We present spectrophotometry spanning 1-5 mu m of 51 Eridani b, a 2-10 M-Jup planet discovered by the Gemini Planet Imager Exoplanet Survey. In this study, we present new K1 (1.90-2.19 mu m) and K2 (2.10-2.40 mu m) spectra taken with the Gemini Planet Imager as well as an updated L-P (3.76 mu m) and new M-S (4.67 mu m) photometry from the NIRC2 Narrow camera. The new data were combined with J (1.13-1.35 mu m) and H (1.50-1.80 mu m) spectra from the discovery epoch with the goal of better characterizing the planet properties. The 51 Eri b photometry is redder than field brown dwarfs as well as known young T-dwarfs with similar spectral type (between T4 and T8), and we propose that 51 Eri b might be in the process of undergoing the transition from L-type to T-type. We used two complementary atmosphere model grids including either deep iron/silicate clouds or sulfide/salt clouds in the photosphere, spanning a range of cloud properties, including fully cloudy, cloud-free, and patchy/intermediate-opacity clouds. The model fits suggest that 51 Eri. b has an effective temperature ranging between 605 and 737 K, a solar metallicity, and a surface gravity of log(g) = 3.5-4.0 dex, and the atmosphere requires a patchy cloud atmosphere to model the spectral energy distribution (SED). From the model atmospheres, we infer a luminosity for the planet of -5.83 to -5.93 (logL/L circle dot),leaving 51 Eri b in the unique position of being one of the only directly imaged planets consistent with having formed via a cold-start scenario. Comparisons of the planet SED against warm-start models indicate that the planet luminosity is best reproduced by a planet formed via core accretion with a core mass between 15 and 127 M-circle plus.

This dissertation combines several new observations of the Io sodium cloud to create a consistent picture of the extended Io atmosphere and its interaction with the Jovian plasma torus. I used the LPL echelle spectrograph to obtain three types of high-resolution spectra of the extended sodium cloud at the sodium D-lines (5890, 5896Å). The first class of observations made use of the mutual satellite eclipses of 1985 to probe the density profile of the atmosphere in the range 1.4 to 10 Io radii, a previously unstudied region. The second type of observation examined the sodium emission in Io's immediate vicinity, allowing an accurate measurement of the velocity structure around Io. The final method employed a high-sensitivity detector to study faint jets of high-speed sodium farther out in the extended cloud. The synthesis of these three data sets results in a better understanding of how sodium is distributed about Io as a function of position and velocity. Io's extended atmosphere is composed of many kinematically distinct components. The distribution in space is linked to their characteristic velocities, with low-energy sodium confined near Io and faster atoms (10 to 100 km sec⁻¹) prevalent beyond ∼25 Io radii. The sodium density profile is steep near Io and shallower outside 5.6 Io radii, the effective limit of Io's gravity. The data indicate that the atmosphere is collisionally thick near the surface, but becomes thin by an altitude of ∼700 km. The upper limit of the exobase location is derived from reliable sodium density measurements made during the satellite eclipses. The lower limit is indirectly inferred from the velocity distribution of sodium near Io and the nature of high-speed jets far from Io. The high-speed sodium jets reveal a new type of close interaction between the corotating plasma and Io's atmosphere. The morphology and brightness of the jets require a two-reaction process, in which atmospheric sodium is ionized, accelerated to high speeds, and then charge-exchanges with other sodium atoms. These processes must occur near the atmospheric exobase, indicating that Io's atmosphere is not completely protected from the plasma flow.

The design of BOLTS (Broad Area Lightning Telescope Sensor) is presented. This sensor will provide full-time (day/night) coverage of the continental U.S. from a geosynchronous orbit. The average ground resolution will be 8 km and the system will be able to detect ≃ 10⁷ watt strokes during nighttime and ≃ 4 x 10⁷ watt strokes during daytime with a probability of detection of 0.9. We present the system's requirements and projected performance, together with the design rationale. Contrast enhancement is achieved using a narrow band interference filter deposited on a curved surface inside the F/2.5, 101.7 mm optical system. Deposition of the interference layers on the curved surface reduce the passband wandering caused by off-axis bundles. The focal plane constitutes an 800 x 800 element virtual phase CCD array with a multiple outputs option. The central 800 x 400 elements are used for imaging while the outer 2x (800 x 200) elements serve as buffer memory for one frame storage. An additional 2x (800 x 200) array serves for storing a second frame. Signal detection is achieved via a frame-to-frame subtraction algorithm that is hardware implemented immediately following the CCD arrays. An integration time of 5 msec is used, which stems from SNR optimization requirements and from the fact that lightning strokes occur randomly in time and space. The data obtained after frame-to-frame subtraction is subjected to a threshold test and the resulting positive events are digitized and stored in an on-board digital memory using 48 bits/event. Each record contains intensity information over a dynamic range of 4000, location information and time of occurrence information. A prototype instrument built to perform measurements from aboard a U-2 plane is described. The purpose of this instrument is to refine some of the lightning data used in defining the system's parameters. A short discussion about the changes required to expand the design to either a global coverage instrument or a high resolution, smaller field instrument is presented.

