On adaptive multiband signal detection with GLR algorithm

An adaptive multiband detector based on the principle of the generalized likelihood ratio test (GLR) is presented. Its detection performance is studied and compared with that of the corresponding single-band GLR detector. The multiband detector is shown to significantly outperform the single-band under the chosen system constraint, especially when the amount of data available from a single frequency band is severely limited by the environment     

Global Imaging of Proton and Electron Aurorae in the far Ultraviolet

The IMAGE spacecraft carries three FUV photon imagers, the Wideband Imaging Camera (WIC) and two channels, SI-12 and SI-13, of the Spectrographic Imager. These provide simultaneous global images, which can be interpreted in terms of the precipitating particle types (protons and electrons) and their energies. IMAGE FUV is the first space-borne global imager that can provide instantaneous global images of the proton precipitation. At times a bright auroral spot, rich in proton precipitation, is observed on the dayside, several degrees poleward of the auroral zone. The spot was identified as the footprint of the merging region of the cusp that is located on lobe field lines when IMF B_z was northward. This identification was based on compelling statistical evidence showing that the appearance and location of the spot is consistent with the IMF B_z and B_y directions. The intensity of the spot is well correlated with the solar wind dynamic pressure and it was found that the direct entry of solar wind particles could account for the intensity of the observed spot without the need for any additional acceleration. Another discovery was the observation of dayside sub-auroral proton arcs. These arcs were observed in the midday to afternoon MLT sector. Conjugate satellite observations showed that these arcs were generated by pure proton precipitation. Nightside auroras and their relationship to substorm phases were studied through single case studies and in a superimposed epoch analysis. It was found that generally there is substantial proton precipitation prior to substorms and the proton intensity only doubles at substorm onset while the electron auroral brightness increases on average by a factor of 5 and sometimes by as much as a factor of 10. Substorm onset occurs in the central region of the pre-existing proton precipitation. Assuming that nightside protons are precipitating from a quasi-stable ring current at its outer regions where the field lines are distorted by neutral sheet currents we can associate the onset location with this region of closed but distorted field lines relatively close to the earth. Our results also show that protons are present in the initial poleward substorm expansion however later they are over taken by the electrons. We also find that the intensity of the substorms as quantified by the intensity of the post onset electron precipitation is correlated with the intensity of the proton precipitation prior to the substorms, highlighting the role of the pre-existing near earth plasma in the production of the next substorm.     

Understanding Interplanetary Coronal Mass Ejection Signatures

While interplanetary coronal mass ejections (ICMEs) are understood to be the heliospheric counterparts of CMEs, with signatures undeniably linked to the CME process, the variability of these signatures and questions about mapping to observed CME features raise issues that remain on the cutting edge of ICME research. These issues are discussed in the context of traditional understanding, and recent results using innovative analysis techniques are reviewed.     

Coronal Mass Ejections: Overview of Observations

We survey the subject of Coronal Mass Ejections (CMEs), emphasizing knowledge available prior to about 2003, as a synopsis of the phenomenology and its interpretation.     

Strategy to search fragments from breakups in GEO

This paper proposes a strategy to search fragments from breakups in the Geosynchronous Earth Orbit (GEO) region based upon population prediction and motion prediction by means of ground-based optical observations. Breakup fragments have uncertainties in the states such as their position and motion, or even in their existence. Population prediction and motion prediction resolve those uncertainties. Population prediction evaluates the time-averaged distribution of fragments, whose position at a given time is unknown, in the celestial sphere. Motion prediction evaluates the expected motion of fragments appeared in image series acquired by a telescope’s CCD camera. This paper logically describes procedures of the search strategy, and provides mathematical expressions of population prediction and motion prediction. This paper also validates the search strategy via actual observations, in which a confirmed breakup in the GEO region is selected as a target. It is concluded that the proposed strategy is valid even for searching uncataloged fragments from breakups in the GEO region.     

A two-position SINS initial alignment method based on gyro information

This paper presents a method to improve the accuracy of and reduce the time needed for the initial alignment of strapdown inertial navigation systems. The new method is based on the conventional two position method enhanced by the use of gyro information. After presenting the problem of initial alignment and identifying the key issues – low accuracy and long convergence time, the paper introduces the two position method showing the improvement of performance but not on convergence time. By using gyro information in the new method, precision is improved and time for alignment reduced. The discussion is illustrated with simulations.     

