NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Upper Atmosphere Mass Spectrometer (UAMS)

NSSDCA ID: 1975-075C-12

Mission Name: Viking 1 Lander
Principal Investigator:Prof. Alfred O. C. Nier


The Viking entry science neutral atmospheric composition experiment (one of three that were part of the entry science investigation) was designed to provide the composition data for the various neutral species that were needed to define the present physical and chemical state of the Martian atmosphere. Mounted in an opening in the aeroshell with its electron-impact open ion source recessed below the surface of the aeroshell, a double-focusing (electrostatic and magnetic) mass spectrometer was used to measure the concentrations of the atmospheric species that have mass-to-charge ratios from 1 to 49. Two collectors were used, one for the mass range from 1 to 7 u, and the other simultaneously measuring in the mass range from 7 to 49 u. Mass spectra were obtained by sweeping the ion acceleration voltage and the deflection voltage across the electrostatic plates. The sweep period was approximately 5 s, and a dynamic range of 1.E5 was provided within each spectrum.

Alternate Names

  • NMS
  • Neutral Mass Spectrometer Accel., Press. and Temp Sensors Retard. Poten. Analyzer
  • UAMS
  • Viking1Lander/NMS

Facts in Brief

Mass: 6.2 kg
Power (avg): 13.3 W

Funding Agency

  • NASA-Office of Space Science (United States)


  • Planetary Science: Atmospheres

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Prof. Alfred O. C. NierTeam LeaderUniversity of Minnesota
Dr. Michael B. McElroyTeam MemberHarvard
Dr. Nelson W. SpencerTeam MemberNASA Goddard Space Flight Center

Selected References

  • Seiff, A., and D. B. Kirk, Structure of the atmosphere of Mars in summer at mid-latitudes, J. Geophys. Res., 82, No. 28, 4364-4378, doi:10.1029/JS082i028p04364, Sept. 1977.
  • Seiff, A., The Viking atmosphere structure experiment - techniques, instruments, and expected accuracies, Space Sci. Instrum., 2, 381-423, 1976.
[] NASA Logo -