Cold Finger
E1234 Practice for Handling, Transporting, and Installing Nonvolatile Residue (NVR) Sample Plates Used in Environmentally
Controlled Areas for Spacecraft
E1235 Test Method for Gravimetric Determination of Nonvolatile Residue (NVR) in Environmentally Controlled Areas for
Spacecraft
E1549E1546 Specification for ESD Controlled Garments Required in Cleanrooms and Controlled Environments for Spacecraft
for Non-Hazardous and Hazardous OperationsGuide for Development of Fire-Hazard-Assessment Standards
E1559 Test Method for Contamination Outgassing Characteristics of Spacecraft Materials
E1560 Test Method for Gravimetric Determination of Nonvolatile Residue From Cleanroom Wipers
E1731 Test Method for Gravimetric Determination of Nonvolatile Residue from Cleanroom Gloves
E2311 Practice for QCM Measurement of Spacecraft Molecular Contamination in Space
This test method practice is under the jurisdiction of ASTM Committee E21 on Space Simulation and Applications of Space Technology and is the direct responsibility
of Subcommittee E21.05 on Contamination.
Current edition approved Nov. 1, 2012Feb. 1, 2019. Published December 2012March 2019. Originally approved in 2012. Last previous edition approved in 2012 as E2900
– 12. DOI: 10.1520/E2900-12.10.1520/E2900-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2900 − 19
2.2 Other Standards:
IEST-STD-CC1246 Product Cleanliness Levels and Contamination Control Program
4,5
MIL-STD-1246 Product Cleanliness Levels and Contamination Control Program
MIL-P-27401 Propellant Pressurizing Agent, Nitrogen
ISO-14644 Cleanrooms and associated clean environments
5,6
FED-STD-209 Federal Standard, Airborne Particulate Cleanliness Classes in Cleanrooms and Clean Zones
Available from Institute of Environmental Sciences and Technology (IEST), Arlington Place One, 2340 S. Arlington Heights Rd., Suite 100, Arlington Heights, IL
60005-4516, http://www.iest.org.
MIL-STD-1246 may be used in lieu of IEST-STD-CC1246 by mutual agreement of the parties in the contract.
Available from DLA Document Services, Building 4/D, 700 Robbins Ave., Philadelphia, PA 19111-5094, https://assist.daps.dla.mil/quicksearch/https://assist.daps.dla.mil/
quicksearch/.
FED-STD-209 may be used in lieu of ISO-14644 by mutual agreement of the parties in the contract.
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3. Terminology
3.1 Definitions:
3.1.1 ambient conditions, n—room temperature and pressure.
3.1.2 pre-bakeout, n—to clean or condition, or both, a vacuum chamber prior to its use for flight hardware.
3.1.2 bakeout, n—a process by which volatile molecular contaminants are removed from a spacecraft component or article by
exposing it to vacuum and elevated temperature”. When the intent is to describe an action, this should be two words: to “bake
out”.temperature.
3.1.2.1 Discussion—
When the intent is to describe an action, this should be two words: to “bake out.”
3.1.3 cold finger, n—the device that is used in collecting the sample of the residual gases in an evacuated vacuum chamber.
3.1.4 cold plate, n—a vacuum stable metal plate filled with liquid nitrogen used to condense the volatile molecular (or
outgassing) contamination generated by the space component undergoing the bakeout.
3.1.5 cold shroud, n—the metal lining of the vacuum chamber (usually black painted or black anodized) used as a heating device
or when filled with liquid nitrogen, used to simulate deep space.
3.1.6 cold wall test, n—a test configuration used to simulate deep space, requiring analytical view factors for the calculation of
outgassing rates.
3.1.7 hot wall test, n—a test configuration, in which the hardware is isothermal with the surrounding environment.
Itenvironment; it assumes homogenous mixing for calculating outgassing rates.
3.1.8 outgassing, n—the evolution of a gas from a material, usually in a vacuum.
3.1.9 outgassing rate (g/s), n—the net rate of mass loss from a material sample as a result of outgassing. Outgassing rate can
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be normalized per unit sample surface area and expressed as g·cm ·s or it can be normalized per unit initial sample mass and
-1 -1
expressed as g·g ·s .
