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We present results from the first observations of the Hubble Space Telescope (HST) Panchromatic Comparative Exoplanet Treasury program for WASP-101b, a highly inflated hot Jupiter and one of the community targets proposed for the James Webb Space Telescope (JWST) Early Release Science (ERS) program. From a single HST Wide Field Camera 3 observation, we find that the near-infrared transmission spectrum of WASP-101b contains no significant H2O absorption features and we rule out a clear atmosphere at 13 sigma. Therefore, WASP-101b is not an optimum target for a JWST ERS program aimed at observing strong molecular transmission features. We compare WASP-101b to the well-studied and nearly identical hot Jupiter WASP-31b. These twin planets show similar temperature-pressure profiles and atmospheric features in the near-infrared. We suggest exoplanets in the same parameter space as WASP-101b and WASP-31b will also exhibit cloudy transmission spectral features. For future HST exoplanet studies, our analysis also suggests that a lower count limit needs to be exceeded per pixel on the detector in order to avoid unwanted instrumental systematics.

Shallow water bathymetry is important for both safe navigation and natural resource management purposes. Extracting depth information from spectral imagery allows identification of benthic features and characterization of coral reef habitats, especially in remote islands. Techniques have been developed to extract water depth from multispectral imagery (Lyzenga, 1978; Philpot, 1989). These techniques can be difficult to apply in optically shallow waters with heterogeneous bottom types and varying albedo, and require tuning of multiple parameters. An improved algorithm to extract water depth from multispectral satellite imagery was proposed by Stumpf et al. (2003) to generate bathymetric maps with limited a priori information. The algorithm is based on the ratios of transformed reflectance values in the visible bands, retrieving greater depths than previous algorithms and compensating for variable bottom type and albedo. This method requires fewer tunable parameters and can be applied to low-albedo features. Although Stumpf et al. (2003) conclude that the method is robust and works well over variable bottom types, recent studies have pointed out limitations, mostly attributable to varying albedo (Clark, 2005; Densham, 2005). This research attempts to quantify the contribution of variable benthic substrates to the algorithmâ s accuracy by classifying the scene into its main bottom types and tuning the coefficients separately. The algorithm is evaluated using a QuickBird high resolution multispectral image of the remote Midway Atoll, in the Northwestern Hawaiian Islands. Classifying the image into two main bottom types and tuning the coefficients separately produced a small improvement in the accuracy of the bathymetric estimates when bottom reflectance is included as a factor. This result indicates that Stumpf et al. (2003)â s ratio method is not insensitive to variable bottom type, and that knowledge of the distribution and extent of different benthic substrates in optically shallow waters has the potential to improve bathymetric derivation in remote coastal areas such as coral reef environments in the Pacific.

Over a large range of equilibrium temperatures, clouds shape the transmission spectrum of hot Jupiter atmospheres, yet their composition remains unknown. Recent observations show that the Kepler light. curves of some hot Jupiters are asymmetric: for the hottest planets, the light. curve peaks before secondary eclipse, whereas for planets cooler than similar to 1900 K, it peaks after secondary eclipse. We use the thermal structure from 3D global circulation models to determine the expected cloud distribution and Kepler light. curves of hot Jupiters. We demonstrate that the change from an optical light. curve dominated by thermal emission to one dominated by scattering (reflection) naturally explains the observed trend from negative to positive offset. For the cool planets the presence of an asymmetry in the Kepler light curve is a telltale sign of the cloud composition, because each cloud species can produce an offset only over a narrow range of effective temperatures. By comparing our models and the observations, we show that the cloud composition of hot Jupiters likely varies with equilibrium temperature. We suggest that a transition occurs between silicate and manganese sulfide clouds at a temperature near 1600 K, analogous to the L/T transition on brown dwarfs. The cold trapping of cloud species below the photosphere naturally produces such a transition and predicts similar transitions for other condensates, including TiO. We predict that most hot Jupiters should have cloudy nightsides, that partial cloudiness should be common at the limb, and that the dayside hot spot should often be cloud-free.

We have used the Spitzer Space Telescope to observe two transiting planetary systems orbiting low-mass stars discovered in the Kepler K2 mission. The system K2-3 (EPIC 201367065) hosts three planets, while K2-26 (EPIC 202083828) hosts a single planet. Observations of all four objects in these two systems confirm and refine the orbital and physical parameters of the planets. The refined orbital information and more precise planet radii possible with Spitzer will be critical for future observations of these and other K2 targets. For K2-3b we find marginally significant evidence for a transit timing variation between the K2 and Spitzer epochs.

