Engineering topics

Suomi, V. E.

Publications and source records attributed to Suomi, V. E..

At least 37 records · Page 2

NASA NTRS1981

Cloud motions on Venus - Global structure and organization

Results on cloud motions on Venus obtained over a period of 3.5 days from Mariner 10 television images are presented. The implied atmosphere flow is almost zonal everywhere on the visible disk, and is in the same retrograde sense as the solid planet. Objective analysis of motions suggests the presence of jet cores (-130 m/s) and organized atmospheric waves. The longitudinal mean meridional profile of the zonal component of motion of the ultraviolet features shows presence of a midlatitude jet stream (-110 m/s). The mean zonal component is -97 m/s at the equator. The mean meridional motion at most latitudes is directed toward the pole in either hemisphere and is at least an order of magnitude smaller so that the flow is nearly zonal. A tentative conclusion from the limited coverage available from Mariner 10 is that at the level of ultraviolet features mean meridional circulation is the dominant mode of poleward angular momentum transfer as opposed to the eddy circulation.

Limaye, S. S.↗

NASA NTRS1980

The thermal balance of Venus in light of the Pioneer Venus mission

Pioneer Venus orbiter and probes measured many of the properties of the Venus atmosphere which control its thermal balance and support its high surface temperature. Estimates based on orbiter data yield an effective radiating temperature of Venus of 228 + or - 5 K, corresponding to a solar emission of 153 + or - 13 W/sq cm. A mode of submicron particles is suggested as an important source of thermal opacity near the cloud tops to explain the orbiter and probe thermal flux measurements. A comparison of the measured solar flux profile with thermal fluxes computed from the measured temperature structure and composition shows that the greenhouse mechanism explains essentially all of the 500-K difference between the surface and radiating temperatures of Venus.

Tomasko, M. G.↗

NASA NTRS1980

Net radiation in the atmosphere of Venus - Measurements and interpretation

Aerodynamic testing of the Pioneer Venus small probe net flux radiometer (SNFR) has led to a better understanding of transient errors in the net flux measurements immediately following deployment. Corrections to the net flux profiles in this region produce profiles that are reasonably consistent with constraints imposed by ground-based and orbiter results for fluxes above the atmosphere. The tests raised questions about possible steady state errors associated with the changing atmospheric temperature encountered as the probes descended. However, the lack of sensor-to-sensor variability of the transient error (caused by a newly discovered flow-through mechanism) suggests that any related errors discovered by future testing will be correctable and will not alter the conclusions that net fluxes in the lower atmosphere vary considerably with location and are relatively large at the north and night probe sites.

Suomi, V. E.↗

NASA NTRS1980

Pioneer Venus small probes net flux radiometer experiment

The University of Wisconsin net flux experiment on the Pioneer Venus mission investigated the distribution of radiative energy deposition and loss which drives atmospheric circulation on Venus. The instrument used an external sensor and a novel method of chopping to measure the net flux of solar and planetary radiation during descent through the thick Venus atmosphere. The sensor, consisting of a high temperature flux plate detector and protective diamond windows, was designed to make accurate flux measurements while exposed to the severe Venus environment.

Sromovsky, L. A.↗

NASA NTRS1979

Extended record length of atmospheric data gathered via Nimbus-6

A low-power nonvolatile data memory unit was developed for free floating balloons in the TWERL experiment. By means of multiple identification codes data records, several hours long, could be transferred in compressed form to the Nimbus-6 satellite for retransmission to ground stations. Eight of these units were flown on constant density balloons to investigate atmospheric wave motions throughout the Southern Hemisphere. One returned valid data for ten months. Similar techniques could be used with other types of observing platforms.

Afanasjevs, J.↗

NASA NTRS1979

A 'special effort' to provide improved sounding and cloud-motion wind data for FGGE

Enhancement and editing of high-density cloud motion wind assessments and research satellite soundings have been necessary to improve the quality of data used in The Global Weather Experiment. Editing operations are conducted by a man-computer interactive data access system. Editing will focus on such inputs as non-US satellite data, NOAA operational sounding and wind data sets, wind data from the Indian Ocean satellite, dropwindsonde data, and tropical mesoscale wind data. Improved techniques for deriving cloud heights and higher resolution sounding in meteorologically active areas are principal parts of the data enhancement program.

