Space shuttle post-entry and landing analysis. Volume 2: Appendices

Four candidate navigation systems for the space shuttle orbiter approach and landing phase are evaluated in detail. These include three conventional navaid systems and a single-station one-way Doppler system. In each case, a Kalman filter is assumed to be mechanized in the onboard computer, blending the navaid data with IMU and altimeter data. Filter state dimensions ranging from 6 to 24 are involved in the candidate systems. Comprehensive truth models with state dimensions ranging from 63 to 82 are formulated and used to generate detailed error budgets and sensitivity curves illustrating the effect of variations in the size of individual error sources on touchdown accuracy. The projected overall performance of each system is shown in the form of time histories of position and velocity error components

SMC SMP 24: A newly radio-detected planetary nebula in the small magellanic cloud

In this paper we report new radio-continuum detection of an extragalactic PN: SMC SMP 24. We show the radio-continuum image of this PN and present the measured radio data. The newly reduced radio observations are consistent with the multi-wavelength data and derived parameters found in the literature. SMC SMP 24 appear to be a young and compact PN, optically thick at frequencies below 2 GHz.Comment: accepted for publication in Serbian Astronomical Journa

Homoclinic snaking in bounded domains

Homoclinic snaking is a term used to describe the back and forth oscillation of a branch of time-independent spatially localized states in a bistable, spatially reversible system as the localized structure grows in length by repeatedly adding rolls on either side. On the real line this process continues forever. In finite domains snaking terminates once the domain is filled but the details of how this occurs depend critically on the choice of boundary conditions. With periodic boundary conditions the snaking branches terminate on a branch of spatially periodic states. However, with non-Neumann boundary conditions they turn continuously into a large amplitude filling state that replaces the periodic state. This behavior, shown here in detail for the Swift-Hohenberg equation, explains the phenomenon of “snaking without bistability”, recently observed in simulations of binary fluid convection by Mercader, Batiste, Alonso and Knobloch (preprint)

Losing Weight: A KECK Spectroscopic Survey of the Massive Cluster of Galaxies RX J1347-1145

We present a sample of 47 spectroscopically confirmed members of RX J1347-1145, the most luminous X-ray cluster of galaxies discovered to date. With two exceptions, all the galaxies in this sample have red B-R colors and red spectral indices, with spectra similar to old local ellipticals. Using all 47 cluster members, we derive a mean redshift of 0.4509\pm 0.003, and a velocity dispersion of 910\pm130 km/sec, which corresponds to a virial mass of 4.4 x 10^{14} h^{-1} Solar masses with an harmonic radius of 380 h^{-1} kpc. The derived total dynamical mass is marginally consistent with that deduced from the cluster's X-ray emission based on the analysis of ROSAT/ASCA images (Schindler et al. 1997), but not consistent with the more recent X-ray analyses of Allen (2000), Ettori, Allen & Fabian (2001) and Allen, Schmidt & Fabian (2002). Furthermore, the dynamical mass is significantly smaller than that derived from weak lensing (Fischer & Tyson 1997) and from strong lensing (Sahu et al. 1998). We propose that these various discrepant mass estimates may be understood if RX J1347-1145 is the product of two clusters caught in the act of merging in a direction perpendicular to the line of sight, although there is no evidence from the galaxy redshift distribution supporting this hypothesis. Even with this hypothesis, a significant part of the extremely high X-ray luminosity must still arise from non-virialized, presumably shocked, gas. Finally, we report the serendipitous discovery of a lensed background galaxy at z=4.083 which will put strong constraints on the lensing mass determination once its counter-image is securely identified.Comment: Minor changes to conform to version accepted by Ap

A simple derivation of the electromagnetic field of an arbitrarily moving charge

The expression for the electromagnetic field of a charge moving along an arbitrary trajectory is obtained in a direct, elegant, and Lorentz invariant manner without resorting to more complicated procedures such as differentiation of the Lienard-Wiechert potentials. The derivation uses arguments based on Lorentz invariance and a physically transparent expression originally due to J.J.Thomson for the field of a charge that experiences an impulsive acceleration.Comment: The following article has been accepted by the American Journal of Physics. After it is published, it will be found at http://scitation.aip.org/ajp; 12 pages, 1 figur

X-ray emission from the field of the hyperluminous IRAS galaxy IRASF15307+3252

We report on a 20-ks observation of the z = 0.93 hyperluminous galaxy IRAS F15307+3252 with the ROSAT HRI. No X-ray source is detected at the position of F15307+3252 at an upper limit of ∼4 × 10⁴³ erg s⁻¹. This is less than 2 × 10⁻⁴ of the bolometric luminosity of the object, and indicates either that the nucleus emits an unusually small fraction of its total power in X-rays, or that little of the nuclear X-ray flux is scattered into our line of sight by electrons. The lack of an X-ray detection around F15307+3252 also rules out it being at the centre of a cluster, such as is observed for IRAS P09104+4109. A weak, possibly extended, X-ray source is detected 13 arcsec south of the galaxy, spatially coincident with a clump of faint objects visible in a Keck K_s-band image of the field. This may be the core of a cluster near the line of sight to F15307+3252

LRS-II: A Specialized Knowledge System For Launch Resource Scheduling

This research used the Level 5 expert system software to develop a specialized knowledge system called the Launch Resource Scheduling system (LRS-II). LRS-II will be used as a decision aid by USSPACECOM to determine if there is sufficient launch capability to meet future satellite requirements and to quickly assess the impact of contingencies such as launch or on-orbit failures. LRS-II uses multiple knowledge bases to match satellite launch requirements to available launch vehicles, launch pads, and upper stages. Specialized knowledge about resources are stored in dBase III files, specific fields of the satellite record records to schedule the earliest launch requirement. During manifesting, the constraints of satellite and resource availability, site processing time, shuttle mission duration, and satellite on-orbit checkout time are used to insure the selected launch date is accurate