3.1.9.1 Discussion—
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Outgassing rate can be normalized per unit sample surface area and expressed as g·cm ·s or it can be normalized per unit initial
-1 -1
sample mass and expressed as g·g ·s .
3.1.10 QCM deposition rate stabilization (Hz/hr/hr), pre-bakeout, n—the acceleration of the QCM deposition rate.to clean or
condition, or both, a vacuum chamber prior to its use for flight hardware.
3.1.12 quartz crystal microbalance or QCM, n—a device for measuring small quantities of mass using the properties of a quartz
crystal oscillator.
3.1.11 QCM deposition rate, n—the QCM output (or beat) frequency change per unit time caused by the mass of a molecular
species condensing on the QCM crystal. The QCM deposition rate units may be converted to g/cm /s by multiplying by the mass
loading constant (m) provided by the vendor for the crystal used (i.e., for a 10 Mhz crystal, m=4.42E-9g/cm Hz).
3.1.11.1 Discussion—
The QCM deposition rate units may be converted to g/cm /s by multiplying by the mass loading constant (m) provided by the
vendor for the crystal used (that is, for a 10 Mhz crystal, m = 4.42E-9g/cm Hz).
3.1.12 QCM deposition rate stabilization (Hz/hr/hr), n—the acceleration of the QCM deposition rate.
3.1.13 QCM thermogravimetric analysis or QTGA, (QTGA), n—a technique in which a QCM is heated at a constant rate to
remove a collected deposit.
3.1.14 quartz crystal microbalance (QCM), n—a device for measuring small quantities of mass using the properties of a quartz
crystal oscillator.
3.1.15 temperature stabilization, n—temperature stabilization has been reached when the unit temperature is within 2°C2 °C of
the specified temperature and the rate of change is less than 3°C3 °C per hour as measured with the unit control thermocouple.
This rate can be extrapolated over a 20 min sample time. For example, stabilization has been achieved if two temperature
measurements taken 20 min apart are within 1°C of each other.
3.1.15.1 Discussion—
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This rate can be extrapolated over a 20 min sample time. For example, stabilization has been achieved if two temperature
measurements taken 20 min apart are within 1 °C of each other.
3.1.16 total collection area, n—the sum of the surface area in the vacuum chamber that is equal to or colder than the QCM
crystal temperature.
3.1.17 visibly clean highly sensitive, VCHS,sensitive (VCHS), n—visual inspection conducted at a distance of 15–50 cm (6–18
in.) with white light of at least 1076 lumens/m (100 fc) intensity. Itintensity; it may be accompanied by ultraviolet (UV) inspection
as well.
3.2 Acronyms:
3.2.1 GN2—Gaseous Nitrogen
3.2.2 LN2—Liquid Nitrogen
3.2.3 MLI—Multi-Layer Insulation
3.2.4 NVR—Nonvolatile Residue
3.2.5 RGA—Residual Gas Analyzer
3.2.6 QCM—Quartz Crystal Microbalance
3.2.7 QTGA—QCM Thermogravimetric Analysis
3.2.8 TQCM—Temperature controlled Quartz Crystal Microbalance
3.2.9 VCHS—Visibly Clean Highly Sensitive
4. Summary of Practice
4.1 A vacuum chamber is configured in the same manner it would be configured for the hardware bakeout, except that the test
article is omitted.
4.2 The empty chamber and its support equipment is cleaned and inspected to VCHS. Then, the chamber is evacuated and
pre-baked at a temperature 10°C10 °C above the hardware bakeout temperature, using the same procedure used for the component
hardware.
4.2.1 For Method A, the chamber is ready for installation of flight hardware after 24 h under vacuum and temperature and a
visual inspection.
4.2.2 For Methods B and C, the chamber is ready when the measured QCM deposition rate, witness sample data, and visual
inspection results are acceptable.
4.3 The spacecraft component to be thermal vacuum baked is exposed to an elevated temperature and a vacuum of 5.0E-5 torr
or less for a specified amount of time or until the desired outgassing rate is reached.
