repair, post repair measurements of these
compounds by VCAM and GSC yielded
concentrations at least 20 times less than
VCAM requirements. VCAM also did not
report any “false positives” for the 17
chemicals detected by GSC measurements
that were below the quantification limit of
0.05 mg/m^3. Measurements of the
compound perfluoropropane showed only
fair agreement between VCAM and GSC data.
VCAM also detected a large number of
unknown chemical species not part of the
original VCAM requirements list, which were
later identified during ground analysis. Additionally, VCAM performed autonomous
measurements of the major constituents of the ISS atmosphere. VCAM’s measurements of N 2
and O 2 were in excellent agreement with measurements taken by the Major Constituents
Analyzer (MCA) of the same constituents. CO 2 measurements were in agreement as well
through February 2011, but thereafter, VCAM measurements diverged and the instrument
error increased, likely because of instrument contamination (Darrach 2011, 2012).
PUBLICATION(S)
Darrach MR, Chutjian A, Bornstein BJ, et al. Trace chemical and major constituents
measurements of the International Space Station atmosphere by the vehicle cabin atmosphere
monitor. 42 nd International Conference on Environmental Systems, San Diego, CA; July 15-19,
2012.
Darrach MR, Chutjian A, Bornstein BJ, et al. On-orbit measurements of the ISS Atmosphere by
the vehicle cabin atmosphere monitor. 41 st International Conference on Environmental Systems,
Portland, OR; July 17-21, 2011.
PATENT(S)
Schaefer RT, Mojarradi M, Chutjian A, Darrach MR, MacAskill J, Tran TA, Burke GR, Madzunkov
SM, Blaes BR, Thomas JL, Stern R, Zhu DQ, inventors; Electronic drive and acquisition system for
mass spectrometry. US patent. 7,772,550. August 10, 2010.
This investigation is complete and all results are published.
NASA astronaut Ron Garan prepares to install a Gas
Supply Orbital Replacement Unit into the VCAM.