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

No description available.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / The Consultative Committee on Space Data Systems (CCSDS) did not create a specification like the IRIG 106, but rather a recommendation [1-4]. That means that each country, community, and application is free to select subsets, adapt techniques, and even alter the structure to suit particular needs. This variability places new demands on a decommutation system. The implementation of the CCSDS Recommendation in the Loral 550 accommodates this "variability within a structure" by using a modular and adaptable collection of structured components. The result covers the two most popular versions of CCSDS: Conventional/Telecommand and the Advanced Orbital Systems (AOS) in both operational and test modes, and couples the CCSDS inputs and outputs to a host of other data format and processing options.

Approved for public release; distribution is unlimited. / NPSAT1 is a gravity-gradient friendly, prolate body designed to fly at 600 Å 40 km inclined to 34.5 degrees. The satellite uses a magnetic 3-axis active attitude control system (ACS) using magnetic torque rods that interact with the Earth's magnetic field. This thesis accomplishes three goals. The first objective was to verify and to validate the magnetic attitude control system program and model developed by Leonard. The verification and validation process was completed in two steps. The first step accomplished an independent modeling of the Earth's magnetic field using MATLAB. The second step completed a verification via inspection of Leonard's ACS SIMULINK model. The verification confirmed that Leonard's modular sub-components of the disturbance torques, the quaternion vectors, the Euler angles, the spacecraft kinematics and dynamics, and the ACS control laws conformed to current ACS empirical theory. The second goal was to establish a laboratory used to demonstrate the ACS robustness and ability to perform as designed. The laboratory was created to house an air-bearing platform that simulates NPSAT1 characteristics. The third goal was to perform hardware-in-the-loop experiments with the NPSAT1 ACS software and model. Hardwarein- the-loop tests were performed to the magnetic torque rods, torque rod driver circuit board, micro-controller computer, and control interfaces. Specifically, solenoid current tests, magnetic field determination tests, and digital-to-analog conversion tests were completed. / Lieutenant Commander, United States Navy

The warfighter constantly needs increased accuracy from GPS and a means to increasing this accuracy to the decimeter level is a broadcast ephemeris message containing GPS satellite orbit and clock corrections. The ephemeris message is produced at the GPS MCS (Master Control Station) which receives GPS signal data from NGA and Air Force worldwide and uses sophisticated software to produce the orbit and clock corrections. The problem is getting the ephemeris message to the tactical user in a forward operating area. This thesis proposed a notional architecture for pushing the ephemeris message to the tactical user. It then modeled the architecture and simulated the broadcast of the ephemeris message to a tactical user using NETWARS. The baseline architecture was simulated and analyzed and then additional constraints were placed upon the network to simulate a real-world model. The simulation results demonstrated that the architecture was feasible for ephemeris message broadcast with the constraints on time intervals between broadcasts, residual traffic and message size.

The concept of controlling optical laser beams on spacecraft for acquisition, tracking and pointing purposes is quickly becoming a reality. As a result, fine pointing of laser beams is turn out to be an increasingly important research topic. A unique testbed was constructed in order to study and develop new methods for laser beam control. This testbed, the Moving Target-Source Test Fixture (MTSTF), hosts a laser source, the Extremely Agile Relaying Laser Source (EARLS), which has the capability of automatically acquiring and directing a laser beam onto a satellite simulator while in motion. The purpose of this thesis is to make the EARLS platform operational by developing a tracking control system. The ultimate goal is to point the laser beam at the satellite simulatorâ s receiving telescope and maintain the laser within the telescopeâ s limits in the presence of structural disturbance induced by the EARLS motion.

en the connection is idle. Research into available amateur radio satellite assets lead to testing Automated Position Reporting System (APRS) satellites and terrestrial networks for common operational picture development in large geographical areas either too remote for common infrastructure or affected by disasters. The expansion of CENETIX's research opportunities led us to explore DIRECWAY and iDirect technologies as methods for expanding the Tactical Network Topology (TNT) network, and to test Nemesis' new DIRECWAY functionality. Additionally, we explored potential communications usage for future satellites in The Office of the Secretary of Defense's TacSat program.