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Video observations of lunar impact flashes have been made by a number of researchers since the late 1990's and the problem of determination of the impact energies has been approached in different ways Bellot Rubio et al. (2000a, b), Yanagisawa et al. (2008), Bouley et al. (2012), Suggs et al. (2014), Rembold and Ryan (2015), Ortiz et al. (2015), Madiedo et al. (2015). The wide spectral response of the unfiltered video cameras in use for all published measurements necessitates color correction for the standard filter magnitudes available for the comparison stars but this is not typically considered. In our approach, the published color of the comparison star and an estimate of the color of the impact flash is used to correct it to the chosen filter bandpass. Magnitudes corrected to standard filters are then used to determine the luminous energy in the filter bandpass according to the stellar atmosphere calibrations of Bessell et al. (1998). In this paper we compare the various photometric calibration techniques and calculation of luminous energy (radiometry) of impact flashes. This issue has significant implications for determination of luminous efficiency, predictions of impact crater sizes for observed flashes, and the determination of the flux of meteoroids in the 10 s of grams to kilograms mass range.

Lunar Reconnaissance Orbiter Camera images acquired both before and after the formation of an 18.8 m diameter crater on 17 March 2013 reveal intricate details of ejecta distribution and the structure of the top two meters of the regolith. Our observations indicate that (1) the regolith is mature down to several tens of cm and immature below one meter, (2) surface reflectivity properties are affected for distances greater than fifty crater radii, and (3) large numbers of secondary impacts (splotches) formed up to 30 km distant from this new primary crater. These observations provide new knowledge of the distribution of ejected materials from small impact craters on the Moon, the modification of the top few cm of the regolith by micrometeorite impacts, and potential hazards to future explorers.

Lynx is a concept under study for prioritization in the 2020 Astrophysics Decadal Survey. Providing orders of magnitude increase in sensitivity over Chandra, Lynx will examine the first black holes and their galaxies, map the large-scale structure and galactic halos, and shed new light on the environments of young stars and their planetary systems. In order to meet the Lynx science goals, the telescope consists of a high-angular resolution optical assembly complemented by an instrument suite that may include a High Definition X-ray Imager, X-ray Microcalorimeter and an X-ray Grating Spectrometer. The telescope is integrated onto the spacecraft to form a comprehensive observatory concept. Progress on the formulation of the Lynx telescope and observatory configuration is reported in this paper.

We present the results of new calibration tests performed by the NASA Meteoroid Environment Office (MEO) designed to help quantify and minimize systematic uncertainties in meteor photometry from video camera observations. These systematic uncertainties can be categorized by two main sources: an imperfect understanding of the linearity correction for the MEO's Watec 902H2 Ultimate video cameras and uncertainties in meteor magnitudes arising from transformations between the Watec camera's Sony EX-View HAD bandpass and the bandpasses used to determine reference star magnitudes. To address the first point, we have measured the linearity response of the MEO's standard meteor video cameras using two independent laboratory tests on eight cameras. Our empirically determined linearity correction is critical for performing accurate photometry at low camera intensity levels. With regards to the second point, we have calculated synthetic magnitudes in the EX bandpass for reference stars. These synthetic magnitudes enable direct calculations of the meteor's photometric flux within the camera band pass without requiring any assumptions of its spectral energy distribution. Systematic uncertainties in the synthetic magnitudes of individual reference stars are estimated at ∼ 0.20 mag, and are limited by the available spectral information in the reference catalogs. These two improvements allow for zero-points accurate to ∼ 0.05 - 0.10 mag in both filtered and unfiltered camera observations with no evidence for lingering systematics. These improvements are essential to accurately measuring photometric masses of individual meteors and source mass indexes.

Presented here are results from photometric analysis on broadband images taken of comet 21P/Giacobini-Zinner from May 24, 2011 to October 24, 2011. As the parent body of the Draconids, a meteor shower known for outbursting, 21P was studied for its dust production activity, Afρ, focusing on how it changes with heliocentric distance. An expected increase in dust production with a decrease in heliocentric distance was observed. The comet went from heliocentric distance of 3.05 –1.77 AU during the observed time that corresponded to an apparent magnitude of 19.61 to 15.72 and Afρ of 16.48 cm to 284.17 cm. These values can be extrapolated to estimate a peak Afρ value at perihelion of 3824 cm. The images were obtained using a 0.5-meter f/8.1 Ritchey-Chretien telescope located in Mayhill, New Mexico.