Greaves, J. R.↗

NASA NTRS1978

Venus - Further evidence of vortex circulation

A space-time composite of polar stereographic ultraviolet images of Venus from Mariner 10 shows a remarkable circumpolar vortex. The vortex is characterized by a cloud which appears similar to dense terrestrial stratus having an albedo that is 50 percent higher. Spiral streaks converge into it from low latitudes, akin to the spiral bands of a hurricane. The bright visible polar cloud is not axisymmetric but has roughly an elliptical shape. The high brightness of the polar cloud suggests that it has a different origin from the rest of the Venus cloud cover.

Suomi, V. E.↗

NASA NTRS1977

Antarctic topography from balloons

A description is presented of an investigation involving the collection of Antarctic ice sheet surface topography data by means of balloons, floating at an altitude of about 12.5 km, which traversed the Antarctic during its 1975 summer. These balloons were part of 411 constant density balloons launched in the Southern Hemisphere during the Tropical Wind, Energy conversion and Reference Level Experiment. The three sensors carried by each balloon included a radio altimeter, a pressure sensor, and an ambient temperature sensor. Data transmitted by a balloon are received by a measuring system on board the Nimbus-6 satellite. A synoptic map is presented of the 150 mbar pressure surface at 1200 GMT, December 11, 1975.

Levanon, N.↗

NASA NTRS1977

Dynamics, winds, circulation and turbulence in the atmosphere of Venus

With the possible exception of the lowest one or two scale heights, the dominant mode of circulation of Venus' atmosphere is a rapid, zonal, retrograde motion. Global albedo variations in the ultraviolet may reflect planetary scale waves propagating relative to the zonal winds. Other special phenomena such as cellular convection in the subsolar region and internal gravity waves generated in the interaction of the zonal circulation with the subsolar disturbance may also be revealed in ultraviolet imagery of the atmosphere. We discuss the contributions of experiments on the Orbiter and Entry Probes of Pioneer Venus toward unravelling the mystery of the planet's global circulation and the role played by waves, instabilities and convection therein

Schubert, G.↗

NASA NTRS1977

The thermal balance of the atmosphere of Venus

Current knowledge of the temperature structure of the atmosphere of Venus is briefly summarized. The principal features to be explained are the high surface temperature, the small horizontal temperature contrasts near the cloud tops in the presence of strong apparent motions, and the low value of the exospheric temperature. In order to understand the role of radiative and dynamical processes in maintaining the thermal balance of the atmosphere, a great deal of additional data on the global temperature structure, solar and thermal radiation fields, structure and optical properties of the clouds, and circulation of the atmosphere are needed. The ability of the Pioneer Venus Orbiter and Multiprobe Missions to provide these data is indicated.

Tomasko, M. G.↗

NASA NTRS1977

Antarctic ice topography and 150 mb circulation from the Nimbus-6 TWERL Experiment

Many TWERLE balloons floating at an altitude of about 12.5 km, traversed the Antarctic during its 1975/6 summer. The balloons' positions were accurately determined by the Nimbus-6 satellite, which also received their sensors' data: radio altimeter, pressure and temperature. Subtracting the altimeter readings from the calculated balloon altitude above sea-level (a.s.l.) provides the Antarctic surface elevation at the balloon subtrack. The balloon altitude a.s.l. is calculated from daily synoptic maps covering latitudes south of 45 deg S. These maps are prepared using the regular radiosonde network supplemented by four times as many TWERLE balloons.