4.3.1 Method A—The bakeout is terminated at a specified time limit and stabilized chamber pressure.
4.3.2 Method B—The bakeout is terminated when the QCM deposition rate stabilizes to a specified level.
4.3.3 Method C—There is a bakeout phase and a certification phase. The hardware is exposed to the program specific
o
qualification temperature (usually 1010 °C C above maximum predicted on-orbit operating temperatures) or the maximum
tolerable temperature of the component in accordance with Method B. In the certification phase, the temperature is lowered to the
predicted maximum on-orbit operating temperatures and the rate is measured. This provides realistic information that can be used
to obtain outgassing rates in on-orbit conditions and also provides information about the dependency of the component outgassing
rates on temperature. The bakeout is terminated when the QCM deposition rate reaches a specified level.
4.3.4 At the end of the bakeout, witness plates are removed and NVR wipe samples are taken of the cold plate.
5. Apparatus
5.1 Description—The bakeout apparatus consists of three main subsystems: a vacuum chamber (including ground support
equipment), a temperature control system, and a data acquisition system. Methods B and C require a QCM.
5.1.1 Vacuum Chamber—The principle components of the vacuum chamber are the pump, the chamber shrouds, and the
cryogenic cold plate if needed.
5.1.1.1 The pump should be capable of maintaining the required pressure for a mean free path greater than the largest dimension
of the chamber. Diffusion pumps use oil to capture gases and will increase deposition on the QCM. A cold trap between the
diffusion pump and vacuum chamber is recommended to reduce backstreaming. Clean, oil-free pumps such as cryogenic, sorption,
and turbomolecular are preferred to avoid backstreaming.
5.1.1.2 High Vacuum Gauge—An ion gauge or other gauge capable of monitoring pressures below 1e-4 torr. See Practice E296
for guidance in using ionization gauges.
5.1.1.3 Chamber Shrouds—The chamber shall be equipped with an inner lining or shroud that provides temperature control
which is maintained cold for “cold wall” testing and hot for “hot wall” testing. A bakeout box may be substituted for the shroud
for hot wall testing.
(1) Cold wall testing requires the hardware to be heated while the chamber shroud is kept cold, typically at LN temperatures.
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(2) Hot wall testing requires an environment that is isothermal with the hardware, this is typically accomplished with a bakeout
box or the chamber shrouds. The bakeout box is an enclosed structure which surrounds the hardware and provides uniform heating
of components. There are only holes in the box to allow for a small planned vent and a view port for the QCM. The chamber shroud
is normally heated with hot GN and the heater plates operate using heater tapes or circulating hot fluid. Whichever heating system
is chosen, it should be sufficient to heat the item uniformly. Thermocouples should be placed appropriately to insure uniform
heating of the hardware.
5.1.1.4 Cold Traps—There are three different types of equipment that can be used to trap contaminants: a LN filled cold wall
of the shroud, ana LN filled cold plate/cold finger, or the cryopump/diffusion LN trap. The cold trap is kept cold throughout the
2 2
test and may be analyzed afterward for contaminant identification.
5.1.2 Temperature Control System—All temperatures of the bakeout hardware and the QCM are maintained by independently
controlled heaters to a precision of 62°C.62 °C.
5.1.2.1 Heating Equipment—In general, six different types of equipment may be used to heat the component: a bakeout box,
heat lamps, resistance bars, heater plates, heater tapes, or the chamber shroud. Methods A and B are independent of the method
of creating the environment temperature, while Method C requires either a hot wall or cold wall configuration.
(1) Arrays of heat lamps or resistance bars are commonly used for solar panels.
(2) The chamber shroud or aluminum heater plates are commonly used for electrical components. The chamber shroud is
normally heated with hot GN and the heater plates operate using heater tapes or circulating hot fluid.
(3) Heater tapes can be used on the component directly, but heater tape adhesives can bias the results and possibly contaminate
the hardware.
5.1.3 Data Acquisition System—Data acquisition, storage, and manipulation can be accomplished by any method that is capable
of monitoring QCM frequencies, QCM temperatures, QCM heater/cooler voltages, hardware temperatures, chamber pressure, and
data collection times at specified intervals. The system should be able to store collected data for later retrieval and analysis. An
automated, computer operated data collection system is recommended.