Monitoring the lunar surface for impacts is a highly rewarding approach to study small asteroids and large meteoroids encountering the Earth–Moon System. The various effects of meteoroids impacting the Moon are described and results from different detection and study techniques are compared. While the traditional statistics of impact craters allow us to determine the cumulative meteoroid flux on the lunar surface, the recent successful identification of fresh craters in orbital imagery has the potential to directly measure the cratering rate of today. Time-resolved recordings, e.g., seismic data of impacts and impact flash detections clearly demonstrate variations of the impact flux during the lunar day. From the temporal/spatial distribution of impact events, constraints can be obtained on the meteoroid approach trajectories and velocities. The current monitoring allows us to identify temporal clustering of impacts and to study the different meteoroid showers encountering the Earth–Moon system. Though observational biases and deficiencies in our knowledge of the scaling laws are severe, there appears to be an order-of-magnitude agreement in the observed flux within the error limits. Selenographic asymmetries in the impact flux (e.g., for equatorial vs. polar areas) have been predicted. An excess of impacts on the lunar leading hemisphere can be demonstrated in current data. We expect that future missions will allow simultaneous detections of seismic events and impact flashes. The known locations and times of the flashes will allow us to constrain the seismic solutions. While the numbers of flash detections are still limited, coordinated world-wide observations hold great potential for exploiting this observation technique. The potential for identification of fresh craters in high-resolution orbital image data has just barely been tapped, but should improve significantly with the LRO extended mission.

著者人数: 87名, Accepted: 2011-02-08, 資料番号: SA1004099000

Lunar meteoroid impact flashes provide a method to estimate the flux of the large meteoroid flux and thus their hazard to spacecraft. Although meteoroid impacts on the Moon have been detected using video methods for over a decade, the difficulty of manually searching hours of video for the rare, extremely brief impact flashes has discouraged the technique’s systematic implementation. A prototype has been developed for the purpose of automatically searching lunar video records for impact flashes, eliminating false detections, editing the returned possible flashes, and archiving and documenting the results. Several utilities for measurement, analysis, and location of the flashes on the moon included in the program are demonstrated. Application of the program to a year’s worth of lunar observations is discussed along with examples of impact flashes.

NASA’s Meteoroid Environment Office has implemented a program to monitor the Moon for meteoroid impacts from the Marshall Space Flight Center. Using off-the-shelf telescopes and video equipment, the Moon is monitored for as many as 10 nights per month, depending on weather. Custom software automatically detects flashes which are confirmed by a second telescope, photometrically calibrated using background stars, and published on a website for correlation with other observations. Hypervelocity impact tests at the Ames Vertical Gun Range facility have begun to determine the luminous efficiency and ejecta characteristics. The purpose of this research is to define the impact ejecta environment for use by lunar spacecraft designers of the Constellation manned lunar program. The observational techniques and preliminary results will be discussed.

In an attempt to overcome some of the deficiencies of existing meteoroid models, NASA’s Space Environments and Effects (SEE) Program sponsored a 3 year research effort at the University of Western Ontario. The resulting understanding of the sporadic meteoroid environment – particularly the nature and distribution of the sporadic sources – were then incorporated into a new Meteoroid Engineering Model (MEM) by members of the Space Environments Team at NASA’s Marshall Space Flight Center. This paper discusses some of the revolutionary aspects of MEM which include (a) identification of the sporadic radiants with real sources of meteoroids, such as comets, (b) a physics-based approach which yields accurate fluxes and directionality for interplanetary spacecraft anywhere from 0.2 to 2.0 astronomical units (AU), and (c) velocity distributions obtained from theory and validated against observation. Use of the model, which gives penetrating fluxes and average impact speeds on the surfaces of a cube-like structure, is also described along with its current limitations and plans for future improvements.