Hydrogen gas evaporating from the atmosphere of the hot-Neptune GJ436b absorbs over 50% of the stellar Lya emission during transit. Given the planet's atmospheric composition and energy-limited escape rate, this hydrogen outflow is expected to entrain heavier atoms such as C and O. We searched for C and Si in the escaping atmosphere of GJ436b using far-ultraviolet Hubble Space Telescope COS G130M observations made during the planet's extended H I transit. These observations show no transit absorption in the C II 1334,1335 angstrom and Si III 1206 angstrom lines integrated over [-100, 100] km s(-1), imposing 95% (2 sigma) upper limits of 14% (C II) and 60% (Si III) depth on the transit of an opaque disk and 22% (C II) and 49% (Si III) depth on an extended highly asymmetric transit similar to that of H I Ly alpha. C+ is likely present in the outflow according to a simulation we carried out using a spherically symmetric photochemical-hydrodynamical model. This simulation predicts an similar to 2% transit over the integrated bandpass, consistent with the data. At line center, we predict the C II transit depth to be as high as 19%. Our model predicts a neutral hydrogen escape rate of 1.6 x 10(9) g s(-1) (3.1 x 10(9) g s(-1) for all species) for an upper atmosphere composed of hydrogen and helium.

Tsz-Shing Tam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 84-87). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgments --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Literature Review --- p.6 / Chapter 3 --- System Model --- p.12 / Chapter 3.1 --- Static Architecture --- p.12 / Chapter 3.2 --- Dynamics --- p.15 / Chapter 3.3 --- Communication Paradigm --- p.16 / Chapter 3.4 --- Metric --- p.17 / Chapter 4 --- Routing Algorithms --- p.19 / Chapter 4.1 --- Minimum Hops Algorithm (MHA) --- p.20 / Chapter 4.2 --- Minimum Cost Algorithm (MCA) --- p.21 / Chapter 4.3 --- Mesh Algorithm (MA) --- p.24 / Chapter 4.3.1 --- Construction of the Set of Min-hop Paths --- p.24 / Chapter 4.3.2 --- Choosing a Path in S0 --- p.29 / Chapter 4.4 --- k-mesh Algorithm (KMA) --- p.29 / Chapter 4.4.1 --- Finding Sk --- p.30 / Chapter 4.4.2 --- Choosing a path in Sk --- p.34 / Chapter 4.5 --- Revised Mesh Algorithm (RMA) --- p.34 / Chapter 5 --- Reservation Strategies --- p.36 / Chapter 5.1 --- Introduction --- p.36 / Chapter 5.2 --- Notations --- p.38 / Chapter 5.3 --- Basic Reservation Strategy (BRS) --- p.39 / Chapter 5.4 --- Enhanced Reservation Strategy (ERS) --- p.41 / Chapter 5.5 --- Successor Reservation Strategy (SRS) --- p.43 / Chapter 6 --- Experiment --- p.45 / Chapter 6.1 --- Comparison on Routing Algorithms --- p.47 / Chapter 6.2 --- Comparison on Reservation Strategies --- p.64 / Chapter 7 --- Conclusion --- p.72 / Chapter A --- Existence of paths in Sk --- p.75 / Chapter B --- Estimation of basic reservation strategy guaranteed time --- p.79 / Chapter B.1 --- Basic reservation strategy --- p.79 / Chapter B.2 --- Estimation on Guaranteed Duration --- p.80 / Bibliography --- p.83

Detailed observations of geosynchronous satellites from earth are very limited. To better inspect these high altitude satellites, the use of small, refuelable satellites is proposed. The small satellites are stationed on a carrier platform in an orbit near the population of geosynchronous satellites. A carrier platform equipped with deployable, refuelable SmallSats is a viable option to inspect geosynchronous satellites. The propellant requirement to transfer to a targeted geosynchronous satellite, perform a proximity inspection mission, and transfer back to the carrier platform in a nearby orbit is determined. Convex optimization and traditional optimization techniques are explored, determining minimum propellant trajectories. Propellant is measured by the total required change in velocity, delta-v. The trajectories were modeled in a relative reference frame using the Clohessy-Wiltshire equations. Mass estimations for the carrier platform and the SmallSat were determined by using the rocket equation. The mass estimates were compared to the mass of a single, non-refuelable satellite performing the same geosynchronous satellite inspection missions. From the minimum delta-v trajectories and the mass analysis, it is determined that using refuelable SmallSats and a carrier platform in a nearby orbit can be more effcient than using a single non-refuelable satellite to perform multiple geosynchronous satellite inspections.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves.

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