Instrument Information
IDENTIFIER urn:nasa:pds:context:instrument:pvo.onms::2.2
NAME Orbiter Neutral Mass Spectrometer (ONMS) for Pioneer Venus
TYPE Mass Spectrometer
DESCRIPTION The Neutral Mass Spectrometer (ONMS) is designed to measure the concentration of neutral atoms and molecules in Venus's upper atmosphere, ranging from 150 km to 500 km in altitude. The instrument is housed in a compact tube and includes a cylindrical chamber for ion source operations. It employs a quadrupole mass spectrometer with multiple ion-source modes to measure both noble gases in open mode and chemically active gases in closed mode, as well as a "flip-flop" mode for alternate measurements. The instrument can accurately analyze gas particles based on their mass, with a resolution of 0.0001 for mass readings from 1 to 46 amu. After being activated, the ONMS successfully detected and measured density variations of key atmospheric constituents including helium, oxygen, carbon dioxide, and nitrogen, contributing to a better understanding of Venus's atmospheric dynamics, chemistry, and thermal state.
MODEL IDENTIFIER
NAIF INSTRUMENT IDENTIFIER
SERIAL NUMBER not applicable
REFERENCES Hedin, A.E., H.B. Niemann, W.T. Kasprzak and A. Seiff, Global Empirical Model of the Venus Thermosphere, Journal of Geophysical Research, vol. 88, 73-83, 1983.

Niemann, H.B., J.R.Booth, J.E. Cooley, R.E. Hartle, W.T. Kasprzak, N.W.Spencer, S.H. Way, D.M. Hunten and G.R. Carignan, Pioneer Venus Orbiter Neutral Gas Mass Spectrometer, IEEE Trans. on Geoscience and Remote Sensing, vol. GE-18 (1), 60-65, 1980.