Meteor44 is a software system developed at MSFC for the calibration and analysis of video meteor data. The photometric range of the (8 bit) video data is extended from a visual magnitude range of from 8 to 3 to from 8 to −8 for both meteors and stellar images using saturation compensation. Camera and lens specific saturation compensation coefficients are derived from artificial variable star laboratory measurements. Saturation compensation significantly increases the number of meteors with measured intensity and improves the estimation of meteoroid mass distribution. Astrometry is automated to determine each image’s plate coefficient using appropriate star catalogs. The images are simultaneously intensity calibrated from the contained stars to determine the photon sensitivity and the saturation level referenced above the atmosphere. The camera’s spectral response is used to compensate for stellar color index and typical meteor spectra in order to report meteor light curves in traditional visual magnitude units. Recent efforts include improved camera calibration procedures and long focal length “treak” meteor photometry. Meteor44 has been used to analyze data from the 2001, 2002 and 2003 MSFC Leonid observational campaigns as well as several lesser showers.

The International Space Station (ISS) regularly passes through the southern auroral oval south of Australia. The ISS has two plasma contactors that emit the electron currents needed to balance electron collection by surfaces such as the lattice of bare rods on the solar array masts. These electron currents exceed 0.1 A at times. The largest currents are observed in the auroral oval south of Australia. On the space station, the solar array 40 m long masts each have over 400 m of stainless steel tensioning rods. When subject to orbital v × B· l induced potentials, the rods collect substantial currents from the ionosphere. Maximum v × B· l potentials are generated near the magnetic poles. The plasma contactor emission current can be converted to an estimate of plasma density and calibrated using Floating Potential Probe (FPP) and other data. These measurements show that the plasma density in the nighttime auroral ionosphere is frequently several times that predicted by the International Reference Ionosphere (IRI)-90 and IRI2001 models.

The Lunar CRater Observation and Sensing Satellite (LCROSS) mission was designed to search for evidence of water in a permanently shadowed region near the lunar south pole. An instrumented Shepherding Spacecraft followed a kinetic impactor and provided--from a nadir perspective--the only images of the debris plume. With independent observations of the visible debris plume from a more oblique view, the angles and velocities of the ejecta from this unique cratering experiment are better constrained. Here we report the first visible observations of the LCROSS ejecta plume from Earth, thereby ascertaining the morphology of the plume to contain a minimum of two separate components, placing limits on ejecta velocities at multiple angles, and permitting an independent estimate of the illuminated ejecta mass. Our mass estimate implies that the lunar volatile inventory in the Cabeus permanently shadowed region includes a water concentration of 6.3±1.6% by mass.

[1] We observed the Lunar Crater Observation and Sensing Satellite (LCROSS) lunar impact on 9 October 2009 using three telescope and instrument combinations in southern New Mexico: the Agile camera with a V filter on the Astrophysical Research Consortium 3.5 m telescope at Apache Point Observatory (APO), a StellaCam video camera with an R filter on the New Mexico State University (NMSU) 1 m telescope at APO, and a Goodrich near-IR (J and H band) video camera on the NMSU 0.6 m telescope at Tortugas Mountain Observatory. The three data sets were analyzed to search for evidence of the debris plume that rose above the Cabeus crater shortly after the LCROSS impact. Although we saw no evidence of the plume in any of our data sets, we constrained its surface brightness through analysis of our photometrically calibrated data. The minimum surface brightness that we could have detected in our Agile data was 9.69 magnitudes arc sec−2, which is 177 times fainter than the brightest part of the foreground ridge of Cabeus. In our near-IR data, our minimum detectable surface brightness was 8.58 magnitudes arc sec−2, which is 370 times fainter than the brightest part of the foreground ridge in the J and H bands. The debris plume was detected by the LCROSS shepherding spacecraft and the Diviner radiometer on the Lunar Reconnaissance Orbiter. Given the plume radiance observed by LCROSS, we cannot distinguish between a conical or cylindrical plume geometry because when seen from Earth, both are below our detection thresholds.

This paper describes the development of CRMFLX, an ion model for the outer magnetosphere developed for scheduling periods when the Advanced CCD Imaging Spectrometer (ACIS) instrument onboard the Chandra X-ray Observatory can be safely moved into the focal plane position required for science observations. Because exposure to protons with energies of approximately 100 keV to 200 keV has been shown to produce an increase in the charge transfer inefficiency (CTI) of the ACIS instrument, a tool for predicting encounters with magnetospheric regions rich in these particles is required. The model is based on data from the EPIC/ICS instrument onboard the Geotail satellite and provides the user with flux values for 100 kev to 200 keV protons as a function of satellite position and the geomagnetic activity Kp index.