5.1.3.1 The QCM heater/cooler voltage is used as a diagnostic tool. If there is significant variation in the QCM frequency, it
may be related to poor QCM heater/cooler control.
5.1.3.2 Data storage intervals should be short enough to collect inherent variability of the QCM collection device. It has been
found that 1 to 5 min between records is satisfactory.
5.1.4 QCM—The placement of the QCM has a significant effect on the measurement of outgassing rates. If the QCM views hot
chamber surfaces capable of re-emitting contamination, such as it would in a hot box, the readings may be artificially high. If it
views a cold shroud, the readings will be too low.
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5.1.4.1 The QCM used for this test shall have a sensitivity of at least 1.0E-08 g·cm ·Hz . 10 MHz or 15 MHz crystals meet
this requirement and are typically used for this application.
5.1.4.2 The QCM shall be thermally connected to a heat sink enabling the QCM to operate in its full temperature range. It may
be necessary to cool the heat sink mounting bracket with fluid or gas to keep the temperature stable.
(1) The sink for a TQCM must be maintained at no more than 40°C40 °C above the crystal operating temperature (see TQCM
manual for details). This ensures that the indium seals will not melt due to internal heat generated by the TQCM. It may be
necessary to heat a TQCM if the surrounding area is too cold for its electronics. An alternative is to provide multi-layer insulation
to thermally decouple the TQCM electronics from the cold environment.
(2) CQCMs are designed to withstand and perform at cryogenic temperatures as well as any temperature up to the maximum
allowed by the manufacturer. This is often 80°C.80 °C.
5.1.4.3 For a cold wall test, the QCM deposition rate must be monitored by the QCM positioned such that its field of view is
completely filled by the item undergoing bakeout. Since the QCM has a field of view between 143° and 150°, this means placing
the QCM within several centimetres of the hardware. If the QCM cannot be placed appropriately, which may be the case due to
support equipment or thermal requirements, the rate must be adjusted by modeling and analysis. For this reason it is important
to document the exact dimensional location of the QCM with respect to the hardware. Photographs of the test set-up are
recommended as well. If several components or parts are baked-out at once, multiple QCMs may be used to get an accurate
representation of the outgassing rates. For assembled electronics boxes, the QCM(s) should be placed as close to the box vent as
possible, or near a connector if there is no vent.
5.2 Ideal Chamber Internal Configuration—Commonly, the outgassing rate data generated by the thermal vacuum bakeout is
used as an input to spacecraft system level contamination analyses. For this reason, the ideal chamber configuration is one that
closely simulates the component’s on-orbit environment and its configuration installed onto the spacecraft.
5.2.1 Electronic boxesBoxes are generally situated inside of the spacecraft bus, thereforebus; therefore, the most likely choice
for a vacuum chamber set up would be the "hot box" or to have heated chamber shrouds with a cold plate at one end of the chamber
simulating a vent to cold space.
QCM readings may not be accurate unless the QCM field view is completely filled by the bake-out object. Exact measurements of the chamber and its equipment may
be made so that it the appropriate view factors and outgassing rates can be calculated using a contamination analysis tools such as TRASYS® and MOLFLUX®. If chamber
modeling is used, the source and limits of the model must be given. Method C offers an alternative.
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5.2.2 Electrical harnessesHarnesses are notoriously high outgassing items. An often used method is to place them on an
aluminum grating plate, heat them with warm chamber shrouds, and collect the contamination with a large cold plate. This allows
the harnesses to be heated uniformly and provides a large cold surface area to collect great amounts of contamination that will most
likely evolve from the harnesses.
5.2.3 Because the thermal environment for thermal blankets can vary so drastically, it is hard to simulate. Therefore, the most
efficient way to bakeout thermal blankets and provide uniform heating would be hang them on aluminum or stainless wires inside
of a bakeout box or warm shrouds/cold plate configured chamber.
5.3 Optional Equipment:
5.3.1 Cold Finger—An additional cold plate/finger is often used at the end of the bakeout during the certification phase to
determine the identity and relative amount of any contamination remaining after the bakeout phase. Cold finger operations are
described in Practice E834.
5.3.2 Residual Gas Analyzer (RGA)—An RGA may be installed into the vacuum chamber for chemical identification of
outgassing species.
