Entire Orbit Research Articles

Tidal disruption of NEAs - a case of Příbram meteorite

This work studies the dynamical evolution of a possible meteor stream along the orbit of the P\v{r}\'{i}bram meteorite, which originated in the tidal disruption of the putative rubble-pile-like parent body during a close approach to the Earth. We assumed the disruption at the time when the ascending or descending node of the parent orbit was close to the Earth's orbit. In the last 5000 years, the P\v{r}\'{i}bram orbit has crossed the Earth orbit twice. It happened about 4200 years and 3300 years ago. In both cases, we modeled the release of particles from the simplified model of rotating asteroid, and traced their individual orbital evolution to the current date. It takes several hundred years to spread released meteoroids along the entire orbit of the parent body. Even today, the stream would be relatively narrow. Considering a model parent body with physical parameters of the asteroid Itokawa, the complete disintegration of the object produced 3.8$\times10^{11}$ meteoroid particles with diameter $\geq$ 1\,cm. The meteor activity observed from the Earth is revealed and justification of follow-up observation during suggested activity of the shower in the first two weeks of April is discussed. The Earth's tidal forces would disintegrate a fraction of NEA population into smaller objects. We evaluate the upper limit of mass of disintegrated asteroids within the mean NEA lifetime and the contribution of disrupted matter to the size distribution of the NEA.

Fuel-optimal eccentricities for precise formation keeping of spacecraft on Keplerian orbits

In this paper, the problem of precise relative position keeping associated with the formation flying of two spacecraft is discussed. Taking into account of the applications to astronomic observation, the relative position of spacecraft is controlled to be precisely retained on a part of an orbit rather than on the entire orbit; moreover, the relative position is retained in the inertial coordinates rather than in the local vertical local horizontal coordinates. The fuel-optimal eccentricities are computed for each length of control time. Then, it is shown that the fuel-optimal eccentricity is close to 1 when the control time is shorter than approximately 90% of the orbit period; on the contrary, the fuel-optimal eccentricity is in the neighborhood of 0 when the control time is close to the orbit period. Moreover, several analytic expressions including the propellant consumptions at the eccentricities of 0 and 1 are obtained.

T2-weighted fast spin-echo magnetic resonance imaging of extraocular muscles

Magnetic resonance imaging (MRI) can provide unique information about extraocular muscle (EOM) structure and function. Previous high-resolution motility imaging studies used T1 weighting, which provides intrinsic contrast of dark-appearing EOMs against bright orbital fat and is suitable for intravenous contrast. However, time-consuming T1 sequences are subject to motion artifacts. We evaluated an alternative T2-weighted fast spin-echo pulse sequence that emphasizes tissue-free fluid. We prospectively used high-resolution, surface coil technique for orbital MRI at 1.5T in 21 orthotropic and 113 living strabismic subjects and 2 monkey cadavers by using T2 fast spin-echo (T2FSE) weighting (long repetition time, short echo time). T2FSE was compared with T1 in 17 subjects, and with T1 in 506 different living subjects, and 12 cadavers. For 2 mm thick coronal MRIs of 312 μm resolution spanning the entire orbit, T1 acquisition required 218 seconds, whereas T2FSE required 150 seconds (31% faster). T2-defined the globe border better, and provided intrinsic contrast between EOMs and their pulleys. Although both T1 and T2 demonstrated motor nerves to EOMs in living subjects, only T1 was satisfactory with injected contrast and in cadavers. For motility imaging, T2FSE is faster than T1 MRI and demonstrates superior tissue details of EOMs and other orbital tissues. T2FSE of the orbits can be performed by the use of widely available standard equipment. We suggest that T2FSE be the preferred method for clinical imaging of EOM structure, function, and innervation, although T1 may be more appropriate when intravenous contrast must be used.

Solution of Kepler’s equation for rectilinear motion

The properties of the solution of the kinematic equation (Kepler’s equation) presented as a series in powers of a function of time are considered for the case of unperturbed, rectilinear elliptical and rectilinear hyperbolic motion. Kepler’s equation for unperturbed, rectilinear elliptical motion has the form E − sinE = z 3/6, where E is the eccentric anomaly determining the position in the orbit, z 3/6 is the mean anomaly, which is proportional to the time measured from an encounter, and its solution can be represented as a series in powers of z. It is established that the coefficients of the series are positive. The asymptotic for the coefficients in the region of convergence of the series is found, which covers the entire orbit. The series continues to converge over the entire boundary of the circle of convergence. The kinematic equation for unperturbed, rectilinear hyperbolic motion has the form sinhH − H = ζ 3/6, where, as before, ζ 3 is proportional to time. The substitution E = iH, z = iζ reduces one equation to the other. The series for the solution in the hyperbolic case differs from the series for the elliptical solution only in its alternating-sign coefficients. However, the region of convergence covers only part of the orbit in the hyperbolic case.

