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.
We have assembled a high-speed time-series CCD photometer named Agile for the 3.5 m telescope at Apache Point Observatory, based on the design of a photometer called Argos at McDonald Observatory. Instead of a mechanical shutter, we use the frame-transfer operation of the CCD to end an exposure and initiate the subsequent new exposure. The frame-transfer operation is triggered by the negative edge of a GPS pulse; the instrument timing is controlled directly by hardware, without any software intervention or delays. This is the central pillar in the design of Argos that we have also used in Agile; this feature makes the accuracy of instrument timing better than a millisecond. Agile is based on a Princeton Instruments Acton VersArray camera with a frame-transfer CCD, which has 1K × 1K active pixels, each of size 13 μm × 13 μm. Using a focal reducer at the Nasmyth focus of the 3.5 m telescope at Apache Point Observatory, we yield a field of view of 2:2 × 2:2 arcmin 2 with an unbinned plate scale of 0:13″ pixel À1 . The CCD is back-illuminated and thinned for improved blue sensitivity and provides a quantum efficiency ≥80% in the wavelength range of 4500-7500 Å. The unbinned full-frame readout time can be as fast as 1.1 s; this is achieved using a low-noise amplifier operating at 1 MHz with an average read noise of the order of 6:6 e rms. At the slow read rate of 100 kHz to be used for exposure times longer than a few seconds, we determine an average read noise of the order of 3:7 e rms. Agile is optimized to observe variability at short timescales from one-third of a second to several hundred seconds. The variable astronomical sources routinely observed with Agile include pulsating white dwarfs, cataclysmic variables, flare stars, planetary transits, and planetary satellite occultations.
Understanding, prioritizing, and mitigating methane (CH4) emissions requires quantifying methane budgets from facility scales to regional scales with the ability to differentiate between source sectors. We deployed a tiered observing system for multiple basins in the United States (San Joaquin Valley, Uintah, Denver-Julesberg, Permian, Marcellus). We quantify strong point source emissions (>10 kg CH4 h-1) using airborne high spatial resolution imaging spectrometers, then attribute them to sectors, and assess their intermittency with multiple revisits. We contextualize these point source emissions by comparing to total basin CH4 fluxes derived from inversion of Sentinel-5p satellite observations. We find that across basins point source make up on average 40% of the regional flux. We sampled some basins several times across multiple months and years and find a distinct bimodal structure to emission lifetimes: the total point source budget is split nearly in half by short- and long-lived emission events. With the increasing airborne and satellite observing capability planned for the near future, tiered observing systems can more fully account and attribute emission sources, which is needed to effectively and efficiently reduce methane emissions.
A" = (0.8482t-18o) A"' (0.8482t-73°50') It is of extraordinary iliterest to note that the transient term arising from the reaction of the steady-state component of current with a flux component of very low damping coefficient has a magnitude of 2.287 as against a value of 115.5 obtained in the previous case and discussed at length in Appendix IV. The startinig torque attains its final steady-state value in less than l/2 cycle while, in the previous case, it took over 30 cycles for the transient term to die down completely. The dotted curve in Fig. 10 indicates the starting torque as a function of t.
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