6. Support Equipment/Materials
6.1 Garments—Cleanroom smocks, cleanroom snoods or shower caps, and gloves should be worn during cleaning operations
and for handling the hardware after the completion of the bakeout. Cleanroom latex, polyethylene, or Nitrilegloves shall be used.
For bakeout items sensitive to particulate contamination, full bunny suits may be required as designated by the contractor.
6.2 Witness Samples and NVR Sample Wipes—Witness plates such as those described in Practice E1234 may be used for
collecting contamination during the pre-bakeout and the hardware bakeout. Pre-extracted low NVR sample wipes can also be used
to verify chamber cleanliness by sampling chamber walls or the cold plate.
6.2.1 High Purity, Low NVR Solvents are required for cleaning the chamber and other hardware prior to insertion of the
components to be baked-out. Suitable reagent grade solvents include isopropyl alcohol and ethanol (or other low NVR solvents
which meet local safety standards). The suitability of these solvents for the specific application must be determined by the user.
6.2.2 Wipers—Suitable wipers for cleaning include low NVR cleanroom quality polyester or nylon.
6.3 HEPA Filtered Portable Clean Tent—For items undergoing a bakeout that are sensitive to particulate contamination, a clean
tent, certified to the required ISO-14644 [Fed-Std-209][FED-STD-209] cleanliness class, may be used installed over the opening
to the chamber.
7. Procedure
NOTE 1—There are three bakeout processes that can be used:
Method A (Time and Temperature) is generally used for components that do not have a line-of-sight to contamination sensitive hardware.
Method B (Outgassing Stabilization) may be used for components that do not have a line-of sight to sensitive hardware, yet have TQCM monitoring
requirements.
Method C (Outgassing Measurement) is commonly used for contamination sensitive hardware and components which have a direct line-of-sight to
that hardware.
See Table 1 for typical descriptions of test parameters for each method.
7.1 Chamber Preparation:
7.1.1 Chamber preparation includes a chamber cleaning and a pre-bakeout/chamber cleanliness certification.
7.1.2 Don appropriate cleanroom smocks and gloves described in 6.1.
7.1.3 The empty chamber shall be cleaned with non-linting cleanroom wipers per 6.3 and a solvent compatible with the chamber
materials of construction and the suspected contaminants to be removed (isopropyl alcohol is generally compatible with vacuum
chamber paints, see 6.2). (Warning—Cleaning with solvents in an enclosed space may be hazardous. A special breathing
apparatus, such as a respirator with the appropriate solvent cartridge filter may be necessary. All procedures should be reviewed
for conformance to local safety requirements.)
NOTE 2—Cleaning with solvents in an enclosed space may be hazardous. A special breathing apparatus, such as a respirator with the appropriate solvent
cartridge filter may be necessary. All procedures should be reviewed for conformance to local safety requirements.
7.1.4 Solvent wipe clean all support fixtures, cabling, heaters, a cold wall or plate, using a solvent compatible with materials
of construction and install into the chamber. Support equipment may be cleaned and verified to an IEST-STD-CC1246
[MIL-STD-1246] level as necessary.
7.1.5 The QCM shall be chemically cleaned according to instructions provided in Test Method E1559 and placed within the
chamber per 5.1.4 as it will be installed for the hardware bakeout.
Garments and gloves are available commercially but should be tested for suitability prior to use. Testing may be performed according to Guide E1546 and Test Method
E1731 respectively, or according to contractor requirements.
Wipers are available commercially but should be tested prior to use for suitability and NVR per ASTM Test Method E1560 or contractor requirements.
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TABLE 1 Description of Typical Test Parameters for Bakeout Methods A, B and C
NOTE 1—Unit acceptance or qualification temperature (10°C above maximum on-orbit operating predictions).
NOTE 2—May be adjusted to meet hardware design or program requirements. Because bakeout time and efficiency are dependent on temperature, the
chosen temperature should be the highest possible without damage to hardware. Blankets baked above 100°C may shrink several percent.
NOTE 3—A minimum bakeout time may be estimated by 960/T(°C). Specified nominal times can be used for planning purposes or may be adjusted
to meet specific program requirements. A minimum bakeout time of 16 to 24 h is recommended.
