Contamination Control Planning

Skip to content | Skip to navigation

Site Actions

Site Sections


Home Genesis SamplesContamination Control Planning

Genesis Contamination Control Planning

Contamination control is a keystone for extraterrestrial sample curation and it begins when a mission is conceived and follows throughout sample curation. Genesis contamination control was incorporated into mission design and the details of hardware fabrication. JSC Genesis team provided modeling and assessment of spacecraft outgassing and station-keeping thruster exhaust contamination to the collector plates, analyzed and tested the contamination associated with micrometeoroid impacts, wrote the mission contamination control plan, and constructed two Class 10 rooms in which to process the spacecraft collection surfaces and sample canister.

Contamination exists in two forms: 1) particulate material, such as dust and flakes, from ground-handling and re-pressurization of the spacecraft after re-entry; and 2) molecular film from ground handling, spacecraft outgassing, station-keeping thrusters, and micrometeoroid impact vaporization. Tests have revealed that most contaminants will adhere to the first few nanometers of collector surface. However, since the solar wind particles are traveling hundreds of kilometers per second, atoms and ions from the solar wind will embed themselves in the top 100 nanometers of collector material—deep enough to differentiate the solar particles from superficial contamination from the spacecraft.

Figure showing the relationship of solar wind atoms and contaminants on collector material

Figure showing the relationship of solar wind atoms and contaminants on collector material

JSC's contamination control strategy is a simple 4-step process:

  • Start with clean collector materials.
  • Minimize surface contamination until sample received for analysis.
  • Clean the surface, if necessary, prior to analysis.
  • Use analytical techniques that provide depth resolution.

The following table contains a list of some of the contamination sources identified and the pre-recovery strategy used to control the contamination.

Ground Handling
  • Use ultra-pure collector materials.
  • Clean collectors and science canister with ultra-pure water in a class 10 clean room prior to installing in the science canister.
  • Purge science canister after assembly with clean, dry nitrogen.
  • Maintain returned samples in a contaminant-free environment.
  • Clean the collectors with acceptable technique (e.g., sputtering of molecular films) prior to analysis.
  • Open cover of Sample Return Capsule (SRC) and allow to outgas for up to 3 months.
  • Keep science canister closed until spacecraft has completed the outgassing procedure and is in orbit around L1.
  • Stow collectors and seal science canister prior to return.
  • Use low outgassing materials.
  • Provide minimum "line-of-sight" between the spacecraft and the collector tops.
Micrometeoroid Impacts
  • Analysis and experiments with a light-gas gun indicate that wafer casualty rate is very low.
  • Vaporized material that settles on the collector material has been estimated to be negligible.
Station-Keeping Thrusters
  • Use ultra-pure hydrazine thrusters.
  • No line-of-sight to collectors for station keeping.
  • Limit the size and duration of thrust.
Re-entry re- pressurization
  • Use ultrapure filter to equalize pressure.