measures O2 concentration (reported as O2/N2 ratio) using a vacuum-ultraviolet absorption technique

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NCAR Airborne Oxygen Instrument (AO2)

• measures O2 concentration (reported as O2/N2
  ratio) using a vacuum-ultraviolet absorption
  technique
• based on earlier shipboard and laboratory
  instruments, but designed specifically for
  airborne use to minimize motion and thermal
  sensitivity and with a pressure and flow
  controlled inlet system
• flew on the Wyoming King-Air during ACME-2007
• switches between sample gas and air from a
  high-pressure reference cylinder every 2 seconds
  and has a precision of /- 5 per meg on a
  5-second measurement
• consists of a pump module, a cylinder module, an
  instrument module, and a dewar

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NCAR Airborne Oxygen Instrument (AO2)
Contact name Britton Stephens, NCAR EOL/TIIMES,
303-497-1018, stephens_at_ucar.eduDimensions
19" rack wide X 30" tall X 22" deep plus a 6"
diameter X 14" tall dewar Instrument weight 200
lbs. Power 110 AC Hazmat 4 kg of solid CO2
(dry ice) Inlet(s) dedicated aft facing 1/4"
inlet, unheated stainless steel or
Synflex secondary inlet to rule out
fractionation Number of operators 1 (eventually
planned for 0 as instrument matures) Altitude
requirements max. alt 60,000 feet Ground
requirements 30 minute preflight
Stephens, B.B., R.F. Keeling, and W.J.
Paplawsky, Shipboard measurements of atmospheric
oxygen using a vacuum-ultraviolet absorption
technique, Tellus Series B, 55, 857-878, 2003.
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NCAR MEDUSA Flask Sampler

• collects cryogenically dried air into 16 1.5 L
  glass flasks under actively controlled flow and
  pressure conditions
• designed to sample for laboratory measurements of
  O2/N2, Ar/N2, 13CO2, and C18OO
• earlier version flew on the UND Citation II
  (COBRA-2000 and 2003) and on the NCAR C130
  (IDEAS, ACME-2004)
• integrated control and data acquisition system
  logs housekeeping variables every second
• consists of a pump module, a flask module, and a
  dewar

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NCAR MEDUSA Flask Sampler
Contact name Britton Stephens, NCAR
EOL/TIIMES, 303-497-1018, stephens_at_ucar.edu Dimen
sions 19" rack wide X 27 " high X 18 " deep,
plus a 6" diameter X 14" high dewar Weight 100
lbs. Power 28 VDC Hazmat 4 kg of solid CO2
(dry ice) Inlet dedicated forward facing 3/8"
inlet, unheated stainless steel or Synflex Number
of operators 1 (can be shared) Altitude
requirements max. alt 52,000 feet Ground
requirements 30 minute preflight
COBRA-NA 2003
Graven et al., Causes of Observed Summertime
Variability in Tropospheric O2/N2 above North
America, manuscript in preparation, 2008
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NCAR MEDUSA Flask Sampler

• nominal flow rate is 3.3 SLPM and the flask
  volume is 1.5 L, resulting in a 30-second
  quasi-integrated sample.
• GV cabin throughflow 24,000 SLPM (unofficial
  value fromGulfstream)
• Flask rupture would lead to an addition of lt 3
  SLPM of air into cabin ( 0.01 change)
• Flask rupture combined with upstream
  flow-controller failure to full-closed and
  downstream flow-controller failure to full-open
  would lead to a removal of lt 4 SLPM of air from
  cabin ( - 0.015)