NOTE 4—Collection at –110°C captures all non-water volatiles while collection at –20°C has been used frequently when no temperature is specified.
NOTE 5—QCM temperature may be adjusted to meet program requirements. Chosen QCM temperature is generally based on the on-orbit predictions
for the coldest contamination sensitive surface.
Method(s) Affected A, B, C A B, C B, C
Nominal Bakeout Time (hrs) QCM Temp (°C)
Bakeout Item Minimum Bakeout Temp (°C) Bakeout Rate Stabilization
(Note 3) (Note 4 and Note 5)
Electronic components Note 1 48 –20 or –110 <3%/hr change in rate
Solar Array Note 1 48 –20 or –110 <3% change in rate
Thermal Blankets 95 ± 5(Note 2) 72 –20 or –110 <3% change in rate
Electrical Harnesses 95 ± 5(Note 2) 96 –20 or –110 <3% change in rate
TABLE 1 Description of Typical Test Parameters for Bakeout Methods A, B, and C
Method(s) Affected A, B, C A B, C B, C
Nominal Bakeout Time (hrs) QCM Temp (°C)
Bakeout Item Minimum Bakeout Temp (°C) Bakeout Rate Stabilization
C D, E
A
Electronic Components 48 –20 or –110 <3 % ⁄hr change in rate
A
Solar Array 48 –20 or –110 <3 % change in rate
B
Thermal Blankets 95 ± 5 72 –20 or –110 <3 % change in rate
B
Electrical Harnesses 95 ± 5 96 –20 or –110 <3 % change in rate
A
Unit acceptance or qualification temperature (10 °C above maximum on-orbit operating predictions).
B
May be adjusted to meet hardware design or program requirements. Because bakeout time and efficiency are dependent on temperature, the chosen temperature should
be the highest possible without damage to hardware. Blankets baked above 100 °C may shrink several percent.
C
A minimum bakeout time may be estimated by 960/T(°C). Specified nominal times can be used for planning purposes or may be adjusted to meet specific program
requirements. A minimum bakeout time of 16 to 24 h is recommended.
D
Collection at –110 °C captures all non-water volatiles, while collection at –20 °C has been used frequently when no temperature is specified.
E
QCM temperature may be adjusted to meet program requirements. Chosen QCM temperature is generally based on the on-orbit predictions for the coldest contamination
sensitive surface.
7.1.6 Visually inspect chamber with white light and ultraviolet light (optional) illumination for complete removal of adhesive
residues, grease, oil, particles, metal shavings, or other foreign materials. Areas not adequately cleaned shall be re-cleaned.
7.1.7 Install witness plates described in 6.2 into the chamber such that they will have a view to the same equipment or chamber
wall that the actual hardware will have during its bakeout.
7.2 Chamber Pre-Bake:
7.2.1 For Method A, the pre-bake may or may not be performed depending on the heritage of the chamber. The need for a
pre-bakeout must be determined by the user.
NOTE 2—If the final chamber pressure for a proceeding measurement is significantly less than the required final chamber pressure for the bakeout under
consideration, indicating a “clean chamber”,chamber,” then consideration can be given to waiving the chamber bakeout portion of the processing cycle.
This decision should be recorded in the processing paperwork for the sample being processed and include specific information on the chamber pressure,
temperature, and sample identity for the proceeding sample.
7.2.2 For Methods B and C, the pre-bake shall be performed so that the outgassing rate measurements are not biased by high
background chamber rates.
NOTE 3—If performing Method A, QCM monitoring during a chamber pre-bakeout certification is not necessary. Therefore, disregard following
statements including the QCM if using Method A.
7.2.3 Close chamber door and evacuate chamber to 5.0E-05 torr or better vacuum. Maintain QCM at 25°C25 °C during
evacuation if present.
7.2.4 Once the desired vacuum level is reached, fill cold plate or other support hardware (i.e. (that is, chamber shroud), or both,
with LN according to configurations described in 5.2. For Method A, this step is not necessary if a bell jar type chamber without
a cold plate is used.
7.2.5 Increase heating element (lamps, hot box, etc)etc.) temperature until it stabilizes to 10°C10 °C
...