Radio observations of total solar eclipse of November 3, 1994 at Chapecó (Brzil)

Radio observations of the eclipse on November 3, 1994, were carried out at Chapecó, Brazil by using a decimetric spectrograph having high spectral and time resolution. The light curve shows that: (1) Time variation of the radio flux before the totality was more compared to that after. (2) During the totality radio emission at 1.5 GHz was observed. Advantage of high spatial resolution ( 3.2 arc sec) possible during solar eclipse enabled us to determine the height of radio emission at 1.5 GHz. (3) Microwave bursts were observed associated with metric Type III-RS bursts. The source size of one of the microwave bursts was 7 arc sec and its physical parameters have been estimated. (4) The time difference between radio and optical contacts suggested for the first time asymmetrical limb brightening at 1.5 GHz.     

Status of the Stratospheric Observatory for Infrared Astronomy (SOFIA)

The Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint US/German project, is a 2.5-m infrared airborne telescope carried by a Boeing 747-SP that flies in the stratosphere at altitudes as high as 45,000 ft (13.72 km). This facility is capable of observing from 0.3 μm to 1.6 mm with an average transmission greater than 80% averaged over all wavelengths. SOFIA will be staged out of the NASA Dryden Flight Research Center aircraft operations facility at Palmdale, CA. The SOFIA Science Mission Operations (SMO) will be located at NASA Ames Research Center, Moffett Field, CA. First science flights began in 2010 and a full operations schedule of up to one hundred 8 to 10 hour-long flights per year will be reached by 2014. The observatory is expected to operate until the mid-2030s. SOFIA’s initial complement of seven focal plane instruments includes broadband imagers, moderate-resolution spectrographs that will resolve broad features due to dust and large molecules, and high-resolution spectrometers capable of studying the kinematics of atomic and molecular gas at sub-km/s resolution. We describe the SOFIA facility and outline the opportunities for observations by the general scientific community and for future instrumentation development. The operational characteristics of the SOFIA first-generation instruments are summarized. The status of the flight test program is discussed and we show First Light images obtained at wavelengths from 5.4 to 37 μm with the FORCAST imaging camera. Additional information about SOFIA is available at http://www.sofia.usra.edu and http://www.sofia.usra.edu/Science/docs/SofiaScienceVision051809-1.pdf.     

COLUMBUS Orbital Facility and Automated Transfer Vehicle: a challenge for agency & industry

Long term continuous operation of the COLUMBUS Orbital Facility (COF) flight- and ground segment requires continuous mission control and operations support capability to ensure proper operation and configuration of the COF systems in support of ongoing science and technology payloads. The ISS logistics scenario will be supported by the Automated Transfer Vehicle (ATV). These operational needs require the built-up of a new ground infrastructure in Europe and USA, enabling an efficient operations for preparation, planning and mission execution. The challenge for the European space community consists in the development and operation of a user friendly operational environment but keeping costs within budgetary constraints. Results of detailed definition studies performed by both agency and industry for the ground infrastructure indicate solutions to those technical and programmatic requirements by using of existing centers and facilities, re-use of C/D phase products (Hardware, Software) and COTS equipment to avoid costly new developments, using engineering expertise of the industrial personnel from flight element phase C/D. The concept for operations execution defines the task sharing between Operations Control Facilities (OCF), Operations Support Facilities and User Operations Sites. Operations support consists of on-line engineering support, off-line engineering support, payload integration, logistics support and crew training support performed by industry. DASA RI has made internal investments in organizational concepts for mission operations as well as in mission technologies and tools based on the standard COLUMBUS Ground Software (CGS) toolset and on knowledge based systems to enable an efficient industrial operations support. These tools are available as prototypes being evaluated in a simulated operational environment.     

Fault diagnostics and fault tolerant control

A novel simultaneous fault detection and diagnostics (FDD) and fault tolerant control (FTC) strategy for nonlinear stochastic systems in closed loops based on a continuous stirred tank reactor (CSTR) is presented. The purpose of control is to track the reactant concentration setpoint. Instead of output feedback we propose here to use proportional-integral-derivative (PID) state feedback, which is shown essential to achieve FTC against sensor faults. A new concept of “equivalent bias” is proposed to model the sensor faults. Both the states and the equivalent bias are on-line estimated by a pseudo separate-bias estimation algorithm. The estimated equivalent bias is then evaluated via a modified Bayes' classification based algorithm to detect and diagnose the sensor faults. Many kinds of sensor faults are tested by Monte Carlo simulations, which demonstrate that the proposed strategy has definite fault tolerant ability against sensor faults, moreover the sensor faults can be on-line detected, isolated, and estimated simultaneously