Transfrontal orbitotomy in the dog: an adaptable three-step approach to the orbit

To describe an adaptable and extensive method for orbitotomy in the dog. An adaptable three-step technique for orbitotomy was developed and applied in nine consecutive cases. The steps are zygomatic arch resection laterally, temporalis muscle elevation medially and zygomatic process osteotomy anteriorly-dorsally. The entire orbit is accessed with excellent exposure and room for surgical manipulation. Facial nerve, lacrimal nerve and lacrimal gland function are preserved. The procedure can easily be converted into an orbital exenteration. Exposure of the orbit was excellent in all cases and anatomically correct closure was achieved. Signs of postoperative discomfort were limited, with moderate, reversible swelling in two cases and mild in seven. Wound infection or emphysema did not occur, nor did any other complication attributable to the operative procedure. Blinking ability and lacrimal function were preserved over follow-up times ranging from 1 to 4 years. Transfrontal orbitotomy in the dog offers excellent exposure and room for manipulation. Anatomically correct closure is easily accomplished, postoperative discomfort is limited and complications are mild and temporary.

Use of Normal Tissue Complication Probability Models in the Clinic

The Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) review summarizes the currently available three-dimensional dose/volume/outcome data to update and refine the normal tissue dose/volume tolerance guidelines provided by the classic Emami et al. paper published in 1991. A "clinician's view" on using the QUANTEC information in a responsible manner is presented along with a description of the most commonly used normal tissue complication probability (NTCP) models. A summary of organ-specific dose/volume/outcome data, based on the QUANTEC reviews, is included.

NSVS 06507557: a low-mass double-lined eclipsing binary

In this paper we present the results of a detailed spectroscopic and photometric analysis of the V=13$^m$.4 low-mass eclipsing binary NSVS 06507557 with an orbital period of 0.515 d. We obtained a series of mid-resolution spectra covering nearly entire orbit of the system. In addition we obtained simultaneous VRI broadband photometry using a small aperture telescope. From these spectroscopic and photometric data we have derived the system's orbital parameters and determined the fundamental stellar parameters of the two components. Our results indicate that NSVS 06507557 consists of a K9 and an M3 pre-main-sequence stars with masses of 0.66$\pm$0.09 \Msun and 0.28$\pm$0.05 \Msun and radii of 0.60$\pm$0.03 and 0.44$\pm$0.02 \Rsun, located at a distance of 111$\pm$9 pc. The radius of the less massive secondary component is larger than that of the zero-age main-sequnce star having the same mass. While the radius of the primary component is in agreement with ZAMS the secondary component appers to be larger by about 35 % with respect to its ZAMS counterpart. Night-to-night intrinsic light variations up to 0$^m$.2 have been observed. In addition, the H$_{\alpha}$, H$_{\beta}$ lines and the forbidden line of [O{\sc i}] are seen in emission. The Li{\sc i} 6708 \AA absorption line is seen in most of the spectra. These features are taken to be the signs of the classic T Tauri stars' characteristics. The parameters we derived are consistent with an age of about 20 Myr according to the stellar evolutionary models. The spectroscopic and photometric results are in agreement with those obtained by theoretical predictions.

