Trace Gas Analyzer for Extra-Vehicular Activity 2001-01-2405

The Trace Gas Analyzer (TGA, Figure 1) is a self-contained, battery-powered mass spectrometer that is designed for use by astronauts during extravehicular activities (EVA) on the International Space Station (ISS). The TGA contains a miniature quadrupole mass spectrometer array (QMSA) that determines the partial pressures of ammonia, hydrazines, nitrogen, and oxygen. The QMSA ionizes the ambient gas mixture and analyzes the component species according to their charge-to-mass ratio. The QMSA and its electronics were designed, developed, and tested by the Jet Propulsion Laboratory (1,2). Oceaneering Space Systems supported JPL in QMSA detector development by performing 3D computer for optimal volumetric integration, and by performing stress and thermal analyses to parameterize environmental performance. Oceaneering led in the packaging and integration of the QMSA detector to meet the electro-magnetic interference, thermal, vibration, and volumetric constraints that are imposed by the extra-vehicular environment and by the TGA’s use as an astronaut tool. Oceaneering developed and furnished the battery power conditioning and distribution module, interlock telemetry module, sunlight-legible display with associated

interface, miniaturized ion pumps with integrated power supply, interconnect cabling, and casings. Oceaneering also carried out the performance, flight-qualification and certification testing. An EVA-qualified battery pack was used in order to maintain commonality with existing EVA tools.

The TGA program was placed on a fast-insertion track in order to meet a critical need for ammonia (NH₃) detection in the cooling lines exterior to the ISS. Such leaks were expected to occur in cases where the quick-disconnect (QD) fittings in these lines did not seal properly. Oceaneering and JPL led the transformation of a 19-inch rack-mounted laboratory instrument into an EVA tool that can be operated while hand-held, mounted to the astronaut’s mini workstation, or mounted to the body restraint tether (BRT). The TGA system was launched on schedule aboard STS-98 in January, 2001. It is presently aboard the ISS awaiting use in the event of a QD failure.

The TGA can detect trace concentrations of all hydrazine species in the EVA environment, and with modifications it could be used for measuring hydrazine concentrations in the airlock of the ISS or the Shuttle Orbiter. When outfitted with a gas chromatograph front-end, it could also be used to monitor the quality of cabin air during long-duration human missions to the Moon, Mars, and beyond (3).