N. Mastrodemos

One of the most plausible scenarios for the formation of asymmetric molecular envelopes from AGB stars and bipolar preplanetary nebulae, involves a mass losing red giant in the presence of a binary companion in a detached or common envelope configuration. The likelihood of the detached binary system scenario in the formation of asymmetric and bipolar flows is assessed by constructing 3-Dimensional Smooth Particle Hydrodynamic wind models. We investigate the effects of the binary companion, on an otherwise spherically symmetric dust-driven wind, as a function of the binary mass ratio and separation and we examine the importance of various heating and cooling mechanisms. We also produce models of outflows emanating from a tidally spun-up primary. In particular we examine whether appropriate conditions can arise that will allow the formation of an accretion disk around the secondary and of an exterior disk beyond the outer Lagrangian point of the system as proposed by Morris (1987,PASP...

Lunar topography is being created at several hundred meter resolution by applying stereophotoclinometry to Clementine and Lunar Orbiter images. This will provide a framework for the rapid inclusion of data from current and upcoming missions.

Detailed global and local digital topographies of eight of Saturn's satellites are being constructed from ensembles of overlapping maplets which completely cover the visible surfaces. Each maplet is a digital representation of a piece of the surface topography and albedo constructed from imaging data with stereophotoclinometry. Multiple images projected onto the maplet provide brightness values at each pixel which are used in a least-squares estimation for slope and relative albedo. The slopes are then integrated to produce the topography solution. The central pixel of each maplet represents a control point, and the ensemble of these points is used in an estimation for their body-fixed locations, the rotational state of the body, and the position and attitude of the spacecraft. Applications of these data products include studies of cratering of icy bodies and the subsequent relaxation of the surface, while detailed shapes for the small, irregular satellites can be used to predic...

ABSTRACT This year two spacecraft, MESSENGER and Dawn, were placed into orbit around Mercury and the asteroid Vesta, respectively. We have been using stereophotoclinometry (SPC) to analyze MESSENGER and Dawn images both for navigation and to determine the precise shapes and topography of these bodies. Because SPC requires images at different local Sun elevations and azimuths to distinguish between albedo and topographic variations, Mercury presents the challenges of a slow spin rate and a long solar day. Vesta, on the other hand, rotates more than four times per Earth day, allowing a given area of surface to be viewed under rapidly changing illumination and topographic information to be built up rapidly. The essence of SPC is that small pieces of surface called maplets and modeled with digital elevation and albedo are illuminated and correlated with images. Hundreds of these maplets are found in each image, providing a valuable data type for spacecraft navigation. Hundreds of images go into the construction of each maplet, and the resulting multi-image stereo over a wide range of viewing conditions provides a precise determination of the maplet's body-fixed position. The construction of topography with SPC uses each pixel, allowing resolutions comparable to the images themselves. Mercury's topography varies by about 5 km above and below that of a sphere of radius 2440 km. We compare the SPC-derived shape and topography with data from MESSENGER's Mercury Laser Altimeter (MLA). Vesta, although a tenth of Mercury's size, exhibits variations in elevation between 17 km below and 12 km above the equipotential that best matches its surface. The lowest areas lie on the floor of the south polar impact crater, and the highest points lie on the crater's rim.

Page 1. Space Sci Rev DOI 10.1007/s11214-011-9863-z The Dawn Topography Investigation CA Raymond · R. Jaumann · A. Nathues · H. Sierks · T. Roatsch · F. Preusker · F. Scholten · RW Gaskell · L. Jorda · H.-U. Keller · MT Zuber · DE Smith · N. Mastrodemos · S. Mottola ...

Calibration of NASA's Deep Impact spacecraft instruments allows reliable scientific interpretation of the images and spectra returned from comet Tempel 1. Calibrations of the four onboard remote sensing imaging instruments have been performed in the areas of geometric calibration, spatial resolution, spectral resolution, and radiometric response. Error sources such as noise (random, coherent, encoding, data compression), detector readout artifacts, scattered light, and radiation interactions have been quantified. The point spread functions (PSFs) of the medium resolution instrument and its twin impactor targeting sensor are near the theoretical minimum [~1.7 pixels full width at half maximum (FWHM)]. However, the high resolution instrument camera was found to be out of focus with a PSF FWHM of ~9 pixels. The charge coupled device (CCD) read noise is ~1 DN. Electrical cross-talk between the CCD detector quadrants is correctable to <2 DN. The IR spectrometer response nonlinearity is correctable to ~1%. Spectrometer read noise is ~2 DN. The variation in zero-exposure signal level with time and spectrometer temperature is not fully characterized; currently corrections are good to ~10 DN at best. Wavelength mapping onto the detector is known within 1 pixel; spectral lines have a FWHM of ~2 pixels. About 1% of the IR detector pixels behave badly and remain uncalibrated. The spectrometer exhibits a faint ghost image from reflection off a beamsplitter. Instrument absolute radiometric calibration accuracies were determined generally to <10% using star imaging. Flat-field calibration reduces pixel-to-pixel response differences to ~0.5% for the cameras and <2% for the spectrometer. A standard calibration image processing pipeline is used to produce archival image files for analysis by researchers.

