Small spacecraft power and thermal subsystems

This white paper provides a general guide to the conceptual design of satellite power and thermal control subsystems with special emphasis on the unique design aspects associated with small satellites. The operating principles of these technologies are explained and performance characteristics of current and projected components are provided. A tutorial is presented on the design process for both power and thermal subsystems, with emphasis on unique issues relevant to small satellites. The ability of existing technology to meet future performance requirements is discussed. Conclusions and observations are presented that stress cost-effective, high-performance design solutions

High fidelity imaging of geosynchronous satellites with the MROI

Interferometry currently provides the only practicable way to image satellites in Geosynchronous Earth Orbit (GEO) with sub-meter spatial resolution. The Magdalena Ridge Observatory Interferometer (MROI) is being funded by the US Air Force Research Laboratory to demonstrate the 9.5 magnitude sensitivity (at 2.2 µm wavelength) and baseline-bootstrapping capability that will be needed to realize a useful turn-key GEO imaging capability. This program will utilize the central three telescopes of the MROI and will aim to validate routine acquisition of fringe data on faint well-resolved targets. In parallel with this effort, the University of Cambridge are investigating the spatial resolution and imaging fidelity that can be achieved with different numbers of array elements. We present preliminary simulations of snapshot GEO satellite imaging with the MROI. Our results indicate that faithful imaging of the main satellite components can be obtained with as few as 7 unit telescopes, and that increasing the number of telescopes to 10 improves the effective spatial resolution from 0.75 meter to 0.5 meter and enables imaging of more complex targets.This is the author accepted manuscript. The final version is available from SPIE via http://dx.doi.org/10.1117/12.223247

Prediction of heat of melting and heat capacity of inorganic liquids by the method of group contributions

Complex salts and salt/oxide combinations are being considered for the immobilization and storage or disposal of hazardous or radioactive wastes. There is very little information concerning such fundamental properties as heat of fusion and heat capacities for many of these inorganic materials. This work focuses on the use of elements or simple functional groups to estimate some of these fundamental thermodynamic properties for a variety of inorganic compounds. The major emphasis will be on properties for a variety of inorganic compounds. The major emphasis will be on properties for which some ancillary information may be easily measured, but which may be very difficult to measure directly. An example of such a property is the heat of fusion (or melting). The melting temperature for most pure materials is relatively easy to measure. However, the actual amount of energy required to liquefy, or conversely, the amount of energy which must be removed to solidify those same materials has not been measured. Similarly, important properties such as heat capacities of liquids are unavailable for many compounds. Such information is essential in the chemical industry and are paramount for chemical engineers if they are to design, build and operate plants and facilities in an economical and efficient manner

The cool atmospheres of the binary brown dwarf eps Indi B

We have imaged $\epsilon$ Indi B, the closest brown dwarf binary known, with VISIR at the VLT in three narrow-band mid-infrared bandpasses located around 8.6$\mu$m, 10.5$\mu$m and 11.3$\mu$m. We are able to spatially resolve both components, and determine accurate mid-infrared photometry for both components independently. In particular, our VISIR observations probe the NH$_3$ feature in the atmospheres of the cooler and warmer brown dwarfs. For the first time, we can disentangle the contributions of the two components, and find that % our photometry of $\epsilon$ IndiBb is in good agreement with recent ``cloud-free'' atmosphere models having an effective temperature of $T_\mathrm{eff}=800$ K. With an assumed age of 1 Gyr for the $\epsilon$ Indi system, component Ba agrees more with $T_\mathrm{eff} \approx 1100$ K rather than with $T_\mathrm{eff}=1200$ K, as suggested by SPITZER spectroscopic observations of the combined $\epsilon$ Indi B system (Roellig et al., 2004). Even higher effective temperatures appear inconsistent with our absolute photometry, as they would imply an unphysical small size of the brown dwarf $\epsilon$ IndiBa.Comment: 4 pages, 2 figure

Planet Formation Imager (PFI): Introduction and Technical Considerations

Complex non-linear and dynamic processes lie at the heart of the planet formation process. Through numerical simulation and basic observational constraints, the basics of planet formation are now coming into focus. High resolution imaging at a range of wavelengths will give us a glimpse into the past of our own solar system and enable a robust theoretical framework for predicting planetary system architectures around a range of stars surrounded by disks with a diversity of initial conditions. Only long-baseline interferometry can provide the needed angular resolution and wavelength coverage to reach these goals and from here we launch our planning efforts. The aim of the "Planet Formation Imager" (PFI) project is to develop the roadmap for the construction of a new near-/mid-infrared interferometric facility that will be optimized to unmask all the major stages of planet formation, from initial dust coagulation, gap formation, evolution of transition disks, mass accretion onto planetary embryos, and eventual disk dispersal. PFI will be able to detect the emission of the cooling, newly-formed planets themselves over the first 100 Myrs, opening up both spectral investigations and also providing a vibrant look into the early dynamical histories of planetary architectures. Here we introduce the Planet Formation Imager (PFI) Project (www.planetformationimager.org) and give initial thoughts on possible facility architectures and technical advances that will be needed to meet the challenging top-level science requirements.Comment: SPIE Astronomical Telescopes and Instrumentation conference, June 2014, Paper ID 9146-35, 10 pages, 2 Figure

Infrared interferometric observations of young stellar objects

We present infrared observations of four young stellar objects using the Palomar Testbed Interferometer (PTI). For three of the sources, T Tau, MWC 147 and SU Aur, the 2.2 micron emission is resolved at PTI's nominal fringe spacing of 4 milliarcsec (mas), while the emission region of AB Aur is over-resolved on this scale. We fit the observations with simple circumstellar material distributions and compare our data to the predictions of accretion disk models inferred from spectral energy distributions. We find that the infrared emission region is tenths of AU in size for T Tau and SU Aur and ~1 AU for MWC 147.Comment: 11 pages, 3 figures, to appear in the Astrophysical Journa

X-Ray Emission from Young Stars in the Massive Star Forming Region IRAS 20126+4104

We present a $40\,$ks Chandra observation of the IRAS$\,$20126+4104 core region. In the inner $6^{\prime\prime}$ two X-ray sources were detected, which are coincident with the radio jet source I20S and the variable radio source I20Var. No X-ray emission was detected from the nearby massive protostar I20N. The spectra of both detected sources are hard and highly absorbed, with no emission below $3\,$keV. For I20S, the measured $0.5-8\,$keV count rate was $4.3\,$cts$\,$ks$^{-1}$. The X-ray spectrum was fit with an absorbed 1T APEC model with an energy of kT$\,=10\,$keV and an absorbing column of N$_H = 1.2\times 10^{23}\,$cm$^{-2}$. An unabsorbed X-ray luminosity of about $1.4\times 10^{32}\,$erg$\,$s$^{-1}$ was estimated. The spectrum shows broad line emission between 6.4 and 6.7\, keV, indicative of emission from both neutral and highly ionized iron. The X-ray lightcurve indicates that I20S is marginally variable; however, no flare emission was observed. The variable radio source I20Var was detected with a count rate of $0.9\,$cts$\,$ks$^{-1}$ but there was no evidence of X-ray variability. The best fit spectral model is a 1T APEC model with an absorbing hydrogen column of N$_H = 1.1\times 10^{23}\,$cm$^{-2}$ and a plasma energy of kT = 6.0$\,$keV. The unabsorbed X-ray luminosity is about $3\times 10^{31}\,$erg$\,$s$^{-1}$.Comment: 17pages, 4 figures to appear in Astronomical Journa