Pioneer Venus Orbiter (PVO) Electron Temperature Probe (OETP) Data Bundle
Pioneer Venus Orbiter (PVO) Electron Temperature Probe (OETP) Bow Shock Data Description
PDS3_DATA_SET_ID = PVO-V-OETP-5-BOWSHOCKLOCATION-V1.0
PDS3_DATA_SET_RELEASE_DATE = 1993-10-01
START_TIME = 1978-12-05T15:07:34.817
STOP_TIME = 1992-10-06T20:38:35.000
PRODUCER_FULL_NAME = DR. LARRY BRACE, DR. ROBERT F. THEIS
Collection Overview
===================
The Bow Shock collection gives the orbit-by-orbit times and locations of the bow shock
crossings, which are characterized by distinct changes in Ne. Multiple shock crossing are
listed if they are sufficiently separated to be resolved accurately. (Bow shock crossings will
be evident in the High Resolution Ne File when they occurred within 30 minutes of periapsis).
The ionopause and bow shock crossing times and locations are easily identified in the high
resolution Ne measurements (Theis et al., 1980). These files contain the UT, altitude,
latitude, SZA and local time of each crossing.
The bow shock is a much more discrete feature in the data than the ionopause. Multiple shock
crossings sometimes occur because the shock often moves at higher velocities than the
satellite. In these cases, only the outer most shock crossing is recorded, unless the
separation between the crossings is greater than a minute or two. The occurrence of multiple
shocks in the Bow Shock File provides a record of the orbits in which the solar wind itself was
probably highly variable. Because of the geometry of the orbit, most shock crossings were in
the range of 45 to 135 deg. SZA. However, the nose region of the shock was explored between
1985 and 1987 when PVO periapsis was near the equator and was at altitudes between 2000 and
2300 km. During these years near solar minimum the nose of the shock often moved down into
that altitude range (Russell et al, 1988). During the subsolar passages of these years, the
orbit approximately paralleled the shock, sometimes inside, sometimes outside, thus providing
interesting snapshots of its movements.
Confidence Level Overview
=========================
The bow shock is selected from 200 minute pass plots by marking the UT of the sharp change in
the amplitude of Ne at the shock discontinuity. The resolution of the shock crossing time is
of the order of 1 minute on these plots, but this could be improved to a few seconds if
expanded plots were used. There is no plan currently to provide the ultimate resolution
available in bow shock crossing time and location.
References
==========
Brace, L.H., Global Structure of Ionosphere Temperature, in Space Research X. Amsterdam,
The Netherlands: North-Holland, p.633, 1970.
Brace, L.H., 'Orbiter Electron Temperature Probe', L. Colin and D.M. Hunten, Eds. Space
Sci. Rev., Vol.20, No.4, p.454, June 1977.
Brace, L.H., R.F. Theis, and A. Dalgarno, 'The Cylindrical Electrostatic Probes for
Atmosphere Explorer -C, -D, -E', Science, Vol.8, No.4, p.341, Apr.1973.
Brace, L.H., R.F. Theis, J.P. Krehbiel, A.F. Nagy, T.M. Donahue, M.E. McElroy, and A.
Pedersen, 'Electron Temperatures and Densities in the Venus Ionosphere', Science,
Vol.203, p.763, Feb.23, 1979.
Brace, L.H., H.A. Taylor Jr., P.A. Cloutier, R.E. Daniell Jr., and A.F. Nagy, 'On the
Configuration of the Nightside Venus Ionopause', Geophys. Res. Lett., Vol.6,
p.345, 1979.
Brace, L.H., R.F. Theis, H.B. Niemann, H.G. Mayr, W.R. Hoegy, and A.F. Nagy, 'Empirical
Models of the Electron Temperature and Density in the Nightside Venus Ionosphere',
Science, Vol.205, p.102, 1979.
Colin, L., Pioneer Venus Overview, IEEE Transactions on Geoscience and Remote Sensing,
Vol GE-18, No. 1, pp. 5-10, 1980.
Fimmel R.O., Colin L., and Burgess E., 'Pioneering Venus: A Planet Unveiled',
NASA SP-518, 1995.
Hoegy, W.R., and L.E. Wharton, 'Current to Moving Spherical and Cylindrical Electrostatic
Probes', J. Appl. Phys., Vol.44, No.12, p.5365-5371, 1973.
Krehbiel, J.P., L.H. Brace, J.R. Cutler, W.H. Pinkus, and R.B. Kaplan, 'Pioneer Venus
Orbiter Electron Temperature Probe', IEEE Transactions on Geoscience and Remote
Sensing, GE-18, 49, 1980.
Langmuir, I. and H. Mott-Smith, Jr., 'Studies of the Electric Discharges in Gases at Low
Pressures', Gen. Elec. Rev., p.616, Sept.1924.
Mott-Smith, H. and I. Langmuir, 'The Theory of Collectors in Gaseous Discharges', Phys.
Rev., Vol.28, pp.727-763, 1926.
Nothwang, G.T., Pioneer Venus Spacecraft Design and Operation, IEEE Transactions on
Geoscience and Remote Sensing, Vol GE-18, No. 1, pp. 5-10, January 1980.
Russell, C. T., E. Chou, J. G. Luhmann, P. Gazis, L. H. Brace, and W. R. Hoegy, Solar and
interplanetary control of the location of the Venus bow shock, J. Geophysic. Res., 93,
5461, 1988.
Shai, M.C., 'Formulation of Electrically Conductive Thermal-Control Coatings ', NASA Tech.
Paper 1218, Apr.1978.
Smith, D., 'The Application of Langmuir Probes to the Measurement of Very Low Electron
Temperatures', Planet. Space Sci., Vol.20, p.1721, 1972
Spencer, N.W., L.H. Brace, G.R. Carignan, D.R. Taeusch, and H.B. Niemann, 'Electron and
Molecular Nitrogen Temperature and Density in the Thermosphere', J. Geophys. Res.,
Vol.70, pp.2665-2698, 1965.
Theis, R. F., L. H. Brace, K. H. Schatten, C. T. Russell, J. A. Slavin, J. A. Wolf, The
Venus ionosphere as an obstacle to the solar wind, Advances in Space Research, 1, 47,
1980.
Yang, L., 'Preparation and Evaluation of CVD Rhenium Thermionic Emitters', in The Third
Annual Conference on Chemical Vapor Deposition, F.A. Glaski, Ed., American Nuclear
Society, 1972.
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