ABSTRACT The Dawn gravity investigation utilizes the precision X-band Doppler tracking and landmark tracking from optical images to measure the gravity fields of Vesta to a half-wavelength surface resolution better than 90-km. For given error budget assumptions, the spherical harmonic gravity field will be determined to somewhere between degrees 15 and 25. The gravity fields together with shape models determined from Dawn's framing camera constrain models of the interior from the core to the crust. The gravity field is determined jointly with the spin pole location, rotation, Vesta ephemeris and spacecraft modeling parameters; precision orbits incorporating surface landmarks from images will be used to improve positioning to aid in geodetic control. The second-degree harmonics together with assumptions on obliquity or hydrostatic equilibrium may determine the moments of inertia; they constrain the core size and density. To date, data from the survey and high altitude orbital phases (HAMO) have lead to a determination of GM to better than 0.1 percent and a gravity field of degree 6 with 140-km resolution. J2 is consistent with the core size of one half the mean radius. Models of crustal and mantle structure will be developed constrained by bulk composition estimates derived from HED meteorites and observations of surface composition from Dawn's VIR.

We present a high-resolution global topography model (GTM) of Saturn's satellite Phoebe, derived from Cassini images taken during the flyby on June 11, 2004. The model is composed of about 1.57 million vectors and was synthesized from 523 maplets. Each maplet is a 99x99 pixel topography and albedo map constructed from the ensemble of images using stereophotoclinometry. The central point of each maplet is a control point. The 523 control points were determined from 22708 observations, about 43 per control point, and the RMS measurement residuals were about 180 meters per degree of freedom. The model has a volume of about 5 million cubic kilometers and a surface area of about 150000 square kilometers, so the model's resolution is about 300 m. The pole was determined from the set of control points to be at RA 356.86 +/- .02 degrees and DEC 77.878 +/- .004 degrees. This study is part of ongoing work on Saturn's satellites. We shall also present preliminary models for several...

This data set contains raw comet 9P/Tempel 1 and calibration images acquired by the Deep Impact Impactor Targeting Sensor Visible CCD during the encounter phase of the mission. These observations were used for optical and autonomous navigation (NAV) of the impactor spacecraft as well as for scientific investigations. These data were collected from 6 May to 4 July 2005. In this version 1.1 of the data set, the values for the INTEGRATION_DURATION keyword in the PDS data labels were corrected. This revised data set supersedes version 1.0.

This data set contains raw calibration and test images acquired by the Deep Impact High Resolution Instrument Visible CCD during the cruise phase of the mission. These observations were used for optical and autonomous navigation (NAV) of the flyby spacecraft. These data were collected from 14 January to 25 April 2005. Test images of comet 9P/Tempel 1 were acquired on 25 April.

This data set contains raw calibration and test images acquired by the Deep Impact Medium Resolution Instrument Visible CCD during the cruise phase of the mission. These observations were used for optical and autonomous navigation (NAV) of the flyby spacecraft. These data were collected from 14 January to 25 April 2005. Test images of comet 9P/Tempel 1 were acquired on 25 April. In this version 1.1 of the data set, the values for the INTEGRATION_DURATION keyword in the PDS data labels were corrected. This revised data set supersedes version 1.0.

While Deep Impact was approaching 9P/Tempel 1, three outbursts were observed. The first occured on June 14 and was first reported by L. Lara It was also seen in data from HST and DI. No reports have been received of other detections of the outburst on June 22, even though the cometary brightness, as observed at 4-hour intervals by DI,

The Deep Impact (DI) project provided unprecedented, intensive monitoring of comet Tempel 1 not only by the DI spacecraft, but also by numerous ground-based and Earth-orbital facilities. This led to the serendipitous discovery of frequent, small outbursts by the comet prior to impact. The initial realization of outbursts came from processed observations at Calar Alto (Lara 2005) but a combination