The Chandra X-ray Observatory lies in a highly elliptical orbit which dips into the outer radiation belt. During the initial stages of orbital operations, Chandra's front-illuminated CCD's (but not the back-illuminated ones) experienced an unanticipated degradation of the charge-transfer efficiency. The subsequent anomaly investigation determined that moderately low-energy protons (or other ions) propagated through the mirror assembly, causing the observed damage. This paper summarizes the effort to determine the radiation environment at the Chandra focal plane and the steps taken to prevent further performance degradation by magnetospheric and solar-wind protons and other ions.

The Next Generation Space Telescope (NGST) will operate in a halo orbit about the L2 point, 1 .5 million km from the Earth,where the spacecraft will periodically travel through the magnetotail region. There are a number of tools available to calculatethe high energy, ionizing radiation particle environment from galactic cosmic rays and from solar disturbances. However,space environment tools are not generally available to provide assessments of the charged particle environment and itsvariations in the solar wind, magnetosheath, and magnetotail at L2 distances. An engineering-level phenomenology code(LRAD) was therefore developed to facilitate the definition of charged particle environments in the vicinity of the L2 point insupport of the NGST program. LRAD contains models tied to satellite measurement data of the solar wind and magnetotailregions. The model provides particle flux and fluence calculations necessary to predict spacecraft charging conditions and thedegradation of materials used in the construction of NGST. This paper describes the LRAD environment models for the deepmagnetotail (XGSE < -100 Re) and solar wind, and presents predictions of the charged particle environment for NGST.Keywords: NGST, L2, plasma, environment, magnetotail, magnetosheath, solar wind

Multi-aperture photometry of Comet 29P/Schwassmann-Wachmann 1 was conducted on Johnson-Cousins R-band observations spanning 2011 May 1-9 and 2012 June 6-July 3. The comet was observed in outburst on 2011 May 3 and 2012 July 1, during which its brightness increased by 2.2 and 2.1 mag, respectively, as measured through a 10 arcsec aperture. Dust production before and after each outburst is calculated using the parameter Af ρ, which is converted to a lower limit on the dust production rate based on dust models and derived nuclear properties from other studies. Both outbursts are accompanied by large increases in dust production, Af ρ by a factor of ~6.5-7 and dust production rate by a factor of ~18-23. In addition, variations in the dust brightness profile of the coma are examined during the events. The profile is observed to steepen significantly at the beginning of each outburst and then slowly return to pre-outburst values, mirroring the behavior of Af ρ. The start of an outbound ripple of dust in the profile might be observed as the comet returns to its pre-outburst state, although this cannot be confirmed. Using a simple model of the 2011 May 3 outburst, an estimated lower limit of (2.6 ± 0.7) × 108 kg of dust was released during the event. If this is representative of a typical outburst of 29P, then it is estimated that outbursts account for a lower limit of 80 of the total material ejected by the comet per year.

Noctilucent clouds (NLC) are observed in the northern latitudes during the summer months. The clouds, thought to be composed of crystalline ice, occur between 80- and 85-km altitude where the temperature of the mesopause can dip to 120 K. These clouds can be seen by ground-based observers when the sun is 6-16° below the horizon. This viewing geometry assures that the clouds will be illuminated by the sun while the lower atmosphere is dark. Imagery collected by Delta Star is presented as well as correlated ground-based and aircraft-based observations. Narrow field of view images obtained by Delta Star resemble NLC photographs made from the ground and from aircraft. Delta Star imaged NLCs on four of the six nights the experiment was attempted, three over central Alaska and one over Finland. Corroborating observations are available for three of these four nights. Altitude measurements made from Delta Star data place the NLCs at 81-km altitude with an estimated thickness of 4 km.

A selected set of planetocentric latitudes is used in calculations of the seasonal solar radiation pattern incident on top of the Jovian atmosphere, thereby demonstrating the combined effect of solar distance and declination. Attention is given to hemispheric asymmetries in the Jovian atmosphere's average zonal winds and cloud system morphologies. Marked hemispheric asymmetries are noted in the cloud morphology and in the magnitude and latitudinal position of eastward and westward maxima in the average zonal winds, suggesting seasonal forcing on the order of magnitude presently considered. Supporting observations by Voyagers 1 and 2 are cited.