Levanon, N.↗

NASA NTRS1975

An aneroid pressure sensor for constant-level balloons

The pressure sensor for the Tropical Wind Energy conversion and Reference Level Experiment (TWERLE) is described. Key design features of the sensor are: capacitive coupling, reference at midrange, up-down counting, passive oven, storage at flight pressure and prelaunch calibration. Sensor specifications are given which are based on the production results of 440 units. Drift, as estimated from simulated life tests, is 1 mb per 6 months. The overall weight of the sensor, including thermal package, is 180 g.

Levanon, N.↗

NASA NTRS1975

Earth radiation budget measurement from a spinning satellite: Conceptual design of detectors

The conceptual design, sensor characteristics, sensor performance and accuracy, and spacecraft and orbital requirements for a spinning wide-field-of-view earth energy budget detector were investigated. The scientific requirements for measurement of the earth's radiative energy budget are presented. Other topics discussed include the observing system concept, solar constant radiometer design, plane flux wide FOV sensor design, fast active cavity theory, fast active cavity design and error analysis, thermopile detectors as an alternative, pre-flight and in-flight calibration plane, system error summary, and interface requirements.

Sromovsky, L. A.↗

NASA NTRS1975

Man-Computer Interactive Data Access System (McIDAS). Continued development of McIDAS and operation in the GARP Atlantic tropical experiment

The complete output of the Synchronous Meteorological Satellite was recorded on one inch magnetic tape. A quality control subsystem tests cloud track vectors against four sets of criteria: (1) rejection if best match occurs on correlation boundary; (2) rejection if major correlation peak is not distinct and significantly greater than secondary peak; (3) rejection if correlation is not persistent; and (4) rejection if acceleration is too great. A cloud height program determines cloud optical thickness from visible data and computer infrared emissivity. From infrared data and temperature profile, cloud height is determined. A functional description and electronic schematics of equipment are given.

Suomi, V. E.↗

NASA NTRS1975

Meteorological Measurements from Satellite Platforms

The stability of stochastic satellites and the stability and control of flexible satellites were investigated. The effects of random environmental torques and noises in the moments of inertia of spinning and three-axes stabilized satellites were first compared analytically by four methods and by analog simulations. Among the analytical methods, it was shown that the Fokker-Planck formulation yields predictions which most coincide with the simulation results. It was then shown that the required stability criterion of a satellite is quite different from that obtained by a deterministic approach, under the assumption that the environmental and control torques experienced by the satellite are random. Finally, it was demonstrated that, by monitoring the deformations of the flexible elements of a satellite, the effectiveness of the satellite control system can be increased considerably.

Suomi, V. E.↗

NASA NTRS1975

The TWERLE balloon-to-satellite data transmitting system

This paper describes the balloon instrumentation system which provides the one-way link for data gathering and navigation in the Tropical Wind, Energy conversion and Reference Level Experiment (TWERLE). In this experiment, 400 instrumented constant-level balloons will be launched at the southern hemisphere during 1975. The Random Access Measurement System (RAMS) on board the Nimbus-F satellite, will comprise the receiving end of the link. The data encoder, stable oscillator, transmitter and antenna are described, as well as two supporting components, the power source and the magnetic cutdown. These six items weigh 850 g. The oscillator-transmitter consume 1.9 W dc power to provide 0.6 W phase modulated RF power.

Levanon, N.↗

NASA NTRS1974

A new approach to lightweight radar altimeters

Test results and key principles are given for a radar altimeter designed for meteorological balloons. The instrument, which weighs 160 g and consumes 0.7 W, will fill a gap in meteorological sensing using balloons - an area where pressure altitude was formerly the prevailing reference. The instrument is basically a delay-lock radar utilizing a superregenerative RF stage. Long-term absolute accuracy of plus or minus 10 m and short-term stability of better than 2 m rms were measured at altitudes of 20 km.

Levanon, N.↗

NASA NTRS1974

On the behavior of superpressure balloons at 150 mb

Review of measurement data intended to show how constant are 'constant-level' superpressure balloons. The data were obtained during four superpressure-balloon 150-mb flights in the Southern Hemisphere and should be of help in distinguishing between balloon- and atmosphere-induced phenomena as well as in preparing specifications for future balloon sensors.

Levanon, N.↗