PROBING THE PULSAR WIND IN THE γ-RAY BINARY SYSTEM PSR B1259–63/SS 2883

The spectral energy distribution from the X-ray to the very high energy regime (>100 GeV) has been investigated for the γ-ray binary system PSR B1259–63/SS 2883 as a function of the orbital phase within the framework of a simple model of a pulsar wind nebula. The emission model is based on the synchrotron radiation process for the X-ray regime and the inverse Compton scattering process boosting stellar photons from the Be star companion to the very high energy (100 GeV-TeV) regime. With this model, the observed temporal behavior can, in principle, be used to probe the pulsar wind properties at the shock as a function of the orbital phase. Due to theoretical uncertainties in the detailed microphysics of the acceleration process and the conversion of magnetic energy into particle kinetic energy, the observed X-ray data for the entire orbit are fitted using two different methods. In the first method, the magnetization parameter and the Lorentz factor of the wind at the shock are allowed to vary for a given power law index characterizing the accelerated particles at the shock. In this case, the observed photon index of ~1.2 in the 1-10 keV energy band near the periastron passage can be understood provided that (1) the electron energy distribution is described by a broken power law and (2) there is a break at an energy of about 8 × 106 in units of the electron rest mass energy. In the second method, the magnetization parameter and the power law index are varied for a fixed Lorentz factor. Here, the photon index of ~1.2 can result from a particle distribution described by a power law index of ~1.5. The calculated emission in the energy band corresponding to 10 MeV-1 GeV from the shocked pulsar wind indicates that these two cases can be distinguished by future Fermi observations near the periastron. It is also found that the emission from the unshocked wind could be detectable by the Fermi telescope near the periastron passage if most of the kinetic energy of the flow is carried by particles with Lorentz factors of Γ ~ 105.

Effects of satellite dimensions in the solar pressure formulation for formation flying

In highly elliptical orbits, the solar pressure can perturb the motion of a constellation through the entire orbit because of the longer exposure of the satellites to the Sun. The Tschauner—Hempel equations for a perturbed motion will be used to explain the motion of a pair of satellites about the Earth in a highly elliptical orbit. In this set of equations, the solar pressure formulation will be written differently to determine how the satellite dimensions can affect the control effort to perform the drift correction. To maintain the separation distance constraints, the authors developed a hierarchical control scheme, in discrete format, that takes care of the perturbation effects of the Earth and the Sun. In summary, this article will show how the differences of the satellite dimensions in the solar pressure formulation can cause variations in the control effort.

Retrobulbar 99mTc-Diethylenetriamine-Pentaacetic-Acid Uptake May Predict the Effectiveness of Immunosuppressive Therapy in Graves' Ophthalmopathy

In Graves' ophthalmopathy (GO), only patients with immunologically active disease respond to immunosuppressive therapy. Previous studies and theoretical considerations suggest that elevated orbital (99m)Tc-diethylenetriamine-pentaacetic-acid (DTPA) single photon emission computed tomography (SPECT) reflects inflammatory disease activity. We studied whether corticosteroid treatment causes a substantial decrease in DTPA uptake in GO, a result consistent with successful immunosuppressive treatment of GO and referred to as a favorable treatment outcome. One hundred fourteen orbits in 57 patients with active GO (CAS >or= 4) were entered into the study. All patients received corticosteroid treatment. Orbital DTPA uptakes were numerically quantified for the entire orbit as well as the anterior and posterior segments separately. DTPA SPECT was performed before, and 2 to 9 months after the initiation of immunosuppressive treatment. The normal range for DTPA uptake was established in 34 orbits of 17 patients who were being worked up for Raynaud's phenomenon and had no thyroid disease. The mean DTPA uptake of the 114 orbits of GO patients was higher prior to corticosteroid therapy than after this treatment (11.03 +/- 4.26 MBq/cm(3) and 9.84 +/- 3.51 MBq/cm(3), respectively, p < 0.001) but a substantial decline in DTPA uptake was seen in only 39.5% of GO patients. The positive predictive value of an initial DTPA >12.28 MBq/cm(3) for a substantial decline in DTPA uptake (favorable treatment outcome) was 76%, while a negative predictive value of a pretreatment DTPA <or=12.28 MBq/cm(3) was 78%. Corticosteriod treatment is associated with a decline in DTPA uptake in a fraction of GO patients. GO patients with a DTPA uptake above 12.28 MBq/cm(3) are more likely to have a favorable response to corticosteroid therapy while patients with lower values are less likely to have this potentially favorable response. An elevated DTPA uptake may identify patients who are most likely to benefit from immunosuppressive treatment.

