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The extremely long mission of the two Viking Orbiter spacecraft produced a wealth of photos of surface features. Many of these photos can be used to form stereo images allowing the student of Mars to examine a subject in three dimensional. This catalog is a technical guide to the use of stereo coverage within the complex Viking imaging data set.
The first samples of high resolution Viking Orbiter topographic and stratigraphic data for the layered polar deposits of Mars are presented, showing that these deposits are with respect to both slopes and angular relief similar to those in the south. It is also demonstrated that, in conjunction with stereophotogrammetry, photoclinometry holds promise as a tool for detailed layered deposit studies. The spring season photography, which lends itself to photoclinometric analysis, covers the entire area of the north polar deposits. Detailed tests of layered terrain evolution hypotheses will be made, upon refinement of the data by comparison with stereo data. A more promising refining technique will make use of averaging perpendicular to selected sections to enhance SNR. Local reliefs of 200-800 m, and slopes of 1-8 deg, lead to initial calculations of average layer thickness which yields results of 14-46 m, linearly correlated with slope.
It is found that layered ice and dust deposits accumulate on the smooth and banded terrains of the north and south polar cap deposits of Mars, while erosion exposes these layers on the equator-facing slopes of layered terrain. The stripping of layers occurs in areas of strong and multidirectional wind, forming striped terrain. Also noted is the production of steep scarps with crescentic planform by local wind scour, in frequent association with dune fields positioned immediately downwind. Unconformities, which are common within layered deposits in areas of complex topography at the north pole, indicate that deposition episodes of 5-10 layers alternate with the slight erosion of pole-facing trough walls. It is suggested that poles may migrate poleward, replacing the relief increase by depositional infilling when they near the poles.
Photoclinometry is useful for the determination of topography for areas which have a uniform albedo. The technique is applied to early spring Viking images of the Martian north polar cap, taken when the surface was covered by a nearly uniform frost cover. Unlike earlier approaches, the topographic profiling can be used for surfaces with any photometric function, but the strike of the planetary surface relative to the illumination angle must be specified along the profile. The resultant profiles are relatively insensitive to misestimation of the photometric function and slope orientation, but are quite sensitive to the assumed values of the reflectance of an equivalent level surface and the atmospheric opacity (if it is large).
The vertical distribution of the pressure, temperature, and density of the atmosphere varies from day to day. Thus, rates of climb on different days cannot be compared directly, but must be corrected with reference to a standard rate of diminution of air density with increasing altitude. The following problem, therefore, has to be solved. An airplane has climbed on a certain day under prevailing atmospheric conditions as shown by the barograph. How would the same airplane climb in a standard atmosphere? This problem has already been dealt with by Everling, using the monthly and yearly mean of the vertical temperature distribution. Von Mises solved the problem by arithmetical methods. Here, conditions are examined which shorten or lengthen the climbing time. In establishing the corrected barogram, computation seems more practical than graphical treatment. The basis of the answer to the question answered here is summed up in the remark that lift, drag, propeller thrust, and torque and engine power depend only on the density of the air and do not change with the pressure and temperature, provided that the density remains constant.
Santa Barbara Remote Sensing (SBRS), Raytheon Company, is pleased to submit this quarterly progress report of the work performed in the third quarter of Year 2 of the Advanced THEMIS Project, July through September 2002. We review here progress in the proposed tasks. During July through September 2002 progress was made in two major tasks, Spectral Response Characterization and Flight Instrument Definition. Because of staffing problems and technical problems earlier in the program we have refocused the remaining time and budget on the key technical tasks. Current technical problems with a central piece of test equipment has lead us to request a 1 quarter extension to the period of performance. This request is being made through a separate letter independent of this report.
The vortices forming in flowing water behind solid bodies are not represented correctly by the solution of the potential theory nor by Helmholtz's jets. Potential theory is unable to satisfy the condition that the water adheres at the wetted bodies, and its solutions of the fundamental hydrodynamic equations are at variance with the observation that the flow separates from the body at a certain point and sends forth a highly turbulent boundary layer into the free flow. Helmholtz's theory attempts to imitate the latter effect in such a way that it joins two potential flows, jet and still water, nonanalytical along a stream curve. The admissibility of this method is based on the fact that, at zero pressure, which is to prevail at the cited stream curve, the connection of the fluid, and with it the effect of adjacent parts on each other, is canceled. In reality, however, the pressure at these boundaries is definitely not zero, but can even be varied arbitrarily. Besides, Helmholtz's theory with its potential flows does not satisfy the condition of adherence nor explain the origin of the vortices, for in all of these problems, the friction must be taken into account on principle, according to the vortex theorem.
While the importance of dusty asymptotic giant branch (AGB) stars to galactic chemical enrichment is widely recognised, a sophisticated understanding of the dust formation and wind-driving mechanisms has proven elusive due in part to the difficulty in spatially-resolving the dust formation regions themselves. We have observed twenty dust-enshrouded AGB stars as part of the Keck Aperture Masking Experiment, resolving all of them in multiple near-infrared bands between 1.5 m and 3.1 m. We find 45% of the targets to show measurable elongations that, when correcting for the greater distances of the targets, would correspond to significantly asymmetric dust shells on par with the well-known cases of IRC +10216 or CIT 6. Using radiative transfer models, we find the sublimation temperature of Tsub(silicates) = 1130 90K and Tsub(amorphous carbon) = 1170 60 K, both somewhat lower than expected from laboratory measurements and vastly below temperatures inferred from the inner edge of YSO disks. The fact that O-rich and C-rich dust types showed the same sublimation temperature was surprising as well. For the most optically-thick shells ( 2.2 m > 2), the temperature profile of the inner dust shell is observed to change substantially, an effect we suggest could arise when individual dust clumps become optically-thick at the highest mass-loss rates.