High Resolution Imaging Systems For Spin-Stabilized Probe Spacecraft

A novel design for a high-resolution imaging system which includes on-board data editing and optical navigation, suggests high quality images can be acquired from spin-stabilized spacecraft oriented towards high velocity, short duration planetary missions ("Probes"). The approach to designing imaging systems requires that mission objectives be met within the physical and fiscal constraints imposed by the spacecraft and mission design. Severe constraints imposed on a Comet Halley probe (for example, 57km/sec encounter velocity with a small, 10km diameter, object coupled with a great uncertainty in encounter time and distance, were overcome by innovative use of existing technology. Such designs suggest that 3-axis stabilization or non-spinning platforms are not necessary to acquire high resolution, high quality planetary images

Acquisition and description of Mariner 10 television science data at Mercury

The Mariner 10 television science subsystem was an improved version of the Mariner 9 system, using 1500-mm-focal-length optics. An elaborate picture-taking sequence resulted in transmission of over 4000 frames back to earth during two flyby encounters with Mercury. These sequences utilized a real-time data rate of 117.6 kbit/s, resulting in coverage of about 75% of the lighted portion of Mercury's surface at a resolution of better than 2 km. The complete set of useful images, which amounted to about 3000 frames, was processed with three different types of digital image-processing enhancements

High Resolution Imaging Systems For Spin-Stabilized Probe Spacecraft

A novel design for a high-resolution imaging system which includes on-board data editing and optical navigation, suggests high quality images can be acquired from spin-stabilized spacecraft oriented towards high velocity, short duration planetary missions ("Probes"). The approach to designing imaging systems requires that mission objectives be met within the physical and fiscal constraints imposed by the spacecraft and mission design. Severe constraints imposed on a Comet Halley probe (for example, 57km/sec encounter velocity with a small, 10km diameter, object coupled with a great uncertainty in encounter time and distance, were overcome by innovative use of existing technology. Such designs suggest that 3-axis stabilization or non-spinning platforms are not necessary to acquire high resolution, high quality planetary images

Oscillations and velocity structure of a long-lived cyclonic spot

Dark brown cyclonic spots ('barges') at 14°N were studied by using Voyager 1 and 2 images of Jupiter. Movie sequences were made to study the spots' behavior over intervals of 50 days and longer. These movies revealed that the length and width vary by ±9% with a period of about 15 days, while the area remains approximately constant. The horizontal velocity field was investigated for an interval of about 1 day. Flow around the largest barge (feature 6) occurs as a ring current. The vorticity inferred is about 2½ times that of the ambient cyclonic zonal circulation, and about one-half the value of the local planetary vorticity. Length and width variations appear to be associated with a nonzero horizontal divergence field. If the oscillations are a natural mode of the system, the 15-day period will provide an important datum for testing models of stable closed vortices

Acquisition and description of Mariner 10 television science data at Mercury

The Mariner 10 television science subsystem was an improved version of the Mariner 9 system, using 1500-mm-focal-length optics. An elaborate picture-taking sequence resulted in transmission of over 4000 frames back to earth during two flyby encounters with Mercury. These sequences utilized a real-time data rate of 117.6 kbit/s, resulting in coverage of about 75% of the lighted portion of Mercury's surface at a resolution of better than 2 km. The complete set of useful images, which amounted to about 3000 frames, was processed with three different types of digital image-processing enhancements

Martian oases? Feasibility of orbital thermal emission detection

We review the motivation for searching out modem "oases" on Mars, and examine methods of detecting them from orbit. We use the term "oasis" to refer to sites with anomalous thermal behavior at, or near the planet's surface. Such sites may be more likely than other locations on Mars to have liquid water nearby, hence the terminology reminiscent of Earth's deserts. Three types of "oases" are considered here: small-scale volcanic eruptions, hot springs, and subsurface intrusions. The general consensus is that such oases are highly unlikely on Mars today, and probably do not exist at all. How much investment is worthy of such a high-risk, unlikely return? We argue that the potential long-term importance of such a discovery does merit a significant investment. We propose a detection strategy based on a high spatial resolution infra-red thermal emission instrument, though other techniques are briefly discussed. We conclude that such an instrument could feasibly detect surface lavas, and quite likely any surface hot springs, but would not be able to unambiguously determine the presence of a buried geothermal anomaly that does not manifest itself sufficiently at the surface in one of the two other forms

Imaging of the gravitational lens system PG 1115+080 with the Hubble Space Telescope

This paper is the first of a series presenting observations of gravitational lenses and lens candidates, taken with the Wide Field/Planetary Camera (WFPC) of the Hubble Space Telescope (HST). We have resolved the gravitational lens system PG 1115 + 080 into four point sources and a red, extended object that is presumably the lens galaxy; we present accurate relative intensities, colors, and positions of the four images, and lower accuracy intensity and position of the lens galaxy, all at the epoch 1991.2. Comparison with earlier data shows no compelling evidence for relative intensity variations between the QSO components having so far been observed. The new data agree with earlier conclusions that the system is rather simple, and can be produced by the single observed galaxy. The absence of asymmetry in the HST images implies that the emitting region of the quasar itself has an angular radius smaller than about 10 milliarcsec (100 pc for H_0=50, q_0=0.5)

Preliminary imaging results from the second Mercury encounter

The second Mercury encounter has resulted in the acquisition of about 360 pictures of the south polar regions which provide a reliable cartographic and geologic tie between the two sides of the planet photographed on the first encounter. Stereoscopic coverage of large areas of the southern hemisphere was obtained by combining Mercury 1 and 2 pictures taken at different viewing angles. The south polar regions consist of heavily cratered terrain and intercrater plains interspersed with patches of smooth plains. No large areas of smooth plains similar to those surrounding Caloris occur in the south polar regions. No new types of terrain have been recognized, but lobate scarps are common. The second largest basin seen by Mariner 10 (∼600-km diameter) has been confirmed on the new photography. At high solar elevations the surface displays an abundance of rays and rayed craters

Ionization fronts and shocked flows - The structure of the Orion Nebula at 0".1

We present HST Wide-Field Camera images of a field in the Orion Nebula obtained in emission from [S II], Hβ, and [O II]. The morphology of the [S II] emission is markedly different from the other lines. While Hβ and [O II] are distributed fairly smoothly, [S II] is dominated by filamentary features with widths between 0".1 and 1" which sharply highlight ionization fronts moving into dense neutral material. These photoionization fronts act as probes of the structure of the cavity walls of this blister H II region. Their morphology indicates that while the surfaces into which they are moving are textured, subarcsecond clumps with high density contrast are uncommon. An exception is a bow shock-shaped ionization front seen along the face of a solar system-sized (0".6 = 270 AU) clump which is itself seen in extinction. The field contains a number of HH objects and related structures, many of which were previously recognized as such, but whose complex structure is revealed here by the resolution of HST. These include M42 HH 1, which is seen to be an intricate structure of knots and filaments with a head-tail morphology. M42 HH 2 shows structure from both the shocked cavity walls and the shocked atomic outflow. M42 HH 5-7 break into numerous condensations with an appearance reminiscent of HH 7-11. All objects with a bow shockshaped structure (i.e., M42 HH 1, 5, 7, and 10) show enhanced Hβ emission at the apex of the structure where the shock should be strongest. M42 HH 8 and 9 may be HH objects viewed face-on, or alternatively condensations photoionized by a nearby A or B star. Emission from [S II] traces shocks at the walls of an ionized jet apparently emanating from a star in a dark cloud. This cloud seen in extinction is coincident with H_2 Peak 1, which we propose is on the near side of the nebula