Modelling ultrafine structure in dark matter haloes

Various laboratory-based experiments are underway attempting to detect dark matter directly. The event rates and detailed signals expected in these experiments depend on the dark matter phase space distribution on sub-milliparsec scales. These scales are many orders of magnitude smaller than those that can be resolved by conventional N-body simulations, so one cannot hope to use such tools to investigate the effect of mergers in the history of the Milky Way on the detailed phase-space structure probed by the current experiments. In this paper we present an alternative approach to investigating the results of such mergers, by studying a simplified model for a merger of a sub-halo with a larger parent halo. With an appropriate choice of parent halo potential, the evolution of material from the sub-halo can be expressed analytically in action-angle variables, so it is possible to obtain its entire orbit history very rapidly without numerical integration. Furthermore by evolving backwards in time, we can obtain arbitrarily-high spatial resolution for the current velocity distribution at a fixed point. Although this model cannot provide a detailed quantitative comparison with the Milky Way, its properties are sufficiently generic that it offers qualitative insight into the expected structure arising from a merger at a resolution that cannot be approached with full numerical simulations. Preliminary results indicate that the velocity-space distribution of dark matter particles remains characterized by discrete and well-defined peaks over an extended period of time, both for single and multi-merging systems, in contrast to the simple smooth velocity distributions sometimes assumed in predicting laboratory experiment detection rates.

Space Weather and the Global Positioning System

Space Weather and the Global Positioning System

Special Sensor Microwave Imager Sounder (SSMIS) Radiometric Calibration Anomalies—Part I: Identification and Characterization

Two calibration anomalies of the Defense Meteorological Satellite Program's (DMSP) Special Sensor Microwave Imager Sounder (SSMIS) radiometer are examined by using several sources of data. Early orbit mode data from the SSMIS are used to create radiometric images of the warm calibration load that evolve over an entire orbit to elucidate the effects of direct and reflected solar illumination of the warm-load (WL) emissive surface. Analysis of the radiometric gain and apparent WL radiometric brightness temperature observed during the solar intrusion events show the impact of these events on the SSMIS calibration. A graphical simulation of the SSMIS and DMSP spacecraft is used to define the regions where solar intrusion occurs and to characterize the WL anomalous regions for the specific DMSP F-16 orbit. The graphical simulation is also used to determine the cause of additional calibration errors that were identified by using comparisons to numerical weather prediction (NWP) models, as emission from the SSMIS reflector antenna. Mitigation of these calibration anomalies is critical if the operational SSMIS radiometers achieve their full utility in NWP, climate monitoring, forecasting, and other emerging applications. A detailed characterization of the SSMIS calibration provides a basis for this process.

The pre-main-sequence eclipsing binary ASAS J052821+0338.5

In this paper we present the first results of a detailed spectroscopic and photometric analysis of the V = 11.7m eclipsing binary ASAS J052821+0338.5. With the FIES spectrograph at the Nordic Optical Telescope we have obtained a series of high-resolution spectra (R=47000) covering the entire orbit of the system. In addition we obtained simultaneous broadband photometry from three small aperture telescopes. From these spectroscopic and photometric data we have derived the system's orbital parameters and determined the fundamental stellar parameters of the two components. Our results indicate that ASAS J052821+0338.5 is a K1/K3 pre-main-sequence eclipsing binary, with component masses of 1.38 M_sun and 1.33 M_sun and a period of 3.87 days, located at a distance of 280 +/- 30 pc. The kinematics, physical location and the evolutionary status of the two stars suggest that ASAS J052821+0338.5 is a member of the approximately 11 Myr old Orion OB1a subassociation. The systems also exhibits smooth 0.15m out-of-eclipse variations that are similar to those found in RS CVn binaries. Furthermore the parameters we derived are consistent with the 10-13 Myr isochrones of the popular Baraffe stellar evolutionary models.

Lateral Retrocanthal Orbitotomy

To develop and evaluate a minimally invasive technique of lateral orbitotomy that provides improved orbital access with fewer complications. A cadaver study was undertaken to develop a technique of transconjunctival lateral orbitotomy that preserves the structural integrity of the eyelid support system and provides extended access to the orbit from floor to roof. We then evaluated the procedure in an outcome study of 30 consecutive patients. The cadaver investigations demonstrated that a transconjunctival lateral retrocanthal approach is technically possible and provides improved direct access to the lateral orbit. In the study of 30 consecutive procedures, there were no complications resulting from the surgical access. The wound healing was rapid, without tissue distortion or scars. The exposure was ample for all surgical interventions. Lateral retrocanthal orbitotomy is a new approach that provides extended access to the entire lateral orbit. The technique is rapid and can be extended in a single continuous incision to the medial orbit. The structural integrity of the lateral retinaculum is preserved, which appears to improve the postoperative cosmetic and functional result.

Be Aware of the Patient with an Eye Patch

To the Editor: A 78-yr-old woman was scheduled for right upper lobectomy under general anesthesia. She weighed 54 kg and was 5 feet 10 in. tall. Her medical history was significant for hypertension, a 50-yr history of cigarette smoking, and an enucleation of the right eye for an unknown tumor 10 years previously. She had a glass eye but preferred to wear a large black (pirate) eye patch that covered the entire orbit including the eyebrows. Her physical examination was unremarkable with a class 2 airway. After induction of anesthesia with fentanyl and thiopental, vecuronium was given for muscle relaxation. Mask ventilation with sevoflurane in 100% oxygen proved difficult as a large leak was detected around her face. A new larger and well-inflated face mask was placed on her face but a large leak was still detected. A second anesthesiologist assisted by holding the mask with both hands, but the leak was still present. Only by increasing the fresh gas flow to 12 L were the lungs ventilated adequately despite the leak. A repeat pressure leak test of the anesthetic machine was done but no abnormality was seen. The cause of the problem was discovered when the eye patch was removed. The orbital cavity had no glass eye and an anatomical passage from the mouth cavity to the orbit of the eye was clearly seen. The problem was easily solved by packing the orbit with a 4 in. moist vaginal pack. Be aware of the patient with an eye patch. Should it be difficult to ventilate via mask due to a large orbital leak a moist vaginal pack can be used.

2531: Local Radiation Therapy Alone for Marginal Zone B-Cell Lymphoma Confined to the Orbit

2531: Local Radiation Therapy Alone for Marginal Zone B-Cell Lymphoma Confined to the Orbit

Mass distribution of Perseid meteoroids

An analysis of the Perseid meteoroid mass distribution is given. It is shown that particle mass distributions are qualitatively the same along the entire orbit of the stream. The extra minima in the cross sections of the stream at the ascending and descending branches of the curve of the parameter S indicate a jetlike nature of the stream. The variations of the nodal longitudes of maximum stream activity versus the minimum observed mass of meteoroids are found along the entire orbit of the stream. The positions of maximum activity for particles with minimum detectable masses larger than 1 and 10−3 g are shifted by 1.4 degrees in solar longitude, with larger longitudes for smaller particles.

Infrared observations of comets with the Spitzer Space Telescope

The scientific motivation for infrared studies of comets is reviewed and the capabilities of Spitzer for cometary observations are described. We present Spitzer Space Telescope images and spectra of several comet comae, tails, and debris trails. Spitzer observations of Comet 29P/Schwassmann-Wachmann 1 are reviewed. The 24 μm images of the inner coma reveal structure consistent with jet activity on a rotating nucleus that otherwise appears to be ablating according to the “standard model”. Spitzer spectra of the coma and nucleus indicate that the nucleus is large ( R = 27 ± 5 km) and that the grains released from the nucleus have compositions similar to that of the grains in some stellar debris disks. Debris trails of several comets have now been imaged with Spitzer. The debris trail of Comet 2P/Encke is particularly noteworthy because its uniform intensity is consistent with the interpretation that the entire orbit is well populated by sand to gravel sized particles. A thermal infrared search for debris trails of several comets is described. We present a Spitzer spectrum of C/2001 HT50 (LINEAR-NEAT) showing that the grains populating its coma at a heliocentric distance of 3.3 AU are substantially larger than the grains in the comae of more pristine comets. Spitzer 3.6–8 μm images of C/2002 T7 (LINEAR) reveal a high-quality image of the extended dust tail.

Investigating CaiiEmission in the RS Canum Venaticorum Binary ER Vulpeculae Using the Broadening Function Formalism

The synchronously rotating G stars in the detached, short-period (0.7 days), partially eclipsing binary ER Vul are the most chromospherically active solar-type stars known. We have monitored activity in the Ca II H and K reversals for almost an entire orbit. Rucinski's broadening function formalism allows the photospheric contribution to be objectively subtracted from the highly blended spectra. The power of the broadening function technique is also demonstrated by the good agreement of radial velocities with those measured by others from less crowded spectral regions. In addition to strong Ca II emission from the primary and secondary, there appears to be a high-velocity stream flowing onto the secondary, where it stimulates a large active region on the surface 30°–40° in advance of the subbinary longitude. A model light curve with a spot centered on the same longitude also gives the best fit to the observed light curve. A flare with ~13% more power than at other phases was detected in one spectrum. We suggest that ER Vul may offer a magnified view of the more subtle chromospheric effects synchronized to planetary revolution seen in certain 51 Peg–type systems.